Why Sleep is the Most Important Pillar of Health with Professor Matthew Walker | FBLM Podcast

Dr. Rangan Chatterjee 0:00 I'm absolutely delighted that I've got the opportunity to interview my next guest. He is one of the world's leading sleep researchers, and he's author of the absolutely fantastic book, the international bestseller, Why We Sleep. It's Professor Matthew Walker. Matthew, welcome to the podcast.

Matthew Walker 0:18 Thank you so much for having me. It's a delight to be chatting again. Lovely.

Dr. Rangan Chatterjee 0:22 Yeah. Matt, we, obviously, we, we sort of first had contact over email, um, and we got to do a Facebook Live conversation on my Facebook page, which proved a huge hit, uh, with my audience. But, you know, talking over Skype with technology, albeit fantastic, it isn't quite the same as being face-to-face here. So I'm delighted that you're over here now in London doing a bit of promotion for your book.

Matthew Walker 0:47 It's lovely to finally meet you in person, Rangan.

Dr. Rangan Chatterjee 0:49 Yeah, it's, it, it's superb. But I thought we might start just by asking you, how many days have you been in London now for?

Matthew Walker 0:59 Um, I arrived on Saturday, so this is my fourth day.

Dr. Rangan Chatterjee 1:03 Your fourth day. So, look, at the moment, it's about, well, we've probably just gone past 11:00 AM in the UK, which probably means, I'm guessing it's about 3:00 AM in San Francisco.

Matthew Walker 1:16 [laughs]

Dr. Rangan Chatterjee 1:16 So what's going on with your body clock at the moment?

Matthew Walker 1:19 So I've-- You can't cure jet lag. There are no cures right now. But if you understand how it works, you sort of can hack the system a little bit. What we know is that for every day that you've been in a new time zone, your body can actually catch up by about one hour. So that sort of extra day basically acts like a set of fingers on a wristwatch, and it will just kind of tweak it one hour every day. So I am now four days in. I am only offset by

Matthew Walker 1:50 four hours relative to California time. Normally, I'm offset by a total of eight hours. I've been here four days, one hour for every day. I'm now four hours separated. That would be the classic case if you just sort of let passage of time work. However, you can speed up that sort of tweak. You can get those fingers to work harder on the wristwatch dial, sort of get closer and faster to the natural new time zone in the following ways. Firstly, you should get lots of daylight exposure in the morning in the new time zone. So whenever you arrive, and then for all of the days afterwards, make sure that you get about 20 to 30 minutes of natural daylight. Doesn't matter if it's cloudy, just that brightness alone is key. If you do go outside, the temptation is to put shades on. Don't do that. Even, even if it looks, you know, you look fantastic and you look very cool-

Dr. Rangan Chatterjee 2:41 [laughs]

Matthew Walker 2:41 ... just for the morning, all I would ask you is don't put shades on because it will diminish that light reset function, because it's light that's going to help reset and fast-forward that clock. The other critical thing is diet or at least eating. Food is just as powerful a trigger for resetting your circadian rhythm as light is. We only discovered this probably about sort of eight or nine years ago. And so start eating meals at the regular times in the new time zone. Eat when everyone else is eating. Don't eat when you, your body tells you that you're hungry. It's harder to do, but that will help you get back into set as well. The other trick, however, is that if you go out in the afternoon, um, that's fine, no problem at all. But the afternoon is the time to wear shades. That's the time to start blocking the light, to start to force your body to think it's nighttime, it's darkness. Even though your body clock, California for me, is just starting to wake up, I need to shroud my brain in darkness to try and help reset it. So bright light in the morning. Get out in the afternoon, that's fine, but wear shades, and then lots of darkness at night. Eat meals regularly, and then try and exercise, usually in the morning if you can. If you do those three things, you can strategically treat jet lag. You can't cure it. You'll still feel a little bit miserable. Um, the only other trick I would say is during traveling. I see a lot of people make the mistake of when they sleep during travel. It's very natural. If I'm flying over from San Francisco, um, to London, usually leave around 5:00 PM in the evening.

Dr. Rangan Chatterjee 4:22 Yeah.

Matthew Walker 4:22 Most people, and let's say it's an 11-hour flight, most people will wait until the last sort of four or three hours and go to bed then and sort of sleep late, and I normally arrive about 11:00 in the morning London time. That's not the ideal thing to do. Try to sleep on your flight either in, early in the flight or in the middle of the flight. And the rule of thumb is make sure that whatever time of, uh, you want to go to bed in the new time zone that evening, let's say it's, you know, 10:00, count back at least 12 hours or 10 hours. That's the time that you have to wake up on the plane and then stay awake.

Dr. Rangan Chatterjee 5:01 Yeah.

Matthew Walker 5:01 You need to build up lots of that healthy sleepiness for you to then fall asleep and stay asleep in the new time zone. Don't sleep too late into the flight. If it's late and you still haven't been sleepy, I would suggest forgo sleep, which sounds strange-

Dr. Rangan Chatterjee 5:16 Wow

Matthew Walker 5:16 ... from someone like me. Push through for the rest of the day and then just get to bed early and you'll get into set.

Dr. Rangan Chatterjee 5:22 So thanks for sharing those tips, um, in terms of how you have tried to combat jet lag. But what's interesting as I hear them is that some of the tips are actually pretty similar to the recommendations you would make to people who are not crossing time zones but are just simply trying to improve their quality of sleep. Um, so we'll get into that in just, just a, a, a few moments. I actually am, I'm 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 have 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-

Matthew Walker 6:40 Yeah

Dr. Rangan Chatterjee 6:40 ... my screen-

Matthew Walker 6:41 Yeah

Dr. Rangan Chatterjee 6:41 ... 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.

Matthew Walker 6:53 Hm.

Dr. Rangan Chatterjee 6:54 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.

Matthew Walker 7:12 Yeah.

Dr. Rangan Chatterjee 7:12 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-

Matthew Walker 7:22 [laughs]

Dr. Rangan Chatterjee 7:23 ... you know, let's go into caffeine. I mean, how much of a sleep disruptor is caffeine?

Matthew Walker 7:28 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.

Dr. Rangan Chatterjee 7:42 Yeah.

Matthew Walker 7:42 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 them those will, will actually take away those fingers on the wristwatch-

Dr. Rangan Chatterjee 8:01 [laughs]

Matthew Walker 8:01 ... and sort of, or slow the progression down. Um, but caffeine is a misunderstood drug. Certainly m- everyone-

Dr. Rangan Chatterjee 8:08 It's a drug, right?

Matthew Walker 8:08 It is-

Dr. Rangan Chatterjee 8:09 You use the term drug, and that's interesting

Matthew Walker 8:10 ... 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 [laughs] about-

Dr. Rangan Chatterjee 8:30 Yeah. Wow

Matthew Walker 8:30 ... 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.

Dr. Rangan Chatterjee 9:15 Wow.

Matthew Walker 9:15 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-

Dr. Rangan Chatterjee 9:27 Yeah

Matthew Walker 9:27 ... '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.

Dr. Rangan Chatterjee 9:37 Yeah, it's a, it's a, it's a huge problem. Yeah.

Matthew Walker 9:38 It- it's, it's a m- I th- I think it's a big problem in society if you... I mean, [laughs] 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-

Dr. Rangan Chatterjee 9:59 And well, cafe culture is just growing at, you know, exponentially now.

Matthew Walker 10:03 Yeah.

Dr. Rangan Chatterjee 10:03 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.

Matthew Walker 10:08 Yeah.

Dr. Rangan Chatterjee 10:08 You know, you hang out with your friends. You meet up. You get your drink. Typically, it'll be a caffeinated drink.

Matthew Walker 10:14 Yeah.

Dr. Rangan Chatterjee 10:14 Um, we've now got school kids. You know, I saw in a local village I was walking through recently, you know, after school, you know, I popped into a cafe to get, I think, a, a bottle of water. Uh, I can't actually remember, but I, I popped in, and I saw a group of school kids. They must have been maybe 13 or 14. After school, they're sitting in the cafe with their caffeinated drinks, you know, doing their homework together, catching up or whatever. I thought, "Wow, you know, this has become endemic in society now." We, you know, you call it a drug. I agree with you. It is a psychoactive substance that we, you know, we, we use liberally. We let our children have it. We, you know, we're not even... You know, we often don't think about the implications of that, and so many patients of mine tell me that, "Dr. Chatterjee, I know, you know, if caffeine can be a problem for some people. I'm not one of those. Caffeine is fine for me." But more often than not, when they either reduce their intake or cut it out completely, the sleep quality goes up.

Matthew Walker 11:12 Yeah.

