Oxford Neuroscientist Reveals How POOR SLEEP Leads To Chronic Disease! | Russell Foster

Russell Foster 0:00 Chronic sleep loss is associated with obesity, type 2 diabetes, higher rates of infection, and indeed cancer. Because we haven't ever passed this information on, people don't know. And I think the key thing is-

Dr. Rangan Chatterjee 0:12 [upbeat music] A phrase I've heard you say in one of your talks before is, "Alarm clocks stop the single most important behavioral experience we have."

Russell Foster 0:26 Yeah, and that's sleep, of course. And, and we've, we've so undervalued sleep. You know, we, we... it's been treated as almost an illness that needs a cure or an indulgence. And of course, in the '80s, those of us that remember the '80s, um, you know, people used to come and say, "Oh, I've done an all, a- another all-nighter." And then people used to clap them on the back. And in fact, you don't want people like that in the workplace. I mean, essentially, what we've discovered over the past sort of twenty years or so is that sleep consolidates our memory, but it's not just the retention of facts. It- we're actually problem-solving. So if you wanna come up with innovative solutions to complex problems, a night of sleep achieves that. We're also discovering that, uh, that, that the elimination of, of, of beta amyloid, this, this misfolded protein that's been associated with dementia, is packaged up and got rid of whilst we sleep. So much of the stuff going on within the brain and the body whilst we sleep defines our ability to function during the day. And you know, it's, it's really, we've got to start embracing sleep.

Dr. Rangan Chatterjee 1:27 You know, as I, as I read through your book and as I think about the literature, the work you're putting out there, I think about the impact that sleep deprivation has on our entire physiology. You know, this idea that's been sticking with me the last few days is that, number one, a lot of us don't realize how sleep-deprived we are.

Russell Foster 1:50 Yeah.

Dr. Rangan Chatterjee 1:51 And I think in many ways, the way we experience the world is influenced by our levels of sleep.

Russell Foster 1:59 Yeah. I think that's what, you know, doing the research for the, for the book, the realization that the tired brain remembers negative experiences but forgets the positive ones. So tired individuals' entire worldview is influenced by, by a negative salience. You know, we're making decisions remembering the negative stuff and not the positive stuff. Um, that's just one example, I think.

Dr. Rangan Chatterjee 2:24 Yeah. That's really profound, Russell, because if, if as a doctor, I, I look around and I see how many problems we have these days with excessive negative thoughts that people struggle with-

Russell Foster 2:38 Yeah

Dr. Rangan Chatterjee 2:38 ... and then if you look at the data in terms of how sleep-deprived we are-

Russell Foster 2:42 Yeah

Dr. Rangan Chatterjee 2:43 ... potentially this is the smoking gun that's sitting there that if all of us started to pay a little bit more attention to-

Russell Foster 2:50 Yeah

Dr. Rangan Chatterjee 2:50 ... perhaps that would have a profound impact on the way we feel and, as you say, these negative thoughts.

Russell Foster 2:55 And across the whole demographic, from, from youngsters, uh, and young youngsters all the way through to the, to the elderly. Uh, it-- I think it could make a, a huge difference.

Dr. Rangan Chatterjee 3:05 Yeah.

Dr. Rangan Chatterjee 3:06 So we're recording this, uh, late morning. Uh, it is just past midday. So I know from your book now that we've just passed the danger zone-

Russell Foster 3:16 [laughs]

Dr. Rangan Chatterjee 3:16 ... the most dangerous part of the day, right?

Russell Foster 3:18 Absolutely.

Dr. Rangan Chatterjee 3:18 So I feel good. So we should celebrate with a glass.

Russell Foster 3:20 True, yeah. [laughs]

Dr. Rangan Chatterjee 3:21 It's twelve oh one. So can you explain a little bit about what is so dangerous about mornings, and in particular, this six AM to twelve PM time period?

Russell Foster 3:29 Yeah. W- w- well, well, the, the biggie, of course, is stroke and heart attacks. Between six AM and twelve noon, there's almost a fifty percent greater chance of having a stroke or a heart attack.

Dr. Rangan Chatterjee 3:39 Wow.

Russell Foster 3:39 And of course, it represents the sort of the biological switch from the sleep resting state to the active state. So, so what our internal clocks are doing is anticipating increased activity. So even before we wake, blood pressure is going up, the mobilization of glucose is going up. Um, interestingly, the s- the stickiness of platelets is going up, presumably anticipating an increased risk of, of damage, and therefore the need to clot. Uh, and, and some-- so cortisol is all, all going up, mobilizing our bodies for activity. Now, if you're healthy, it's not an issue. In fact, it's a, it's a wonderful adaptive response, so you can get out into the new environment and exploit it to the full. But if you have health problems, then that surge in blood pressure, that increased stickiness of the blood-

Dr. Rangan Chatterjee 4:28 Mm

Russell Foster 4:28 ... is gonna predispose to things like heart attack and stroke. And, and what's become very clear is that when you take your anti-stroke medication, your antihypertensives really matters. So for example, [clears throat] taking them before you go to sleep, before bedtime, rather than first thing in the morning, over a sort of, uh, four, five-year window, uh, can actually halve your chances of having a stroke or a heart attack. Now, that information isn't widely known. And, and I think we've got to try and get this sort of, this, this, this sort of knowledge m- more widely accepted.

Dr. Rangan Chatterjee 5:04 Yeah. A couple of things came up for me there, Russell. I remember, I'm gonna guess seven or eight years ago, uh, I was getting quite frustrated as a medical doctor with my lack of awareness over all kinds of things to do with our lifestyle and how it influences health.

Russell Foster 5:19 Yeah.

Dr. Rangan Chatterjee 5:19 And I was thinking, "If I knew a bit more about this and how to manipulate it, I'm sure I could help my patients more."

Russell Foster 5:26 Mm-hmm.

Dr. Rangan Chatterjee 5:26 And so I would go on my holidays around the world to various conferences. And I remember in America sitting at a conference, and there was a cardiologist called Dr. Mark Houston. And I remember him saying exactly this to me. Years ago, he was saying something like, "Most blood pressure medications should be taken in the evening." And I'm thinking, "Wait a minute, we're giving them all that in the morning."

Russell Foster 5:48 Yeah.

Dr. Rangan Chatterjee 5:48 And people are just taking them in the morning because it's easy. It's with breakfast.

Russell Foster 5:52 Yeah.

Dr. Rangan Chatterjee 5:52 I'll just take it. So I think that was the first time that that lodged in my head-

Russell Foster 5:57 Yeah

Dr. Rangan Chatterjee 5:57 ... that, oh, the timing of these medications is important. The other thing, Russell, that came up for me as you were speaking there- On the show, we've spoken a lot about stress in the past and what happens when the stress response gets activated.

Russell Foster 6:10 Yeah.

Dr. Rangan Chatterjee 6:11 And what you just described happening then in the early hours, just before we wake up, those are the, those are the things that the stress response, blood being more prone to clotting, blood pressure going up, cortisol going up. So it's almost like a mini stress response first thing in the morning.

Russell Foster 6:28 Indeed it is. Yes, absolutely. Yeah. Stress gets a bad rap. I mean, you know, it's, it's a, it's a shame. I mean, I, I liken stress, um, as the sort of the first gear in, in, in, in a car. You know, it gives you that wonderful acceleration, so it's great, you know? Um, but if you keep the engine in first gear, of course you'll destroy it. And, and that's the problem with so much of our stress these days. It's not that it's an acute quick shift where, for example, night shift workers, they're running on stress to keep awake and to keep functional during the night shift. And so no wonder there's all those health problems associated with that group.

Dr. Rangan Chatterjee 7:03 Yeah. You mentioned the clock, and there's, there's a lot in your book about our body clock, our body clocks-

Russell Foster 7:12 Yeah, yeah

Dr. Rangan Chatterjee 7:12 ... I should say. And what they all do, what influences them. One thing I've felt, an experience when people, when my patients, when members of the public are thinking about sleep, they're often thinking about the evening. They're thinking about, "What do I do just before bed?"

Russell Foster 7:29 Yes.

Dr. Rangan Chatterjee 7:29 "What do I do in those hours preceding me going to my bedroom?" And of course, that's important. We're definitely gonna get to that.

Russell Foster 7:36 Yep.

Dr. Rangan Chatterjee 7:36 But I thought it would be useful, particularly through the lens of the clock, I guess, talk about the morning.

Dr. Rangan Chatterjee 7:43 Why is what we do first thing in the morning so important for our ability to sleep at night?

Russell Foster 7:48 Yeah. So we have this, this circadian system, this sort of internal representation of a d- a biological day. And what it does is anticipate the very demands of the rest activity, the sleep-wake cycle. Now, for it to be of any use, the internal day needs to be set to the real day, the astronomical day. And the classic mismatch between biological time and environmental time is jet lag. And we eventually get over jet lag as a result of exposure to the, the light-dark cycle in the new time zone. But what we require in any time zone is daily exposure to the light-dark cycle, and particularly morning light for 90% of us. Most of us have either a long body clock or a body clock that's slightly longer, and so it will naturally drift a little bit later and later and later each day. And the effects of light are not the same. Morning light advances the clock, makes, makes us get up earlier and go to bed earlier, whereas dusk light delays the clock. It makes us go to bed later and get up later. And so what morning light does to us is take this drifting clock and shoves it forward a bit in time so it's beautifully aligned. Now, o- of course, this is important at every level. I mean, we did a study a few years ago on, on teenagers, and we found that... And, and all over the world. Um, and found that the later the chronotype, the evening-ness versus morning-ness, uh, the greater the evening light these young people got. So they were getting up after morning, um, so not getting the morning light, which would advance the clock, but they were getting evening light, which would delay the clock. So part of their, their going to bed late and getting up late is when they were actually seeing light. And so morning light, for most of us, is really important to set the biological clock, which then aligns all of our activity, including the sleep-wake cycle, to the appropriate time of day.

Dr. Rangan Chatterjee 9:46 Yeah. So this is fascinating. There, there's so much there. So we live according to 24-hour days.

Russell Foster 9:55 Yeah.

Dr. Rangan Chatterjee 9:55 Okay. But one thing I'm aware of from your book and other research is that our internal clocks are not set to exactly 24 hours.

Russell Foster 10:03 Exactly.

Dr. Rangan Chatterjee 10:04 So I wanna, I wanna talk about that and why you think that might be, because we certainly, I guess, didn't evolve for plane travel in the future.

Russell Foster 10:13 [laughs] Yeah.

Dr. Rangan Chatterjee 10:14 You know? Do you know what I mean? So, so, so when we go on a 12-hour flight to LA from London-

Russell Foster 10:18 Yeah

Dr. Rangan Chatterjee 10:19 ... we can adapt straight away, right? So that presumably wasn't evolution's goal. So I'm interested as to why it's not 24 hours-

Russell Foster 10:27 Mm

Dr. Rangan Chatterjee 10:27 ... in your view. But also, you say morning light. So does it matter what time of morning light that is? You know, can people get it at lunchtime? Are we talking as soon as people wake up? And of course, that changes in the seasons-

Russell Foster 10:45 Yes

Dr. Rangan Chatterjee 10:46 ... right? So can you help us-

Russell Foster 10:47 Okay

Dr. Rangan Chatterjee 10:47 ... put all those things together?

Russell Foster 10:48 Okay. So why isn't the human body clock exactly 24 hours? Well, now here's, here's some hand-waving. Because the, the modelers say that if you want two oscillators to align to each other, two rhythms, one is fixed. Obviously, the, the rotation of the Earth is fractionally under 24 hours. And if you want to fit a, a body clock to that, it helps if it's slightly different from 24 hours-

Dr. Rangan Chatterjee 11:13 Oh

Russell Foster 11:13 ... because then it can a- a- align more easily. Now, I don't pretend to understand the mathematics behind it-

Dr. Rangan Chatterjee 11:17 [laughs]

Russell Foster 11:18 ... but that's why, why it is. But there's a, there's an even-

Dr. Rangan Chatterjee 11:20 So Mother Nature knew what she was doing-

Russell Foster 11:22 She, of course-

Dr. Rangan Chatterjee 11:22 ... is what you're saying

Russell Foster 11:23 ... as always.

Dr. Rangan Chatterjee 11:24 [laughs]

Russell Foster 11:24 I mean, but the really interesting question, I think, for me, is why is there such diversity in the human chronotype? So the, you know, the fact that we have some people, you know, are really early larks, and some people really late owls. There's a huge diversity, you know, to the extent that you could almost bed share in some extremes. Whereas if you look at the mice or any other s- animal you want to study, it's all very, very similar. And I think this is something that, that's puzzled me for ages. And it may well be that in our society, you know, and we've, we've only moved very rapidly from sort of essentially small groups, tribes- interacting, [clears throat] it may have been useful under those circumstances to have vigilance across the-

Dr. Rangan Chatterjee 12:10 Mm

Russell Foster 12:10 ... 24-hour day. And having some people that were sort of awake early, um, and could perhaps alert the group that there was danger from another tribe, for example, or, or, or some sort of animal. And that may be why we've retained this extraordinary diversity. It's very-

Dr. Rangan Chatterjee 12:25 Yeah

Russell Foster 12:25 ... we're very weird as a species in that regard.

Dr. Rangan Chatterjee 12:28 Yeah, I mean, that makes a lot of sense, doesn't it? You mentioned the word chronotype.

Russell Foster 12:31 Yeah.

Dr. Rangan Chatterjee 12:32 I wonder if you could just elaborate exactly what does chronotype mean. And then you also mentioned owls and larks. And I'm really interested in this because, A, me and my wife appear to have slightly different body clocks. But many people, I feel, certainly if I look at my clinical experience, Russell, and this also I think speaks to this idea that the body clock isn't quite 24 hours, that we can manipulate it depending on what we need it to do or what the tribe needs or what the weather is, right? A lot of the time I think, well, are evening types really evening types or are they evening types because of the modern light environment?

Russell Foster 13:12 Yes.

Dr. Rangan Chatterjee 13:13 Um, so yeah, quite a lot there. [laughs]

Russell Foster 13:15 Yeah, yeah. Okay, so, so what defines your chronotype, whether you're a morning person or an evening person? And there are a number of factors. The first of all is one's genetics. We now know that the clock genes and the proteins that they make, subtle changes, subtle polymorphisms in those genes are associated with morningness and eveningness. So by their contribution to our genes, our parents are still telling us what time to get up and go to bed [laughs] at, at some level. So that's the first thing. Through development, our chronotype changes. So from about the age of 10, we want to start to go to bed a bit later and a bit later. Our lateness peaks in males at around about 21, 21 and a half. In females, about 19, 19 and a half. And males peak later, uh, or they have a later chronotype than females. Then from those late teens, early 20s, we start to move to a more morning chronotype. So by the time we're in our late 50s, early 60s, we're getting up and going to bed on average when we got up and went to bed when we were 10. And that sort of basically maps the changes in some of the sex steroids, testosterone and estrogen. So it's thought that there's a, a very important hormonal mod- modification of, of, of, of the clock.

Dr. Rangan Chatterjee 14:29 So that's within individuals. We've all got like-

Russell Foster 14:31 That's within individuals

Dr. Rangan Chatterjee 14:31 So whatever I'm born with, let's say I was born a morning type, and I think I'm a morning type. Then when I'm 10, in my teenage years, that's gonna be pushed, it's gonna be later and later.

Russell Foster 14:43 Yeah.

Dr. Rangan Chatterjee 14:44 As you say, for most males will peak at 21, and then it's gonna start going back again. But what about between individuals? There's variation there as well, right?

