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Dr Rangan ChatterjeeDr Rangan Chatterjee

WHY YOU'RE ALWAYS TIRED - Big Myths Ruining Your Sleep & How To Get The Best Sleep Of Your Life!

In this sleep masterclass, Neuroscientist Professor Russell Foster & Sleep Researcher Professor Matthew Walker share their very best tips about getting the best sleep of your life. Hope you enjoy!

Dr. Rangan ChatterjeehostRussell FosterguestMatthew Walkerguest
Aug 30, 20232h 52mWatch on YouTube

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Partial transcript

  1. 0:00 – 1:43

    Busting the “8 hours” myth: finding your personal sleep need

    1. RC

      Sleep is highly individual.

    2. RF

      Yeah.

    3. RC

      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.

    4. RF

      Yeah. Yeah. I mean, that was part of the motivation for, for writing Life Time because I, 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 10, 10 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.

  2. 1:43 – 4:48

    Does activity or goals change sleep needs? Federer, Einstein, and Dali

    1. RC

      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-"

    2. RF

      Yeah.

    3. RC

      "... 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?

    4. RF

      Yeah.

    5. RC

      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.

    6. RF

      Yeah.

    7. RC

      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?

    8. RF

      Well, of course, the, the famous long sleeper was Albert Einstein, um-

    9. RC

      [laughs]

    10. RF

      ... 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.

    11. RC

      Right.

    12. RF

      Uh, a-and I think, you know, Federer just needs that amount of sleep-

    13. RC

      Yeah

    14. RF

      ... 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.

    15. RC

      You do?

    16. RF

      Um, and, um, you know, I sort of... It, it's great. You know, undergraduate lectures, you know. I say, "Well, Einstein, a classic sort of slept ten, ten 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 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- [laughs]

    17. RC

      So it depends what's the goal.

    18. RF

      It depends what the goal is. [laughs]

    19. RC

      Right. If the goal is to hallucinate and have an altered state of consciousness-

    20. RF

      Yeah

    21. RC

      ... and you need that for your job, you know what?

    22. RF

      Yeah.

    23. RC

      Sleep deprive yourself all you want.

    24. RF

      Yeah, that's true.

    25. RC

      [laughs]

    26. RF

      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, d-d-deprive yourself of sleep.

  3. 4:48 – 6:09

    How sleep-deprived society is—and what it does to mood and thinking

    1. RC

      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?

    2. RF

      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.

    3. RC

      Hmm.

    4. RF

      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, uh, reduced capacity to remember things. We are less creative. Um, so all the things... W-reduced sense of humor. I mean, you know-

  4. 6:09 – 9:38

    Long-term consequences: accidents, immunity, and serious disease risk

    1. RC

      Yeah

    2. RF

      ... all the things that make us this extraordinary creature, uh, 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- uh, I, I think the really key point is that chronic sleep loss is so much more than feel- feeling tired at an inappropriate time. It's associated with an impact upon our health at every level.

    3. RC

      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-

    4. RF

      Yeah

    5. RC

      ... with partners, children, work colleagues, family?

    6. RF

      Mm.

    7. RC

      We need empathy.

    8. RF

      Yeah.

    9. RC

      I mean-

    10. RF

      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-

    11. RC

      Yeah

    12. RF

      ... often a good sense of humor, and so really we should be really promoting good sleep to im- improve productivity.

    13. RC

      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-

    14. RF

      Yeah

    15. RC

      ... which of course completely alters your view and perception of the world.

    16. RF

      Yeah.

    17. RC

      It feels like this dark, scary place-

    18. RF

      Yeah

    19. RC

      ... rather than an uplifting, hopeful, joyful place.

    20. RF

      Hmm.

    21. RC

      You mentioned, yes, these short-term consequences, but also these pretty scary long-term consequences. Now-

    22. RF

      Yeah

    23. RC

      ... 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.

    24. RF

      Yeah.

    25. RC

      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.

    26. RF

      Yeah.

    27. RC

      That's probably only gonna increase. That's a lot of people.

    28. RF

      Yes.

    29. RC

      And I can't imagine what it's like for a shift worker to just hear what you said the WHO say, which is-

    30. RF

      Yeah

  5. 9:38 – 14:36

    Avoiding fear: what sleep science means for parents of young children

    1. RC

      ... 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, w- love what you, love what you said. You know, I understand about sleep, but I'm really worried."

    2. RF

      Hmm.

    3. RC

      "My three-month-old doesn't sleep through the night." You know, or whatever is 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 [chuckles] that if you can.

    4. RF

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

    5. RC

      Yeah

    6. RF

      ... 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, uh, 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 y- 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 t- 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-

    7. RC

      Hmm

    8. RF

      ... 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.