Dr. Rangan Chatterjee 11:12 And, um, uh, and you know, Satchin Panda, um, Professor Panda, who, you know, I know you know very well. You both sort of follow each other's research. He was on the podcast a few weeks ago, and, you know, he was saying routinely every year he will, he will have a bit of a detox from caffeine. He'll go off caffeine.

Matthew Walker 11:29 Yeah.

Dr. Rangan Chatterjee 11:29 And he says, "When I do that, yeah, I have a headache for a few days, but my sleep always improves. I've got more energy, and my productivity dramatically increases." And I think that says it all, really.

Matthew Walker 11:40 It does, and I, you know, a number of points that you made that I'd love to circle back around to. Firstly, caffeine is the only psychoactive stimulant that we do give to our children readily, which, you know, is, I think, a concern. And I'm not trying to be sort of, you know, f- finger-pointing or finger-wagging. Again, I think it's just that parents probably don't understand the impact of caffeine in that regard. Um, I think the, the second point comes onto your comment of some people say, "Look, I'm one of those people who can drink a cup of coffee in the evening, have an espresso after dinner, and I fall asleep fine, and I stay asleep." Now, even if that's true, there was an alarming study that was done where they gave people just one single cup of coffee, a dose of 200 milligrams of caffeine, standard cup of coffee, and then they measured the quality of their deep sleep by tracking these big, powerful brainwaves, these glorious, beautiful, deep brainwaves that bathe, um, uh, all of our brain during deep sleep at night, and it helps also restore the body. And what they found was that just one dose of caffeine in the evening decreased the amount of deep sleep by 20%. Now, you would have to normally age by about 15 years to produce that type of a deficit in your deep sleep, or you can do it every single night by having a cup of coffee. And what's interesting is that those people will wake up the next morning, they won't remember waking up 'cause they may not have woken up, but the quality of their deep sleep was so poor that they will still then feel unrestored and unrefreshed by their sleep. They-

Dr. Rangan Chatterjee 13:12 I need more caffeine.

Matthew Walker 13:13 And, and so here is the irony, that now they're starting to reach for two cups of coffee rather than one, and so develops this dependency cycle, this sort of addiction spiral, as it were. So I think people are perhaps unaware of the, the true impact of caffeine, how long it sticks around within your system, and even if you feel that you're immune to that evening cup of coffee, how it will still impact your sleep even though n- consciously you know nothing about it.

Dr. Rangan Chatterjee 13:39 Well, I think, you know, you raised a really important point there, Matthew, about, you know, knowledge and awareness. You know, none of us are pointing fingers, you know, we, you know, I understand caffeine is everywhere, you know. I probably used to over-drink caffeine, uh, and I've altered my behavior as I've learnt more and more about the research. And I think what we're trying to do is raise awareness of, you know, caffeine is a sleep disruptor. There's just no question about that. Uh, and s- you know, we can dress it up any way we want, but it is a sleep disruptor. So if anyone is listening to this, if that story that Matthew just mentioned resonates with you, I'd really sort of encourage you to have a little think about your caffeine usage and just see if, can you, you know, can you wind it down a little bit? Can you see, you know, bit by bit, if by reducing it, it improves your quality of sleep? The recommendation I make h- uh, in my book is enjoy your caffeine before noon. And I say enjoy 'cause I get it. Uh, people love it. Well, I love a good cup of coffee, but I will not have caffeine after midday.

Matthew Walker 14:39 Yeah. And I, you know, I've now actually done what Satchin has done. I, I would, I routinely go through sort of a caffeine detox, um, and right now I'm caffeine-free. But you know, I too would enjoy that cup of coffee or a nice strong cup of, you know, um, Yorkshire tea - [laughs] I have no relationship with them, by the way - um, in the mornings. And I also love the, the coffee culture as well. You know, I go out with friends, and we grab coffee all the time, and I love that, and I, I want people to embrace it 'cause I think it's fantastic that there's a social movement sort of circulating around that. Um, all I would say, though, is that, you know, decafe- caffeinated coffee is, is actually really quite good. And I would struggle, you know, I'd love to do the sort of the, you know, the Coke-Pepsi challenge with decaf and caffeinated. Just in terms of the taste, you would probably notice that it wouldn't give you sort of the shakes or that sort of slightly anxious state, and you probably know the difference. But I've really become enamored with decaffeinated coffee-

Dr. Rangan Chatterjee 15:37 Wow

Matthew Walker 15:37 ... and all of its flavors, and I love the cafe bar culture, so love to embrace that. But I do like what you're saying, uh, about sort of patients just thinking a little bit about caffeine and considering it, and just trying the, try the experiment, you know. Sort of set yourself the task, give it a go, and see if it works for you.

Dr. Rangan Chatterjee 15:55 Yeah. I, I remember about a month after my book came out, uh, someone tweeted me and said, "I, I never, ever thought that caffeine was a problem for me, but I've, I've read your book. I've taken your recommendation. I've, I've, how, I now only have two cups of coffee, and I have it before noon, and I've never slept this well in over 30 years." And it's just incredible how such a common thing that people are doing day to day may be impacting our sleep. And I think you make a really good point that it's like a self-fulfilling prophecy. The more caffeine you drink, the more you need. The more dependent you become, the less good your sleep is, and, and it just continues. I think we also have to highlight, we're talking about coffee, but I think tea-

Matthew Walker 16:35 Yeah

Dr. Rangan Chatterjee 16:35 ... w- would be similar 'cause it contains caffeine. Green tea, you know, a herbal tea that often people switch to when they're not having tea or coffee, is also a highly caffeinated drink, so may affect you. You mentioned decaf coffee. You know, I've read some reports are saying that decaf coffee does contain some caffeine.

Matthew Walker 16:53 Yeah.

Dr. Rangan Chatterjee 16:53 Do you know much about that?

Matthew Walker 16:54 So decaffeinated coffee is not no-caffeinated coffee. [laughs] So you do have to be, uh, you know, somewhat mindful of that. Um, and they looked, and you can sort of search around on the internet. There's some good sites that will describe exactly how much. Some brands have very little caffeine at all. Um, other brands, however, I was surprised to find, can have up to 20%, uh, caffeine in. So you have five cups of those, you know, and you're well on your way to a standard cup of coffee. So you do have to be a little bit careful. Um, but it's certainly a good way, if you're thinking about trying to come off caffeine, to sort of psychologically still treat yourself with that, you know-

Dr. Rangan Chatterjee 17:31 Exactly

Matthew Walker 17:32 ... pleasure. Um-

Dr. Rangan Chatterjee 17:32 And, and, and it tastes great, right?

Matthew Walker 17:33 Yeah, it does.

Dr. Rangan Chatterjee 17:34 [laughs]

Matthew Walker 17:34 It do- really, it, it, it's, it's not too bad.

Dr. Rangan Chatterjee 17:37 So caffeine is something that a lot of us do in the morning. Um, we're also gonna talk a little bit later about alcohol, which is something that people often use in the early evening or late evening to help them unwind for bed. But you know, before we go deep into alcohol, 'cause I think that's something that people are incredibly fascinated about, 'cause I think that whole term of a nightcap, you know, people-

Matthew Walker 17:57 [laughs]

Dr. Rangan Chatterjee 17:58 It's there in, in our vernacular now, how it's something that can help you just slip off into sleep. Or can it? We'll fi- we'll find out shortly.

Matthew Walker 18:04 [laughs]

Dr. Rangan Chatterjee 18:05 But, um, you know, listeners to my podcast know that I, I talk about these four key pillars of health that I think have the most impact on the way that we feel, but also that we've got some degree of control over.

Matthew Walker 18:19 Mm.

Dr. Rangan Chatterjee 18:19 Food and movement, 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.

Matthew Walker 18:36 Yeah. You know, I used to think that sleep maybe 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.

Dr. Rangan Chatterjee 19:15 Wow.

Matthew Walker 19:15 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 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, increase in 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.

Dr. Rangan Chatterjee 20:25 Wow.

Matthew Walker 20:25 What's even more frightening, however, is that your risk for injury increases when you are exercising but not well-slept.

Dr. Rangan Chatterjee 20:32 This is incredible.

Matthew Walker 20:33 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.

Dr. Rangan Chatterjee 21:17 Yeah.

Matthew Walker 21:17 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.

Dr. Rangan Chatterjee 21:39 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, um, 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.

Matthew Walker 22:22 Yeah.

Dr. Rangan Chatterjee 22:22 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?

Matthew Walker 22:28 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.

Dr. Rangan Chatterjee 22:36 Of course.

Matthew Walker 22:36 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-

Dr. Rangan Chatterjee 22:51 A hot bath, right?

Matthew Walker 22:52 A hot bath is best-

Dr. Rangan Chatterjee 22:53 Yeah

Matthew Walker 22:53 ... 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.

Dr. Rangan Chatterjee 23:28 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 have, 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?