Russell Foster 14:53 Huge, huge, uh, yeah, a, a huge in- individual variation. I think that's a really important point because, you know, in terms of our sleep-wake patterns, um, and our chronotype, there's massive individual variation. And, and you know, um, [clears throat] it, there's a, on average, about a two-hour difference from somebody in their, from the, in their late 50s, early, uh, uh, early 60s, uh, to somebody in their late teens. So asking a, a teenager to get up at 7:00 in the morning is like asking a, a 60-year-old to get up at 5:00 in the morning.

Dr. Rangan Chatterjee 15:23 Now, does that matter? I guess there's a real interest here for me, given that my son's 12 and about to enter, uh, these teenage years.

Russell Foster 15:32 Yes.

Dr. Rangan Chatterjee 15:33 And as a family, we prioritize sleep, or we certainly have done, but I'm, I'm already noticing with him a change-

Russell Foster 15:39 Yep

Dr. Rangan Chatterjee 15:39 ... in terms of his desire to do what he has done in the past. Let's put it like that. It's okay.

Russell Foster 15:45 Yeah, test- I think they call it testosterone poisoning, don't they? [laughs]

Dr. Rangan Chatterjee 15:47 And what I'm interested in is when we say teenagers wanna go to bed later and wake up later, and we think about their chronotype, what if that teenager still went to bed early? So-

Russell Foster 16:02 Mm

Dr. Rangan Chatterjee 16:02 ... what's driving the change? Is it the fact that they're going to bed late, therefore they're having to stay in bed later? Like, could that be environmental, school pressure, that sort of stuff? Or do-

Russell Foster 16:12 Yeah

Dr. Rangan Chatterjee 16:12 ... do you know what I'm getting at?

Russell Foster 16:13 Yeah, absolutely. Well, well, of course, the o- the other factor, the sort of, as it were, the, the, the biological factor would be when you see light. As we, as we d- just discussed, sort of morning light advances the clock, evening light delays the clock. And teenagers, particularly over the weekend, will miss the morning light, making them get up earlier, but they get the evening light, so they're, or the afternoon, evening light, and so they'll go to bed later. So those are the three sort of biological, uh, factors. But then we have to add a couple of other things. One is, of course, the use of social media. Uh, it's very interesting. Many tee- teenagers appreciate that they shouldn't be using social media into the early hours of the morning. Uh, but they feel, uh, that sense of being connected to their group over- overrides that knowledge about why it's important to be asleep. So there's that element. And in fact, it's really fascinating. Some studies have shown that that lateness can be hugely late. So what happens, of course, is that they have very shortened sleep.

Dr. Rangan Chatterjee 17:13 Mm.

Russell Foster 17:13 They're driven out of bed by an alarm clock or a parent. They struggle through the school day. Often, and when you te- you know, talk to many teachers, kids are actually falling asleep at the desks. So then they finish school, and then they have not just a short nap, but it can be a nap of two hours or so-

Dr. Rangan Chatterjee 17:31 Mm

Russell Foster 17:31 ... which then pushes back the pressure to sleep that night. And so, so, you know, the, the, the desire to use social media and the fact that they're not as tired because they had a sleep in the late afternoon means that they can function later, um, uh, a- at night, and they get that shortened sleep. And in fact, you have to be very careful because it can lead to increasingly shortened sleep at night and longer naps after school, which, you know, and you can fall into this sort of feedback loop of really disrupting the sleep.

Dr. Rangan Chatterjee 18:03 If that teenager could Go to sleep, let's say, on time, at a more suitable time, given what time they have to get up for school or the school bus or whatever-

Russell Foster 18:16 Yeah

Dr. Rangan Chatterjee 18:16 ... the sort of fixing that they can't move. Does the later chronotype still matter, i.e., if they shift their environment? So actually I'm still going- I'm gonna go to bed earlier. I'm not gonna expose myself to evening lights. Uh, this may sound [laughs] optimal and hypothetical-

Russell Foster 18:37 [laughs]

Dr. Rangan Chatterjee 18:37 ... as something that's practically impossible, but-

Russell Foster 18:39 Yeah

Dr. Rangan Chatterjee 18:39 ... in theory, would that then normalize things, do you think?

Russell Foster 18:44 Yeah, you can shift teenagers to an earlier chronotype because of light exposure, absolutely. Uh, practically it's, it's, it's very difficult. Um, but it's, it, it's in theory-

Dr. Rangan Chatterjee 18:53 Yeah

Russell Foster 18:53 ... possible, yeah.

Dr. Rangan Chatterjee 18:55 And this light exposure, whereas in the morning it advances the clock, and in the evening it delays the clock, so pushes it back. What light exposure are we talking about here? Because let's say in the evening or at dusk you saw natural lights, not artificial lights.

Russell Foster 19:12 Yeah.

Dr. Rangan Chatterjee 19:13 Does that still do the same thing at pushing it back? Or does that have a different wavelength that doesn't affect us in the same way?

Russell Foster 19:18 Well, you're, you're, you're sort of impinging upon what I've, I've sort of been working on for a long time, which is how does, how does light interact with the body clock? And the first sort of extraordinary finding was that the visual cells within the eye, the rods and the cones, are not required to detect that dawn-dusk cycle. There's a third photoreceptor within the eye. And, and, and those, and we've been working out most recently how those receptors interact with this sort of master clock within the brain. So that's one thing. The second thing is that these photoreceptors need quite a bit of light. So we don't really appreciate, because our visual system is so good, but we live our lives in dim, dark caves. So-

Dr. Rangan Chatterjee 20:03 [laughs]

Russell Foster 20:04 ... uh, shortly after dawn, um, natural light is some 50 to 100 times brighter than average domestic light conditions. Um, and, and so really what the clock is looking for is a bright light signal, and so we're talking in the hundreds to thousands of lux range. So if you think of, of natural light, okay, moonlight would be .01 lux. Um, and a bright sunny day, even in, even in the UK, can just about get up to 100,000 lux.

Dr. Rangan Chatterjee 20:35 Mm-hmm.

Russell Foster 20:35 And those, those weird, amazing photoreceptors need, as I say, this sort of hundred to thousand lux range. Now, it's complicated because it depends upon how long you're exposed to that light. So you can compensate to some extent for a lower light intensity by increasing the duration. And it's worth bearing in mind, until the late '80s it was thought that the human circadian clock was not regulated by light at all. Uh, because when people use sort of relatively low levels of light that would shift the biological clock or entrain the biological clock of a mouse, it had no effect at all on humans.

Dr. Rangan Chatterjee 21:13 But this is in the 1980s, right?

Russell Foster 21:14 Yeah, in the late, late '80s.

Dr. Rangan Chatterjee 21:15 Yeah, I read that this morning in your book, and, and that shocked me, because 1987, right?

Russell Foster 21:21 Yeah.

Dr. Rangan Chatterjee 21:21 I was just finishing primary school. It does not-- maybe it is, but it doesn't seem that long ago to me, and I thought when I read that, I, I had to reread it. This idea that back then, which wasn't that long ago, we didn't think light hugely influenced our circadian rhythm, and now that's considered fact, and I think, "Well, what else is going on that we don't know at the moment?" [laughs]

Russell Foster 21:41 Well, that's what's so exciting about this field. But I, I remember, you know, doing, doing my, my PhD, um, and I, I got my PhD in, in, in '84. And, uh, you know, when you did public talks or anything, people say, "Well, how is it regulated?" You say, "Oh, it's primarily social cues and food." And I remember being actually at that first presentation in, in 1987, and, you know, it was an audible gasp around me. "Oh, my God," you know. "You just need a lot of light." And of course, now we know light is incredibly important for the regulation of human circadian rhythms, but you need quite a bit of it. And this is where we fall into some problems, because there's a lot of stuff out there saying, [clears throat] "You shouldn't look at a, at a Kindle immediately before you go to bed, 'cause it'll shift the biological clock." So the most detailed study, which was from a group at Harvard, asked people to look at a, a Kindle on its brightest intensity four hours before bedtime, and they asked them to do this on five consecutive nights. And after that, on the, on the fifth day, uh, sleep was delayed by an average of 10 minutes, and it was just statistical. And as one of my colleagues said, um, "Well, it may be statistically significant, but it's biologically meaningless."

Dr. Rangan Chatterjee 22:52 Wow.

Russell Foster 22:53 And so, but [clears throat] we do know that light in the evening can delay the clock. But how much, and what intensity, and for how long is still being resolved. Clearly, the brighter the light and the longer you see it before bedtime could shift the clock. But what we do know that light is doing is increasing alertness and therefore delaying sleep onset. So it's probably not the light from the devices changing the clock, but it's the light from the devices changing alertness and therefore delaying sleep.

Dr. Rangan Chatterjee 23:25 Yeah. Super, super interesting. So if we just stick to what that study showed, that was on a Kindle. I know when I've heard you speak before that you regard Kindles as quite different from smartphones or looking at social media. Perhaps you could explain why that is.

Russell Foster 23:43 Well, because a Kindle is, is, is fairly, you know, you're just reading it basically. Whereas a smartphone, you're checking your emails, you're looking at social media, you're checking the news. You might even be listening to music at the same time. And so these are really interactive devices, and they will be increasing alertness and therefore delaying sleep onset.

Dr. Rangan Chatterjee 24:02 Yeah. Super interesting. In terms of light, just to finish off in the evening then- We're talking about the complexities of light, you know, how much, how long for, all these kinds of things. Some people who are promoting health and wellbeing are talking about the importance of morning light, morning natural light. I know there's one neuroscientist in America who talks about getting ten to thirty minutes, if you can-

Russell Foster 24:29 Yeah

Dr. Rangan Chatterjee 24:29 ... within half an hour of waking up. Okay, so that's very clear guidance. I wanna, I wanna know your view on that.

Russell Foster 24:35 The data are good for that. I mean, really, really, I mean-- So, for example, the, the Ken Wright studies have shown beautifully that bright morning light, real light, not artificial light, can advance the clock and ha- un- and really shift individuals, you know, two hours earlier. So there's, there's no question about it. And you can mimic this in, in the lab as well. So for example, ten thousand lux for thirty minutes, uh, from a light box will also set the clock. So, so the data are there pretty solid.

Dr. Rangan Chatterjee 25:03 Now, we say advance the clock. What if someone doesn't want to advance their clock-

Russell Foster 25:07 [laughs] Yeah

Dr. Rangan Chatterjee 25:07 ... and they wake up, and they're like, "You know what? I've got a, a late work night out tonight, and I won't be back for my normal time."

Russell Foster 25:15 [laughs]

Dr. Rangan Chatterjee 25:15 I know. I've never thought of this question before, but I'm just intrigued. Might one then think, "Hey, for tonight, I'm actually gonna not expose myself to light for a couple of hours because I wanna delay that"? Or is that hard to say?

Russell Foster 25:28 It, it, it, you-- It probably will have a small effect.

Dr. Rangan Chatterjee 25:31 [laughs]

Russell Foster 25:31 I mean, the, the tricky thing is for those ten percent of individuals who are really morning types, and, and, and it's f- it's a shame really because most of their, their colleagues will be intermediate to late types. And of course, they will be then forced on a Friday and a Saturday evening to stay up way-

Dr. Rangan Chatterjee 25:48 Yeah

Russell Foster 25:48 ... beyond where they want to be, and they sort of complain bitterly that, um, you know, "God, all my friends want me to stay up." Of course, for the work environment, it's great.

Dr. Rangan Chatterjee 25:57 Yeah.

Russell Foster 25:57 They can get up, you know, go to the gym early, and then go on to work, whereas most of us who are late types find that a struggle.

Dr. Rangan Chatterjee 26:04 So you're happy with that ten to thirty minutes natural light recommendation.

Russell Foster 26:07 Yes.

Dr. Rangan Chatterjee 26:08 Would you, would you, would you ideally have people do that as soon as they can after waking?

Russell Foster 26:13 Yes. Certainly. The, the, the, the earlier, the bigger the, the effect, yes. And, and it's, and it's very important, um, acr- across the spectrum. So for example, in the nursing home environment, up until fairly recently, the light in those, uh, nursing homes was really low. I mean, terribly low. Some cases in the television room, it would be just sort of ten, twenty lux. I mean, crazy low. Uh, now people are realizing that if you increase the light in the day spaces, then you can actually improve the sleep-wake behavior of, of, of individuals in a nursing home. And where it's been looked at in individuals, uh, showing mild dementia, you could actually improve cognition-

Dr. Rangan Chatterjee 26:50 Wow

Russell Foster 26:50 ... by ten percent simply by increasing the light with inside, and, and also using other tricks like, you know, having breakfast by a window-

Dr. Rangan Chatterjee 26:58 Okay

Russell Foster 26:58 ... where there's a lot of light coming through.

Dr. Rangan Chatterjee 26:59 Wow. That's fascinating. And then in terms of evening, I wanna draw a distinction between natural light and artificial light. So let's say you live in a country where you have long light evenings at particular times of the year, like the UK, for example.

Russell Foster 27:17 Yeah.

Dr. Rangan Chatterjee 27:19 You wanna get your morning light in the morning, which is clearly a lot easier in a UK summer than it is in the winter.

Russell Foster 27:25 Yep.

Dr. Rangan Chatterjee 27:26 What happens if you wanna be outside in the evening? So it's, it's still natural. It's not your screen. It's not social media. It's not the news. It's not all that attention-stimulating information.

Russell Foster 27:39 Mm.

Dr. Rangan Chatterjee 27:40 Is there something going on in natural light where actually, you know, the evening light perhaps doesn't shift the clock as much, or, or, or, or, or does that still do it?

Russell Foster 27:49 Well, of course, when we were all agricultural workers, we got symmetrical exposure to dawn and dusk.

Dr. Rangan Chatterjee 27:56 Yeah.

Russell Foster 27:56 And so, you know, the morning light would advance us, but then that was counteracted by the e-- the dusk light, which would delay us. And so it, so it was fine. And the problem that many of us face now is that we get asymmetrical exposure to the dawn-dusk cycle, which invariably means most of us will miss morning but get lots of, of dusk light, uh, a- and therefore get up later. We'll de-delay the clock. Now, in terms of the quality, we've, we've talked about the intensity. We've talked about the duration. Um, but we should also touch about the color, the wavelength of light. Now, those specialized photoreceptors are maximally sensitive in the blue part of the spectrum. In fact, intriguingly, if you look at the blue of a really beautiful blue sky, that's where they're maximally sensitive. Um, so, so there's been a suggestion that actually only blue light is important. But again, it's more complicated than that because the response is like a bell-shaped curve. It's maximally sensitive in, in, in the blue, but of course it, it doesn't mean that they won't-- the, the receptors won't detect shorter, uh, wavelengths-

Dr. Rangan Chatterjee 29:01 Right

Russell Foster 29:01 ... uh, or indeed longer wavelength light. Again, it's how long you're exposed to it. We also now know, which is turn out to be really confusing, that the rods and cones, which we know are not required for the regulation of the clock, talk to those specialized photoreceptors so they can modulate their activity. Some of them, some of the rods and cones seem to add sensitivity, and others seem to inhibit the responses. So it's turning out to be really complicated.

Dr. Rangan Chatterjee 29:30 Yeah.

Russell Foster 29:30 Um, and we don't fully understand why.

Dr. Rangan Chatterjee 29:33 So the best advice would be, let's say someone is trying to get on top of their circadian rhythm and their sleep, and they feel, either for work reasons or for other reasons, they're going to bed too late. The best advice at the moment would be to try and limit light exposure in the evening. Even if it's natural light, you still wanna be a bit careful.

Russell Foster 29:54 Yeah. And, and if you are an extreme late type and you really are struggling, then what you need to do is, um, set the alarm and either get outside first thing in the morning or get a light box which will advance the clock and make it easier for you to get up- For job or, or whatever reason.

Dr. Rangan Chatterjee 30:12 Yeah.

Russell Foster 30:12 Yeah.