    9. RC

      Yeah.

    10. RF

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

    11. RC

      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.

    12. RF

      Yeah.

    13. RC

      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-

    14. RF

      Yeah

    15. RC

      ... his family. And my mother-in-law has been staying with us on and off for a couple of months.

    16. RF

      Mm.

    17. RC

      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-

    18. RF

      Yes

    19. RC

      ... when it comes to childcare, it, it, it's not just one more person. It seems to have changed everything.

    20. RF

      The whole dynamic changes, really.

    21. RC

      The whole dynamic changes.

    22. RF

      Yeah. Absolutely.

    23. RC

      I, I was like, "This is incredible. This is what humans have always done."

    24. RF

      Yeah.

    25. RC

      Yet 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.

    26. RF

      Mm.

    27. RC

      You're not, you're not broken. It's not that you can't cope.

    28. RF

      No.

    29. RC

      None of us can cope with that.

    30. RF

      Yep.

  6. 14:36 – 17:57

    Shift work realities: why most people don’t adapt (and why light matters)

    1. RC

      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.

    2. RF

      Yeah.

    3. RC

      We mentioned the potential health problems of that.

    4. RF

      Yes.

    5. RC

      You know, something I read in your book, which I found fascinating, was that over 90% of night shift workers, was it even 97%?

    6. RF

      97, yeah.

    7. RC

      They don't adapt.

    8. RF

      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-

    9. RC

      The clock, just... The clock always defers to the brighter light signal. I think that's a really-

    10. RF

      Yeah

    11. RC

      ... powerful thing for me to sit with.

    12. RF

      And that's why we don't shift. And in fact, there, there's one group, I mean, 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.

    13. RC

      Ah.

    14. RF

      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.

    15. RC

      Wow.

    16. RF

      Then, of course, it's really tough for them because then they have two weeks of shore leave [laughs] completely maladapted to their friends and family. But the, you know, the serious issue is you, you, 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, 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.

    17. RC

      We're not machines.

    18. RF

      No.

    19. RC

      We're human beings, right?

    20. RF

      Absolutely, yes.

    21. RC

      And I think you could, you could [laughs] you could apply that across all kinds of different things in society.

    22. RF

      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, as a species. Um, but we are, it comes with some, some massive arrogance. Um, 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.

    23. RC

      That's interesting. It was only in the 1950s when we-

    24. RF

      Big acceleration, yeah

    25. RC

      ... when we've really aggressively invaded the night.

    26. RF

      Yeah.

    27. RC

      That's not long.

    28. RF

      No.

    29. RC

      Through an evolution lens, that's just a blink.

    30. RF

      Yeah. And, and clearly, you know, we've been creeping in.

  7. 17:57 – 20:59

    Driving at 4:00 AM: fatigue risk compared to legal intoxication

    1. RC

      We'll stay on shift work for the minute, but this doesn't just apply to shift work. Driving.

    2. RF

      Yeah.

    3. RC

      Driving tired. And a pretty alarming statistic in your book about what it means to drive at 4:00 AM for most people.

    4. RF

      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 four o'clock in the morning, where, 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 four o'clock in the morning, it was minus 20. So, so if, if listeners take nothing from, from this at all, other than the fact that you are driving at four o'clock in the morning, your ability to process information is worse than if you were legally drunk.

    5. RC

      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-

    6. RF

      Yes

    7. RC

      ... versus what's biologically optimal. Some people, of course, have to get up early for work.

    8. RF

      Yeah.

    9. RC

      Some people now drive through the night.

    10. RF

      Yes.

    11. RC

      Lorry drivers, you know, [chuckles] big-

    12. RF

      Yep

    13. RC

      ... big cargo in the back.

    14. RF

      Mm-hmm.

    15. RC

      Um, now I'm sure they've got certain regulations, certain things that they do in order to be less tired-

    16. RF

      Yes

    17. RC

      ... uh, at that time. But, you know, driving at 4:00 AM-

    18. RF

      Yeah

    19. RC

      ... for most of us, being worse than when we might be legally drunk, that's pretty alarming.

    20. RF

      It's extraordinary. Yeah.

    21. RC

      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 twenties and thirties, you know, you go to a mate's wedding-

    22. RF

      Mm.

    23. RC

      Right? There'll be some late nights, a few drinks, and then you drive home on a Sunday, you know.

    24. RF

      Mm.

    25. RC

      Yeah. You're, you're, you know, uh, just to be super clear, you know, you're, you're, you're fully sober-

    26. RF

      Yes

    27. RC

      ... you know? But it-- culturally, it's okay. "Oh, yeah, I'm knackered. I've just gotta drive now for four hours."

    28. RF

      Yeah.

    29. RC

      But w-we're putting people's lives at risk.

