The Megyn Kelly Show - Alcohol and Caffeine, Naps, and the Science of Sleep, with Dr. Matt Walker | Ep. 284

Episode Date: March 23, 2022

It's Wellness Week at the Megyn Kelly Show. Megyn Kelly is joined by Dr. Matt Walker, sleep expert and author of "Why We Sleep," to talk about the science of why we get tired at night and feel rested, the effect of melatonin and sleep aids, how caffeine and alcohol affect our sleep, the science of dreams and nightmares, how sleep helps with our memory, how better sleep leads to better sex (and vice versa), and more.Follow The Megyn Kelly Show on all social platforms: YouTube: https://www.youtube.com/MegynKellyTwitter: http://Twitter.com/MegynKellyShowInstagram: http://Instagram.com/MegynKellyShowFacebook: http://Facebook.com/MegynKellyShow Find out more information at: https://www.devilmaycaremedia.com/megynkellyshow

Welcome to The Megyn Kelly Show, your home for open, honest, and provocative conversations. Hey everyone, I'm Megyn Kelly. Welcome to The Megyn Kelly Show. You're not getting enough sleep and it's killing you. Sorry to be so blunt, but lack of quality sleep is a very serious issue. You're going to love today's show. It's so fascinating. We are going to learn all about the science of sleep and why this mysterious chunk of our 24-hour day is so important to every aspect of our biology, indeed, our lifespan. Joining me now to discuss it all is Professor of Neuroscience and Psychology at the

University of California, Berkeley, and the founder of the Center for Human Sleep Science, Dr. Matt Walker. Welcome, Matt. So good to have you here. It's a delight and a privilege to be with you, Megan. Thanks so much for having me. Oh my gosh. I was reading the packet that my team prepared for me, started on the research. And I was sitting on an airplane sandwiched in between my oldest child and my husband. And I just kept interrupting their movies every two seconds. So you got to read this, read this. I'm showing Doug the stuff about the, you know, the steroid, the testosterone and the, you know, look at how it affects sex drive. I'm showing my little guy about how it can perform, it can affect test performance. And so it's just

every part of how we live starts right here in our bed at night. It's really very difficult to find almost anything that isn't wonderfully enhanced by sleep when we get it or demonstrably impaired when we don't get enough. And I think I was wrong. I used to think of sleep almost like the third pillar of good health alongside things like diet and exercise. But I've changed my tune. When you look at the data, it really tells a story that sleep is the very foundation on which those two other things sit. And we can talk about why that's the case. But I think very simply put, sleep is the single most effective thing that we can do each and every day to reset the health

of our brain and our body. And yet people don't tend to be thoughtful about it. It just tends to be something we do at the end of the day when we can't go any longer and then lather, rinse, repeat. But you argue for a very different approach, which we're going to get into and gave really specific recommendations, which I love. I love just an action plan. Okay, these are the hours, this is the temperature, this is sort of the setting, this is how to ease into the sleep and so on. We're going to go through all of it. But before we get to all that, just tell us a little bit about your background. I understood that you were doing some sort of research on dementia patients back in London and trying to figure out, okay, this one has Alzheimer's, this one has a different disease. And how did that spark your interest in sleep?

Yeah. During my initial PhD work, I was trying to differentially diagnose people with dementia very early on in the course of their disease. And I was using brainwave recordings to see if I could do that. And I was failing miserably. And each weekend I'd go home with my little set of journals and I'd keep reading, which tells you everything about the degree of social life I was having at the weekend. But one weekend I started to read that some of these dement life I was having at the weekend. But one weekend, I started to read that some of these dementias would eat away at the sleep centers in the brain, and others would leave them untouched. And I realized that I was measuring the brainwave activity of my patients at the wrong time, which is when they were awake, and I should be measuring

it when they were asleep. So I started measuring the sleeping brainwave activity, got some fantastic results. And at that point, I wondered, perhaps the sleep problems are not just a symptom of the dementia. I wonder if it's an underlying cause of the dementia. And 20 years ago, which is when I was doing that work, no one could actually answer a very simple fundamental question. Why do we sleep? And in fact, the crass answer at the time was that we sleep to cure sleepiness, which is the fatuous equivalent of saying, you eat to cure hunger. Well, that doesn't really tell you much about the benefits of nutrition. But now, 20 years later, we've had to upend that question and ask, is there anything in the body or any operation of the mind that isn't benefited by sleep?

And as I said, the answer seems to be no. And so that's how I was essentially an accidental sleep researcher. I didn't think about sleep until I got to that stage. And then I just fell desperately and deeply in love with this thing called sleep. It is a love affair that has remained with me for the past 20 years. I'm biased, but I think it is the most beguiling topic in all of science. And I can't imagine studying anything different for the rest of my career. It's funny because I think to myself, before we choose any topic for a show, will people be interested in this? I mean, we did a show on love. Of course, everyone is interested in love in general. They tend to want love in their life and have love in their life. But would they listen

to a show for two hours about love? I don't know. you know, figure, okay, I like it, so we'll do it. This one, I know everybody will listen. You spend, I mean, it could be up to half of your day, but certainly a good third of your day doing this thing that gets almost no attention from you. And you really tend to be rather thoughtless about it unless it creeps up as a problem in your life, and then you know it needs tending to. So let's start with that question then. Why do we sleep and what is sleep? So sleep, at least in human beings, is broadly separated into two main types. On the one hand, we have something called non-rapid eye movement sleep or non-REM sleep for short. And then on the other hand, we have something called non-rapid eye movement sleep or non-REM sleep

for short. And then on the other hand, we have rapid eye movement sleep or REM sleep. And non-REM sleep has been further subdivided into four separate stages. They are unimaginatively called stages one through four, increasing in their depth of sleep. So stages one and two of non-REM sleep, that's what you would think of as light non-REM sleep. When you look at your sort of sleep tracker data, let's say stages three and four, that's the really deep stage of deep non-REM sleep.