Matthew Walker 24:13 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 9 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]

Dr. Rangan Chatterjee 24:50 Oh, love it

Matthew Walker 24:50 ... 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.

Dr. Rangan Chatterjee 25:32 Yeah.

Matthew Walker 25:32 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.

Dr. Rangan Chatterjee 26:12 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.

Matthew Walker 26:42 Yeah.

Dr. Rangan Chatterjee 26:43 They want to get to work and perform well in their job 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 talks about this idea of 90-minute sleep cycles. I don't know if you've read his book or you're familiar with, with-

Matthew Walker 27:34 Yeah

Dr. Rangan Chatterjee 27:34 ... his recommendation.

Matthew Walker 27:35 Yeah.

Dr. Rangan Chatterjee 27:35 But I find it, you know, he talks about this whole idea of five 90-minute cycles that we need throughout the day, and I know some people found that quite helpful to take the pressure off them at night. So quite a few questions there, Matt-

Matthew Walker 27:47 [laughs] Yeah

Dr. Rangan Chatterjee 27:47 ... but I wonder if we could try and, just try and go into those, those areas a little bit.

Matthew Walker 27:51 Yeah. So right now, the recommendation is for most adults get seven to nine hours of sleep. And to get, by the way, to get seven hours of sleep, you probably need at least a seven-and-a-half-hour sleep opportunity. I think that's what many people miss in recommendations from sort of experts. They say, "Get your seven hours of sleep," so people think that means, you know, "Well, if I go to bed at, you know, 11:00 PM and I wake up at 6:00 AM, then I've got my seven hours of sleep." That's not true. You probably will have only logged about sort of six hours and 40 minutes, and, and that's, that's not enough. So you need to think about the sleep opportunity time as being probably around about eight hours optimally. What we also know is that once you get below seven, we can start to measure objective impairments in your body and in, in your brain as well. The problem is that most people don't realize that they're sleep-deprived when they're sleep-deprived. This is a big problem with sleep loss. And, you know, the analogy I guess would be, um, a drunk driver at a bar. You know, they've had a couple of pints, maybe a few shots, and they pick up their car keys, and they say to you, you know, "Look, I'm fine to drive home."

Dr. Rangan Chatterjee 28:58 [laughs] Yeah.

Matthew Walker 28:58 And you say, "No, I know that you think you f- you're fine to drive home, but trust me, you're not. You are, objectively, you're impaired." It's the same way with a lack of sleep, that our subjective sense is a miserable predictor of objectively how well we're doing with a lack of sleep, and I think that's one of the, um, one of the issues that, um, I try to sort of help dismiss, uh, in terms of a notion. I think the other thing that's problematic too about getting too little sleep is that your baseline level of how you think your health and your wellness is just becomes chronically low, and you accept that as if, "That's just where I am in life. This is just me. This is as good as it can be." And people don't realize that if you're to change something like sleep or stress or diet or physical activity, there's actually a better form of you waiting on the other side of those things.

Dr. Rangan Chatterjee 29:50 Yeah, absolutely.

Matthew Walker 29:51 It just requires perhaps, you know, some knowledge and an invitation to go there.

Dr. Rangan Chatterjee 29:55 Matthew, I c- I call this podcast Feel Better, Live More for a reason, and, uh, it really just echoes what you, what you just said then. You know, when we feel better by, you know, prioritizing sleep, by, you know, looking at these other pillars that I talk about, we get more out of life. We're, we're a better version of ourselves. We have better relationships. We have, you know, you know, much deeper, more meaningful interactions with the world around us when we're feeling better, and I guess you would argue that when we sleep better, we live more.

Matthew Walker 30:25 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.

Dr. Rangan Chatterjee 30:40 Wow.

Matthew Walker 30:41 And so, you know, I think that-

Dr. Rangan Chatterjee 30:42 I think we just need to stop and just let, let that sink in for a minute.

Matthew Walker 30:44 [laughs]

Dr. Rangan Chatterjee 30:45 I think depriving ourselves from sleep will shorten our life.

Matthew Walker 30:49 Yeah.

Dr. Rangan Chatterjee 30:50 Yeah, I mean-

Matthew Walker 30:51 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.

Dr. Rangan Chatterjee 31:07 That's a very powerful statement, one that I absolutely would agree with. Um, have we as a society, I don't think 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?

Matthew Walker 31:36 T- 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-

Dr. Rangan Chatterjee 32:23 Yeah

Matthew Walker 32:23 ... into the public knowledge base or even into medicine.

Dr. Rangan Chatterjee 32:25 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.

Matthew Walker 32:32 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-

Dr. Rangan Chatterjee 33:47 Yeah

Matthew Walker 33:47 ... 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 de-stigmatize 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.

Dr. Rangan Chatterjee 34:25 Yeah. Yeah, absolutely. I mean, I, you know, I've shared this before on the podcast, that a few years ago, for, for me, it was probably when I had kids, actually, because my kids were early risers, and, uh, you know, that's, that's the understatement of the year [laughs] that they were early risers.

Matthew Walker 34:43 [laughs]

Dr. Rangan Chatterjee 34:44 But I realized that if I didn't alter my going to bedtime, I was gonna be exhausted every single day, which is what was happening. And I, and I sort of altered my whole sleep schedule a few years back, and it's something now that I really do prioritize. You know, I will have a shutoff time in the evening after which I'm not on my computer. I'm not working. I will wait 'cause I know that if I don't do that, the next day I won't be performing at anywhere near the level I want to. Um, and, and it [laughs] actually reminds me of that, that Facebook conversation we had, the Facebook Live chat we did.

Matthew Walker 35:17 Yeah.

Dr. Rangan Chatterjee 35:17 So guys, we were trying to schedule this chat for a little while, and-

Matthew Walker 35:20 Oh, I love this. Yeah

Dr. Rangan Chatterjee 35:21 ... we, we, we put a date in, and then, uh, Matthew had to move, move the time, and I got an email, I think, from your publicist saying, you know, "Can we move this time?" And I thought, "Well, that's 9:00 PM UK time. Man, that's really late," because, you know, I've just, I've just written a book saying how important sleep is as well. [laughs] I'm, I'm, you know, trying to educate and inspire my audience that actually these things are really important. So I actually declined your very kind invitation to do it at 9:00 PM.

Matthew Walker 35:46 No, I just actually asked to see if we could change the time.

Dr. Rangan Chatterjee 35:49 Yeah, you probably didn't know.

Matthew Walker 35:49 I certainly, yeah, I certainly wouldn't have suggested that.

Dr. Rangan Chatterjee 35:51 Yeah, I said, "Guys, look, if, if we chat between 9:00 and 10:00, and we talk about how detrimental sleep is and, you know, the, you know, a- and, and all the problems associated with it, yet we're doing it late in the evening for my UK audience, um, we're ex- I'm gonna expose everyone to blue light in the evening-

Matthew Walker 36:08 Yeah [laughs]

Dr. Rangan Chatterjee 36:09 ... on, on their devices, emotionally work them up before bed." I thought, "Actually, you know what? Let's just decline that and do it another time." So I thought that was, that was quite annoying.

Matthew Walker 36:17 That was brilliant.

Dr. Rangan Chatterjee 36:17 Yeah, that was great, wasn't it, though?

Matthew Walker 36:18 Yeah. It was just, you know, for someone to embrace, you know, sort of, uh, w- and practice what they preach. And, you know, and I think for the two of us, you know, a, a lot of people, of course, will ask me, "Well, so how much sleep do you get?" And I will tell them that I do honestly get a non-negotiable eight-hour sleep opportunity every night, and it's n- I'm not trying to be, you know, a poster child for sleep. I'm not trying to just sort of promote the book. If you knew the data as I do, and as I hope people, um, will after reading the book, honestly, you just would not choose to do anything else. And, you know, I don't want to live a shorter life, and I don't want to live a, a shorter life that is filled with, with disease or sickness. And from everything I can tell, sleep is perhaps one of the most democratic, freely available, efficacious forms of, um, of health insurance that you could ever wish for. And as a consequence, the reason I get that much is because for selfish reasons. You know, I just want to be alive and well for as long as possible, and I think, you know, it's interesting hearing you say why you prioritize it. You know, again, it's, uh, selfish is the wrong word, but it's for self-preservation reasons. Um, and one of the things I actually, if I, if you don't mind, I know [laughs] y- this is your podcast and you're interviewing me, but-

Dr. Rangan Chatterjee 37:43 Hey, Matthew, talk about whatever you want. Fire away

Matthew Walker 37:45 ... but, but, but, but I would love to just ask you the question 'cause, you know, when I saw the title of, of the book, you know, and I saw that, you know, there on the front cover was this word called sleep, and it was-

Dr. Rangan Chatterjee 37:55 On, on my book?