    30. RF

      We are.

  8. 20:59 – 28:10

    Mitigations for night work: employer duty of care, monitoring, food, and scheduling

    1. RC

      Yeah

    2. RF

      ... 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-

    3. RC

      Yeah

    4. RF

      ... 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, that, you know, a-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-

    5. RC

      Do they really?

    6. RF

      ... 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 two, 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-

    7. RC

      Mm

    8. RF

      ... 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.

    9. RC

      But why, why high protein?

    10. RF

      Um, because it doesn't have the same impact as carbohydrates and fats on coronary heart disease and indeed cancer.

    11. RC

      But that would be quite easy, right? Let's say for-

    12. RF

      Yes

    13. RC

      ... a hospital which is staffed at night-

    14. RF

      Yeah

    15. RC

      ... it would be quite easy either to have those snacks or to work with a nutritionist and make in bulk protein shakes full of phytonutrient-

    16. RF

      I know

    17. RC

      ... rich foods that are easy to digest, that are tasty, that they could give people. It w- it's not that hard.

    18. RF

      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.

    19. RC

      Yeah. Yeah.

    20. RF

      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-

    21. RC

      Six times higher.

    22. RF

      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-

    23. RC

      Mm

    24. RF

      ... which is a, is 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.

    25. RC

      Yeah. We don't wanna be too scary, but, um, I can't stop thinking about that As a doctor myself, that 57% figure-

    26. RF

      Yeah

    27. RC

      ... 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.

    28. RF

      Yeah.

    29. RC

      Certainly between 30 and 36 hours, I properly fell asleep on the M60 in traffic. Um-

    30. RF

      Yeah.

  9. 28:10 – 30:30

    Microsleeps and disasters: uncontrollable sleep episodes with high stakes

    1. RC

      ... I think that possibly has played into my head for many years about that. Um, number two, I think, I think a point here is that you, you bring up this term microsleeps.

    2. RF

      Mm.

    3. RC

      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.

    4. RF

      Yeah. Yeah.

    5. RC

      Right? So, so can you speak to that a little bit?

    6. RF

      So it's, it's really, th- so a microsleep is ess- essentially an uncontrollable and, 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 can all just sort of have a, have a microsleep, and then, uh, 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-

    7. RC

      Yeah

    8. RF

      ... you would be killed, or you'd have killed somebody else.

    9. RC

      Well, you mention in your book all these things, what, Chernobyl, the, the Chernobyl-

    10. RF

      Oh, yeah

    11. RC

      ... nuclear disaster. Was it a Selby crash in Air India?

    12. RF

      Yeah.

    13. RC

      Like, you've mentioned all this stuff. Can you maybe speak to some of those?

    14. RF

      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-

    15. MW

      Chronic tiredness, uh, f- prevents you from processing information accurately. And you know, a- a- we- 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-

    16. RC

      Yeah

    17. MW

      ... and we can fool ourselves that we're okay, whereas we're not.

  10. 30:30 – 43:04

    Jet lag experiments, caffeine on flights, and caffeine as a powerful sleep disruptor

    1. RC

      I actually am, am doing that flight to California relatively regularly these days, maybe three to four times a year. And two weeks ago I went, and I tried something different for the very first time, and I've got to say, I had the least jet lag I've ever had on one of my trips to California. And, you know, I changed multiple variables. It's very hard to say which one exactly it was, but on the flight out there, so it was a morning flight from London, so that would be the middle of the night in California, I put on some blue light blockers on the flight. And blue light blockers for a little bit of time, and I was reading, but then I would close my eyes. I put a shade on my eyes, and I would just try and sleep. I couldn't sleep that well, but at least I didn't expose myself to light. Then at the time of morning, or what would've been morning in California, I took off my nightshades. I did not put on my blue light blockers, and I actually watched a film, so I was exposing myself to blue light from-

    2. MW

      Yeah

    3. RC

      ... my screen-

    4. MW

      Yeah

    5. RC

      ... to sort of trick my body, say, "Hey, you're on morning time." So I've never done that before. The other thing is, and I think we'll go here next, the n- the other thing I've done a lot recently is reduce my caffeine intake a lot.

    6. MW

      Mm.

    7. RC

      And I think that often when I used to travel, I was so habituated to having caffeine that sometimes I would wake up, um, in the new time zone with a bit of a headache 'cause my body was expecting caffeine earlier. It didn't have it, and I th- think that that was artificially waking me up.

    8. MW

      Yeah.

    9. RC

      So, you know, a few things I did differently, but, you know, caffeine is such a popular topic, right? And we don't want to be, um, you know, start off this conversation on a downer, but-

    10. MW

      [laughs]

    11. RC

      ... you know, let's go into caffeine. I mean, how much of a sleep disruptor is caffeine?