Dr. Rangan Chatterjee 30:12 I know you were on, uh, the Chris Evans Breakfast Show recently talking about your book, and, um, I remember in that conversation, Chris said, because he for many years is, you know, presenting on live radio, I think at the moment it's 6:30 AM, and I think he said to you that he goes to bed at 7:00 PM-

Russell Foster 30:31 Yeah

Dr. Rangan Chatterjee 30:31 ... or he at least puts an eye mask on at 7:00 PM, so it's reducing how much light is coming through his eyes. I think he said on that conversation with you-

Russell Foster 30:39 Yeah

Dr. Rangan Chatterjee 30:39 ... it had a massive difference. And then when he wakes up at 4:00 AM, he puts all the lights on in his bedroom as bright as possible.

Russell Foster 30:46 Yeah.

Dr. Rangan Chatterjee 30:47 And that's really interesting, and, and I know he was saying it's had a huge difference for him.

Russell Foster 30:50 And of course, it, it maps onto exactly what we know about the system. He's doing exactly the right thing for what his requirements are, which is to get up early and then perform early. Yeah.

Dr. Rangan Chatterjee 31:00 And this is where I feel it's very empowering for people, even if they were to find out their chronotype and then to find out that, "Man, my job is actually in disharmony with my natural chronotype-"

Russell Foster 31:17 Mm.

Dr. Rangan Chatterjee 31:18 ... you can do things, can't you-

Russell Foster 31:19 Yes

Dr. Rangan Chatterjee 31:19 ... to manipulate it so you're maybe not as vulnerable as you might have been.

Russell Foster 31:23 That's right. And, and I, I, I think we tend to feel as though our body clock is this fixed thing, just like our sleep-wake cycle, and it's not. It's dynamic and influenced by a whole range of different factors that can be tweaked to our advantage.

Dr. Rangan Chatterjee 31:35 Yeah. So interesting.

Russell Foster 31:37 Mm.

Dr. Rangan Chatterjee 31:37 You know, Russell, one of the things that's helped my sleep a lot over the past years, quite a few things recently. One is to avoid any sort of emotional stimulation in the evening.

Russell Foster 31:45 Yeah.

Dr. Rangan Chatterjee 31:45 So I've... This has probably been going on for six or seven years now. I've had to educate the people around me, particularly my family-

Russell Foster 31:53 Yeah

Dr. Rangan Chatterjee 31:53 ... that I, I, I go to bed early. I wake up early. I just, it suits me. I don't know if I am actually a morning type. I certainly live like a morning type. But then I set everything up around that because ever since my kids were born, they've always got up really early. And I know for me, I'm a much better human being when I've had time to myself in the morning before anyone else is there. So I would shift it back so that I could have an hour to myself before they wake up. So I'm, I'm now in a position where I usually go to bed by 9:00 at the latest, and I'm up by 5:00 AM at the latest. When I can stick to that consistently, I feel fantastic.

Russell Foster 32:33 Yeah. And that's exactly what we should all be doing. We should be fi- defining, you know, what, what our biological needs are and also, of course, what our s- social needs are, our societal needs are, and particularly our work, and try and tune, uh, ourselves accordingly.

Dr. Rangan Chatterjee 32:46 Yeah.

Russell Foster 32:46 Um, it, it, you know, it's, it's so important.

Dr. Rangan Chatterjee 32:49 Yeah. And so that, that process required me to help people around me understand that, "Look, after 7:00, half 7, I really do not want to be contacted with anything-

Russell Foster 33:02 [laughs]

Dr. Rangan Chatterjee 33:02 ... unless it's an emergency."

Russell Foster 33:03 I know. And, and of course, it's very difficult because, of course, um, towards bedtime is the only time when many couples get chance to talk about stuff.

Dr. Rangan Chatterjee 33:12 Yeah.

Russell Foster 33:13 But of course, it can be charged. And so, so for example, I have banned any discussion of family finances before we go to bed or anything like that. You have to carve out time at a [laughs] at a-

Dr. Rangan Chatterjee 33:24 Yeah

Russell Foster 33:24 ... different time. The other thing that's interesting about your earlier bedtimes, of course, is you'll be eating much earlier.

Dr. Rangan Chatterjee 33:30 Yeah.

Russell Foster 33:31 And that can be very important. And, I mean, the, the data now are very clear that trying to concentrate one's calorie intake during breakfast and lunchtime and a very light supper or an earlier supper that, that you can possibly manage, um, is better for our metabolic health and reduces the chances of weight gain, uh, uh, uh, obesity, and, and type 2 diabetes. So, so you, you ha- have a, a double advantage there by going to bed earlier.

Dr. Rangan Chatterjee 33:56 Yeah. We'll, we'll come back to that 'cause I think that's a really important point, and that really speaks, I think, to this wider issue, which is a lot of the things that we would optimally do to optimize our circadian rhythms, optimize our sleep, optimize all these different functions in, in our bodies sometimes have to be done in conflict with what society-

Russell Foster 34:20 Yeah

Dr. Rangan Chatterjee 34:20 ... is driving us to. And I think there's a much wider piece there.

Dr. Rangan Chatterjee 34:23 Just to finish off on light, at least for the, for the moment, 'cause I think it will keep coming back and it's so important-

Russell Foster 34:30 Yeah

Dr. Rangan Chatterjee 34:31 ... one of the things that has really helped me over the last years is, you know, I, I try my best not to be on my screen before beds. Uh, usually I'm good with that, although I'm human and-

Russell Foster 34:41 Mm-hmm

Dr. Rangan Chatterjee 34:41 ... you know, I, I fall prey to the temptation like anyone else might do. I try and read before beds.

Russell Foster 34:47 Mm-hmm.

Dr. Rangan Chatterjee 34:47 And in my bedside lamp, I've now changed, maybe for a couple of years, maybe not even quite that long, but certainly recently I've put these low lux bulbs in.

Russell Foster 34:59 Yep.

Dr. Rangan Chatterjee 34:59 So I've got this, like, amber low lux bulb. Now, I really feel it's made a massive difference the way I feel. It just feels softer. And whenever, if I'm in another room or staying somewhere where they've got a usual bulb and I think, "Wow, this is quite obnoxiously bright." So are these things helpful in your view?

Russell Foster 35:19 They are indeed. Um, it, it sort of maps on, again, to the, to the biology. This is what you'd, you'd certainly recommend, um, because the lower the light, uh, you'll reduce, uh, alertness, and it'll be easier to get to sleep. And of course, if it's bright light, then of, of course, you, you will shift the clock. But, but, um, you know, most, most artificial light is not gonna have much of an effect. Uh, but the other thing, of course, is that what you're doing is defining the sleeping space. Um, and so for example, y- you know, w- we've, w- we need to sort of reinforce the fact that the bedroom or the sleeping space is what you do when you wanna go to sleep.

Dr. Rangan Chatterjee 35:56 Mm-hmm.

Russell Foster 35:56 So you, you know, have a, a, a lovely mattress. You have great pillows. You, you might even have a distinctive smell, like lavender or something else-

Dr. Rangan Chatterjee 36:05 Mm

Russell Foster 36:05 ... because you associate that distinctive smell with the sleep state. And I know people who when they go and they travel and they're staying in a hotel room, they'll take a partner's perfume or aftershave-

Dr. Rangan Chatterjee 36:16 Mm

Russell Foster 36:16 ... because that defines the sleeping space for them. So the extent to which those are almost placebo effects, it doesn't matter. If they work, then it, it... you should embrace them.

Dr. Rangan Chatterjee 36:28 When it comes to blue light blocking glasses-

Russell Foster 36:30 Yeah

Dr. Rangan Chatterjee 36:30 ... I'm interested what your views are. Before you answer that, I will say as a clinician, what I have found is for some people, they appear to have been transformative.

Russell Foster 36:42 Mm-hmm.

Dr. Rangan Chatterjee 36:43 Now, what does the science say? What is your view based upon all your years of research?

Russell Foster 36:48 Yeah, I mean, I mean, blue light blocking glasses were sort of originally introduced because it was thought that blue light would promote age-related macular degeneration, and the evidence for that is a bit mixed. Certainly, you'll get more damage with blue light in, uh, a laboratory setting, so sort of if you expose cells to, to, to blue light, there's a greater chance of, of those cells, um, undergoing apoptosis. They're, you know, th- those cells dying, as it were. But when that's translated to the n- natural realm, it's not clear that blue light is having, um, uh, much of a f- an effect on age-related macular degeneration. This has also been studied in the context of, of, um, cataracts. So for example, uh, blue-blocking lenses have, have been introduced to reduce, uh, the blue light getting in and therefore age-related macular degeneration. The evidence for that, um, is not great. There was a lot of concern that these blue-blocking lenses were also going to disrupt the clock because after all, the clock is maximally sensitive to blue light. Uh, we've done some studies showing that it doesn't matter whether you use a blue blocking or a UV blocking.

Dr. Rangan Chatterjee 38:05 Mm.

Russell Foster 38:05 Uh, y- it, it doesn't, and in fact, [laughs] it's quite interesting. Most artificial lenses allow less blue light through than a natural lens. So we would be naturally exposed to more blue light anyway. So, uh, I don't... I, I think that's where the sort of, the origins of these, these, these len- these blue-blocking, um, glasses and things are used. Now, in terms of the circadian system and the arousal systems, we do know that blue light is the most effective wavelength, and Christian Cajochen has done this from Switzerland, in, uh, increasing alertness. So if you want to reduce alertness in the evening, it's likely that a blue-blocking, uh, set of glasses will be useful. Will it be useful in terms of the clock? Well, possibly.

Dr. Rangan Chatterjee 38:50 Mm.

Russell Foster 38:50 Um, but it depends again, how long, how bright the, the environmental light is.

Dr. Rangan Chatterjee 38:55 I guess this speaks to a much wider point, which I think comes through in all the work, all the talks I've seen of yours, everything I've read in your book. It's this idea that sleep is highly individual.

Russell Foster 39:10 Yeah.

Dr. Rangan Chatterjee 39:11 And I know there's many myths out there that you're keen to bust, one of them being that we all need eight hours.

Russell Foster 39:17 Yeah, yeah. I mean, that was part of the motivation for, for writing Lifetime because, uh, I think th- there's been a tendency to, to, to feel that, you know, we have to have a certain... We've got to get eight hours, and I remember one person came up to me and they said, "I don't get eight hours of sleep. Am I going to die?" And I sort of said, "Well, I can assure you, you will die, but it may not be anything to do with not getting eight hours of sleep." And you know, of course, I'm being a bit flippant, but, but actually the natural sort of span for humans is six hours to maybe ten, ten and a half hours. And so that's in the, in the natural range, and I think people get very anxious that if they're not getting eight hours, you know, they're going to... It's, it's going to be a disaster. Now, I think you have to be careful, um, because the, the tired brain is very good at fooling itself that it's okay. So you need to really be, uh, tough about assessing what your sleep needs are. Um, and if you can function optimally during the day, if you're feeling fine, then chances are you've had a good night of sleep. If you need an alarm clock to drive you out of bed in the morning, if it takes you a long time to wake up, if you crave caffeinated drinks, if your family, friends, work colleagues say, "Oh, you're being a bit..." You know, where's your sense of humor? You know, you're a bit more irritable. And critically, if given the opportunity to sleep longer on free days or indeed on holiday, you sleep much longer. That's all telling you you're not getting enough sleep. So what we all have to do as individuals is define how much sleep that we need for optimal daytime performance.

Dr. Rangan Chatterjee 40:52 And I guess that would also depend on what we're doing, right? Because let's say, I don't know, that you have defined that, "Hey, you know what? I keep hearing about this eight hours, but I think I sleep for, I don't know, six hours thirty each night or six hours forty-five."

Russell Foster 41:09 Yeah.

Dr. Rangan Chatterjee 41:10 "And I'm fine, and I wake up without an alarm clock, and I'm... got energy, and I feel emotionally quite with it." You know?

Russell Foster 41:17 Yeah.

Dr. Rangan Chatterjee 41:17 But then let's say you start, I don't know, training for a half-marathon or maybe at the weekends you go on long runs or something. It's also having that awareness to go, "Well, yeah, in the week I may be okay with this amount, but actually if I'm really exerting myself physically and I have a desk job Monday to Friday, maybe I need more at the weekend." And I guess the reason... I don't know what your view would be on that. One of the reasons I ask that is because I, I think Roger Federer is well known to... Is it ten hours or twelve hours a night? He-- I think he talks a lot about how much sleep he has and how important that is to his optimal performance as a tennis player.

Russell Foster 41:59 Yeah.

Dr. Rangan Chatterjee 42:00 A few little subtleties there. Do you think physical activity levels, um, make a difference in terms of how much we need? And I guess, how would you put all that together?

Russell Foster 42:09 Well, of course, the, the famous long sleeper was Albert Einstein, um, who basically sat at his desk, uh, for, for every day. Um, and he needed, he, he craved ten hours of sleep. So I think that it's probably influenced by athletic performance. Uh, and certainly, um, there are some data suggesting that really strong training is associated with slightly longer sleep. But it's not An overwhelmingly increased amount of sleep

Dr. Rangan Chatterjee 42:38 Right

Russell Foster 42:38 Uh, a- and I think, you know, Federer just needs that amount of sleep-

Dr. Rangan Chatterjee 42:42 Yeah

Russell Foster 42:42 ... um, and for his optimal performance, same way that Ei- Einstein did. And I, you know, in the book I talk, I compare Einstein to Salvador Dali.

Dr. Rangan Chatterjee 42:50 You do?

Russell Foster 42:51 Um, and, um, you know, I sort of... It, it is great, you know, undergraduate lectures, you know. I say, "Well, Einstein, you know, classic sort of slept 10, 10 and a half hours. So yeah, perfect example of long sleep genius." And then, you know, one of the students said, "Well, what about Salvador Dali?" You know, he only, he, he didn't sleep at all, really. And, and his trick was, of course, to hold a, a metal spoon, um, uh, in his hand and sit in a chair, and when the spoon dropped from his hand, when he fell asleep, it hit a metal plate on the floor and woke him up. But of course, Dali was the first to recognize that his altered state of mind, because of his chronic lack of sleep, gave him the sort of surreal vision to generate the art that he generated. Um, yeah, um-

Dr. Rangan Chatterjee 43:34 So it depends what's the goal.

Russell Foster 43:35 [laughs] It depends what the goal is.

Dr. Rangan Chatterjee 43:36 Right. If the goal is to hallucinate and have an altered state of consciousness-

Russell Foster 43:40 Yeah

Dr. Rangan Chatterjee 43:41 ... and you need that for your job, you know what?

Russell Foster 43:43 Yeah.

Dr. Rangan Chatterjee 43:43 Sleep deprive yourself all you want.

Russell Foster 43:45 Yeah, it, that's true. It, it may make you impossible to live with, um, as, uh, Dali, of course, was. [laughs] So yeah, but, but if you want an altered state of consciousness, then decide, you know, de- de- deprive yourself of sleep.

Dr. Rangan Chatterjee 43:57 Well, maybe now is a good point in the conversation to make the case for sleep, right? First of all, how sleep-deprived are we as a society? And then secondly, what are those consequences?