Matthew Walker 37:56 On your, on the-

Dr. Rangan Chatterjee 37:57 Yeah, yeah

Matthew Walker 37:57 ... on the front cover of your book-

Dr. Rangan Chatterjee 37:58 Yeah

Matthew Walker 37:58 ... there was this thing called sleep. Relax, eat, move, and sleep, and I well imagined that the first three would be there, of course, from, you know, a, an eminent clinician. But I was surprised by the, the fourth. I was ec- lovely, excited. You know, it was wonderful.

Dr. Rangan Chatterjee 38:14 [laughs]

Matthew Walker 38:14 But tell me, you know, w- where did that decision come from to include sleep? You know, where did you get the awareness from? Where did you get the sensitivity to sleep? You know, was it boots on the ground with patients? Was it in a medical curriculum? Was it personally? Tell me. I, I'd love to know.

Dr. Rangan Chatterjee 38:31 Yeah, I think, Matthew, that's a, it's a great question, really. I mean, my... I guess my journey into this, um, of, of really being keen to promote lifestyle comes from a, you know, a, a real feeling that in medicine we've lost our way a little bit. Now, we're not putting blame on anyone.

Matthew Walker 38:49 Yeah, yeah.

Dr. Rangan Chatterjee 38:49 Um, but I, but I sort of feel that the medical system is set up around acute diseases, acute problems that respond very well to our magic bullet pharmaceutical interventions. But I think the health landscape, even in my career, and I've nearly been seeing patients now for about 20 years, even in my career, I have seen the health landscape of the patients that, that I see change dramatically. Whereas now the bulk of what I see in my daily practice, you know, I say 80% of it is in some way driven by our collective modern lifestyles.

Matthew Walker 39:22 Mm.

Dr. Rangan Chatterjee 39:23 And so I've been delving deep for a few years now in terms of, you know, what are those lifestyle factors that I can leverage with my patients to get a better outcome. And of course, when I first started going on this journey, it was all about food, right?

Matthew Walker 39:37 [laughs]

Dr. Rangan Chatterjee 39:37 You know, it was like, okay, you know, it's all about diet, you know. And if we were having this chat five or six years ago, I would be saying, "You know, most of what happens to us, you know, w- most of our health determinant is, is basically foods." But I disagree now, you know, because I think when you know the science, when you have seen the science, um, as you detail so beautifully in your book, the, the case is compelling. You can't really ignore sleep. So I'm a doctor who wants to get my patients better, like every other doctor. I want to do this in as harmless a way as possible, and I also get very tired of suppressing downstream symptoms. So I wanna go upstream as far as possible to see what lever can I turn that's gonna have all these downstream consequences. And food is one of those things that, you know, food isn't just calories. You know, it's not just fat and carbs. It's information. It changes our genetic expression. So it's information for the body. In a similar way, physical activity can change hormones, can change genetic expression, all these kind of things. And, you know, so obviously, um, that's food. That's movement. Relaxation is a whole piece about stress, you know, which, you know, some research is showing that nine- up to 90% of what we see in primary care may have stress as a factor, which is incredible. And but I always felt I was missing one piece of the puzzle, and, you know, I would see... Like, like if we take autoimmune disease for, for an e- as, as an example. When I see my patients, I often do what's called a timeline, and I look... You know, I say, "Okay, you've got symptoms here today, but let's look at your whole life. Let's see what's been happening sequentially," because I don't think a lot of these chronic conditions just happen overnight. There's been a buildup for a period of time, for a period of years. And I would often see with autoimmune conditions that, you know, just a few months,

Dr. Rangan Chatterjee 41:27 sometimes just one month before the onset of symptoms, I would see either a, either, you know... Well, not either. I would often see a really stressful episode happen that would reduce the quality of people's sleep, and then I'd see symptoms come on.

Matthew Walker 41:43 Yeah.

Dr. Rangan Chatterjee 41:44 And as a doctor, I always want to learn from my patients. So, you know, your question is, where does this come from? Well, primarily, it's come from listening to my patients and listening to the stories that they tell me because, you know, you're, you know, one of the world's eminent researchers of sleep. I love research, but I also love real life, what happens at the coalface when I'm seeing patients. What do they tell me is working? What do they tell me they're struggling with? That also influences a lot of my recommendations as well as the science. You know, if you can marry those two together, I think that's when we can make a real difference with people. And I also went to a conference in, uh, San Diego about two years ago, and the whole conference was on sleep and relaxation and, and rest and, and I think it was, uh, Phyllis Zay. Do you know Phyllis?

Matthew Walker 42:28 Phyllis Z. Yeah, yeah.

Dr. Rangan Chatterjee 42:29 Yeah, Phyllis Z.

Matthew Walker 42:29 Yeah.

Dr. Rangan Chatterjee 42:30 She gave a couple of keynotes there. Um, and I thought, God, this really is whetting my appetite. It's really reinforcing what I'm seeing in my practice. As I say, when you look at the research, I thought, well, how can I write a lifestyle book that is, that is to empower people to take control of their health and not cover sleep? You know-

Matthew Walker 42:49 [laughs]

Dr. Rangan Chatterjee 42:49 ... I can't do it. I, I just, you know, I can't, I just can't do it.

Matthew Walker 42:52 Well, what's so, so interesting about that is, you know, you had, you know, all of this time at medical school in practice, you know, and it took a conference-

Dr. Rangan Chatterjee 42:59 Yeah

Matthew Walker 42:59 ... you know, that you, you know, through your own sheer interest and desire to try and help-

Dr. Rangan Chatterjee 43:04 My own money, my own sort of annual leave to go and do this stuff-

Matthew Walker 43:06 Yeah, yeah

Dr. Rangan Chatterjee 43:06 ... 'cause I'm interested.

Matthew Walker 43:07 That's where you got your sleep education. And, you know, that, that strikes me as, as so, you know- Unfortunate. I, you know, I want to think, I want to work with medical systems to try and increase, you know, a sleep education component, because wouldn't it be wonderful if all of our primary care physicians here in the United Kingdom were, you know, as sleep-aware and sleep-motivated as you are. And I'm sure they would be delighted to receive that information. You know, I know, have lots of friends here who are, who are doctors and, you know, I know that they would embrace that and would love to try and increase wellness in their patients. But there's just no pathway that we've engineered in the medical system to gift them with that knowledge and dispense wellness to their patients, because sleep really is the tide that raises all of the other health boats. It's just as you said, it's the superordinate node that if you manipulate it, you know, it's like the Archimedes lever, you pull that, everything else-

Dr. Rangan Chatterjee 44:04 It's-

Matthew Walker 44:04 ... you know, can start to come into place.

Dr. Rangan Chatterjee 44:05 Yeah, this, you get the sleep, but it affects your brain, it affects your hormones, it affects your genetic expression. It affects-

Matthew Walker 44:10 Yeah

Dr. Rangan Chatterjee 44:11 ... all these sort of things that we might be looking for drugs to, to affect those individual pathways, but you can improve a lot of them-

Matthew Walker 44:17 By-

Dr. Rangan Chatterjee 44:17 ... by improving your sleep.

Matthew Walker 44:18 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, 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-

Dr. Rangan Chatterjee 45:08 Yeah

Matthew Walker 45:09 ... 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's say-

Dr. Rangan Chatterjee 45:35 Just from sleep deprivation

Matthew Walker 45:36 ... 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]

Dr. Rangan Chatterjee 45:56 Yeah.

Matthew Walker 45:56 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.

Dr. Rangan Chatterjee 46:06 That's just incredible, isn't it?

Matthew Walker 46:07 But in the autumn, you know, when we gain an hour of sleep, we see a 21% reduction in heart attacks.

Dr. Rangan Chatterjee 46:12 So, so the data's there on a, on a global level-

Matthew Walker 46:15 The data's-

Dr. Rangan Chatterjee 46:15 ... let's say, just from that

Matthew Walker 46:16 ... 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.

Dr. Rangan Chatterjee 46:22 So what do- T- tell us, what does sleep do for the immune system?

Matthew Walker 46:26 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.

Dr. Rangan Chatterjee 46:39 Wow.

Matthew Walker 46:39 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.

Dr. Rangan Chatterjee 47:12 Yeah.

Matthew Walker 47:13 And-

Dr. Rangan Chatterjee 47:13 And, and help us fight infection-

Matthew Walker 47:14 And fight infection

Dr. Rangan Chatterjee 47:14 ... part of our innate immune system.

Matthew Walker 47:16 The, 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.

Dr. Rangan Chatterjee 47:57 Yeah.