    12. MW

      I mean, it, it is quite significant, and one of the problems, um, you know, with those long-haul flights, and I would actually love to speak with, you know, Virgin or British Airways about this, um, th- they serve caffeine liberally.

    13. RC

      Yeah.

    14. MW

      And the other thing they serve is alcohol, and I'd love to speak about that, too, because both of those are the very best ways to, A, disrupt your sleep, and B, actually make your, uh, make it much harder for your 24-hour biological circadian clock to readjust. Both of those will, will actually take away those fingers on the wristwatch and sort of will slow the progression down. Um, but caffeine is a misunderstood drug. Certainly m- everyone-

    15. RC

      It's a drug, right?

    16. MW

      It is.

    17. RC

      You use the term drug, and that's interesting.

    18. MW

      It is a drug. Um, it's what we call a psychoactive stimulant. Um, everyone knows that caffeine can help alert you and sort of keep you awake. That's the thing that's most known. Um, caffeine, if you look at some data, is probably the second-most traded commodity on the surface of the planet after oil, which I think says everything about-

    19. RC

      Wow

    20. MW

      ... our sleep-deprived state. The other thing about caffeine, however, that most people don't realize is the time that it is in your system. So most drugs have what we call a half-life, the amount of time it takes for half of that drug to be essentially excreted out your system. Caffeine has a half-life of about six or seven hours, and it's a little dependent on what type of gene that you have to sort of metabolize the caffeine, but on average, it's about that. But what's interesting is that caffeine has a quarter life of about 12 hours. What this means is that if you have a cup of coffee at noon, a quarter of that caffeine is still circulating around your brain at midnight.

    21. RC

      Wow.

    22. MW

      So to put that in context, it would be the equivalent of getting into bed, and just before you turn the light out, you swig a quarter of a cup of Starbucks and you hope for a good night of sleep. It, you know, you would never do that-

    23. RC

      Yeah

    24. MW

      ... 'cause you know, but that's exactly, unfortunately, what people do, you know, um, completely innocently by drinking caffeine, you know, still too late in the afternoon.

    25. RC

      Yeah, it's a, it's a, it's a huge problem. Yeah.

    26. MW

      It is, it's, um, I, I think it's a big problem in society if you... I mean, another way to quantify this is if you just look, and I've checked out the data from the Financial Times, the number of Starbucks coffee houses that have arisen [laughs] over, over the past 30 years is just, like, an exponential increase, and I think that is an expression of how we're self-medicating our state of sleep deprivation in developed nations. Um-

    27. RC

      And well, cafe culture is just growing, uh, you know, exponentially now.

    28. MW

      Yeah.

    29. RC

      Right? It's the new, you know, I, I talk about sometimes it's almost like a new, new pub culture. It's cafe culture.

    30. MW

      Yeah.

  11. 43:04 – 55:10

    Sleep as the foundation pillar: why diet and exercise depend on it

    1. RC

      Food and movements, which people have been talking about for years, but also sleep and relaxation. Now, in your book, right at the start, you make a very powerful case why sleep is the foundational pillar of health. I'd love you to talk more about that.

    2. MW

      Yeah. You know, I used to think that sleep may be the third pillar of good health, alongside diet and exercise, but the more I sort of did my research and the more I read from other people, I realized I was probably wrong, that in fact sleep is the foundation on which those two other things sit. Um, and I'll give you an example in each. Firstly, for diet and exercise, we know that if people are trying to lose weight and they're being judicious about their food intake, they're trying to, um, diet, but they're not getting sufficient sleep, 70% of all the weight that they lose will come from lean muscle mass and not fat.

    3. RC

      Wow.

    4. MW

      Because your body becomes very stingy in giving up its fat when you are underslept, so dieting becomes, you know, quite redundant in that regard. You know, you, you want to keep the [laughs] muscle, you want to let go of the fat, and sleep deprivation will do the opposite to you. So that's the first thing. It's a foundational element on which, you know, nutrition sits. And by the way, I'd love to talk all about sort of diet, appetite, uh, sort of increased caloric intake, increasing exactly what you desire to eat when you're underslept. There's great data there. But let me move over to activity. We've spoken about the foundation on which diet sits. When you are not sleeping sufficient amounts, firstly, the likelihood that you will actually exercise decreases significantly. Your motivation to be physically active drops away. Even if you are physically active, the intensity of your workout will not be as strong, so it's less effective and less efficient. Your, things like your vertical jump height, your muscle contraction strength, even the exchange of carbon dioxide and oxygen in your respiratory systems, they get worse when you haven't slept.

    5. RC

      Wow.

    6. MW

      What's even more frightening, however, is that your risk for injury increases when you are exercising but not well-slept.