And then we have rapid eye movement sleep, as I said, and that's the state of sleep principally associated with dreaming. And when your head hit the pillow last night, it turns out that those two types of sleep, non-REM and REM, will play out and did play out in a battle for brain domination across the night. And that cerebral war between non-REM and REM was won and lost every 90 minutes. And then it was replayed every 90 minutes. And what that produces is this standard cycling architecture of sleep. And as I said, in humans, at least it's 90 minutes.

It's different in different species. So you fall asleep and you go into the light stages of non-REM. Then you go down into the deeper stages of non-REM, then you go down into the deeper stages of non-REM. And then after about 70 or 80 minutes, you'll start to rise back up and you'll pop up and you'll have a short REM sleep period. And then down you go again, down into non-REM and then up into REM. What changes, however, is the ratio of non-REM to REM within that 90-minute cycle as you move across the night. And what I mean by this is that in the first half of the night, the majority of those 90-minute cycles that you had last night were comprised of lots of that deep non-REM sleep and very little

dream sleep. But as you push through to the second half of the night, now that seesaw balance actually shifts. And the majority of those 90 minute cycles are comprised much more of rapid eye movement sleep or dream sleep. And it's actually, I mean, it's a really important question that you raise, which is not just about what sleep is, but how it's structured, because there are practical implications. So let's say that you, Megan, would normally go to sleep at, I'm just going to pull this out the air, let's say you go to sleep at 10 p.m. and you normally wake up at 6 a.m. So there's your eight-hour sleep opportunity. But tomorrow morning, you have to wake up for an early morning flight. So you have to wake up two hours earlier. So you wake up at 4 a.m. rather than 6 a.m. How much sleep have you lost? Well, you've lost two hours from your eight-hour window, so you've lost 25% of your total sleep, but because REM sleep comes in the last few hours of the night, you may have lost 50, 60, even 70% of all of your dream sleep. And as we'll perhaps discuss,

dream sleep is critical for many functions. It's critical for your mental and emotional health. Downstairs in the body, it regulates particular hormones, including things like testosterone and other sex-related hormones. We also know REM sleep is a direct predictor of your lifespan, that the more REM sleep that you're getting each and every night, that's associated with a longer lifespan. So it's not just academic that we think about these different stages of sleep, but there are also practical implications too. So if I were going to do that, let's change the analogy or the situation, the hypothetical to where I have to do two hours of work, two extra hours of work. And I'm either going to have to do it from 10 p.m. to midnight, or I'm going to have to set the alarm and get up at four. Does it behoove me to stay up later?

Can you work it such that you're getting up at the same time and still getting more REM stage? So unfortunately, you can't shortchange sleep on either end of the initiation or the ending of the spectrum. What we've discovered is that all stages of sleep are important, all the ones that we've just discussed. That different stages of sleep, however, perform different functions for your brain and your body at different times of night. And if we remove any one of them, we can see

selective impairments in those different functions. And from an evolutionary perspective, that makes a lot of sense because think about sleep. It is arguably the most idiotic of all inventions that when you're asleep, you're not finding a mate, you're not reproducing, you're not caring for your young, you're not finding food, and worst of all, you're vulnerable to predation. So on any one of those grounds, sleep should have been strongly selected against in the course of evolution. But sleep, and at least in every species that we've carefully studied to date, sleep appears to be present. And what that tells us is that sleep perhaps emerged with life itself on this planet and has fought its way through every step of the evolutionary pathway. In other words,

if sleep doesn't serve an absolutely vital set of functions, then it's the biggest mistake the evolutionary process has ever made. And we're now realizing that mother nature didn't make a spectacular blunder in creating this thing called sleep. But I make this point in regards to your question, because if you could imagine that any one of those stages of sleep was negotiable rather than non-negotiable, that we could perhaps just let go of it and not necessarily need it, Mother Nature would have excised it many years ago because sleep is so deleterious from that evolutionary standpoint. The fact that all of those stages of sleep remain with us

at this late stage of evolution in terms of us homo sapiens tells us that we need all of them, and we just can't burn the candle at either one of those ends, and certainly not at both ends, without expecting some kind of deficit. So every living animal sleeps. I mean, everything, like sharks, elephants, they all sleep. Every species that we've studied to date. Yep. Sharks will sleep. We also know, and it's actually interesting. Sharks will sleep typically with their eyes open. Elephants will sleep, but different species will sleep different amounts.

Elephants are a great example. They will only need somewhere between four to five hours of sleep a night. For those big bodies? Yeah. It's remarkable. My hero, the rock star god of the sleep world is the little brown bat, which will sleep somewhere between 17 to 18 hours every single day. My hero. Yeah, I know. We human beings, we sit somewhere in the middle. Our sleep need is somewhere between seven to nine hours a night. Has it always been that way? You're talking

about evolution and we'll get to how many hours are ideal, but has it always been that around seven or eight is pretty much what a human body will do if left alone? So the best way that we've been able to sort of answer this question is look, for example, at hunter-gatherer tribes whose way of life hasn't changed for thousands of years. And they seem to sleep somewhere in this region of about seven to nine hours, perhaps a little bit less at night than we would typically sleep. But they also have, particularly in the summer, this siesta-like nap behavior. So from best we can tell, that is the requirement. The other way that we can answer that question is we can take human beings, we can bring