Russell Foster 44:12 Yes. Uh, sleep deprivation varies a lot because of course sleep need varies a lot. Um, but I think on average, people are saying that we're sleeping one, maybe two hours less than we were in the 1950s. And I, and I, I'm, I'm, I think those data are, are pretty robust, and certainly that's the case in, in adolescence, big time. Um, and so what are the consequences? Well, short-term sleep loss, we see changes in our emotions, uh, and our cognitive performance. So, uh, we increased levels of irritability, the failure to process information accurately. We do stupid and unreflective things. We are less empathetic. I mean, it's really fascinating. You, we, we fail to pick up the social signals, uh, of friends and family. Um, we're less socially connected. We have a reduced capacity to remember things. We are less creative. Um, so all the things... Reduced sense of humor. I mean, you know, all the things-

Dr. Rangan Chatterjee 45:18 Yeah

Russell Foster 45:18 ... that make us this extraordinary creature, you know, this amazing humans, you know, all this creativity and wonderful and interconnectedness goes as a result of, of, of even short-term sleep loss. Longer term, as many individuals are experiencing at the moment, is associated with this falling asleep uncontrollably, so microsleeps. And it's estimated in the States that 100,000 crashes on the American freeway are as a result of people falling asleep at the wheel. The American Automobile Association suggests it's much greater than that, perhaps as high as 300,000. And of course, if you're falling asleep at the wheel, you, you can't stop yourself. So those crashes tend to be really bad crashes. We also see that there's changes in immune, uh, responses. So it's likely because we're chronically tired, we're activating in a sustained way the stress axis, and that's gonna push up blood pressure. It's gonna throw glucose into the circulation. So it pre then disposes to things like obesity, type 2 diabetes, and indeed, because of the suppression of the immune system, higher rates of infection and indeed, um, cancer. Some very convincing studies showing that night shift work, for example, uh, night shift nurses have higher rates of colorectal cancer and breast cancer. In fact, those data are now so good that the World Health Organization has listed night shift work as a probable carcinogen. So, so w- I, I think the really key point is that chronic sleep loss is so much more than feeling, feeling tired at an inappropriate time. It's associated with an impact upon our health at every level.

Dr. Rangan Chatterjee 47:00 Yeah, I mean, what you just went through there, it, it, it impacts negatively our, our day-to-day lives. You mentioned empathy. I mean, what do we need for good quality relationships-

Russell Foster 47:12 Yeah

Dr. Rangan Chatterjee 47:12 ... with partners, children, work colleagues, family?

Russell Foster 47:16 Mm.

Dr. Rangan Chatterjee 47:16 We need empathy.

Russell Foster 47:17 Yeah.

Dr. Rangan Chatterjee 47:17 I mean-

Russell Foster 47:17 And, and, and, or invariably in the workplace, you need creativity. You need people to be able to work together. You want to reduce irritability. You'd need often-

Dr. Rangan Chatterjee 47:25 Yeah

Russell Foster 47:25 ... a good sense of humor. And so really we should be really promoting good sleep to im- improve productivity.

Dr. Rangan Chatterjee 47:33 Yeah. It speaks to something you said earlier on in our conversation, that when we are sleep deprived, we forget all the positive experiences and remember the negative ones-

Russell Foster 47:42 Yeah

Dr. Rangan Chatterjee 47:42 ... which of course completely alters your view and perception of the world.

Russell Foster 47:47 Yeah.

Dr. Rangan Chatterjee 47:47 It feels like this dark, scary place rather than-

Russell Foster 47:50 Yeah

Dr. Rangan Chatterjee 47:51 ... an uplifting, hopeful, joyful place.

Russell Foster 47:53 Mm.

Dr. Rangan Chatterjee 47:55 You mentioned, yes, these short-term consequences, but also these pretty scary long-term consequences. Now, one thing I really appreciate about the messages you try and put out there into the public is you, you really seem to be trying to help promote health without scaring people.

Russell Foster 48:16 Yeah.

Dr. Rangan Chatterjee 48:16 Now, of course, these statistics are scary, and there's two groups of people I wanna keep at the forefront of our mind now as we think about these negative side effects. We've mentioned shift work, and I wanna talk about shift work because what I read in your book is that one in eight UK workers currently are shift workers.

Russell Foster 48:33 Yeah.

Dr. Rangan Chatterjee 48:34 That's probably only gonna increase. That's a lot of people.

Russell Foster 48:37 Yes.

Dr. Rangan Chatterjee 48:37 And I can't imagine what it's like for a shift worker to just hear What you said the WHO say, which is-

Russell Foster 48:43 Yeah

Dr. Rangan Chatterjee 48:43 ... a probable carcinogen.

Russell Foster 48:44 Yeah.

Dr. Rangan Chatterjee 48:45 That's not a nice thing to hear-

Russell Foster 48:46 No

Dr. Rangan Chatterjee 48:46 ... if you work shifts. If you're a, whatever, if you're a nurse looking after people to help their health and you think, "Yeah, but at the same time, I'm wrecking mine in the process." So shift work is something I wanna talk about. But also, the other thing I've noticed as I've been trying to raise awareness of sleep now in books and podcasts for maybe five years, unwittingly, we can often end up scaring people and making them feel worse and more anxious. Now, young parents often will get in touch and say, "Look, Rangan, you know, uh, love what you, love what you said. You know, I understand about sleep, but I'm really worried. My three-month-old doesn't sleep through the night." You know, or whatever's going on, so many parents get really scared when they hear this sort of stuff. So if we address parents first of all, short-term sleep deprivation, long-term, is it okay for a few years if a parent's sleep-deprived? You know, help us sort of get less scared about [laughs] that if you can.

Russell Foster 49:48 Yeah. Well, I think there's two issues here. Um, one thing that, that our society or the dev- in the developed nations at least, uh, has shifted very rapidly from the extended family-

Dr. Rangan Chatterjee 49:58 Yeah

Russell Foster 49:58 ... to the nuclear family, where the parents become the sole providers for their children. Um, and it's usually the mother. And, uh, what's happened up until fairly recently is that childcare was a distributed activity. And so when the mum got tired, there was an aunt or a sister or a, a friend who would take over so that the mum can get some sleep. And if you look at the primate societies, uh, you see that, uh, care is distributed across the group. We have never evolved to be the sole parents, as it were, of, of our children. And I think the first point to make is that young mums in particular, but, but, but, but both parents, uh, should not be afraid to reach out. And I think there's this sort of terrible guilt that I can't cope because I'm feeling tired. Well, no surprise. We've never evolved to, to, to look after our children in this manner. So before babies are born, it's really important to think about the support network that you can put in place to, to, to try and mitigate some of the-

Dr. Rangan Chatterjee 51:11 Mm

Russell Foster 51:11 ... the chronic sleep loss. Now, what are the long-term consequences of this? It's, it's not clear. Uh, I suspect that there are probably buffers that kick in that actually, um, prevent some of the, some of the damaging effects of, of chronic sleep loss during those sort of few months.

Dr. Rangan Chatterjee 51:31 Yeah.

Russell Foster 51:31 I don't know. Um, and in fact, I think it's a really important area o- o- of study.

Dr. Rangan Chatterjee 51:37 Yeah. Uh, I think, you know, what you said there, I think is really helpful. First of all, just recognize that the way we're bringing kids up now is tough.

Russell Foster 51:47 Yeah.

Dr. Rangan Chatterjee 51:47 We never had to do it like this. You know, recently, Russell, my wife's father has been away in Kenya for a couple of months to see-

Russell Foster 51:53 Mm

Dr. Rangan Chatterjee 51:54 ... his family, and my mother-in-law has been staying with us on and off for a couple of months.

Russell Foster 52:00 Mm.

Dr. Rangan Chatterjee 52:02 And let me tell you the difference. It, you just... It's, it's little things, but just having a third adult in the house-

Russell Foster 52:10 Yes

Dr. Rangan Chatterjee 52:11 ... when it comes to childcare, it, it, it's not just one more person. It, it seems to have changed everything.

Russell Foster 52:18 The whole dynamic changes.

Dr. Rangan Chatterjee 52:19 The whole dynamic changes.

Russell Foster 52:20 Yeah. Absolutely.

Dr. Rangan Chatterjee 52:20 I, I was like, this is incredible. This is what humans have always done. Yet-

Russell Foster 52:24 Yeah

Dr. Rangan Chatterjee 52:24 ... many of us have moved away for work, for opportunity. We don't have those support systems. So I thought that hopefully takes the pressure off people to at least go, "Yes, I know it's hard," but yes, it is hard. It really is hard.

Russell Foster 52:35 Mm.

Dr. Rangan Chatterjee 52:35 You're not, you're not broken. It's not that you can't cope.

Russell Foster 52:38 No.

Dr. Rangan Chatterjee 52:38 None, none of us can cope with that.

Russell Foster 52:40 Yep.

Dr. Rangan Chatterjee 52:40 So I think that's a really nice message. But also that message, you can reach out, you know?

Russell Foster 52:46 Yes.

Dr. Rangan Chatterjee 52:47 Maybe you need to phone a friend and say, "Hey, listen, I'm knackered. Could I just have a nap?"

Russell Foster 52:52 And it's-

Dr. Rangan Chatterjee 52:52 "Could you come while I have a nap, please?"

Russell Foster 52:53 And it's not a sign of weakness.

Dr. Rangan Chatterjee 52:54 Yeah.

Russell Foster 52:54 It's, it's actually, you know, em- embracing our biology in a sense. Um, and, and I... It's, it's tragic that I think that young parents don't know that, um, and feel guilty about it. It's, it's simply wrong. And it, and it's, you know, w- so many unintended consequences that we're facing at the moment. And, and sort of with increased wealth and independence, you know, we think, "Right, you know, we don't have to live with our parents anymore," or we can move a long way away from them. And yet we've, we've lost something in the process. I mean, I was, you know, my, my, I was, my... I'm very close to my grandparents who looked after me while my, my mother was working. And it was a, as you, as you say, it was a meant, you know, a, a big thing. "So Mommy's coming home." And it was all, you know, excitement.

Dr. Rangan Chatterjee 53:35 Yeah.

Russell Foster 53:35 And, and you have that dynamic environment. Um, and clearly, you know, we are where we are, but, but people shouldn't be afraid to reach out. I think that's so important.

Dr. Rangan Chatterjee 53:45 Let's talk about shift work. Um, there's all kinds of things. There's a huge section on shift work in the book, which I think will be very helpful for anyone. We mentioned how many people, of course, are shift workers.

Russell Foster 53:57 Yeah.

Dr. Rangan Chatterjee 53:57 We mentioned the potential health problems of that.

Russell Foster 54:00 Yes.

Dr. Rangan Chatterjee 54:01 You know, something I read in your book which I found fascinating was that over 90% of night shift workers, was it even 97%?

Russell Foster 54:07 Ninety-seven, yeah.

Dr. Rangan Chatterjee 54:08 They don't adapt.

Russell Foster 54:09 No. And, and so that's going back to light again. So you've got relatively dim light, uh, within the workplace, within the office or the factory. And then of course on the journey home, uh, or on the journey in, you're going to ex- or during the day, you're going to experience bright natural light. And the clock always defers to the brighter light signal as being daytime. So the assumption for, b- by employers-

Dr. Rangan Chatterjee 54:33 The clock, just to... The clock always defers to the brighter light signal. I think that's a really-

Russell Foster 54:39 Yeah

Dr. Rangan Chatterjee 54:39 ... powerful thing we need to say again.

Russell Foster 54:40 And that's why we don't shift And in fact, there, there's one group, um, there's a lovely study from the University of Surrey, Josephine Arendt, and w- you know, that, that 3%, some of them are North Sea oil workers.

Dr. Rangan Chatterjee 54:50 Ah.

Russell Foster 54:50 Because what happens is they're out on the rig at night under these great arc lights, and then they're in windowless metal boxes during the day, and they do switch, and so they become nocturnal, as it were.

Dr. Rangan Chatterjee 55:04 Wow.

Russell Foster 55:05 Then, of course, it's really tough for them because then they have two weeks of shore leave [laughs] and they're completely maladapted to their friends and family. But th- th- you know, the serious issue is y- y- you don't adapt. And, and, and so I remember chatting to, uh, the chairman of the CBI, oh, many years ago now, and, and, you know, giving a speech saying, "We're gonna cure the problems of British industry by running it on a 24/7 basis. No need to build lots of offices in London, you know, m- m- the rush hour," et cetera, et cetera. Deeply well-meaning individual, no idea of the biological consequences, and the assumption that, that the clock will adapt to the demands of working at night. And for 97% of people, it doesn't.

Dr. Rangan Chatterjee 55:45 We're not machines.

Russell Foster 55:47 No.

Dr. Rangan Chatterjee 55:47 We're human beings, right?

Russell Foster 55:48 Absolutely, yes.

Dr. Rangan Chatterjee 55:49 And, uh, I think you could, you could [laughs] you could apply that across all kinds of different things in society.

Russell Foster 55:54 Well, it, it is fascinating because we, we are, we've achieved so much. I mean, you know, it's... We shouldn't. I mean, it's phenomenal what we've achieved as, as a, as a, as a s- as a species. Um, but we are, it comes with some, some massive arrogance. And w- what we've assumed is that we can do whatever we like, whenever we choose. And because we've invaded the night cheaply with electricity since the 1950s onwards, we've invaded the night and have thrown away that really important part of our biology, which is sleep.

Dr. Rangan Chatterjee 56:26 That's interesting. It was only in the 1950s when we-

Russell Foster 56:30 Big acceleration, yeah

Dr. Rangan Chatterjee 56:31 ... when we've really aggressively invaded the night.

Russell Foster 56:32 Yeah.

Dr. Rangan Chatterjee 56:33 That's not long.

Russell Foster 56:33 No.

Dr. Rangan Chatterjee 56:34 Through an evolutionary lens, that's just a blink.

Russell Foster 56:36 Yeah. And, and clearly, you know, we've been creeping in.

Dr. Rangan Chatterjee 56:38 Yeah.

Russell Foster 56:38 You know, the aristocrats were using candles, and in fact, a, a sign of wealth was you would eat later in the evening, and y- you'd light your... But remember, a candle, you know, in the early 19th century was the equivalent of a, of a working man's daily wage. So only the rich-

Dr. Rangan Chatterjee 56:53 Yeah

Russell Foster 56:53 ... could, could have light. And of course, why would you burn fat, which is what candles were made of, when this is food? And of course, food was incredibly scarce for so many people, working people, 200 years, 150 years ago.

Dr. Rangan Chatterjee 57:06 We'll stay on shift work for the minute, but this doesn't just apply to shift work. Driving.

Russell Foster 57:14 Yeah.

Dr. Rangan Chatterjee 57:14 Driving tired, and a pretty alarming statistic in your book about what it means to drive at 4:00 AM for most people.

Russell Foster 57:22 Yeah. There's... Well, well, Drew Dawson has done a wonderful study. Drew Dawson's based in, in Australia. And he compared the cognitive performance, the loss of one's ability to process information, um, a- across the day, and found a very, you know, poor cognition around about 4:00 in the morning, where it, where it got to its lowest point. Um, and he compared that with the loss of cognitive ability with consuming sufficient alcohol to make you legally drunk. And on the scale, it was about a minus 15, um, drop in cognition when you were legally drunk. But at 4:00 in the morning, it was minus 20. So, so if, if listeners take nothing from, from this at all, other than the fact that if you're driving at 4:00 in the morning, your ability to process information is worse than if you were legally drunk.

Dr. Rangan Chatterjee 58:10 Okay. This, this is big, right? Because we've touched a few times on this, this whole societal condition, what we're being asked to do now or what we think we have to do to fit in with society-

Russell Foster 58:21 Yes

Dr. Rangan Chatterjee 58:21 ... versus what's biologically optimal. Some people, of course, have to get up early for work.

Russell Foster 58:26 Yeah.

Dr. Rangan Chatterjee 58:26 Some people now drive through the night.

Russell Foster 58:29 Yes.

Dr. Rangan Chatterjee 58:30 Lorry drivers, you know, b- big-

Russell Foster 58:32 Yep

Dr. Rangan Chatterjee 58:32 ... big cargo in the back.

Russell Foster 58:34 Mm-hmm.