    7. RC

      This is incredible.

    8. MW

      And they did this great study where they looked at, um, some athletes across a season, and then they tracked their sleep, and then they bucketed those athletes into the different amounts of sleep, nine hours, eight hours, seven hours, six hours, and what they found was a linear relationship between less and less sleep and increasing risk for serious injury during a sports event. So there is yet another demonstration of how even if you're trying to be physically active but not getting sufficient sleep, it can be harmful. The beauty of that part of the relationship, and the same for diet, is that it's bidirectional, that if you actually, you know, improve your sleep, you can improve those two things, but conversely, those two things will improve sleep.

    9. RC

      Yeah.

    10. MW

      So if you start to correct your diet, you start to sleep better. We've already spoken about caffeine. But physical activity is a great way to enhance both the quality and the quantity of your deep sleep. So physical activity, as long as it's not too close to bedtime, if it's too close, your metabolic rate stays too high, your core body temperature stays too high, and that will prevent sleep.

    11. RC

      I am seeing that a lot as well, you know, and I, I have experienced that myself in terms of, squash is one of my favorite games, um, but if I play squash at about 7:00 or 7:30 PM, I can't sleep that night. You know, I'm lying in bed at night, and I know it's about 5:00-ish for me, really is the last time I can go on the squash court, have a great workout, have an enjoyable game, and everything seems to have sort of gone back down to normal before I try and sleep at night. And I, I'm seeing that a lot with patients, which, again, you know, if people are after work, they're trying to fit their workout in, you know, it becomes challenging because the modern world is making it sometimes quite tricky for us to live in harmony with our natural circadian rhythms.

    12. MW

      Yeah.

    13. RC

      But, but I see that a lot. Working out intensely in the evening is a problem. Have you done research on that in your lab?

    14. MW

      So we've looked at this with body temperature, too, you know, and, and I understand that people... You know, I still want to celebrate and embrace the idea of people exercising.

    15. RC

      Of course.

    16. MW

      I think that's critical. Um, and even if it's late into the night, best not to do that, but if you do do that, a good way, um, to try and solve the higher core body temperature is to have a bath or a shower right before bed. And-

    17. RC

      A hot bath, right?

    18. MW

      A hot bath is best-

    19. RC

      Yeah

    20. MW

      ... yeah, or a hot shower, because what happens is that all of the blood comes to the surface of your skin. You kind of get nice, rosy cheeks, and that acts like this huge thermal radiator, taking all of the heat out of the core of your body. And as a consequence, the core body temperature will actually plummet, and you will fall asleep easier. That's al- the reason that it's always easier to fall asleep in a room that's too cold than too hot, too cold is taking you in the right temperature direction for good sleep. So if you do have to work out at some point late into the night, you can try that trick, but for the most part, try and get your workout in a little bit earlier.

    21. RC

      That's a great tip, though, for people, 'cause I know there'll be many people listening to this who probably do try and get their workouts in in the evening, so that's a great little tip that they can put into practice to see if, if they can, you know, ensure that that workout doesn't hinder their ability to get good sleep. As you were talking about vertical jump, and, you know, you know, as a sportsman myself, I sort of, you know, this really, you know, gets me excited to think, actually, can you improve your performance by sleeping more? And- Immediately what came into my head is an interview. I think it was an interview, or maybe I heard this comment. I mean, you may, uh, may know more, more about this, but I have heard that Roger Federer may get- I think he's been on record say he gets 12 hours of sleep a night. I don't know if that's true or not. Have, have you heard, uh, about that at all?

    22. MW

      Yeah. Yeah. So he does. He gets about, uh, 12 hours of sleep, and if you look at lots of sports athletes, um, you know, LeBron James, the basketball player, he suggests that he gets somewhere between 10 and 11 hours. He splits that. He has a nap routinely during the day of about an hour, and logs about sort of nine to 10 hours at night. Um, Usain Bolt, you know, he is, um, he says he never gets anything less than nine hours, and I believe w- for one of his world records, um, he had only been awake for about, uh, 35 minutes 'cause he'd taken a nap- [laughs]

    23. RC

      Oh, love it

    24. MW

      ... right before. I think it was an Olympic gold and a world record that he broke, and, uh, and he'd only been awake for about 35 minutes because he'd slept. And, you know, this is what... You know, I do some consulting now for, um, some, uh, Premier League football teams as well as NBA, NFL in the United States 'cause they're starting to, to realize that sleep is probably the greatest legal performance-enhancing drug that you could ever wish for. And it's not just in terms of preparation for exercise, by the way, uh, for which it is spectacular. It's also about recovery, and that's one of the places where I see a lot of their sports physios perhaps, um, not recognizing what they can do with sleep.