them into the sleep laboratory, we can say, tell your friends goodbye, no phone gadgets, no nothing. And for the next two weeks, you're staying with us in close quarters. And firstly, we let them sleep off the debt that most people bring in to the sleep laboratory where they oversleep. They'll start to sleep nine, nine and a half hours. But then at some point they throttle back to their sweet spot. And that sweet spot for most human adults seems to be somewhere between seven to nine hours. And that range, and there is a range to be important, but that's the other way that we can address the question. We can just let human beings, free of all of the trappings of modernity, start to sleep in however they want to sleep. And we look at that biological need and it expresses that same range of seven to nine. Now, we are going to talk about the benefits of sleep. But one of the things I've heard you say is that sleep is your superpower. And you gave an example of, and I think everyone can relate to this, that sleep is like clicking the save button on the things that you've learned that day,

which is why it's so important to do after you're studying or after you're learning, but it also can prime your brain for learning. So, I mean, it's important in both stages, but I think everybody who's gone through school, college, whatever, law school understands if you manage to get that eight hours in after you've done your cramming or your reading, you know it so much better the next morning versus having to pull an all-nighter. And that evidence is now so powerful and so well replicated that when it comes to your learning and memory abilities, sleep is actually critical in three unique ways. First, we need sleep before learning to get your brain ready to initially lay down those new memories. In other words, sleep almost prepares your brain like a dry sponge,

ready to initially soak up those new pieces of information. And without sleep, the memory circuits of the brain effectively become waterlogged and you can't absorb new memories. And we did a study, for example, where we asked, is pulling the all-nighter a wise idea? And first, what we found was that the memory centers in the brain were shut down by a lack of sleep. And they were just bouncing that information, almost like a full inbox in your email. The second thing that we learned, however, was that you not only need sleep before learning to get those memories into the brain initially, just as you said, you then need sleep after learning to cement and solidify those new

memories into the brain. And in fact, during sleep, it's a very active process, by the way, we transfer memories from that short-term vulnerable reservoir to a more permanent long-term storage site. And that's the process of saving them, as you said, almost like hitting the save button on those memories. But then more recently, we've discovered that sleep is much more intelligent than we ever imagined possible. That sleep not only saves individual pieces of memories, but sleep will intelligently start to associate and integrate that new information together. And I liken it to informational alchemy. It's that you wake up the next morning and you have a revised mind-wide web of associations. Definitely. And that's the reason that, I'm sure you've probably experienced this and people listening

may have, that you can come up with solutions to previously impenetrable problems. And I think it's the reason that no one has probably ever told you, Megan, that you should stay awake on a problem. They don't. Instead, they tell you to sleep on a problem. And that's exactly what the evidence is telling us. Now, this may be outside of your area of expertise, but when you say that it can actually sleep, sleep can help move the memory to a more long-term storage part of your brain, do you know whether that place has got all the memories in it, that all the memories are potentially accessible if only the hardware would work the way we wish it would? It's a very challenging question in memory science, and I do a lot of work in this area.

How much information is actually stored in the human brain, and how much capacity do we have for storage of information? We don't have the answer yet, but I think what we've learned is a surprising fact that we probably have a lot more information stored in our brain than we ourselves are consciously aware of. And you gave a lovely analogy, and I think it's absolutely correct. There are some times when someone asks you a question, you say, I just can't remember. No, it's gone. And then all of a sudden, you get a little bit of a cue that you look at something, a label on a bottle, and all of a sudden it unlocks the memory and it comes flitting back. And what that tells us is something fundamental, that the

information was in your brain, it was available, but it wasn't accessible. And sometimes we make the mistake that a lack of accessibility reflects the fact that the memory is not there. That's perhaps not true. The memory is there. It's available. It's just not accessible. It's almost as though sometimes we lose the IP address to that memory and we can't go and find it. And in fact, there was a lovely study done several years ago that demonstrated once again, a role for sleep here. That sleep increases the veracity of which you can locate and identify and access those memories. So you could have that information stored within the brain, but you just can't recall it during the exam if you haven't had enough sleep. Wow. I mean, I feel like everyone's had that experience

and you know it's in there. You just have to get the keys somehow, close your eyes, like get better rested, don't drink. You know, there are all sorts of things you can do, but it's fascinating. And I love those stories where you hear about somebody who gets hit on the head and then they go in for the operation or whatever,

and suddenly they can play piano again, which they hadn't been able to do since they were four. You know, unlocking the mystery of our brains is fun science. I want to talk about the basis, like you would talk about the stages of sleep. And I know there's something that you talk about, you call it sleep pressure. And this basically explains why we get tired, why we get tired in the evening, and why we want to wake up in the morning from sleeping. So why is that? What makes us get tired in the evening? Yeah, they're two great questions. And I think certainly if I was not a sleep scientist, I never would have asked that question. Why do I get tired in the evening? And why is it that after a good night of sleep, I'm relieved of that tiredness the next morning and I feel awake? And and everyone listening woke up this morning, a chemical has been building up in our brain. And that chemical is called adenosine. And the more of that chemical that builds up, the sleepier and sleepier you will

feel. And it's what we call sleep pressure. Now, don't worry. It's not a mechanical pressure in your head. It's not going to cause you a headache by any means. It's a chemical pressure. And after about 16 hours of being awake, after about 16 hours of accumulation of this adenosine, of this sleepiness molecule, we feel tired and we feel needing to go to bed. But what's also interesting is what happens when we sleep. And it's during sleep that the brain then gets the chance to actually clear away all of that adenosine. And it's this mass evacuation of all of that chemical sleep pressure. And it seems to take the sleeping brain about eight hours to jettison 16 hours of accumulated wakefulness. And that's why we wake up hopefully without an alarm feeling refreshed. And it can also be one of the reasons why when we wake up, we may need caffeine to help get us more awake, or we don't feel restored by our sleep because we're not giving our brain the