Dr. Rangan Chatterjee 58:35 Um, now I'm sure they've got certain regulations, certain things that they do in order to be less tired-

Russell Foster 58:40 Yes

Dr. Rangan Chatterjee 58:41 ... uh, at that time. But, you know, driving at 4:00 AM-

Russell Foster 58:45 Yeah

Dr. Rangan Chatterjee 58:45 ... for most of us being worse than when we might be legally drunk, that's pretty alarming.

Russell Foster 58:51 It's extraordinary. Yeah.

Dr. Rangan Chatterjee 58:52 And because also then let's think about, look, I'm, I don't really do this anymore, but if I think about my social culture in, in my 20s and 30s, you know, you go to a mate's wedding-

Russell Foster 59:02 Mm

Dr. Rangan Chatterjee 59:02 ... right? There'll be some late nights, a few drinks, and then you drive home on the Sunday. You know-

Russell Foster 59:07 Mm

Dr. Rangan Chatterjee 59:07 ... yeah, you're, you're, you know, uh, just to be super clear, you know, you're, you're, you're fully sober.

Russell Foster 59:13 Yes.

Dr. Rangan Chatterjee 59:13 You know? But it, culturally, it's okay. "Oh, yeah, I'm knackered. I've just gotta drive now for four hours."

Russell Foster 59:18 Yeah.

Dr. Rangan Chatterjee 59:18 But w- we're putting people's lives at risk.

Russell Foster 59:20 We are.

Dr. Rangan Chatterjee 59:21 Not just our own. We're, we're, we're putting-

Russell Foster 59:22 Yeah

Dr. Rangan Chatterjee 59:22 ... other people's lives at risk. So, so culturally-

Russell Foster 59:25 Yeah

Dr. Rangan Chatterjee 59:25 ... this idea of driving when tired, I think is something we all need to face.

Russell Foster 59:28 Well, I think it's like smoking. We're not only, um, endangering our own health, but, um, the collateral damage is that we're harming, uh, other people who are-

Dr. Rangan Chatterjee 59:36 But people will do this.

Russell Foster 59:37 Yes. And, uh, but I think it's, again, it's, it's a matter of education and, and a failure to appreciate. Um, y- you know, junior doctors, a study published fairly recently showed that 57% had either had a crash or a near miss on the drive after the night shift. Uh, so, so now again, we're, we're, we're going into scary territory, but the key point is there's stuff we can do about it. We're not gonna put the 24/7 society-

Dr. Rangan Chatterjee 1:00:03 Mm

Russell Foster 1:00:04 ... you know, genie back in its bottle. So what can we do to mitigate-

Dr. Rangan Chatterjee 1:00:08 Yeah

Russell Foster 1:00:08 ... some of these problems? Well, knowing that we're going to be vulnerable to having a crash on the drive home, then we sh- or, or employers, and I think there's a serious duty of care here-

Dr. Rangan Chatterjee 1:00:19 Yeah

Russell Foster 1:00:19 ... is sh- they should make available or subsidize the use of devices you can put on the dashboard that measure head nod or the fact that the car is veering and alert you to that and, and, and that, you know, an alarm goes off and makes sure you, you know, you're woken up. And of course, many high-end German cars ha- now have this technology-

Dr. Rangan Chatterjee 1:00:38 Do they really?

Russell Foster 1:00:38 ... built, built in. Yeah. Um, but that's something that, that, that, that could be done. Knowing that, um, night shift workers have higher rates of cancer, coronary heart disease, diabetes II, et cetera, et cetera, why don't we institute, uh, higher frequency health checks, you know, every six months for these individuals to catch these conditions before they come-

Dr. Rangan Chatterjee 1:00:58 Mm

Russell Foster 1:00:58 ... become chronic? What food do we provide for our night shift workers? You know, higher rates of cancer, you know, coronary heart disease, all the rest of it, high fat, high sugar. Nobody, to my knowledge, is actually supplying easy to digest, high protein snacks to their workforce throughout the night. Now, it's tricky because if you're tired, you're programmed to eat more sugar. Um, but, but, but at least we should make that option available.

Dr. Rangan Chatterjee 1:01:23 But why, why high protein?

Russell Foster 1:01:25 Um, because it doesn't have the same impact as carbohydrates and fats on coronary heart disease and indeed cancer.

Dr. Rangan Chatterjee 1:01:30 But that would be quite easy, right? Let's say for a hospital- Which is staffed at night

Russell Foster 1:01:36 Yeah

Dr. Rangan Chatterjee 1:01:36 It would be quite easy either to have those snacks or to work with a nutritionist and make in bulk protein shakes full of-

Russell Foster 1:01:46 I know

Dr. Rangan Chatterjee 1:01:46 ... phytonutrient-rich foods that are easy to digest, that are tasty, that they could give people. It w- it's not that hard.

Russell Foster 1:01:53 No. And, and in fact, I think there's a phenomenal commercial opportunity here. Somebody should develop this and make it available to, you know, a, a very significant percentage of the workforce.

Dr. Rangan Chatterjee 1:02:02 Yeah. Yeah.

Russell Foster 1:02:03 Uh, so and the other a- area I think is, is education. In some sectors, uh, the divorce rate is six times higher, uh, in the night shift compared to the day shift. And-

Dr. Rangan Chatterjee 1:02:14 Six times higher

Russell Foster 1:02:15 ... six times. So what we should be providing is education not only for the individual who's doing the night shift, so they're aware of some of the consequences, but so that the people they live with also understand that they're not turning into monsters, but this is a, a kind of the biological consequence of driving your biology outside of its normal range. Um, and one o- other area which I think is worth trying is that we talked about this great diversity of chronotype, whether you're a morning type or an evening type across the population. Well, wouldn't it be smart to chronotype your workforce so that, for example, the late types did the later shift and the morning types did the morning shift? What you want to avoid, of course, is putting a late type onto a morning shift-

Dr. Rangan Chatterjee 1:02:57 Mm

Russell Foster 1:02:57 ... which is a, it's a really bad idea. So, uh, you know, as I say, we've got to be pragmatic, but I think there are things that we can do now to mitigate some of these problems.

Dr. Rangan Chatterjee 1:03:08 Yeah. We don't wanna be too scary, but, um, I can't stop thinking about that. A- as a doctor myself, that 57% figure.

Russell Foster 1:03:17 Yeah.

Dr. Rangan Chatterjee 1:03:17 I have told this story, I think, at least twice on this podcast, where when I was a SHO, a senior house officer, so I think second or third year after qualifying, after a, what would it have been? Probably a 36-hour shift.

Russell Foster 1:03:29 Yeah.

Dr. Rangan Chatterjee 1:03:29 Certainly between 30 and 36 hours. I properly fell asleep on the M60 in traffic. Um-

Russell Foster 1:03:36 Yeah.

Dr. Rangan Chatterjee 1:03:38 Thankfully, I pr- I think I fell asleep in a traffic jam, and then I was only woken up by horns because the jam had s- you know, moved on.

Russell Foster 1:03:47 Yeah.

Dr. Rangan Chatterjee 1:03:47 So, so, you know, it could have been a lot worse.

Russell Foster 1:03:49 Yes.

Dr. Rangan Chatterjee 1:03:49 Right? This is scary 'cause there are people around the country, around the world right now who are vulnerable of dying as a consequence of their jobs. That sounds extreme. I don't think what I've just said is extreme based upon what I'm reading. And you, you mentioned duty of care for employers.

Russell Foster 1:04:09 Yes.

Dr. Rangan Chatterjee 1:04:10 Surely this should have been put in place yesterday. Like, is it justifiable for people in shift work to be getting in a car now? Where does the culpability lie?

Russell Foster 1:04:20 Mm.

Dr. Rangan Chatterjee 1:04:20 What if they have an accident? Is it, is that personal responsibility, or is it, "No, but my, my employer didn't do anything"? Or, and of course, this comes into finance and expenses, but providing taxis.

Russell Foster 1:04:32 Well, that's what the Royal Perth Hospital, at least when I was visiting, yeah, Western Australia, would actually do. They would actually provide taxis to get people home.

Dr. Rangan Chatterjee 1:04:41 Yeah. And I know there's an expense thing here, but we're talking about lives here-

Russell Foster 1:04:45 Yes

Dr. Rangan Chatterjee 1:04:45 ... not just that individual's life. So yeah, that really, that really hits home big time.

Russell Foster 1:04:51 And, and, you know, there's a very poignant description in the book of a police officer, um, who contacted me actually several years ago saying, "What can we do?" You know? "I just had a friend who, after the night shift, fell asleep at the wheel and drove his car into a tree and was killed outright. Um, and nobody's warning us that this is going on." And that's part of the educational piece, because I think if people realized of the danger of doing this, they'd think twice about it-

Dr. Rangan Chatterjee 1:05:17 Yeah

Russell Foster 1:05:18 ... um, and, and try and get some- something else in place. I mean, maybe we should be making sure that there's, I don't know, a, s- s- somewhere to sleep, um, uh, uh, after the night shift so you weren't-

Dr. Rangan Chatterjee 1:05:30 Yeah

Russell Foster 1:05:30 ... driving home chronically tired. You know, it's these sorts of things that, that we need to think about. There's, there are... Again, we're not gonna cure it, but we can mitigate some of the problems, and it's not [laughs] rocket science.

Dr. Rangan Chatterjee 1:05:42 No.

Russell Foster 1:05:42 It's, it's low-hanging fruit that we could institute now across the workforce and make a difference.

Dr. Rangan Chatterjee 1:05:48 I, I don't know when my behavior around this started to change, but I'm pretty diligent these days over one-hour drive now. I don't need to drive much anymore-

Russell Foster 1:05:58 Yeah

Dr. Rangan Chatterjee 1:05:58 ... for work. I remember in one of the practices I used to work at, you know, there was a probably 45 minutes to an hour commute each way on a motorway and depending on traffic conditions, et cetera, et cetera. And, um, I appreciate not everyone is in a position to make active decisions. Depends on work, finances, all kinds of things. But when I'm weighing up how to get somewhere and whether to take my car or not, how tired I'm gonna be absolutely plays in my decision-making.

Russell Foster 1:06:26 Mm.

Dr. Rangan Chatterjee 1:06:26 And I think, you know, as I think about it, Russell, I think one of the first times it really struck me, it was probably 2015, 2016. I was making a documentary for BBC One. I don't think this bit actually aired in the program in the end, but is it in Guildford where is the, uh, driving simulators?

Russell Foster 1:06:45 I think so, yes.

Dr. Rangan Chatterjee 1:06:46 I think, what, what happened, I can't remember the exact ins and outs, but one of the participants-

Russell Foster 1:06:51 Yeah

Dr. Rangan Chatterjee 1:06:52 ... we put them in the simulator, and we watched them drive, and then we compared it with one night's sleep deprivation and then alcohol.

Russell Foster 1:07:00 Yeah.

Dr. Rangan Chatterjee 1:07:00 And it was noticeable after sleep deprivation. It's just like you said with that research. It was worse-

Russell Foster 1:07:06 Yeah

Dr. Rangan Chatterjee 1:07:06 ... than when they'd been drinking.

Russell Foster 1:07:08 Yep.

Dr. Rangan Chatterjee 1:07:09 I was like, wait a minute. That's just fatigue, and their, their reaction time to things popping up in the simulator to when they'd press the brake was significantly increased. So-

Russell Foster 1:07:18 Yep

Dr. Rangan Chatterjee 1:07:18 ... I think that possibly has played into my head for many years about that. Um,

Dr. Rangan Chatterjee 1:07:23 number two, I think, I think a point here is that you, you bring up this term microsleeps.

Russell Foster 1:07:28 Mm.

Dr. Rangan Chatterjee 1:07:28 Right? Number one, what is a microsleep? And number two, I've heard you say before, the thing about these microsleeps is you don't know they're gonna happen.

Russell Foster 1:07:36 Yeah. Yeah.

Dr. Rangan Chatterjee 1:07:36 Right? So, so can you speak to that a little bit?

Russell Foster 1:07:38 So it's, it's really... So microsleep is es- essentially an uncontrollable and, and an unpredictable episode of sleep. And so you can be going along and you will just fall asleep. And of course, that's extremely dangerous if you're, if you're driving. Um, and, uh, s- s- so people think they're okay, and then they could just sort of have a, have a microsleep and then a, a crash or, or, or, or whatever. Um, and it's, it's frightening because so many people say, "Oh yeah, you know, I've had one of those. I was sort of nodding, and then I realized I was sort of in the next lane." And but for the grace of God, you know-

Dr. Rangan Chatterjee 1:08:14 Yeah

Russell Foster 1:08:14 ... you would be killed or you'd have killed somebody else.

Dr. Rangan Chatterjee 1:08:16 Well, you mention in your book all these things, what, Cherno- the, the Chernobyl-

Russell Foster 1:08:19 Oh, yeah

Dr. Rangan Chatterjee 1:08:19 ... nuclear disaster. Was it a Selby crash? And Air India?

Russell Foster 1:08:24 Yeah.

Dr. Rangan Chatterjee 1:08:24 Like, you've mentioned all this stuff. Can you maybe speak to some of those?

Russell Foster 1:08:26 Yeah, I mean, one of the, one of the really interesting ones I think was the, the Air India flight where, where the pilot was, was landing the aircraft and then fell uncontrollably asleep, and the plane hit the deck, um, with a huge loss of life. Now, how do we know he fell asleep? Because you could hear snoring in the cockpit recorder. And you know, this is not something that he would have wanted to do, but, and it, and it sort of really illustrates the, the sort of the, the fact that you have no control over these microsleeps. But if you're chronically tired, that's what's going to happen. And you know, the Exxon Valdez oil tanker that hit the reef off the coast of Alaska. Now everybody says, "Oh, it's 'cause the captain was drunk." Well, yes, he was drunk, and, uh, he was asleep in his cabin, and it was a chronically tired, inexperienced individual. And they were telling him, "Turn the ship. You're going to hit the reef," but he couldn't process the information 'cause he was so tired. And it's a really good illustration, again, of one's chronic tiredness. Uh, it prevents you from processing information accurately. And you know, it, it, we've sort of touched on this, but this is what's so dangerous 'cause the tired brain is so tired it can't detect how tired it is. And we can fool-

Dr. Rangan Chatterjee 1:09:35 Yeah

Russell Foster 1:09:35 ... and we can fool ourselves that we're okay whereas we're not.

Dr. Rangan Chatterjee 1:09:40 Russell, I wanna just ask you your view on my interpretation of my dad's working life. I know from research, you've written a beautiful section on it in, in your new book about the impacts that sleep deprivation has on the immune system-

Russell Foster 1:10:04 Yeah

Dr. Rangan Chatterjee 1:10:05 ... and all kinds of other-

Russell Foster 1:10:06 Yeah

Dr. Rangan Chatterjee 1:10:07 ... biological processes in the body. My dad at the age of 57 got lupus.

Russell Foster 1:10:16 Hmm.

Dr. Rangan Chatterjee 1:10:17 Now, it's very unusual for an Asian man, an Asian man who's slim.

Russell Foster 1:10:21 Mm-hmm.

Dr. Rangan Chatterjee 1:10:21 It's, it's not the profile. It's normally Caucasian women-

Russell Foster 1:10:25 Yeah

Dr. Rangan Chatterjee 1:10:25 ... in their 30s or 40s.

Russell Foster 1:10:27 Mm-hmm.

Dr. Rangan Chatterjee 1:10:27 But typically, of course, there's always variation here. Now, for many years, I cared for my dad until he died, uh, nine and a half years ago, and I didn't know then what I know now since his death, but I am convinced, like I have a deep knowing that my dad's lifestyle gave him lupus. Now, I'm not asking you to say yes or no on that. I just wanna share with you certain aspects of his lifestyle, and I'd be interested as to your perspective. My dad slept three nights a week for 30 years. So f- he'd work his day job as a consultant managerial infirmary, but he'd come home, he'd get ready, and then for four nights a week, a car would pick him up, and he'd be doing GP house calls all night. So he'd be out all night. He'd arrive again at 7:00, 7:15 in the morning, get ready, and then drive through traffic into Manchester and work.