    25. RC

      Yeah.

    26. MW

      They l- front load it about before the game, which is great, but often when teams are playing, they're playing multiple games. It's about a season, and it's all about maintaining their players' health. And that recovery period after a game before you play the next game is key. You know, players will dive into baths of ice to try and reduce swelling and inflammation. Sleep is a critical part of that sports equation. You need sleep on both sides of that. So it's fascinating. Just, uh, I say it just for people who are, you know, really interested in being physically active, maintaining their peak performance. Make sure that you also consider sleep after being physically active as well.

    27. RC

      I mean, when we talk about peak performance, you know, everyone's looking for peak performance these days. Of course, those guys are athletes, right? So their idea of peak performance is probably, you know, when Roger Federer is playing in a, in a Grand Slam tennis match, he wants to be operating at peak performance. But, you know, like, you know, Joe Public also wants peak performance in their lives. You know, they want to be able to wake up feeling refreshed. You know, maybe get their kids to school without there being a whole load of arguments at home because everyone's under-slept and tired.

    28. MW

      Yeah.

    29. RC

      They want to get to work and perform well in their jobs so they feel that they're contributing to whatever work they're doing. They're operating at a high level. So, you know, what c- I guess, you know, some people may think, you know, Roger Federer, LeBron James, you know, yeah, for sure, great for those guys, but, you know, I don't need as much sleep as them. So my question would be: What can we learn from those guys, then, in terms of how they prioritize sleep? How much sleep do we need every day? But also, in episode 14 of this, this podcast, it was a few episodes ago, I interviewed, uh, Nick Littlehales, um, who for, you know, many years has been advising clubs like Manchester United, uh, the England football team, and he talked about this idea of 90-minute sleep cycles. I don't know if you've read his book or you're familiar with-

    30. MW

      Yeah

  12. 55:10 – 1:05:52

    Sleep, longevity, and stigma: from “sleep machismo” to public health urgency

    1. MW

      We do. I mean, firstly, that data is very clear that, um, if you look across epidemiological studies, millions of individuals in these studies, a very simple truth comes out, which is that the shorter your sleep, the shorter your life, that short sleep predicts all-cause mortality.

    2. RC

      Wow.

    3. MW

      And so, you know, I think that-

    4. RC

      I think we just need to stop and just let, let that sink in for a minute.

    5. MW

      [laughs]

    6. RC

      Depriving ourselves from sleep will shorten our life.

    7. MW

      Yeah.

    8. RC

      Yeah. I mean-

    9. MW

      That's the, the, the powerful data that, you know, the global sleep loss epidemic that is underway right now, which I believe is probably one of the greatest public health challenges that we now face, um, in the 21st century, it is a slow form of self-euthanasia.

    10. RC

      That's a very powerful statement, one that I absolutely would agree with. Um, have we as a society... I don't know if overprioritizes the right words, but, um, yeah, let's go with overprioritize. Have we, like have we put too much focus on the right food and the right physical activity at the expense of sleep?

    11. MW

      Yeah, it's a, it's a great question. I've thought about this a lot. Um, I, I don't think we've done it at the expense of sleep perhaps, but I do resonate with your comment that I think sleep has perhaps been the neglected stepsister in the health conversation of today, and I think it's been left out in the cold. There's probably a number of reasons for that. The first is just because scientists like me are to blame. What I mean is that we have not adequately communicated to the public or to medicine or to healthcare professionals in general how critical the importance and necessity of sleep is. You know, and I'd liken where we are with sleep with where we were, um, for smoking 50 years ago. You know, all of the science was there, but it hadn't trickled down-

    12. RC

      Yeah

    13. MW

      ... into the public knowledge base or even into medicine.

    14. RC

      Well, that's what you did so great with your book, is you're, you're bringing that awareness to the general public all over the world, which is fantastic.

    15. MW

      And that was part of the motivation for the book. You know, I could see the disease and sickness and ill health that was caused by insufficient sleep, and there wasn't, you know, um, there wasn't a blueprint guide. There wasn't some kind of a, a manifesto for sleep, and so that was part of the reason to write the book. But I think to come back, um, you know, to why sleep is being left out in the cold, I think part of it is people like, you know, well, at least my fault. Um, I think the other thing, too, is that unlike diet and exercise, sleep has an image problem. You know, I think nobody feels ashamed about saying, "I went out for a run at lunchtime," or, you know, "I, I went, I had a great run this morning." Nobody necessarily feels ashamed about, you know, putting salad on their plate, you know, and making a really healthy meal. But I do think people feel sometimes ashamed by saying, "Well, I, I need at least eight and a half hours of sleep a night." You know, and sometimes I've heard the reaction of people saying, "Really?" And that really has a hint in it to suggest that if you're getting sufficient sleep, and I choose that word carefully, sufficient, then you must be lazy, that you're slothful.