Matthew Walker 47:57 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-

Dr. Rangan Chatterjee 48:18 Wow

Matthew Walker 48:18 ... 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, uh, 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-

Dr. Rangan Chatterjee 48:40 Yeah

Matthew Walker 48:40 ... sort of a, a cold, uh, vaccine or, um, you immediately trigger increased sleepiness and increased amounts of deep sleep. And it turns out that the infection indicates to the immune system that you're under attack, and the immune system will actually signal to the sleep system within the brain We need more sleep. Sleep is the best battle force that we have right now to combat this assault. And so that's why when you're sick, all you tend to want to do is just curl up in bed and go to sleep. The reason is because your body is trying to sleep you well.

Dr. Rangan Chatterjee 49:20 It's an appropriate response to what's going on, right?

Matthew Walker 49:22 Exactly. It-

Dr. Rangan Chatterjee 49:23 Our bodies are pretty clever, right?

Matthew Walker 49:25 It- they are remarkably clever. You know, m- m- again, Mother Nature's figured this out. And so she brings up this thing called sleep, which I would argue is probably like the Swiss Army knife of health. You know, whatever ailment you are facing, it is more than likely that sleep has a tool in the box to try and help fight it.

Dr. Rangan Chatterjee 49:42 That's so key. Whatever ailment you're facing. Guys, if you listen to this, whatever you're suffering from, whether it's, you know, a lack of energy on a day-to-day basis, or whether it's that you're worried about your risk of developing a chronic disease such as type 2 diabetes or heart problems as you get older, you know, what Matthew is saying, what Professor Walker is saying is that sleep, improving your quality of sleep, is gonna help you with all these different facets. It's gonna help reduce your risk, it's gonna help increase your energy. It's also gonna reduce your risk of actually getting disease in the future, which is just absolutely incredible. I mean, we are gonna move on to, um, tips, 'cause I know many of you will be thinking, "Okay, this is all great," you know. "I, I'm sort of hearing about all these things that sleep does, but how do I get more?" So we're gonna, we're gonna come to that shortly. But there's so much I want to talk to you about, Matthew. I mean, I think we could easily make this, like, a, a full-day podcast.

Matthew Walker 50:34 [laughs]

Dr. Rangan Chatterjee 50:34 I, I'm that fascinated in this. But-

Matthew Walker 50:36 I would love to return at some point, should you wish me to.

Dr. Rangan Chatterjee 50:38 Yeah. Well, 100%. But I think, you know, what you said about, um, medical school training, I think, I think it's very important because pretty much everything that I put in here, and then the last quarter of the book is on sleep, I am not convinced that any of that came from my medical school training.

Matthew Walker 50:56 Really?

Dr. Rangan Chatterjee 50:57 So that was all self-taught from, you know, spending hours on PubMed, reading research, going to conferences, trying to learn more because I wanted to help my patients more. And I thought, "You know, I need to know more about this so I can actually do my patients, you know, and give them a better service." Um, so you're saying that, you know, maybe medical students, uh, may, may get maybe, uh, two hours or so, and that you'd love to sort of try and help that and get, you know, maybe a sleep curriculum into medical schools. And-

Matthew Walker 51:26 Yeah

Dr. Rangan Chatterjee 51:27 ... this really, you know, I think one of the reasons we get on so well is there's so much synergy in our, in our viewpoint in terms of how we think this needs to change. So what I've done over the past six months is, um, is develop a brand-new course with a colleague of mine, Dr. Panda, called Prescribing Lifestyle Medicine, and it's a one-day masterclass to teach healthcare professionals, but primarily doctors, on the basics of, you know, lifestyle medicine, as, if you will, as a term. You know, so we go into sleep, and we, we teach this framework where they can simply apply these, these four pillars with their patients to start to actually, you know, implement lifestyle medicine. I'd love to, you know, would love to maybe collaborate with you and show you the slides and-

Matthew Walker 52:08 Ah, I'd love, yeah, I'd love to. And, and I've got, you know ... I teach a whole course at, uh, at the University of California, Berkeley, the Science of Sleep. So I've got lots of, uh, slides I'd love to just share and do whatever I could to try and help sort of perpetuate that movement that you've got going. I, it is wonderful. That's exactly what we need.

Dr. Rangan Chatterjee 52:25 Yeah. I know. Maybe we can talk about how we get that into medical schools and, you know-

Matthew Walker 52:28 Yeah, I was going to actually ask you, you know, you know, how could we, you know, um, even collectively, you know, think about trying to, you know, approach sort of medicine here in the United Kingdom and see if we could-

Dr. Rangan Chatterjee 52:39 Yeah

Matthew Walker 52:39 ... try to influence that.

Dr. Rangan Chatterjee 52:39 Well, we'll talk about that off the, off-air from the podcast.

Matthew Walker 52:41 Uh, absolutely. That sounds good.

Dr. Rangan Chatterjee 52:42 Because I think that could be a great collaboration. Um, okay, Matthew, I know you're short on time, and again, we could just go on for so long. I was gonna ask you about, um, sleep and stress, but I think, you know, guys, for those of you listening to this, I cover that in quite a bit of detail, I think, with you on my chat that's on my Facebook page, which is facebook.com/drchatterjee. Um, so guys, you can actually check it out there. But everything that Matthew and I talk about, including that

Dr. Rangan Chatterjee 53:12 Lancet paper that he mentioned, is gonna be in the show notes, which is gonna be at drchatterjee.com/whywesleep. There's gonna be links there to everything Matthew talks about, some of Matthew's articles, his book, all kinds of things. So guys, do check that out after the podcast, and you can do a bit of further reading on those topics that interest you. Um, so yeah, where to go to next? I mean, one thing that we do talk about on that course, and I think we've not spoken about this yet, is about sleep and its role in mental health.

Matthew Walker 53:43 Mm.

Dr. Rangan Chatterjee 53:43 And you know what's interesting, you mentioned bi-directional relationships before and how a lack of sleep can increase our risk of problems, but also sleep can be a treatment as well for various things. And I wonder if you could talk about that in relation to mental health problems such as anxiety and depression, and maybe from there just move briefly onto Alzheimer's, if possible.

Matthew Walker 54:04 Yeah. So we've done a lot of work in this area of sort of sleep and, and mental health. I think the first point to note is that we have not been able to discover a single psychiatric condition in which sleep is normal.

Dr. Rangan Chatterjee 54:18 Wow.

Matthew Walker 54:19 And I think sleep has a profound story to tell in our understanding, uh, in our treatment, maybe even ultimately at some point, our prevention of grave mental illness, and I don't say that flippantly. Firstly, um, we've done some work where you can take healthy individuals, and you can deprive them of sleep for a, a single night. And then you place them inside an MRI scanner, and you look at how their brain has changed, and what we find is that these deep emotional brain centers erupt when you're sleep-deprived. You become a lot more emotionally reactive, impulsive. There's a deep brain center called the amygdala, which is one of the centerpiece regions for the generation of strong emotions. That part of the brain is up to 60% more reactive when you're sleep-deprived relative to when you've had a good, solid night of sleep. And we've also found out-

Dr. Rangan Chatterjee 55:12 That's a huge amount, Ra-

Matthew Walker 55:13 It's a 60%. It's very difficult to usually see that type of a change in the brain without some kind of pathology or drug-

Dr. Rangan Chatterjee 55:19 And I think-

Matthew Walker 55:19 ... sleep deprivation can do it

Dr. Rangan Chatterjee 55:20 ... I think on an intuitive level, most people recognize that when they haven't slept well, you know, they're just a little bit more reactive to things. That, that email from a boss, from their boss, for example, can be easily misinterpreted. You know, are they annoyed at me? Are they... You know, you suddenly start to see-

Matthew Walker 55:35 Yeah

Dr. Rangan Chatterjee 55:35 ... things that aren't there. And I, I, I've just, as I mentioned this before, I've, I've just completed my second book called The Stress Solution, which is gonna come out in January, and I cover a little bit of this that you're talking about in that to really try and show people that, you know, lack of sleep is a stress on our body. And 60%, that's incredible.

Matthew Walker 55:52 Change in the brain, yeah. And I think it really comes... You know, you, you're absolutely right. Many of us have a sense that, you know, I just snapped, dot, dot, dot. You know, those are the words that usually follow a, you know, bad night of sleep or when you've [laughs] not got enough sleep. And we know it all the way down sort of the, the age chain. You know, you think about a parent holding a child. The child is crying, and they look at you, and they say, "Well, they just didn't sleep well last night."

Dr. Rangan Chatterjee 56:16 Yeah.