right opportunity amount of sleep to get rid of all of that sleepiness chemical. Does caffeine, what does it do to adenosine? Great question. This helps actually explain how caffeine works. So by the way, it's not a coincidence that those two things sound quite similar, caffeine and adenosine. It's because they both latch on to the same receptor sites or welcome sites within the brain. Now, what's interesting, however, is that when caffeine floods your system, it doesn't latch onto those receptors of adenosine and say you're sleepy. Of course it doesn't because caffeine makes us alert. So how does this work? Well, caffeine

races in and it latches onto those receptor sites and it hijacks them. And essentially it blocks them. It inactivates those sleepiness receptors. And so even though you've been awake for 16 hours and before you had that cup of coffee in the evening, you were starting to feel really quite tired. Caffeine races in, it blocks some of that signal. It's almost like caffeine comes in and hits the mute button on the sleepiness signal. So now your brain is no longer aware of that 16 hours of weight of adenosine sort of sinking you down into sleep. It may think now after the cup of coffee, I've only been awake for seven hours or eight hours. And so now you're wide awake again. And this is why caffeine can sort of keep us more alert and wake us up and keep us away

from that sleep. The problem, however, is that while caffeine is in your system, it doesn't mean that the adenosine stops building up. It doesn't. It keeps building up and building up. And then what happens is that when your body starts to metabolize and clear away that caffeine, not only do you go back to the same place of sleepiness that you were before you had the cup of coffee several hours ago, you're hit with that degree of sleepiness plus all

of the additional sleepiness that's been building up while the caffeine is in your system. Oh no. This is while the caffeine is in your system. Oh, no. This is called the caffeine crash. That's why you get that weight. Oh, I did not realize that there's a ricochet rebound effect on caffeine. I feel like I'm always tired. So it's just like to me that I feel like the caffeine barely makes any difference, which you're going to solve for me today.

All right. So let's talk turkey because everyone's wondering, do I really need seven or eight hours? And, you know, can you pay a sleep debt? And should I nap? And the temperature of all this stuff? Let's do it all. So I read that you go to bed at 1030 and wake up at 704 AM, which is fun. So why is that? And is that, I mean, I assume you're giving yourself some time to fall asleep there. Are you trying to go for eight and a half hours

or are you trying to go for eight? Yeah, great question. So first, I'm not suggesting that that is the ideal opportunity window for everyone. Our sleep window is very different. And this comes onto something called chronotype, which we can come onto in just a second. But I'm just someone who I'm in the sort of the middle to maybe slightly higher range in terms of sleep need. I usually require somewhere around about eight to eight hours and 15 minutes to function well. It could be because I'm especially sensitive to knowing the deficits that come by way of a lack of sleep. But my, and so let's come on to chronotype. The reason I say it doesn't mean that that's the opportunity window that everyone should have and stick to it. There is something called

chronotype. And the underlying thing here is that it's not your fault. What I mean by this is whether you're a morning type, evening type, or somewhere in between. And that's what we call chronotype. And there are essentially three different versions. And if you look across the population, it's about a third split between each of those three. Yeah. And you would think that- This is a night owl, that kind of thing, morning person.

Morning type, yeah. Evening type, night owl, what we call a morning lark. And the morning types, they perhaps want to go to bed, say around nine o'clock and they're waking up, you know, five 30, six, whereas the evening types, they may want to be going to bed at 1am or 2am and waking up at, you know, nine or 10am the next morning. I'm sorry, going to bed at 1am or 2am. There is in sleep science, we actually split them even more fine graingrained to five types, which is extreme morning types, morning types, neutrals, evening types, and extreme evening types. So an extreme morning type could be getting into bed at 8 PM and they will naturally wake up

at 4 AM and they'll wake up like an energizer bunny, very happy, full of energy. It's not a struggle for them. Whereas an extreme evening type could be almost completely reversed. They could be wanting to go to bed at three or four in the morning and then waking up around midday. And society, of course, has a desperate bias and a chastising. They have a bias towards the morning types and they chastise the evening types. We label evening types as being slothful or being lazy, and that's not true. And the reason is because it's not a choice. It is largely genetically determined. And we now know

that there are at least nine different genes that determine your chronotype as to whether you're a morning type, evening type, or a neutral like me. And we, I think, need to become a lot more kindly to the night owls. It's often been said that the early bird catches the worm. Maybe that's true. What I would say though, is that the second mouse gets the cheese and it's okay to be an evening type. And when we force evening types to start to sleep against their natural tendency, when we force them to sleep out of synchrony with their chronotype, some very bad things happen. Higher rates of depression, higher rates of obesity, higher rates of diabetes. It doesn't

have to be this way. Well, it does if you have, for example, children, right? I mean, I was just lamenting this, that I always found it so difficult to get up and you had to be in the homeroom by 7.20 and I'm not a morning person. It was painful for the 13 years I had to do it, K through 12. And I remember when senior year ended being so thankful it was over and I was never gonna have to do that again in my life. I wouldn't have to choose a job

that required me to be there at that hour. And I forgot all about what happens when you then have children who have to go through that again. They have no choice. They must be morning people, they have no choice. They must be mourning people. They have no choice. And what's interesting is that our morningness, eveningness preference does change across the lifespan. It does.