    16. RC

      Yeah.

    17. MW

      Because we've tagged and we've associated this thing called necessary sleep with that luggage of, you know, something to be ashamed about. And in fact, if anything, it's, what happens is that people have this braggadocio attitude, this almost sort of sleep machismo attitude that you're very proud to tell people how little sleep that you're getting, as though it's, you know, a badge of honor. I see that in some people, not all, not all people, but some people. So I think to change that part of the sleep discussion and bring it into the health equation, we need to destigmatize sleep, uh, in a way, too. I think those are at least two of the reasons why it's been left out in the cold.

    18. RC

      Alarm clocks stop the single most important behavioral experience we have.

    19. RF

      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-

    20. RC

      Yeah

    21. RF

      ... 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 20 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 want to come up with innovative solutions to complex problems, a night of sleep achieves that. We're also discovering that, uh, the, the, 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.

    22. RC

      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.

    23. RF

      Yeah.

    24. RC

      And I think in many ways, the way we experience the world- ... is influenced by our levels of sleep.

    25. RF

      Yeah. I think that's what, you know, doing the research for, for the book, the realization that the tired brain remembers negative experiences but forgets the positive ones. So tired individual's 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.

    26. RC

      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-

    27. RF

      Yeah

    28. RC

      ... and then if you look at the data in terms of how sleep-deprived we are-

    29. RF

      Yeah

    30. RC

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

  13. 1:05:52 – 1:19:25

    Body clocks and morning light: why the morning matters for nighttime sleep

    1. RC

      Yeah. You mentioned the clock, and there's, there's a lot in your book about our body clock, our body clocks, I should say-

    2. RF

      Yeah. Yeah

    3. RC

      ... and what they all do, what influences them. One thing I've felt and experienced 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?"

    4. RF

      Yes.

    5. RC

      "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.

    6. RF

      Yep.

    7. RC

      But I thought it would be useful, particularly through the lens of the clock, I guess, talk about the morning. Why is what we do first thing in the morning so important for our ability to sleep at night?

    8. RF

      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, 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.

    9. RC

      Yeah, so this is fascinating. There, there's so much there. So we live according to 24-hour days.

    10. RF

      Yeah.

    11. RC

      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.

    12. RF

      Exactly.

    13. RC

      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.

    14. RF

      [laughs]

    15. RC

      Uh, you know, do you know what I mean?

    16. RF

      Yeah, yeah.

    17. RC

      So, so, so when we go on a 12-hour flight to LA from London-

    18. RF

      Yeah

    19. RC

      ... 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-

    20. RF

      Mm

    21. RC

      ... 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-

    22. RF

      Yes

    23. RC

      ... right? So can you help us-

    24. RF

      Okay

    25. RC

      ... put all those things together?

    26. RF

      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-

    27. RC

      Oh

    28. RF

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

    29. RC

      [laughs]

    30. RF

      ... but that's why, why it is. But there's a, there's an even-

  14. 1:19:25 – 1:45:34

    Evening light, devices, and alertness: what matters most before bed

    1. RF

      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-

    2. RC

      But this is in the 1980s, right?

    3. RF

      Yeah, in the late, the late '80s.

    4. RC

      Yeah, I read that this morning in your book, and, and that shocks me because 1987-

    5. RF

      Yeah

    6. RC

      ... right, 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 re-read 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-

    7. RF

      Oh, oh

    8. RC

      ... that we don't know at the moment" [laughs]

    9. RF

      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?" And we'd 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."

    10. RC

      Wow.

    11. RF

      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.

    12. RC

      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.

    13. RF

      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.

    14. RC

      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 10 to 30 minutes if you can-

    15. RF

      Yeah

    16. RC

      ... within half an hour of waking up. Okay, so that's very clear guidance. I wanna, I wanna know your view on that.

    17. RF

      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- and, 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, 10,000 lux for 30 minutes, uh, from a light box will also set the clock. So, so the data there are pretty solid.

    18. RC

      Now, we say advance the clock. What if someone doesn't want to advance their clock-

    19. RF

      [laughs] Yeah

    20. RC

      ... 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."

    21. RF

      [laughs]

    22. RC

      And I, 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?

    23. RF

      It, it, it, you, it probably will have a small effect.

    24. RC

      [laughs]

    25. RF

      I mean, the, the tricky thing is for those 10% of individuals who are really morning types, and, a- a- and it's f- it, 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 beyond-

    26. RC

      Yeah

    27. RF

      ... where they want to be, and they sort of complain bitterly that, um, you know, "God, all my friends didn't want me to stay up." Of course, for the work environment, it's great.