Matthew Walker 56:16 As if there's some universal knowledge that bad sleep the night before equals bad mood and emotional-

Dr. Rangan Chatterjee 56:20 Yeah, of course

Matthew Walker 56:20 ... reactivity the next day. And it doesn't stop in infancy or childhood or adolescence. It's true when we are adults as well, and we've seen this data. What I think is f- concerning is that that neurological signature that we discovered in that, uh, study is not dissimilar to numerous psychiatric conditions. And in fact, we're now finding significant links between sleep disruption and depression, anxiety, uh, including, uh, um, PTSD, schizophrenia, and most recently and tragically, suicide as well. Um, in fact, a short sleep duration is usually predictive of either suicidal ideation, suicidal thoughts, suicide attempts, and tragically, suicide completion. So I think there are, the sc- the scope, uh, through which sleep is impacting mental health disease, I think is considerable. Um, we used to think in psychiatry that the psychiatric disease was perhaps causing the sleep disruption. I think now we've been forced to change our minds. It's not as though it's completely in the opposite direction. It's not that every psychiatric condition is a sleep disorder. That's not true either. But is it a two-way street? I think that that's probably more tenable. In fact, is it, is the dominant flow of traffic perhaps more in one direction than the other? I think that's also reasonable to assume on the basis of the data right now as well. So I think it's, you know, there's clearly an intimate relationship between our mental health and our sleep health.

Dr. Rangan Chatterjee 57:50 Matthew, the, these, you know, the, the implications of what you just said I think are so profound. We've got to accept, in the 21st century, not only do we not prioritize sleep enough, we're a chronically sleep-deprived society. We're now going through a mental health epidemic. You know, Mind, uh, the charity here in the UK, say that about one in four people in the UK now in any given year are gonna be diagnosed with a mental health problem. Right. Now, that's incredible. And when you hear about that research, we think chronically sleep-deprived society, mental health problems on the rise. Yes, there are other factors, okay? I don't think-

Matthew Walker 58:26 Yeah. Yeah

Dr. Rangan Chatterjee 58:27 ... I, I don't think you or-

Matthew Walker 58:27 We both of us agree on that, yeah.

Dr. Rangan Chatterjee 58:28 We're not trying to say it's all to do with sleep, but what we are trying to say is that sleep is a critical part of the equation and one that we can no longer afford to ignore. Um, so I find that research fascinating. You know, and it makes me think as a doctor, you know, you've mentioned already type 2 diabetes, heart disease, mental health problems such as depression and anxiety. You know, I know at our previous discussion, again, guys, I'd point you to that Facebook discussion because we won't have time to go into this today, but we will when I get you back on the podcast. [laughs] Um, on our Facebook discussion, we did go into Alzheimer's and how, you know, sleep deprivation, you feel may be causative now or a c- or one of the causative factors that causes Alzheimer's disease.

Matthew Walker 59:13 That's right.

Dr. Rangan Chatterjee 59:14 I, I'm thinking, well, you know, I, I, I often say this when I'm teaching doctors. You know, why are we not bringing up sleep quality with pretty much every single patient that walks in through our door?

Matthew Walker 59:26 You know, and you could imagine the cost savings to, um, you know, our economy. In fact, the RAND Corporation recently did a survey, the, the enormous cost of sleep deprivation throughout a number of developed nations. What they found was that a lack of sleep costs most nations about 2% of their GDP. So here in the United Kingdom, that's 30 billion pounds of lost economic value caused by insufficient sleep. In the United States, it was $411 billion. In Japan, it was $138 billion. In other words, if you solve the sleep-loss epidemic, you know, imagine you could almost double the budget for education, or you could perhaps even half the healthcare deficit. You know, Theresa May just this week, uh, as we're speaking here, the prime minister of the United Kingdom, um, described a £20 billion injection of funds into the national healthcare system. Um, a- and th- there's uproar about where that money is going to come from.

Dr. Rangan Chatterjee 1:00:22 Sure.

Matthew Walker 1:00:22 Well, you know, if we just simply prioritized and solved the sleep epidemic or the sleep-loss epidemic, um, we could cover that and still have £10 billion left over. [laughs]

Dr. Rangan Chatterjee 1:00:32 Yeah. Oh, no, and, you know, this, this podcast doesn't tend to be too political, but I would, I would say that, you know, I find a lot of the messaging around the NHS in public very short-sighted. It's about pumping more money in to fix downstream issues, whereas we've got to look at, at prioritizing sleep as a society, whether it's the lighting that's used in hospitals when patients are trying to recover from illness-

Matthew Walker 1:00:52 Yeah. Yeah

Dr. Rangan Chatterjee 1:00:53 ... which isn't very helpful a lot of the time, whether it's teaching our children about it and encouraging good habits, you know, at school but also as parents with our kids, really ingraining. And I think, you know, we've not really got into technology today and how the overuse of technology can potentially be problematic for sleep. Um, uh, I agree. Sleep, it's such a, it's such a simple lever to turn. It's also as... Well, we'll come into tips in just a second, but- You know, so many health inequalities are there from people from different socioeconomic groups. We know in the UK that, you know, you could have as much of a 10-year difference in your life expectancy depending on p- where you live. One thing I like about a focus on sleep, and I appreciate that there are many pressures in deprived communities, you know, financial stresses, uh, you know, maybe a lot of shift work, maybe working multiple jobs.

Matthew Walker 1:01:48 That's right.

Dr. Rangan Chatterjee 1:01:49 So I absolutely understand that and recognize that there are significant issues that we have to overcome. But a lot of the recommendations that we're now gonna talk about that I cover in my book and you cover in detail in your book, most of the recommendations to help people to, you know, get more quality sleep are free of charge.

Matthew Walker 1:02:10 Yeah. You know, I often say that I think sleep is perhaps the most democratically freely available healthcare system for everyone around the world. Now, that's a bit of a glib statement on the basis of exactly what you just said. I think about, and the data is quite frightening, um, we've been looking at this too, at sort of low socioeconomic status, um, communities. And there what you'd see is just what you described, you know, higher general social stress that impairs sleep, um, usually working multiple different jobs, split shifts, working the night work. Often people in those communities are working in the service industry. That usually means that you're either up very early or you're staying in work very late, all of which comprise, you know, factors that work against sleep. So I want to be really appreciative of that.

Dr. Rangan Chatterjee 1:02:55 Yeah. Me too.

Matthew Walker 1:02:55 But still, I think, you know, the tips that we can do right now to start sleeping better every night should be applicable and, for the most part, utilized by just about everyone, as long as you don't have a sleep disorder.

Dr. Rangan Chatterjee 1:03:07 Well, Matthew, normally I, I end the podcast off by asking people for four key tips, um, that people can put into practice immediately, but we don't have to limit it to four. You know, I, I, I want this podcast to inspire people to not only take sleep seriously, but to give them some practical help. So immediately after listening to this, they can put their headphones down and go, "Right, I'm gonna do what Professor Walker's asked me to do. I'm gonna try, you know, these five things today." In your experience, and you've been interviewed all around the world now to do with your book, what, what are those common things that people aren't doing that they could do to help improve their sleep?

Matthew Walker 1:03:44 Yeah. So there's probably, um, maybe five things, um, that people can do right now to get better sleep. The first is regularity. Um, going to bed at the same time and waking up at the same time, no matter what. Even if you've had a bad night of sleep, still try to wake up at the same time. Just understand it's gonna be a tough next day. And then get to bed at the same time that following night, and you'll have a good night of sleep. You'll sort of sleep a little bit more soundly that night. Even if it's the weekday or the weekend, don't do so- what we call social jet lag-

Dr. Rangan Chatterjee 1:04:15 Yeah

Matthew Walker 1:04:15 ... which is sort of where you sort of sleep too late at the weekend, and then on Sunday night you've got to drag your body clock all the way back and try and force it to s- to sleep at a time when you haven't been sleeping before. That's torture. Regularity is key. The second thing is temperature. We've spoken a little bit about that, but keep your bedroom cool. Um, probably around about 18 degrees Celsius, which is colder than most people think. But cooling the room down takes your body into that right sort of thermal space for good sleep. It cools it down. Darkness we've spoken about too, but we are, I think, a dark-deprived society in this modern era, and you need darkness at night to allow the release of a hormone called melatonin, which helps time the healthy onset of your sleep. So yes, it's to do with blue light sort of emitting devices, screens, phones. Those are things that you should try and stay away from in the last hour before bed. But it's not just that. It's also overhead lighting. You know, we don't need to be bathed in electric light all night. In the last hour before bed, just try turning half of the lights off in your flat or in your home. You'd be surprised at how soporific and sleepy you become when you're shrouded in darkness. So that's the third thing. The fourth thing is, I would say, walk it out, and what I mean by that is don't stay in bed if you've been awake for 20 or 25 minutes, either trying to fall asleep or you've woken up and you're trying to get back to sleep. The reason is because your brain is this wonderfully associative device, and it will start to very quickly learn that being in bed is about being awake rather than asleep. So what you need to do is after about 25 minutes, just relax, understand that sleep is not quite here yet. Go to a different room. In dim light, read a book or listen to a podcast. Um, but don't check email, don't eat, because it trains your brain to expect that in the middle of the night. Only return to bed when you are very sleepy, and that way your brain will start to relearn the association that your bedroom is the place of sleep rather than the place of wake.