As I said, this is determined by your genetics, it's gifted to you at birth, and you carry it for the rest of your life, your chronotype. But in general, children will typically go to bed earlier and wake up earlier, even though they want to stay up later. They'll say, I want to stay. And then all of a sudden, you're carrying to bed because they couldn't make it. And then when we get into adolescence, into those sort of early teen years, something very different happens. All of a sudden, our sort of rhythm of sleep gets pushed forward in time. And now adolescents want to go to bed much later and wake up later. And this is a biological architected shift. It's not their choice again. It's not that teenagers, if you could just put

them in bed at nine or 10 o'clock at night and say, look, just get to sleep. It doesn't work like that. Their biology does not want to be asleep at 10 PM. It's not a choice. And if you put them to bed, then for the most part, they're probably just going to lie in bed awake, not being able to fall asleep. And then you're waking them asleep. You can see it with those teenagers who sleep. If you leave them alone on a Saturday or Sunday, they will get up at noon every time. Either they're all incredibly lazy or something's going on with the biology. That's right. And it is the biology together with an unfortunate situation that society has developed, which is this early morning start time for schools, this incessant model of early school start times, which then lumbers our teenagers

with a chronic sleep debt so that they're carrying the sleep debt throughout the weekday. They're waking up at a time when they don't want to wake up. They're having to go to bed at a time that's not natural for their biology. And then come the weekend, what's going to happen? Of course, they're going to try and binge on that sleep and see if they can get back some of the sleep that we've lumbered with them in terms of a sleep debt. And the system doesn't work like that. It doesn't. So for all of us, if we only get six hours a night and we really need eight, five nights a week, the five nights we work or go to school, then you can't make up have evolved that way, in part because human beings are the only species that will deliberately deprive themselves of sleep for no apparent biological benefit. And so we don't have an evolved mechanism in place that helps us

almost think about sleep like a bank. It's not as though we can accumulate a debt and then hope to pay it off at some later point in time. Now, it's not to say that you can't get some of that sleep back that you've lost during the weekend, but a good example would be, let's say I take you, Megan, this evening and I deprive you of sleep for an entire night. Let's just take it to the extreme. So I take away eight hours of sleep from you. And then the next night, I give you all of the recovery sleep that you want. You can sleep as much as you like. And then I do that on a second night and a third night. Now, yes, you will sleep longer on those recovery nights of sleep. It's what's called a sleep rebound effect, but you will only get back about 50% of all of the sleep that you've lost.

The system just doesn't seem to have the ability to repay the debt. We can't develop this debt and then come back at the weekend and see if we can pay it off with some kind of oversleeping credit. The other danger there too, is that we go to bed typically later at the weekend and we sleep a lot later, or many people will sleep in at the weekend. And then having woken up late on Sunday morning, now Monday comes around and you have to wake up 6am again. And now you have to get to bed at let's say 10. But the problem is you woke up so late that you're not sleepy. Why is this? It comes back to what we discussed, which is sleep pressure, that you've only been awake for maybe 12 hours or even 11 hours because you slept in so late

on Sunday morning. And then you're tucking yourself into bed to try and get your eight hours of sleep ready for Monday morning. But you're just not sleepy because you haven't been awake long enough to develop enough of that sleepiness, enough of that adenosine chemical. And so now, Sunday evening, it feels like insomnia because you're lying in bed at 10 p.m. and you can't fall asleep. Okay, so I have to ask you about melatonin and whether that could be an aid that's a more natural aid. Some people will use like a Benadryl or a sleeping pill, I guess, to solve that. But before we get to that, I wanted to know, since you are the sleep expert,

how regimented are you on that 1030 to 704? Because like, for example, we go to Montana, right? And we ski and we have vacations there. And that's two hours behind the East Coast. So when we come back, the sleep schedules are all messed up because, you know, whereas in Montana, we were waking up at 7 a.m., that was 9 a.m. East Coast time. And now when we have to get up for school at 6 a.m. East Coast time, it feels like 4 a.m. and nobody wants to do it. We're all hurting. And I thought to myself, would Matt vacation in Montana? Maybe he wouldn't do it. Maybe he's so regimented. He doesn't do intercontinental travel. How seriously do you take the loss of sleep for a night or two? So I want to be relaxed here. I'm not trying to be so puritanical to say don't do anything in life. That's ridiculous. Life is to be lived. And I certainly travel.

I'll travel back home. I live now in California, but as you can tell, home is England. And I also like to go on vacation, do lots of different things. So I that if I start to drift in terms of my sleep schedule, the quality of my sleep is not good enough. And maybe I can feel okay for a day or two, but it starts to catch up with me. And then it's just not worth it for me because I can see the deficits and I need to be really efficient in the different jobs that I have. And I also want to live a long life, but I don't just want to live a longer life. I want to live a longer, healthier life. And we know that a lack of sleep and sleep disruption is not only associated with your lifespan. It's also associated with your health span. So I do keep those things in mind. And yes, I give myself this eight and a half hour-ish sort of sleep opportunity. And that's not because I want to be some poster child for

the sleep campaign cause. It's simply because if you knew what I knew about the benefits of sleep and the harm that happens when you don't get enough. It's a very selfish act on my behalf. You would choose not to do anything other than doing that. But again, I do have some degree of relaxed nature around it. But I also know that when I'm traveling, for example, I know some of the tricks that I can use to try to get over some of that jet lag or that sleep deprivation. And then I'm also just kind to myself on those days when I haven't slept well. And by the way, it doesn't necessarily take a vacation or transcontinental travel. I'm just as vulnerable as most people to having a bad night of sleep. And as I get older, I'm moving solidly into the foothills of middle age right now. I know that my sleep is getting

harder and it is declining. And on those days, I will just try to be kind to myself. I'll try not to push it quite as hard at the gym and I'll just take care of oneself. What about a sleep aid? What about a melatonin? I read, I don't know. I read you said something like the studies show it only gives you 2.42 minutes and 40 seconds advanced sleep. It gives you almost no headstart and it's really not worth doing. Yeah. So melatonin, for those who don't know, is a hormone. It's a naturally occurring and naturally released hormone in the body. It's sometimes called the hormone of darkness or the vampire hormone, not because it makes you bite into people's necks when it's released,