Russell Foster 1:11:21 Hmm.

Dr. Rangan Chatterjee 1:11:22 So for 30 years, he only slept for three nights a week, so that is sleep deprivation, I would say, at a hyper extreme level. He was chronically stressed, of course.

Russell Foster 1:11:33 Mm-hmm.

Dr. Rangan Chatterjee 1:11:34 I hear what you say about empathy, and I think about Mom and Dad's rows.

Russell Foster 1:11:39 Yeah.

Dr. Rangan Chatterjee 1:11:40 Um, and yes, you need a genetic susceptibility for autoimmune disease, but I believe my dad had that genetic susceptibility. I know he did because I've, I've done my genetic, I've done some of my testing, and I know I have a predisposition as well to certain things if the environmental conditions are right. My dad had chronic sleep deprivation, chronic stress. Something maybe out with your expertise perhaps is I think my dad was very unhappy and had a lot of unexpressed emotions and anger about the state of his life. I've spoken to Dr. Gabor Mate, a physician, about the, the link between unexpressed emotion and autoimmune disease, so I'm not necessarily asking you to comment on that. But from what I've shared and from what you know about the immune system and sleep deprivation's impact, do you have any comments at all?

Russell Foster 1:12:32 Yeah. I, I mean, I think it's worth bearing in mind that for our biology to work, you need the right stuff at the right concentration delivered to the right tissues and organs at the right time of day. And of course, our circadian and sleep-wake systems do that. So if you disrupt them, you have a, a whole bunch of vulnerable points where things could fall apart.

Dr. Rangan Chatterjee 1:12:54 Sorry to interrupt. If you are enjoying this content, there's loads more just like it on my channel, so please do take a moment to press Subscribe, hit the notification bell, and now back to the conversation.

Russell Foster 1:13:06 And so if you have a genetic susceptibility, then the disrupted biology will, will play to that, that problem, and so I wouldn't be at all surprised if there was an element of sleep disruption. Did your father show any signs of dementia later in, in life?

Dr. Rangan Chatterjee 1:13:23 It's really hard because Dad was on dialysis for 15 years and all kinds of medications, but yeah, I'd probably say so. Little bits.

Russell Foster 1:13:31 Yeah.

Dr. Rangan Chatterjee 1:13:31 There's no formal diagnosis, but if I think back now, possibly, probably.

Russell Foster 1:13:37 Yeah. And some r- very interesting, uh, data is showing that s- massive sleep-wake disruption in the middle years can increase your risk of dementia, uh, in later years.

Dr. Rangan Chatterjee 1:13:48 What, what do middle years mean?

Russell Foster 1:13:49 Um, so, so in your, your, your sort of 40s, 50s.

Dr. Rangan Chatterjee 1:13:52 Right.

Russell Foster 1:13:52 Um, your, your peak working period-

Dr. Rangan Chatterjee 1:13:55 Got it

Russell Foster 1:13:55 ... you know, where we think of our businessmen, you know, uh, having incredibly shortened, um, sleep periods. And- It's, it's been well known, it's been documented, but a mechanism has not been clear until relatively recently or a potential mechanism.

Dr. Rangan Chatterjee 1:14:10 Mm-hmm.

Russell Foster 1:14:11 And that's this newly discovered thing, which is the glymphatic system, this sort of, um, clearance system within the brain. And whilst we're asleep, um, there's a whole bunch of toxic stuff that is wrapped out and disposed of, not least beta amyloid.

Dr. Rangan Chatterjee 1:14:28 Yeah.

Russell Foster 1:14:28 And just one night of no sleep has been shown to increase beta amyloid deposition within the brain and increase the concentration in the cerebral spinal fluid. So, you know, there's a, there's a very tangible link between sleep disruption in the middle years and, and a mechanism that could, could predispose to dementia in, in later years. And I think we're going to find increasingly these sorts of connections.

Dr. Rangan Chatterjee 1:14:51 Yeah.

Russell Foster 1:14:51 I mean, what we know about the immune system is that it's, it's turned up, or at, at least the adaptive immune system is turned up during the day when we're most likely to encounter people with bugs or bugs in the environment, and then turned down at night. And again, a really interesting question is, well, why? Why don't you have the immune system on full kilter all the time? And that's of course, because if you did, you increase the chances of an autoimmune response.

Dr. Rangan Chatterjee 1:15:17 Yeah.

Russell Foster 1:15:18 And so, you know, disruption of these systems leads to lots of different ripple through effects.

Dr. Rangan Chatterjee 1:15:23 Yeah. There was something in the book where I found fascinating about our skin permeability-

Russell Foster 1:15:29 It-

Dr. Rangan Chatterjee 1:15:29 ... changes-

Russell Foster 1:15:30 Yeah

Dr. Rangan Chatterjee 1:15:30 ... throughout the day.

Russell Foster 1:15:31 Yeah.

Dr. Rangan Chatterjee 1:15:31 Could you speak to that perhaps?

Russell Foster 1:15:32 Yeah. I mean, so, so at night, um, it's, it's a bit more porous. Um, uh, and we're losing... A- as a result, we're losing water. And so also it, it becomes itchier, and so we're more likely to scratch our skin at night and, you know, exacerbated by psoriasis and, and dermatitis and things. And so the skin is an incredibly effective barrier keeping bugs out, and that's why the, the main route of, of infection is the lungs or, uh, but, uh, but, but, but the, if, if, but the skin is again trying to slough off these old cells, um, and presumably the bacteria with them and in a sense sort of cleanse itself-

Dr. Rangan Chatterjee 1:16:09 Yeah

Russell Foster 1:16:09 ... but it increases the vulnerability to infection. Does it at that time of day, of course, 'cause we're far less likely to encounter bugs at that particular time.

Dr. Rangan Chatterjee 1:16:17 Yeah. There was also this fascinating bit of research you shared where I think if, if we get cuts or have a scar-

Russell Foster 1:16:26 Yes. Mm.

Dr. Rangan Chatterjee 1:16:27 Or how well it will heal or how quickly it will heal depends on whether it was done in the morning or the evening.

Russell Foster 1:16:33 Yeah. Absolutely.

Dr. Rangan Chatterjee 1:16:34 I found that fascinating.

Russell Foster 1:16:34 Yes. It, it is, you know, and of course, um, uh, more effective healing during the day than, than at night. Yeah.

Dr. Rangan Chatterjee 1:16:40 Yeah. This relationship between midlife sleep deprivation, so in our forties and fifties and dementia later on is really something just to pause on. Perhaps because I'm in my early forties, um, perhaps 'cause I know many listeners and viewers are, but there is this tendency, I think across society to think we can keep pushing.

Russell Foster 1:17:09 Yeah.

Dr. Rangan Chatterjee 1:17:10 We can keep pushing. We'll get away with it. We'll be okay. Now I've seen firsthand with my dad. Yes, it was quite extreme, but nonetheless, I see that pattern. I've seen it in myself before.

Russell Foster 1:17:21 Yeah.

Dr. Rangan Chatterjee 1:17:22 I've seen it in a lot of my patients and a lot of my friends. You can't keep pushing your biology and not expect a consequence at some point. So I, I just wanted to highlight that point. And then I wanna... You know,

Dr. Rangan Chatterjee 1:17:36 you mentioned sleep and dementia. I know you've done a lot of research on the relationship between sleep and mental health problems.

Russell Foster 1:17:42 Yes.

Dr. Rangan Chatterjee 1:17:43 And I'd love to just talk about this a little bit. You know, is it sleep deprivation that's causing mental health problems? Is it mental health problems that's causing sleep deprivation? Or like most things, is it a bit of both?

Russell Foster 1:17:56 Well, I think this is really important, and I got into this because I was, um, in a elevator with a psychiatrist. And he said to me, "Oh yeah, you work on, on sleep and stuff." I said, "Yeah, kind of." Um, and um, he said, "Well, of course my patients with schizophrenia, um, they have terrible sleep patterns. That's because they don't have a job. So they get up late, uh, miss my clinic and are socially isolated and so don't have friends." And I just thought at the time, that doesn't make any sense at all to me. And so we, we started, um, and Katarina Wolf was one of my colleagues, um, who was very much involved in this, to look at sleep-wake patterns in individuals with a diagnosis of schizophrenia. Uh, same number of individuals age matched who are unemployed and working healthy controls. And the patterns you saw in schizophrenia were some of the most extraordinary observations I've ever made in my career. These weren't just sort of kindly, mildly disrupted. These rhythms were absolutely smashed in everyone we have looked at. Um, and so that stuck in my mind. And then with an increasing understanding of the mechanisms that generate sleep and circadian rhythms, so essentially the sleep w- the consciousness sleep f- flip involves a realignment of every brain neurotransmitter system and an interaction between multiple brain structures. So with these two sort of observations, we thought, "Well, hang on, why do you always find sleep-wake disruption and mental health associated?" And, and of course you see it in bipolar, you see it in depression, you see it everywhere. And we came up with a model Which was perhaps at the core within the brain, there are overlapping neural circuits and neurotransmitter pathways between stable sleep and stable mental health. So if you're predisposed to mental health problems, let's say there's a change in a, a neurotransmitter, dopamine, serotonin, that nudges you towards a mental health crisis, but it's going to have a parallel impact upon the sleep-wake systems at some level because they also draw from those neurotransmitter systems. And so we then tested that hypothesis. And so genes which have been linked to human schizophrenia when mutated in a mouse, um, uh, not only showed weird behavioral patterns, uh, but also smashed sleep-wake cycles. So now there's a, an incredible body of evidence for that mechanistic overlap between mental health circuits and sleep circuits. But it's of course much more complicated than that because the disrupted sleep via its impact upon, um, psychosocial health, um, one's, one's ability to process information, that negative salience, and of course the sort of physiological disruption could, uh, exacerbate the extent to which you're experiencing mental health problems. And of course, the mental health problems will feed back and make the sleep worse. And so you can very rapidly go from sort of this, this sort of overlap at the middle. We know there's a ge- genetic predisposition to certain me- mental health conditions. But it can then amplify massively as a result of these positive feedback loops, the mental health making the sleep worse, the sleep making the mental health worse. So you can exaggerate it completely. So we then thought, "Well, hang on. If we try to stabilize sleep-wake in individuals exhibiting mental health problems, will we reduce the severity of those mental health problems?" So working with Dan Freeman and Colin Espie, a big pa- paper was published a few years ago in The Lancet, uh, which showed that if you can even partially stabilize the sleep-wake in individuals, you can reduce levels of paranoia and hallucinatory experiences. So I think we can, we can think of the sleep-wake systems as being a new therapeutic target for mental health. Now, what's fascinating for me is that we've known about the association between mental health problems and, and sleep disruption back at, you know, Kraepelin's time in the 1880s. He talked about it way before the introduction-

Dr. Rangan Chatterjee 1:22:10 Yeah

Russell Foster 1:22:10 ... of antipsychotics and, and all of the other sort of, um, issues. And so it has a long history. And, uh, of course, the life expectancy of individuals with severe mental health, uh, is hugely reduced. And they all report, you know, what do they report? Um, uh, sort of coronary heart disease, obesity, type two d- diabetes, all of these major health issues dismissed as a, as a byproduct of the antipsychotics. But actually it's, a major contributing factor to that will be the, the poor sleep, and it's never addressed.

Dr. Rangan Chatterjee 1:22:43 Yeah.

Russell Foster 1:22:43 Um, and so this, I'm, I'm hoping that this will, will, will also provide a, a change in our mindset to, to these extraordinarily vulnerable individuals and to take their sleep-wake disruption seriously because we have empirical evidence-

Dr. Rangan Chatterjee 1:22:57 Yeah

Russell Foster 1:22:57 ... that even partial stabilization can reduce the severity of, um, those symptoms.

Dr. Rangan Chatterjee 1:23:02 You're effectively saying bipolar or depression or anxiety, right? Instead of just accepting it as, "Oh, yes, people with these conditions don't sleep well"-

Russell Foster 1:23:12 Yeah

Dr. Rangan Chatterjee 1:23:12 ... it's like, well, hold on a minute. What if we go straight in and give sleep education or sleep CBC or whatever-

Russell Foster 1:23:19 Yes

Dr. Rangan Chatterjee 1:23:19 ... therapy we might deem appropriate? And then if you think about research, I mean, I remember reading a paper, Russell, where it showed that maybe if you go from, is it eight hours a night to five hours a night, your amygdala, the emotional part of your brain, may be up to 50% more reactive.

Russell Foster 1:23:37 Yeah.

Dr. Rangan Chatterjee 1:23:37 I think, well, that's kind of anxiety. You know-

Russell Foster 1:23:40 Yeah

Dr. Rangan Chatterjee 1:23:40 ... if your amygdala's on high alert, you're anxious.

Russell Foster 1:23:43 Yes.

Dr. Rangan Chatterjee 1:23:44 And sleep deprivation by itself will make you anxious.

Russell Foster 1:23:50 Yeah.

Dr. Rangan Chatterjee 1:23:50 So before we go to anti-anxiety medications or-

Russell Foster 1:23:53 Exactly

Dr. Rangan Chatterjee 1:23:54 ... it's like why don't we tackle the sleep?

Russell Foster 1:23:56 Exactly.

Dr. Rangan Chatterjee 1:23:56 Why don't we at least try to?

Russell Foster 1:23:57 And, and it's because the failure to educate our, our general practitioners and indeed our, the entire, um, you know, doc- doctor and nurse community, um, it's just not part of the curriculum.

Dr. Rangan Chatterjee 1:24:09 Yeah.

Russell Foster 1:24:09 And in fairness, um, it's only fairly recently that this stuff has become really clear.

Dr. Rangan Chatterjee 1:24:14 Yeah.

Russell Foster 1:24:14 Um, and, and again, that was part of the, the reason for, for, for writing, you know, Lifetime because wanting to make it accessible to, you know, not only medical practitioners, but everybody so we can take some ownership of this, of this field-

Dr. Rangan Chatterjee 1:24:26 Yeah

Russell Foster 1:24:26 ... this critically important field.

Dr. Rangan Chatterjee 1:24:28 I mean, this is really quite profound because what we're talking about here is sleep as therapy.

Russell Foster 1:24:33 Yes. I mean, this was really sort of shown, shown to me when we were working with, on a project with, with, um, Guy Goodwin, who's a psychiatrist at Oxford, and he was able to identify individuals as a result of family history and questionnaires, whether they were at high risk or low risk of developing bipolar. So these are young, young individuals in their, their teens usually, and what was absolutely fascinating is the sleep-wake patterns of those at low risk were perfectly normal. But all of those who were at high risk were already showing a disrupted sleep-wake pattern-

Dr. Rangan Chatterjee 1:25:06 Mm-hmm

Russell Foster 1:25:06 ... prior to any clinical diagnosis of bipolar. Now, if we can use this as an early marker-

Dr. Rangan Chatterjee 1:25:13 Yeah

Russell Foster 1:25:14 ... and then of course, in therapy, the earlier we, we know something's gonna go wrong, the earlier the chance of an intervention. So wouldn't it be amazing if we could identify those individuals at risk? We could institute sleep-wake stabilization protocols that may either delay the onset of these conditions or knock the brain into a dif- different developmental trajectory whereby it won't necessarily go-

Dr. Rangan Chatterjee 1:25:38 Yeah

Russell Foster 1:25:39 ... uh, inevitably towards that, uh, condition. So again, I think there's, you know, we're, we're, we're just sort of unmasking all this incredibly important stuff that could- Have a major impact upon health-

Dr. Rangan Chatterjee 1:25:50 Yeah

Russell Foster 1:25:50 ... and wellbeing, uh, as, uh, i-in the coming decades.