Dr. Rangan Chatterjee 1:06:23 I think that's a really important tip, Matthew, that, you know, I know even from our first conversation on Facebook, but, you know, whenever I talk about sleep, you know, people can often get really wound up about this and say, "You know, I'm, I'm doing all those things. I, I can't sleep," and they've, you know, they've, they've really just, you know, without, without trying to, their brain has just got into this position where it's been trained not to sleep. It's been trained to not associate the bedroom with sleep or, you know, so many people I see, you know, and I hear about on social media are doing work emails right up to the moment they fall asleep. And, and-

Matthew Walker 1:06:55 Yeah

Dr. Rangan Chatterjee 1:06:56 ... you know, you [laughs] you mentioned children before, and I, I, I often say, you know, children need a bedtime routine. We know that.

Matthew Walker 1:07:02 [laughs]

Dr. Rangan Chatterjee 1:07:04 Why, why, as adults, do we think we're any different?

Matthew Walker 1:07:06 We should. And, and you're absolutely right. You know, we've turned the bed, uh, in this day and age often, you know, into a kitchen. We've turned it into an office. We've turned it into a cinema. [laughs] You know, we do all of these things typically on the bed, which then it does impact the brain's association. It gets quite confused about what this thing called the bed is, is all about. Um, so I think that that's a, a- That's a very helpful tip. And try not to get too anxious if you're sort of falling asleep. I know that probably a lot of what I've been telling people will make you feel anxious if you're not being able to get the sleep that you need. But try not to worry about it. Everyone has a bad night of sleep. Just get up, understand that you're going to be awake for a little bit longer, and then go back to bed, and, and you will start to relearn that association. And, and in fact, a lot of, um, you know, people and patients will say to me, "Well, you know, I've been falling asleep on the settee watching television, and then I get into bed and I'm wide awake and I don't know why." And again, it's because of this association that you've learned with the bed. The final two things, um, one of which we've mentioned, is what you intake into your body, caffeine and alcohol. We've spoken about caffeine, but I'll speak about alcohol quickly. Many people use, uh, alcohol as a sleep aid, and it is anything but an assistant to sleep. Alcohol is a class of drugs that we call the sedatives, um, and sedation is not sleep, unfortunately. It's very-

Dr. Rangan Chatterjee 1:08:28 Sedation is not sleep. I love it

Matthew Walker 1:08:29 ... it's very different. Um, so what you're doing when you have a nightcap or you use alcohol to try and get to sleep, and many people do, understandably so, they mistake one for the other. You're just knocking your cortex out. You're not in natural sleep. The two other problems with alcohol and sleep, firstly, alcohol will fragment your sleep. So if I were to record someone's sleep in the laboratory after they've had a couple of drinks, their sleep is littered with all of these awakenings throughout the night. Now, you tend not to remember waking up, but the next day you feel, again, unrefreshed. You don't feel sort of bright and alert or restored by your sleep. But you don't remember waking up, so you don't link it to the alcohol. But alcohol is bad at fragmenting your sleep, produces poor quality. The final thing alcohol is good at doing is blocking your dream sleep or your REM sleep, and we know, to come back to our conversation, REM sleep is critical for emotional first aid. REM sleep provides, um, overnight therapy. It's a form of emotional convalescence, and alcohol will block that REM sleep quite viciously. So those would be the five tips, I think, for better sleep.

Dr. Rangan Chatterjee 1:09:36 Yeah, Matthew, thanks. I, I love that. Um, j- just, just to say on alcohol, is it dose-dependent? So for example, you know, some people say, "Well, I'm okay with one glass of wine, but two or three glasses is gonna fragment my sleep." You know, uh, can you comment on, on the dosage there, or would you advise people who are struggling with sleep-

Matthew Walker 1:09:55 Yeah

Dr. Rangan Chatterjee 1:09:55 ... to knock it on its head, [laughs] basically?

Matthew Walker 1:09:57 I know, and it's so hard for me to answer this, and this is the reason, or one of the re- many reasons why I'm such a deeply unpopular person. But, um, you know-

Dr. Rangan Chatterjee 1:10:04 I don't think that's fair to say, but [laughs]

Matthew Walker 1:10:05 [laughs] I, I, but, you know, I, firstly, I don't want to sound puritanical. You know, life is to be lived-

Dr. Rangan Chatterjee 1:10:11 Yeah

Matthew Walker 1:10:11 ... to a degree, and all of these things that we're discussing are, we're trying to speak about the extremes. Um, but I also want to empower people with the knowledge. I'm not here to tell you necessarily what you should or you shouldn't do. I just want to give you the scientific facts, and then you can make the choice. I would say, unfortunately, that even just one glass of alcohol in the evening, we can h- we can see that. We can measure that.

Dr. Rangan Chatterjee 1:10:35 You can measure that. In your lab-

Matthew Walker 1:10:36 That change

Dr. Rangan Chatterjee 1:10:36 ... you can see that you're not getting the same deep level of restorative sleep-

Matthew Walker 1:10:40 Yeah

Dr. Rangan Chatterjee 1:10:40 ... even with one drink.

Matthew Walker 1:10:41 Even with one drink. So I know it's hard, but now, you know, everyone, you know, should, you know, have a social life and sort of, you know, enjoy a drink now and again. I think the best advice would be this. If you're going to bed feeling tipsy, you probably have had too much alcohol-

Dr. Rangan Chatterjee 1:10:55 Yeah

Matthew Walker 1:10:56 ... in terms of sleep impairment.

Dr. Rangan Chatterjee 1:10:57 Well, I, I think, you know, I, I, I so resonate with, with so much of what you've just said, which is, you know, this podcast, what I do, what you do, it's not about telling people what to do. You know, I'm, I've got no interest of telling someone what they should do. Uh, I have no right to tell someone-

Matthew Walker 1:11:13 Yeah

Dr. Rangan Chatterjee 1:11:13 ... what they should do with their lives.

Matthew Walker 1:11:14 You don't, absolutely. Yeah.

Dr. Rangan Chatterjee 1:11:14 Um, what I think we're trying to do is to educate people, inspire them, empower them to understand what lifestyle choices they're making and how that could impact their health. And I, I, I always draw the analogy with going out, having a few drinks with your mates on a Friday nights. People know intuitively that if I go out for a drink on a Friday nights and have three or four pints, let's say, you know what? My Saturday morning might be a bit of a write-off. I may not be functioning as well as I might want to. But you're going into that with that knowledge. You're saying, "You know, I know the effects alcohol has on me, but I'm gonna get so much enjoyment out of my night out tonight that I'm willing to put up with the consequences." What I think we're both trying to say is, guys, we just wanna empower you. We wanna help you understand the impact that caffeine might be having on your sleep, that alcohol might be having on your sleep, that the fact that you're on your work emails before you go to bed might be having on your sleep. Do with that information what you will. You know? Um-

Matthew Walker 1:12:15 Yeah. And I think-

Dr. Rangan Chatterjee 1:12:15 ... that's how I would put it.

Matthew Walker 1:12:16 I, I, I so agree because I think, you know, a lot of, you know, what you speak about, um, in your book, which is, you know, far more wide-ranging than mine 'cause I just take one of the things. You go after four of the key-

Dr. Rangan Chatterjee 1:12:26 I know. [laughs]

Matthew Walker 1:12:26 ... the, the key pillars, which is so much more impressive. I think it s- says so much about the difference between, uh, me and, and you, Rangan. But I think-

Dr. Rangan Chatterjee 1:12:33 Well, no, you're a researcher. I'm a, I'm a clinician, right? There's a big difference, right?

Matthew Walker 1:12:35 There, there is, but I, I still think it's, it's a, it's a heroic thing. But what I would say, I think, is that, yes, a lot of people are aware of some of these things. You know, like, it's good to be physically active. You know, I should try and stay away from drinking too much alcohol. But I also think that there's a lot of what we discuss, you know, I hope in both books, that is perhaps knowledge that people aren't aware of.

Dr. Rangan Chatterjee 1:12:57 Yeah.

Matthew Walker 1:12:57 And if only that they were aware of it, they would actually want to do something different. That's the sort of the case that I'm really passionate about, is that people, a- as long as you know the information and you choose to do otherwise, no problem at all. A lot of people just are either misinformed or entirely, when it comes to sleep, uninformed. That's the goal.