but it's simply because it comes out at night, that it's the signal that the brain uses to communicate to the rest of the brain and to the body that it's the signal that the brain uses to communicate to the rest of the brain and to the body that it's darkness now outside and it's time for us to sleep. So melatonin helps regulate the timing of our sleep, but melatonin doesn't actually help in the generation of sleep itself. And I think the analogy that I often use, and I don't know if it's helpful, but think of the hundred meter race at the Olympics. Melatonin essentially is the starting official who has the starting gun and they begin the great sleep race. But melatonin doesn't participate in the race itself. That's a whole different set of brain

chemicals and brain systems. Yeah, but that's you can't fall asleep because you don't have enough of that chemical built up in you, if melatonin just overrides that and says, you're sleeping, start. Isn't that helpful? It is helpful under certain circumstances. And jet lag is one of those where we've seen melatonin being effective and people can strategically use it when melatonin is either going to be delayed many hours in the past because you're in a new time zone and you need to get that signal of melatonin to trick your brain into realizing in the new time zone, it actually is time to be falling asleep. However, when we come back to people once they're stable in a new time zone and we ask, does melatonin help improve the speed with which you fall asleep? And the answer seems to be no. There was a big

what's called a meta-analysis where you gather together all of the smaller scientific studies and you put them in a big statistical bucket to look at the grand average. And what we found was that melatonin only increased the speed with which people fell asleep by about 3.9 minutes. And then it only improved the efficiency of your sleep. So how much sleep you are packing in to that sort of sleep opportunity window, it only increased your sleep efficiency by 2.2%. So melatonin, this is why it's just not an effective sleep aid for people with insomnia. And then we have to also be careful about the dosing as well as the purity. Yeah. And just developing any sort of dependency on an aid to go to sleep is not a great idea. But there are things that can help

you fall asleep naturally that we do, for example, our babies, but we might not do for ourselves. Like you are in favor of a bath or a shower in the evening. And it's not because you get all warm and then you get into bed feeling toasty. To the contrary, it's something else. Can you explain? Yeah. So one of the things that we've realized, the critical factors that controls your sleep and also the quantity and the quality of that sleep is temperature. And many people will know this because you need to drop your core body temperature by somewhere between

about one degree Celsius or about two to three degrees Fahrenheit to fall asleep and then stay asleep. And it's the reason everyone watching will find it a lot easier to fall asleep in a room that's too cold than too hot because the room that's too cold is at least taking you in the right temperature direction for good sleep, which is to drop your core body temperature. And you mentioned the hot bath or a hot shower. This is so reliable in sleep science. We actually call it the warm bath effect, but it's working for the exact opposite reason that you think. When you get into the bath, what happens is that all of the blood races to the surface of your skin. And so that blood

races from the core of your body where it's trapped deep down inside, and it all floods the surface. You get sort of these rosy cheeks and red hands. And then when you get out of the bath, because all of that blood is now close to the surface of the skin, you get this huge radiation of heat out of the core of your body and your core body temperature plummets after a hot bath. And that is why you often fall asleep easier and stay asleep more soundly across the night. Do you have to go right to bed? I mean, how long does that effect last in your body? It's actually quite a slow effect.

The effect can take, you know, 30 or up to 90 minutes in terms of its slow trajectory. Now, of course, some of that depends on how hot the bath was and how long you were in the bath. Have we done those studies to actually slice and dice that question so that I could say to you, Megan, you need to aim for a bath temperature of exactly this much and you need to set your timer for 16 minutes and 23 seconds. We haven't done those scientific studies yet. It's just very difficult to get the funding, but we do know that that seems to benefit. My notes on having read all of your stuff say that I need to set my thermometer to 65 degrees in my bedroom. And that's what I've been doing ever since I read all these materials, 65 degrees. And I've been putting my kids' thermometers at 65 degrees. But if you have a smart thermometer or a smart home, which sadly we do not, but if you've got one of those thermometers that lets story of temperature comes in three parts regarding sleep,

that as I just described, we need to warm up at the surface of our skin, at the shell of our body. We need to warm up at the surface to cool down the core to fall asleep. And then we need to stay cool to stay asleep, which is the recommendation of the ambient temperature being around 65 degrees, 65 to 67 degrees. But then we need to warm up to wake up. We need to reverse engineer the trick. And in fact, that seems to be one of the triggers. If you let people naturally wake up whenever they would want to, one of the determining factors is the rise in their core body temperature. So you can help yourself perhaps wake up more easily. And many of us, of course, struggle to wake up. Even if we're having or we're getting sufficient sleep, some people will have what's called sleep inertia. And I actually suffer from this too, which is that idea where when you wake up for the first 30 minutes or the first hour, you say to your partner, look, darling, I am not the best version of myself in the first hour of the morning. Yes, yes.

Please, I know I left the dishes in the sink. I promise I'll get to them, but please just give me the first hour to wake up. This is all I can manage, Matt. Doug will be chatting. His sink is there. Mine's next door. He'll be chatting. He'll be wanting to go over agenda.

And this is all I can manage. So much talking. Yeah, exactly. Quiet, please. Just let me. You and I were probably almost like, you know, a classic car engine where it just needs time to warm up to operating temperature before you can really start to rev it and, you know, get the good stuff. Um, but warming up can actually help.

By the way, this is the reason that, um, uh, people think that a cup of coffee in the morning helps them very quickly and it's absolute nonsense. It actually takes somewhere between about, um, if you look at the data somewhere between nine to 15 minutes for caffeine to reach its peak plasma concentration. But after a couple of sips of your morning first cup of coffee, people will say after five minutes, okay, now I'm feeling fine. I'm ready to go. How is that?