    28. RC

      Yeah.

    29. RF

      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.

    30. RC

      So you're happy with that 10 to 30 minutes natural light recommendation.

  15. 1:45:34 – 2:37:01

    Sleep as medicine: immune, metabolic, heart, and mental health evidence—and practical sleep rules

    1. MW

      Yeah. You know, and it's no- we, we think, "Well, that sounds almost too good." But don't forget, you know, it took Mother Nature 3.6 million years to evolve this necessity of eight hours of sleep in place. Which I should note, by the way, that if you look at the data, back in the 1940s, the average adult was sleeping about, uh, 7.9 hours of sleep. Now that number here in the United Kingdom is closer to 6 hours and 30 minutes. In other words, within the space of 100 years, which is a blink of an evolutionary eye, we've lopped off almost 20% of our sleep need. You know-

    2. RC

      Wow

    3. MW

      ... how could that not come with demonstrable health and disease consequence? So I think, you know, there's that component there, but I love what you were saying that, you know, in medicine we're often, or even in research and pharmaceuticals, we're often trying to sort of manipulate one pathway in one area of the metabolic system or in one aspect of the immune system-

    4. RC

      Yeah

    5. MW

      ... or one feature of the cardiovascular system, and, you know, sleep affects all of those. And we can... You know, I'll give you an example. Firstly, we know that after, if you get a patient and you have them who- um, sleeping just six hours for one week, this is someone, let's say, who is healthy. At the end of that one week of short sleep, their blood sugar levels are disrupted so significantly that they would be pre-diabetic, that you would diagnose them as being in a state of pre-diabetes, let me say.

    6. RC

      Just from sleep deprivation.

    7. MW

      Just from sleep deprivation. We control all of the factors. Um, you can also speak about sleep loss and, uh, the cardiovascular system, and all it takes is one hour of lost sleep. Because there is a global experiment that's performed on 1.6 billion people across 70 countries twice a year, and it's called daylight savings time. [laughs]

    8. RC

      Yeah.

    9. MW

      And it turns out that when you look at that data, in the spring when we lose an hour of sleep, we see a subsequent 24% increase in heart attacks as a result.

    10. RC

      It's just incredible, isn't it?

    11. MW

      But in the autumn, you know, when we gain an hour of sleep, we see a 21% reduction in heart attacks.

    12. RC

      So, so the data's there on a, on a global level-

    13. MW

      The data's-

    14. RC

      ... let's say, just from that

    15. MW

      ... you know, is striking. You know, and you can even think, you know, you speak a lot about, um, you know, the immune system. It's so key for our health.

    16. RC

      So what do- T- tell us, what does sleep do for the immune system?

    17. MW

      So firstly, we can look on both sides of the coin. What happens when we don't get enough sleep? Firstly, we know that people who are sleeping five hours a night are four times more likely to catch a cold than those people who are sleeping eight hours or more.

    18. RC

      Wow.

    19. MW

      Striking study. Very well-controlled study. Um, we also know that it doesn't take one week of, you know, short sleep deprivation. One night is enough. What we've found is that if you take healthy individuals and then we limit them to just four hours of sleep for one single night, what we see is a 70% drop in critical anti-cancer fighting immune cells called natural killer cells, which are these wonderful sort of immune assassins that, you know, help decrease our, you know, sort of, you know, cancer risk.

    20. RC

      Yeah.

    21. MW

      And-

    22. RC

      And, and help us fight infection.

    23. MW

      And fight infection.

    24. RC

      Part of our innate immune system.

    25. MW

      That, exactly. Part of that critical innate immune response. Flip the, the, the sort of the side of the coin and now what we find is that when you get sleep, there is a change in what we call the autonomic nervous system, which is sort of this automatic part of our nervous system. And that automatic nervous system is split into two branches. One that is sort of like the accelerator pedal that gets us revved up, triggers the fight or flight response. The other is the brake that sort of calms us down. And when we go into deep sleep, we apply that brake to the nervous system and everything quiets down. Heart rate decreases. Deep sleep is the most wonderful form of natural blood pressure medication that you could ever wish for.

    26. RC

      Yeah.

    27. MW

      But one of the other things is that we see, as that nervous system quiets down, levels of things like cortisol drop down, that stress-related chemical, and it's during that time that the body goes into an immune stimulation mode, and it's where essentially you're going to restock the armament of your immune army-

    28. RC

      Wow

    29. MW

      ... so that when you wake up the next day, you can battle and fight infection. What's also fascinating, and I love this data, and this tells you just how critical sleep is to, to a fighting, uh, for our health. If you look at people who become infected, or you actually infect them in the experimental laboratory, let's say, with-

    30. RC

      Yeah

Episode duration: 2:52:29

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