Dr. Rangan Chatterjee 1:25:54 Let's talk about sex and sleep.

Russell Foster 1:25:56 Yeah. [laughs]

Dr. Rangan Chatterjee 1:25:57 Um, you write a little bit about it. Of course, it's a topic of huge interest to many people.

Russell Foster 1:26:02 Yeah.

Dr. Rangan Chatterjee 1:26:03 And I guess there's two facets to it the way I see it. One is to do with fertility.

Russell Foster 1:26:09 Mm.

Dr. Rangan Chatterjee 1:26:09 Right? There is an ideal time to have sex from a fertility standpoint, so I think it'd be great to talk about that.

Russell Foster 1:26:18 Yep.

Dr. Rangan Chatterjee 1:26:19 But then I think also the relationship between sex and sleep, the onset of sleep, I think is also really interesting.

Russell Foster 1:26:26 Yeah.

Dr. Rangan Chatterjee 1:26:26 So, um, in whatever way you want to-

Russell Foster 1:26:29 Well-

Dr. Rangan Chatterjee 1:26:29 ... maybe start to unpack that for me

Russell Foster 1:26:31 I, I mean, I, again, this was something that I wasn't particularly fam-familiar with until I did the research for the book 'cause I'm often asked these questions in public lectures. What was absolutely striking is that every element in the regulation of the female menstrual cycle involves a circadian clock, whether it's the timed release of hormones in the, uh, neurohormones in the hypothalamus, whether it's the pituitary gland, or whether it's the receptors in the ovary, for example, responding to those, those, those hormones. And so you've got, for example, very strong evidence that disruption of the menstrual cycle is much worse in night shift workers. Um, the chances of miscarriage is higher in night shift workers. It's not hugely significant, but it is significant. And you find that in the airline industry, either pilots or flight attendants have fertility problems. So there's, there's clearly a relationship between the circadian system, uh, and the menstrual cycle to produce this extraordinary, exquisitely timed ovulation and the release of the, release of the egg. And it's been shown that sperm needs to be in the reproductive tract, in the fallopian tube, around about two to three days prior to ovulation to have the greatest chances of success. So there's a, there's, there's, there's that. There's the, the circadian system interacting with the hormones that drive the menstrual cycle-

Dr. Rangan Chatterjee 1:27:49 Yeah

Russell Foster 1:27:50 ... uh, which i- and, and that precise window and, and, and that was really fascinating. And then you've got this study suggesting, well, it doesn't really matter, you know, w- humans don't have any real discrimination. They'll just do it whenever they want to do it. Um, and then there's this whole literature on the fact that, in fact, our behavior is subtly altered, so that actually, um, during that sort of pre-ovulatory window, men are less discriminating [chuckles] of women, um, and are much more likely to seek out, you know, copulatory experiences. Um, and females are much more discriminating. They're far more likely to have an affair during that, that window.

Dr. Rangan Chatterjee 1:28:29 Wow.

Russell Foster 1:28:29 And they look for male... They're more interested in male features, so for example, um, a deeper voice, a stronger jawline, all that sort of thing.

Dr. Rangan Chatterjee 1:28:36 Wow.

Russell Foster 1:28:36 I mean, stuff that we never really think about, but, but there is, there is that still biology, you know, underpinning it.

Dr. Rangan Chatterjee 1:28:42 Wow.

Russell Foster 1:28:42 So, so yeah. Um, but also, um, male fertility, uh, seems to peak in the morning. Testosterone rises and has this, you know, morning peak, and that's where sperm motility is, uh, at, at, at its peak. And anyway, I mentioned this, I think, on the Chris Evans', uh, Breakfast Show, and I got this email, uh, several, a month or so later, um, from a couple of young medics who said, um, "You know, we've been trying for the last two years, um, to, um, conceive. And, uh, um, you know, as medics, we thought we'd tried everything, but we'd forgotten circadian rhythms. So we started, um," a-and their words, not mine, "started doing it in the morning. And the first, and the first time we did it, you know, my, my partner got pregnant." Um, now, I mean, an N of one is an N of one, so you can make of it what you will, but I was actually t-t- uh, thrilled [laughing] that, that, that bit of biology had been translated-

Dr. Rangan Chatterjee 1:29:42 Congratulations

Russell Foster 1:29:42 ... at least in one case. [laughing] Yes, I know.

Dr. Rangan Chatterjee 1:29:44 And even that, that, that, that line, "We forgot about circadian rhythms"-

Russell Foster 1:29:47 Yeah

Dr. Rangan Chatterjee 1:29:48 ... I'm not surprised. Like, we didn't learn anything about circadian rhythms-

Russell Foster 1:29:51 Yeah

Dr. Rangan Chatterjee 1:29:51 ... at medical school. I don't think they still do.

Russell Foster 1:29:53 [laughs]

Dr. Rangan Chatterjee 1:29:54 Right? This is a, you know, massive, massive issue.

Russell Foster 1:29:57 Yeah.

Dr. Rangan Chatterjee 1:29:58 So regarding fertility, super, super interesting. I'm sure that's very relevant to many people listening, like, who are actively trying to conceive. It could be something that-

Russell Foster 1:30:08 Mm

Dr. Rangan Chatterjee 1:30:08 ... has practical value for them, or people could share it with people who they also know who are struggling.

Russell Foster 1:30:13 Yeah.

Dr. Rangan Chatterjee 1:30:14 Uh, that might be helpful. In terms of... We mentioned the problems with sleep deprivation, and, um, you've written a section in the book how the timing of sex [chuckles] could-

Russell Foster 1:30:24 Oh, yes

Dr. Rangan Chatterjee 1:30:24 ... potentially help people with sleep.

Russell Foster 1:30:27 Yeah. Uh, I mean, I think anecdotally, um, the, the reports that, you know, sex relaxes individuals, and they're more likely to fall asleep, and, and there are now some studies suggesting that-

Dr. Rangan Chatterjee 1:30:37 Yeah

Russell Foster 1:30:37 ... um, there are, there are hormones that are, that are released which actually promote sleepiness. And so, yes, uh, consensual sex, of course, um, it has been shown to promote sleep. Yeah. Uh, and also masturbation as well.

Dr. Rangan Chatterjee 1:30:51 You have once said that many people don't have a sleep problem.

Russell Foster 1:30:58 Mm.

Dr. Rangan Chatterjee 1:30:58 They've got a stress problem.

Russell Foster 1:30:59 Yep.

Dr. Rangan Chatterjee 1:31:01 And I guess sex, intimacy, you know, switching off, it all kind of feeds into that a little bit, doesn't it?

Russell Foster 1:31:10 Absolutely, yes, and, and, and the bonding following sex, um, uh, you know, relaxes individuals and brings them closer together. I, I, I think that one thing that's very important to distinguish is fatigue from sleepiness. Um, sleepiness is cured by sleep. Fatigue is this overwhelming chronic tiredness that even given the, the ability to- To sleep longer doesn't go away. And it's very important that people distinguish between the two because fatigue, as you know, um, uh, is, is indicative of some underlying health problem.

Dr. Rangan Chatterjee 1:31:43 Mm-hmm.

Russell Foster 1:31:43 And I spoke to somebody fairly recently, really fascinating, and this is, um, a really high-powered individual, very, very active. But she has an immune issue and so is chronically fatigued, and so she can't get done what she wants to do during the day. So she'll fall asleep fine, and then she'll wake up in the middle of the night, and we should talk about that-

Dr. Rangan Chatterjee 1:32:06 Mm-hmm

Russell Foster 1:32:07 ... because that's perfectly normal to wake up in the middle of the night.

Dr. Rangan Chatterjee 1:32:10 Yeah, sure.

Russell Foster 1:32:10 And most of us fall back to sleep again or are awake for a short time, then fall back to sleep again. But because of her, um, stress, because she couldn't do what she wanted to do, she couldn't fall back to sleep again. And so, uh, uh, this is a really interesting. So the fatigue was, was f- not allowing her to do what she wanted to do, which meant that she was immensely stressed, which meant that it was screwing up her, her sleep problems. And so, uh, yeah, I think that so many instance of... I think stress is, is one of the major issues in poor sleep. And as we've just said-

Dr. Rangan Chatterjee 1:32:44 Yeah

Russell Foster 1:32:44 ... it's not a sleep problem, it's a, it's a stress problem. And that's why sort of winding down, um, towards the end of the day, leaving work at home if you possibly can, um, and doing something different, whether it's going to the gym, whether it's doing whatever, is so important. And that's, of course, been the huge problem, um, during the COVID epidemic-

Dr. Rangan Chatterjee 1:33:04 Yeah

Russell Foster 1:33:04 ... where people's workspace and, and home space were the same. And that's probably part of the reason why sleep, um, has been reported to be worse in, in certain sectors.

Dr. Rangan Chatterjee 1:33:15 Yeah, I mean, you spoke before about various scents and what people associate with sleep. And, you know, we know the brain is an associative organ. And so-

Russell Foster 1:33:24 Yeah

Dr. Rangan Chatterjee 1:33:24 ... if you are sitting with your laptop doing your work emails in bed, what does your brain associate [laughs] with bed and the bedroom?

Russell Foster 1:33:32 Precisely. And of course, so many bedrooms became studies.

Dr. Rangan Chatterjee 1:33:34 Yeah. And, and I understand that depends on your space, and it's not-

Russell Foster 1:33:37 Yes

Dr. Rangan Chatterjee 1:33:37 ... it's not a criticism, it's just more a-

Russell Foster 1:33:39 An explanation

Dr. Rangan Chatterjee 1:33:40 ... it's more an explanation.

Russell Foster 1:33:41 Yeah.

Dr. Rangan Chatterjee 1:33:41 This can be problematic. I think, you know, I mentioned the, the, the, the low lux amber bulbs that I have in my bedside lamps, and I think there's a biological explanation in sense of the lower lux, it's not pushing my circadian rhythm back, my clocks back. Sure. But I actually think-

Russell Foster 1:34:03 And, and critically, um, reducing your alertness, which is probably the main, main factor.

Dr. Rangan Chatterjee 1:34:07 Okay.

Russell Foster 1:34:08 Yeah.

Dr. Rangan Chatterjee 1:34:08 So it's reducing my alertness-

Russell Foster 1:34:09 Yeah

Dr. Rangan Chatterjee 1:34:09 ... because of the lower light.

Russell Foster 1:34:10 Exactly. Higher the light, greater the alertness, and the more, more difficult it is to get off to sleep.

Dr. Rangan Chatterjee 1:34:15 Okay. So that's fascinating and I guess speaks to, well, so many bathroom mirrors are-

Russell Foster 1:34:21 [laughs] Yes

Dr. Rangan Chatterjee 1:34:22 ... like bathrooms are full of these bright LEDs, right?

Russell Foster 1:34:25 Yes.

Dr. Rangan Chatterjee 1:34:25 So what do people do before bed?

Russell Foster 1:34:27 Well, I know. I mean, it's, I think it's absolutely spectacularly ironic that what's the last thing we do before we go to bed? We stand in the most brightly lit room of the house-

Dr. Rangan Chatterjee 1:34:35 [laughs]

Russell Foster 1:34:35 ... which is the bathroom, and then we look into an illuminated mirror as we clean our teeth. Um-

Dr. Rangan Chatterjee 1:34:39 Yeah

Russell Foster 1:34:39 ... and, you know, we talked about a, a, a, an investment opportunity in developing night shift food. Another, uh, perfect investment opportunity is developing a bathroom mirror which has bright alerting light in the morning, and you switch it to the evening, which is dimmer, less alerting light, um, i- in, in the evening.

Dr. Rangan Chatterjee 1:34:58 Yeah. I mean, it's simple.

Russell Foster 1:34:59 Yeah. [laughs]

Dr. Rangan Chatterjee 1:34:59 The technology's there to do it.

Russell Foster 1:35:01 Absolutely.

Dr. Rangan Chatterjee 1:35:01 Yeah. So that's, that's something else we can think about, what, how, you know, what sort of light are we exposed to there. But-

Russell Foster 1:35:06 Yeah

Dr. Rangan Chatterjee 1:35:06 ... speaking about these bedside lamps, I think also, as well as the biological explanation, I think there's also, I guess, something behavioral about them for me in terms of it's, it signals to me, oh, it's now evening time. It's-

Russell Foster 1:35:23 Yeah

Dr. Rangan Chatterjee 1:35:23 ... rest time. It's not stimulation time. Do you know what I mean?

Russell Foster 1:35:27 Yeah.

Dr. Rangan Chatterjee 1:35:27 So I think sometimes-

Russell Foster 1:35:27 It's that winding down. It's, we assume that we can go from a fully conscious state-

Dr. Rangan Chatterjee 1:35:31 Yeah

Russell Foster 1:35:31 ... you know, w- again, g- the gear analogy, you know, going from first gear to fifth gear.

Dr. Rangan Chatterjee 1:35:36 Yeah.

Russell Foster 1:35:36 You can't do it. Um, you have to do it through stages. And again, winding down from the wake state to the sleep state requires an adjustment. Um, and whether that's as, as you were saying, you, you enjoy reading, um, some novel, uh, under relatively dim light before going to bed. Some people listen to music or something else that they find relaxing. And it's, and it's f- it's adopting those behaviors that make the transition easier. And again, it's, it's, it's, as you were saying, it's the brain n- knows what's coming next, and what's coming next is sleep.

Dr. Rangan Chatterjee 1:36:07 Yeah.

Russell Foster 1:36:07 And so it can prepare itself.

Dr. Rangan Chatterjee 1:36:08 It's what we do with our kids, right? We give them a routine. You know, we don't-

Russell Foster 1:36:12 We read a story.

Dr. Rangan Chatterjee 1:36:12 We read a story.

Russell Foster 1:36:13 Yeah.

Dr. Rangan Chatterjee 1:36:14 We, we don't [laughs] as I often say to us, we don't give them a ton of sugar, put the lights on bright-

Russell Foster 1:36:18 [laughs]

Dr. Rangan Chatterjee 1:36:18 ... speak loudly. No, no.

Russell Foster 1:36:20 Yeah.

Dr. Rangan Chatterjee 1:36:20 We do the opposite of all those things. But as adults, we kinda think we can somehow-

Russell Foster 1:36:25 Until their favorite uncle visits, you know? [laughs]

Dr. Rangan Chatterjee 1:36:27 Oh, [laughs] exactly. We think we can override them, but we can't. Oh, Russell, I could speak to you for hours. As we come towards the end of this conversation, few things I wanted to, uh, briefly cover, if possible. Sleep trackers.

Russell Foster 1:36:40 Ugh.

Dr. Rangan Chatterjee 1:36:40 Uh, [laughs] yeah. Um, any, any view on sleep trackers?

Russell Foster 1:36:46 Well, I think we should define where they could be useful. So, um, most sleep trackers, uh, if you use them to determine roughly when you went to sleep, um, how many times you woke up in the night, for example, and when you finally woke up, so your sleep timing, your sleep duration, and your sleep fragmentation. That's a tried and tested technology, and it's what we use in the lab. The problem is that most of the, the trackers that people wear these days try and do more than that. They say, "Oh, you've had lots of good deep sleep," or, "You've haven't had enough REM sleep." And, and for that, they're completely useless. And, um, they can, they can generate huge anxiety. Um, so, so I spoke to an individual, uh, again before lockdown, who said I'm not getting, I'm not getting enough slow-wave sleep. I'm really anxious about it. In fact, what I do, I set my alarm clock for 4:00 in the morning, wake my- my- myself up to, to find out how much slow-wave sleep I've had. I mean, that's the kind of level-

Dr. Rangan Chatterjee 1:37:48 Yeah

Russell Foster 1:37:48 ... of anxiety that these things are, um, are developing. And in fact, so, so what, what does it really tell us if we've had lots of slow-wave or lots of REM sleep? We don't really know. And the algorithms, first of all, are not very good at detecting that. Um, and they've been largely worked out for a bunch of 20-year-olds in California. Um, uh, and, and of course our sleep changes [laughs] hugely as we age. Um, and they're not gonna work for somebody in their 70s or indeed, you know, somebody younger. Um, so s- until we got, you know, really sophisticated artificial intelligence, you know, plotting, uh, uh, uh, extracting information to get sleep phase, they're, they're not, they're not accurate.