Because the caffeine hasn't even really entered your system. It's not working yet. The reason is because the cup of coffee is usually hot in its temperature. And when you're drinking that hot drink, it warms the core of your body much more quickly within a couple of minutes. And it's the increase in your core body temperature that you are thinking is the benefit of caffeine, when in fact, it's the temperature benefit of that warm drink that's giving you the alertness improvement.

So you could absolutely try doing this with a decaf tea or just a warm water, just a warm water from the tea kettle and maybe feel the same. You can see that in people who are caffeine naive. But the problem is that in those people who are used to their cup of coffee, they develop a dependency. And a lot of people say, look, when I'm having a cup of coffee, I work better. My focus is better. That's also not true. If you look at the data, what's happened is that over time, they've become dependent on caffeine. And when they don't have caffeine, their performance is worse than it naturally would be at baseline. So when they have the cup of coffee, they say, I am better in my performance.

And technically they're correct. They are better, but they're not above and beyond their baseline. They're simply getting back to where they naturally are based on the deficit that's happened because of the abstinence of caffeine that's happened overnight. So you're not doing caffeine. So I am someone who unfortunately is quite sensitive to caffeine. And we know that different people have different sensitivities. It's based on a specific enzyme. And you can do these genetic tests and you can figure out, are you a caffeine sensitive person or not? And there is a set of liver enzymes called the cytochrome P450s, which I always thought would be a great name for a band, you know, sort of, please welcome, you know,

to New York City. No, it would not. Cytochrome P450s, you know, yeah, I should never, clearly I'm a scientist. And so these liver enzymes, and there's a mutation on or a variant on one of these genes. It's called the CYP1A2 gene. And if you have a version of that gene, it will speed up the clearance of caffeine. So you can not be as sensitive. I am of a version of that enzyme that is slow in its clearance of caffeine. And that means I'm someone who is especially sensitive to caffeine. Now I do sometimes have a cup of coffee in the morning in part because there are many benefits of coffee, many health benefits. That's got nothing to do with the caffeine though. It's because the coffee bean contains a whopping dose of wonderful things called antioxidants. And most people in modern society, we eat what's called the standard Western diet, which is not ideal from a nutritional perspective. It's not full of whole foods and natural foods, some processed food. And we have therefore become reliant on the humble coffee bean to carry most of

the Herculean weight of all of our antioxidant needs. And you can see, and a great example of this is decaffeinated coffee. You see almost the same health benefits from drinking decaffeinated coffee than you do caffeinated coffee. What's common between those two is that they both contain antioxidants. So it's not the caffeine, it's the antioxidants. So sometimes I will have a cup of coffee. Okay. So you can go for decaf. Okay. That's good to know. You can go for decaf too. Yeah. And I usually drink decaf throughout the day. My husband and I used to have a cup of coffee every morning together. And you know what helped him kick his coffee habit? COVID. He got COVID. He didn't want coffee. And he had it, you know, for like 10 days, it was kind of

lingering. And he just, and he did have a headache, but you know, you have a headache when you have COVID. And he was done. And I was just like, I'm kind of envious, except isn't caffeine an appetite suppressant? So I kind of like, I'm kind of drawnvious, except isn't caffeine an appetite suppressant? So I kind of like, I'm kind of drawn to the coffee for that reason too. Yep. It does have appetite suppressing effects as well. And people will use that as well as a way to regulate. Pick your poison. Yeah, exactly. And you know, caffeine is a good demonstration of this, which is once again, not being so puritanical that when it comes to caffeine, I would say the dose and the timing make the poison. So try to stay away from having more than let's say two or certainly three cups of coffee. Once

you get past three cups of coffee, the health benefits actually start to go in the opposite direction, the downward direction. And then timing, because we know that caffeine has a certain duration of action. And the recommendation is try to stop caffeine at least 12 hours before you expect to go to bed. All right. So now we didn't close out that loop on going to bed, because I know you've said if you remember nothing, if you remember nothing else that you get from your talks, from your books, from your interviews, it's that you need regularity. Regularity is king. It's not just you that should go to bed at 1030 and wake up at 704. Everyone should pick. It doesn't have to be those times, but everyone should pick a bedtime and a wake up time. You should set an alarm for your bedtime so that you stay on schedule and

you should keep this schedule even on the weekends, which will have a lot of people recoiling, right? Like, oh, that's the right time to sleep in. Why? Why is that so important? I think when I'm offering these suggestions, these tips for better sleep, I try to stay away from giving just rules because people don't respond to rules. People respond to reasons, not rules. And so I'll explain a little bit. Set deep in the middle of your brain and my brain and everyone's brain, there is a master 24-hour clock and it drums out what we call the circadian 24-hour rhythm, and it just goes back and forth every 24 hours.

And your circadian rhythm, your 24-hour master clock within the brain, expects regularity, and it thrives best under conditions of regularity. And when we give it the signal of regularity, including going to bed at the same time and waking up at the same time, that will anchor your sleep and therefore improve the quantity and the quality of that sleep. And that's why I usually recommend regularity as king. And yes, it does come onto the weekend as well with some, you know, with some degree of wiggle room. You can't tell me that you're not going out to dinner with friends at eight, which spills

out, you know, you don't even get home till 10, 30, 11. Are you saying to friends like, no, we're having dinner at seven because I have to hit my time? I will usually, and people, of course, all my friends know what I do. And so if I say, rather than going out to dinner at 8.30, is there any chance we could do 7, 7.30? Or what if you're going to the theater? Yeah. So usually then what will happen is that if I go to bed late, I will typically still try to wake up at approximately the same time. Now, of course, that sounds like heresy because it means that