Dr. Rangan Chatterjee 1:13:17 That is the goal, and it's, and it's really about, it's that empowerment piece. And, and this is one thing I just wanna end on, is just to say, guys, look It may not be that you can just change one thing and suddenly have a great night's sleep. You might have to change three or four things together. You know, that's certainly my experience. It's like, you know, Matthew, you know, you're a researcher, so a lot, you know, you'll do research and s- and showing what caffeine does, on showing what alcohol does. And, but I would say as a clinician, use that research, but maybe you might have to try a few things. Like, you might try, for example, one week with no caffeine and no alcohol and see how you sleep, because then you can be empowered to dec- to decide what are you gonna do after that. Are you going to go back? Or maybe then, I always try and get people sleeping as well as they've ever slept, then they can start reintroducing some of these-

Matthew Walker 1:14:06 Yeah

Dr. Rangan Chatterjee 1:14:06 ... lifestyle things that they want, and they can say, "Oh, wow, that's interesting. I f- I felt great last week, but now when I have a 2:00 PM coffee, you know what? I'm not quite as good." Okay, that's, that's gonna teach me now that I, I'm gonna, I'm gonna knock it a, a bit earlier in the day. 'Cause I think ultimately nobody's gonna follow your advice or my advice simply because we told them to. I think it's only when they start to feel the difference themselves-

Matthew Walker 1:14:30 Yeah

Dr. Rangan Chatterjee 1:14:30 ... they go, "Wow, you know what? I kinda like feeling good."

Matthew Walker 1:14:33 Yeah. And I think, you know, uh, I love your point about just trying to give it time, too. You know, sleep and starting to change your sleep and seeing the effects of getting better sleep, it's a little bit like exercise at the gym. You know, you're not going to go to the gym one day and wake up looking like Arnold Schwarzenegger, you know? It just takes some time. But if you commit to it, you will see gradual change, and it's the same thing with, with sleep as well. But I also think, I love the idea of you, you know, putting sleep in that bedrock place and then starting to introduce the other factors. What's lovely is that many of them will actually fall in place when sleep is stabilized.

Dr. Rangan Chatterjee 1:15:08 Yeah.

Matthew Walker 1:15:08 And I'll give you a good example of diet. We know that, um, without sufficient sleep, two critical appetite hormones go in opposite bad directions.

Dr. Rangan Chatterjee 1:15:19 Yeah.

Matthew Walker 1:15:19 One of those hormones is called leptin, which is a hormone that sort of signals to your body you're full, you're- you don't want to eat anymore. The other hormone is called ghrelin, which does the opposite. It says you're not satisfied with your food. You want to eat more. Um, and despite leptin and ghrelin sounding like two hobbits, they are actually real [laughs] hormones. Um, what's interesting is that when you sleep deprive people, or even just limit them to maybe just, like, five or six hours of sleep for a week, levels of leptin, which say, "You're full. Don't eat more," they drop down. Levels of ghrelin that ramp up your hunger and say, "I've just eaten a big meal, but I'm not satisfied. I want to eat more," that hormone skyrockets when you're underslept. So no wonder people who are sleeping just five to six hours a night will actually eat on average somewhere between 200 to 300 extra calories every single day.

Dr. Rangan Chatterjee 1:16:09 Yeah. It's-

Matthew Walker 1:16:10 So you can solve sleep, and you will actually start to not want to eat as much. [laughs]

Dr. Rangan Chatterjee 1:16:15 Yeah. And, and this is why a part of weight loss is to sleep better.

Matthew Walker 1:16:18 Yeah.

Dr. Rangan Chatterjee 1:16:18 It's a critical factor, and I think next time I get you on, Matthew, we'll, we'll probably go into detail on that. We'll probably go into detail on Alzheimer's, and maybe even things like menopausal symptoms and hormonal symptoms that I also see sleep deprivation playing a huge role in. I know you're on a really busy schedule. That's happens when you have such a popular international bestselling book.

Matthew Walker 1:16:36 [laughs] Well, and you know all about that too, so... [laughs]

Dr. Rangan Chatterjee 1:16:38 Well, guys, I'd highly encourage you to pick up Matthew's book, Why We Sleep. It's, it's absolutely brilliant. It's got pretty much everything you've ever wanted to know about sleep, I think you'll probably find in that book. Um, I look forwards to when you release a later edition when you've got newer research coming out in the future-

Matthew Walker 1:16:53 [laughs]

Dr. Rangan Chatterjee 1:16:53 ... at some point. But Matthew, one question I, I like to ask my, my guests who are, you know, leading researchers in the field is, you know, as you became more and more aware of all this sleep research, what was the biggest thing in your own lifestyle that you changed on the back of your research?

Matthew Walker 1:17:14 I think it was probably caffeine. Um, I think just seeing the data and then doing s- those types of studies ourselves, and particularly the, the finding that we discussed where even if you're asleep, the quality of that sleep is just not as deep. That really got me concerned, and that's when I really started to pay attention to my, to my caffeine content, and I cut it out.

Dr. Rangan Chatterjee 1:17:37 And are you teetotal now with caffeine, or are you-

Matthew Walker 1:17:40 So right now, yeah, I am. I drink decaffeinated tea, and I drink decaffeinated coffee. Um, I sometimes, you know, I've ebbed and flowed between sort of having coffee in the morning, um, because I do feel it's, it's alerting benefits. But, you know, we didn't necessarily evolve to be medicated with caffeine, and I think anyone who's, you know, drinking caffeine at 11:00 AM, which on the basis of your circadian rhythm, if you li- listen to the wonderful podcast with, uh, Satchin Panda that you did, you know, your peak of your circadian rhythm is right around sort of the 11 o'clock period. That's when it should be almost impossible for you to fall asleep. But yet, you know, I sometimes look around on an airplane when I'm leaving, and people-

Dr. Rangan Chatterjee 1:18:20 [laughs]

Matthew Walker 1:18:20 Half the plane is asleep at 11 o'clock.

Dr. Rangan Chatterjee 1:18:22 Yeah.

Matthew Walker 1:18:22 Um, and if you're self-medicating, um, your sleep deprivation at 11:00 AM with caffeine, it usually means that you're perhaps just not getting enough sleep, and that's probably been one of the greatest, um, I think influential factors. That and the impact on my productivity, I think that was the, the most underrated, and it actually forced me to start doing a lot of research on sleep loss and productivity that maybe on a second podcast we can talk about.

Dr. Rangan Chatterjee 1:18:46 Well, we can get into, yeah.

Matthew Walker 1:18:47 But, you know, my ability to re- maintain focus and produce high-quality output work is dramatically dependent on the sleep that I've been having at night.

Dr. Rangan Chatterjee 1:19:00 That absolutely echoes what Professor Panda said a few weeks ago on this podcast. When he goes off caffeine, his productivity goes up. So guys, look, no one's asking you guys to, to cut out caffeine, you know. I know how much you guys love it. I have certainly had my own, uh, love-hate relation- well, more love of a relationship-

Matthew Walker 1:19:16 [laughs]

Dr. Rangan Chatterjee 1:19:16 ... wi- with coffee in the past. But I have dramatically reduced it, and I'm feeling better than I've ever felt. Matthew, I really want to thank you for the time you've made today to come onto the show to really talk to my listeners who really are big fans of your work, really are looking for those extra bits of information that they can take into their lifestyle. I want to thank you for that. I absolutely will take you up on your promise, I'm gonna call it a promise-

Matthew Walker 1:19:39 [laughs]

Dr. Rangan Chatterjee 1:19:39 ... to come back on the podcast.

Matthew Walker 1:19:40 It is a promise.

Dr. Rangan Chatterjee 1:19:41 Guys, look, that is the end of my conversation with Professor Matthew Walker. Don't forget, you can see all the show notes at drchatterjee.com/whywesleep, everything we've talked about, a lot more articles from Matthew. I'm gonna put them all there so you can continue your learning experience. Guys, I'd love you to take a screenshot of the podcast, share it on social media. We wanna get this information on sleep to as many people as possible, and you can help us do that by promoting and sharing this podcast on social media. If you could tag me, but you could also tag Matthew. Matthew, what social media network do you tend to be on?

Matthew Walker 1:20:17 Yeah, so I am on the internet, uh, all over the place on, uh, @sleepdiplomat, so @sleepdiplomat on Twitter. And you can find me on the web at sleepdiplomat.com. Um, and I would love to, uh, to learn more about what people enjoyed and just hear their thoughts about sleep on Twitter. That would be wonderful.

Dr. Rangan Chatterjee 1:20:36 Yeah, guys, so please do tag me, tag Matthew. I'm gonna put all those social media links on the show notes. Do check them out. As well as sharing this with your friends, if you could go onto whichever podcast platform you are listening to this on and give the podcast a five-star review. What it does is it helps raise the profile of the podcast. It helps get the podcast to more people, but it also helps me attract fantastic guests such as Professor Walker so I can get you more world-class, world-leading information coming in the future. Guys, I hope you've enjoyed today's podcast from Matthew and myself, and I'm looking forward to seeing you next week for the next show.

Matthew Walker 1:21:12 Thank you. Take care, and sleep well, everyone.