Dr. Rangan Chatterjee 1:38:31 Yeah.

Russell Foster 1:38:31 The, and the other, the other problem I have is, so what? You know, do we really know what slow-wave sleep is all about? Well, sort of. I mean, we know that if people are selectively deprived of slow-wave sleep, their memory isn't as good and their problem-solving isn't as good. And if people are selectively deprived of REM sleep, then their emotional processing, they show a bit more anxiety during the day. But in a sense, we, we don't really know.

Dr. Rangan Chatterjee 1:38:58 Yeah.

Russell Foster 1:38:58 And, and so I do get very frustrated because we become, as a society, finally m- m- more sensitive to the importance of sleep. But what's happened is that a large sector have become very anxious about their sleep.

Dr. Rangan Chatterjee 1:39:13 Yeah.

Russell Foster 1:39:13 And, you know, there's these sort of sergeant majors screaming, "You've got to get eight hours. You've got to do this. You can't do that." And we have to define what works for us.

Dr. Rangan Chatterjee 1:39:24 Yeah.

Russell Foster 1:39:25 And, and in fact, so many people think is, the sleep is what you get, but actually it's a highly dynamic, uh, uh, bit of our biology, and we have the ability to work with it-

Dr. Rangan Chatterjee 1:39:34 Yeah

Russell Foster 1:39:34 ... and optimize it. And I think that's, that's something that I... And, and, and the sleep apps, you know, d- drive us in the opposite direction. So I, I get a bit worried. I mean, you know, in principle, good idea because, uh, if you-- It's like losing weight. If you weigh yourself every morning, um, uh, and you see you've lost weight, that'll reinforce your changed eating behavior. And if you wanted to get longer sleep or different timing of sleep, as we've kind of touched on, it would be a useful metric to say, "Yes, well, that changed behavior has worked." So, you know, getting that more morning light-

Dr. Rangan Chatterjee 1:40:06 Yeah

Russell Foster 1:40:06 ... meant I did go to bed, to bed earlier and kind of got up earlier. So in principle, they could be useful. But it's worth bearing in mind, none of the, um, the sleep federations endorse any of the commercially available devices.

Dr. Rangan Chatterjee 1:40:20 Wow.

Russell Foster 1:40:20 And none of them are FDA approved.

Dr. Rangan Chatterjee 1:40:22 Yeah.

Russell Foster 1:40:22 So we're a long way f- from them being, I would say, useful.

Dr. Rangan Chatterjee 1:40:26 Yeah. Tha- thank you for that. That was very, very clear. I mean, that weight loss analogy, if we take it one step further, yes, if you see every day your weight is going down, let's say you are tracking that and you think that's a reasonable thing to track, sure, it can motivate behavior. But on that one day where it goes up, and I, I read a study once which said that actually our weights can vary bet- I think three to 10 pounds on any given day, I think it said.

Russell Foster 1:40:53 Yeah.

Dr. Rangan Chatterjee 1:40:53 Maybe three to five pounds.

Russell Foster 1:40:54 Yeah.

Dr. Rangan Chatterjee 1:40:55 Just from fluid and all kinds of other stuff.

Russell Foster 1:40:57 Yeah.

Dr. Rangan Chatterjee 1:40:57 But I thought, well, actually it could have a really toxic effect when you're, you're making all the right changes-

Russell Foster 1:41:03 Yes

Dr. Rangan Chatterjee 1:41:03 ... for your health and maybe for excess weight, but actually one day it happens to go the wrong way.

Russell Foster 1:41:08 Actually, yes, good point.

Dr. Rangan Chatterjee 1:41:08 Do you know what-

Russell Foster 1:41:09 I mean, what's the point? Yeah.

Dr. Rangan Chatterjee 1:41:10 What's the point?

Russell Foster 1:41:10 Yeah.

Dr. Rangan Chatterjee 1:41:10 Well, I think it could be problematic. And I have a real concern over trackers in general. I'm not at all saying they can't be useful for some people.

Russell Foster 1:41:19 Yeah.

Dr. Rangan Chatterjee 1:41:19 I understand it probably depends on personality type a little bit in terms of what you do with that data. I do have a sleep tracker. I don't think I've used it for about six months. Um, it was considered one of the good ones. And I have no problem with it. You know, it was useful. There were certain things that I felt it helped me understand, which is if I eat late, it appears to really have an impact-

Russell Foster 1:41:40 Mm-hmm

Dr. Rangan Chatterjee 1:41:40 ... on various things. But I kind of learned what I needed to learn from it. And one day, Russell, I remember waking up feeling pretty good, and I looked at my sleep score, and it was rubbish.

Russell Foster 1:41:53 [laughs]

Dr. Rangan Chatterjee 1:41:54 And then my mind starts to play tricks on me.

Russell Foster 1:41:55 Mm.

Dr. Rangan Chatterjee 1:41:56 I was like, "Oh." And then I thought, "God, am I starting to feel tired, like, because I'm tired or because of what I've just seen?"

Russell Foster 1:42:01 Mm.

Dr. Rangan Chatterjee 1:42:01 I thought, "You know what? Screw this. I'm not-

Russell Foster 1:42:03 Yeah

Dr. Rangan Chatterjee 1:42:03 ... I don't need to use this anymore. I need to tune into myself." And I personally, I've seen, even with blood pressure monitors, I've seen patients over the years tie themselves up in knots and have health anxiety. So I guess I would just urge a note of caution as well for people.

Russell Foster 1:42:20 I think that's absolutely right. And we've talked about, you know, how do you know if you're getting enough sleep, what the factors are. That's the most important thing.

Dr. Rangan Chatterjee 1:42:26 Yeah.

Russell Foster 1:42:26 And these are questions we can answer for ourselves without the need of a, of a health, health tracker.

Dr. Rangan Chatterjee 1:42:30 Yeah.

Russell Foster 1:42:30 A good, good, good friend of mine, Ken Wright, who's, um, University of Colorado, um, he, uh, starts his, um, his class, and you know, it's a large number of students, with, uh, "Who here has ever used a sleep tracker?" And you know, essentially the whole class sort of put their hand up. And he said, "Who now is, is using one routinely?" And about three hands go up. And you know, these are smart people. They learn pretty quickly that these devices just don't work.

Dr. Rangan Chatterjee 1:42:57 Yeah.

Russell Foster 1:42:58 Um, and y- as you've discovered, you've, you've, you've, you, you em- you embrace the knowledge from your own personal experiences.

Dr. Rangan Chatterjee 1:43:06 Yeah, yeah. To be a human-

Russell Foster 1:43:08 [laughs]

Dr. Rangan Chatterjee 1:43:08 ... and to really experience what that means. Um,

Dr. Rangan Chatterjee 1:43:11 just very quickly, a lot of people will often say about light exposure, well, what about, let's say Scandinavia, for example. Uh, I guess that's top of mind because I've been recently. The hotel light in which I stayed had pretty poor blackout blinds, and so I woke up in the night.

Russell Foster 1:43:26 Mm.

Dr. Rangan Chatterjee 1:43:27 And then I thought it was morning, and I looked at my watch. It was, it was 3:00 AM. It was bright at 3:00 AM.

Russell Foster 1:43:34 Yes.

Dr. Rangan Chatterjee 1:43:34 How have people in Northern Hemisphere countries or, or other countries where there are these wildly different day and night cycles, have they evolved to that? Have they adapted to that? Do we know?

Russell Foster 1:43:47 The short answer is no. But let me tell you about a, a, a group of animals that have. And, um, uh, from the University of Tromso, they've looked at Arctic reindeer, and during the two months of constant light, they turn their biological clocks off, and during the two months of constant dark, they turn their clocks off. They have no adaptive value. There is no l- day-night cycle. Um, and in fact, during the winter months, these reindeer, uh, feed whenever the weather conditions permit, and during the summer, of course, they have to feed constantly to put on enough fat to survive the winter. So there are instances-

Dr. Rangan Chatterjee 1:44:25 Oh, wow

Russell Foster 1:44:26 ... where clocks have been turned off 'cause they have no adaptive value. What about humans? Well, we've of course been there for a very... Well, the Europeans who've moved into those, those, um, those, those places have, have shown no signs of adaptation. In fact, you know, in Tromso, a family will get up, um, and then they'll go in, in winter, for example, into a room where there's, there's artificial light. So they'll get that morning photon-

Dr. Rangan Chatterjee 1:44:51 Got it

Russell Foster 1:44:52 ... shower. Um, and so, so they can try and stabilize. And, and they use very effect- effective blackout curtains.

Dr. Rangan Chatterjee 1:44:58 Wow.

Russell Foster 1:44:59 Now, what's going on with those peoples, the native peoples who've been there for 30, 40,000 years isn't clear.

Dr. Rangan Chatterjee 1:45:08 Yeah.

Russell Foster 1:45:08 Um, and it may well be that there has been some adaptation, but we're, w- w- we don't know.

Dr. Rangan Chatterjee 1:45:15 Russell, my brain is going so fast in so many different directions. Um, out of respect to your time, I'm gonna stop firing questions at you and hope I can persuade you at some point in the future for a part two.

Russell Foster 1:45:27 [laughs]

Dr. Rangan Chatterjee 1:45:28 Um, to finish off this conversation on an upbeat note, um, for people who feel inspired to prioritize their sleep, to get on top of their sleep, to basically go, "You know what? Maybe it was the bit about being in your 40s to 50s and not pushing it," whatever it might have been that connected with them, this podcast is called Feel Better, Live More. When we feel better in ourselves, we get more out of our lives. Of course, when we're gonna sleep better, we're gonna get more out of every aspect of our lives. So do you have any final words of wisdom, advice, practical, whatever it might be, to leave my listeners with?

Russell Foster 1:46:05 I, I mean, I, I think the key thing for me is that, you know, sleep is like shoe size. Um, one size does not fit all, and we as individuals need to work out what's best for us, um, because there's huge individual variation, and our sleep will change. So good example would be waking up in the middle of the night. Um, so what's happened, uh, is that our, uh, o- our sleep episode has been compressed, and so we, we tend to not wake up i- in the middle of the night. But under, uh, in societies where there's no electric light, and indeed from the literature, uh, we know our sleep patterns in the recent past were very different.

Dr. Rangan Chatterjee 1:46:45 Mm.

Russell Foster 1:46:45 So literature from the preindustrial age, uh, sh- talks about, "I had a wonderful first sleep." Um, or, uh, a- a- and sleep was biphasic, uh, going to sleep, waking up, then going back to sleep again, or indeed polyphasic, which is, uh, you know, several periods of, of waking up. And because we don't know that, when people wake up in the middle of the night, they think, "Oh, my goodness, that's it. I'm never gonna get back to sleep again. I may as well start doing my emails now and, um, start drinking coffee." A- and, and the key thing is that waking up in the middle of the night need not mean the end of sleep. In fact, that polyphasic or biphasic sleep pattern is what all mammals experience.

Dr. Rangan Chatterjee 1:47:25 Wow.

Russell Foster 1:47:25 And so this, again, single block of, of, of consolidated one block of sleep is not the natural state.

Dr. Rangan Chatterjee 1:47:33 That is such an important message, isn't it? The amount of people who feel bad that-

Russell Foster 1:47:37 Mm

Dr. Rangan Chatterjee 1:47:37 ... they wake up. I, I know the amount of questions that get fired at me-

Russell Foster 1:47:41 Mm

Dr. Rangan Chatterjee 1:47:41 ... about this. You know, "Is it okay?" And you're, you're clearly saying, "No, this is not only okay, it's very, very normal."

Russell Foster 1:47:47 Yeah.

Dr. Rangan Chatterjee 1:47:47 I guess this speaks to the problems with having our smartphones in our room-

Russell Foster 1:47:51 Yeah

Dr. Rangan Chatterjee 1:47:51 ... just looping back, and I know you me- mentioned, not in this conversation, I've heard you say about your relationship with your BlackBerry when you were in Australia-

Russell Foster 1:47:59 [laughs]

Dr. Rangan Chatterjee 1:47:59 ... and actually had to ultimately leave it in your lab.

Russell Foster 1:48:01 Yes. I, I have, I ha- I'm just sort of, uh, uh... I think they were ca- used to be called CrackBerries.

Dr. Rangan Chatterjee 1:48:05 [laughs]

Russell Foster 1:48:05 Um, and, and yeah, I was in Australia, and so I would do my Australian, uh, emails on, on the BlackBerry. Then of course the European ones would come in, and then the North American. So, so if you're jet lagged, um... And, and I remember, you know, this, this, this red blinking light, uh, who, those, those who had a BlackBerry. And I was so weak. I, I, I could not... I first of all, it was by the bed, and of course I then moved it very quickly to the room next door, and that was hopeless 'cause I'd wake up, and then I'd go next door. And so, um, I left it in the lab, and of course, as a result, I got much better sleep. [laughs]

Dr. Rangan Chatterjee 1:48:36 Yeah, because when you wake up, if you're not getting your mind actively-

Russell Foster 1:48:39 Exactly

Dr. Rangan Chatterjee 1:48:39 ... engaged back into work-

Russell Foster 1:48:41 Yeah

Dr. Rangan Chatterjee 1:48:42 ... you, a lot of us probably don't realize that we may well have fallen asleep again-

Russell Foster 1:48:47 Yes, and, and-

Dr. Rangan Chatterjee 1:48:47 ... had we not done that

Russell Foster 1:48:48 ... that's what most of us do.

Dr. Rangan Chatterjee 1:48:49 Yeah.

Russell Foster 1:48:49 In fact, you know, we go through cycles of REM and non-REM, and we naturally wake from, from REM sleep, and then we fall back to sleep again without even noticing it.

Dr. Rangan Chatterjee 1:48:56 Yeah.

Russell Foster 1:48:57 Now, that wake-up period can be, you know, a, a, a few seconds, so you don't notice it, or it may be 30 minutes. But the chances are you will go back to sleep as long as you stay relaxed, you keep the lights low, and you do something that is not alerting the brain. And as I say, because we haven't ever passed this information on, you know, people don't know, and they think, "Oh, my goodness, that's the end of sleep. I'm-

Dr. Rangan Chatterjee 1:49:21 Yeah

Russell Foster 1:49:21 ... sleeping terribly." And in fact, if you stay calm, um, it's fine. The other thing, another tip, I guess, would be illuminated alarm clocks 'cause many people clock watch. They'll wake up, and then they think, "Oh, my God, I've only got two hours before I, the alarm goes off." It doesn't matter. You know, if you go back to sleep, you know, it, it... and you have that additional two hours or half an hour, again, it doesn't matter. So if you have an illuminated clock, put a, some tape over the front of it. The only thing that matters, I guess, is the alarm, not how long you've got before the alarm goes off.

Dr. Rangan Chatterjee 1:49:54 Which brings us back to the start of the conversation, which is alarm clocks stop the single most behavioral-

Russell Foster 1:50:00 [laughs]

Dr. Rangan Chatterjee 1:50:00 ... single most important behavioral experience we have. If that conversation resonated with you, here is another incredibly powerful one.

Russell Foster 1:50:07 Digestive issues, mental focus issues, exacerbation of every major psychiatric disorder from OCD to ADHD is closely associated with disruptions in circadian clock function. The foundational practice that I truly believe every person should do every day is