I am then going to be short changed on my sleep by 30 minutes, maybe even an hour that night. And not just any sleep, but your REM sleep. But including my REM sleep. Or if I'm going to bed later, I'll be losing some of my deep sleep because it's the opposite end of the spectrum. But the reason is this, because if I'm going to bed later, I'll be losing some of my deep sleep because it's the opposite end of the spectrum. But the reason is this, because if I go to bed late and then I wake up late, now it creates this vicious cycle. Yeah, you're off. Because I've woken up late that following morning, I'm not going to be tired at my regular

bedtime the following evening. So now I'm going to stay awake even longer. I'm going to go to bed later, which means that I'm going to stay awake even longer. I'm going to go to bed later, which means that then I have to wake up even later. And all of a sudden my sleep window starts sliding forward. And at some point you've just got to draw the line in the stand and you've just got to call it quits. You've got to have a shorter night of sleep to get back into set. And I will nip it in the bud very quickly. I'll just say, look, I'm out with friends and we had a great night. I'm going to get to bed late. That's okay. Next day, I'm still going to

try and wake up at the same time so that I get myself back into my schedule and I don't let this get out of control because that can be a spiral that's very difficult to get back under control once you release it. We have joked, it's true, John Stossel, who was formerly with ABC, then he was with Fox for a number of years while I was there. If you have dinner over at John's house, he will literally just stand up from the dinner table and say, I'm going to sleep right now. You can stay if you'd like, but I'm going upstairs. The night's over. I think John and I would get along very well indeed. You would. Sympathico. Okay. But what about the nap?

Because sometimes if you're off in your sleep schedule, you're barely making it through the day and you think, oh, if I could just get that little nap in the middle of the afternoon. And we all know if you go two hours, you're screwing up your night's sleep. But what about if you go 45 minutes? Like what's your theory on napping? So what you're describing there is what we call prophylactic naps or strategic napping to try to help placate maybe a bad night of sleep or a short night of sleep. And you have to be very careful with naps. Naps are a double-edged sword.

Certainly what we've discovered, we and many other scientists, we've done lots of studies at my sleep center looking at the benefits of naps, and they have some great benefits. Improvements in learning and memory, they can help reset the emotional magnetic north of your compass so that life looks a little bit more rosy as a consequence. We've also found that naps have wonderful cardiovascular benefits, that they can lower blood pressure, they can reduce heart rate. But as I said, there is a danger here, and it comes back once again to our story of sleep pressure and that chemical adenosine. So as we're awake across the day, we're building up that adenosine, that sleepiness. And as we said, when we sleep, we remove that sleepiness. Well, if you take a nap that's either too long or it's too late in the afternoon, that nap acts almost like a pressure valve on a cooker. And when you

take that nap, you open up the pressure valve and you jettison some of that healthy sleepiness that's been building up. What that means is that when it comes to your time to try to fall asleep normally in the evening at your normal bedtime, for me, let's say it would be 1030 PM, I'm no longer going to feel sleepy. So because I took the nap, I'm going to get into bed at 1030 and then I'm just going to be tossing and turning for the first hour, feeling like I've got insomnia, which is miserable because I've lost some of that sleepiness that normally would be nice and heavy and pull me down into sleep and

help me sleep with, you know, remarkable alacrity. So I think the, the advice is probably this with naps. If you are not struggling with sleep at night and you can nap regularly during the day, then naps are just fine. I would try to limit them to around 20 minutes and no more because this comes back to, as we were describing, the cycles of sleep. If you go longer than 20 minutes, you start to go down to those deeper stages of deep non-real sleep. And if you wake up after 40 or 50 minutes from a longer nap, you're going to have this terrible sleep inertia, this sleep hangover, where you can almost feel worse for the first hour when you wake up because your brain was thinking, oh, you know, Megan is in it for the long haul. She's going down for a 90 minute or a full night of sleep. And so keep the nap short. And then finally, don't nap too late in the afternoon. Try not to nap after about 2 p.m. in the afternoon, assuming a typical bedtime. Because if you nap late in the evening, it's a little bit like snacking before your main meal. It just takes the edge, the appetite off your sleep hunger. You know that if you've ever had a baby and your baby's so tired

and you can see he wants to sleep and it's not bedtime yet, you will not let that baby take a nap, but you will play with that baby. It's like, oh no. Exactly. Yeah, yeah, yeah. You're bouncing them. You're doing everything. You're doing pantomimes, anything to keep them awake, to build up that sleepiness. And I would note two final things. As I said, if you are struggling with sleep at night, then you should absolutely not nap during the day. That's the best advice we can give people. Give yourself, build up all of that healthy sleepiness to try to guarantee the highest chance of an ease with which you fall asleep and then stay asleep. The other thing,

sometimes when we're taking in research participants or patients into the sleep center, we'll do an interview and I can say to people, do you nap during the day? And they say, no, I really never nap. And then I'll ask them a different question. As you're watching television in the evening before bed, do you ever fall asleep on the couch watching TV? And they'll say, yeah, I sometimes do. That's what we call an accidental nap. And that is the worst of all kind of naps because when is it happening? It's happening right before you're going to bed. And once again, that's going to shave the appetite off your sleep hunger. Okay. But what about, this is one of the

items I showed to Doug on the plane, the siesta, which is leading to men in foreign countries like Spain living to 90. I'm like, Doug, all you have to do is take a 20-minute nap in the middle of the day. You're going to live to be 90. Yeah. It's the Mediterranean siesta culture. And what we've discovered is that there's a Greek island, a great example called Icaria, and there people live extraordinary long lives. And what we found is that men who are there in Ikaria who take these Mediterranean naps frequently, they are four times more likely to reach the age of 90 than their American counterparts. Now, I'm not suggesting that all of that is simply because they're taking a nap during the day. It's because in part of their active lifestyle, it's their diet, it's the Mediterranean diet, but some of that is a contribution by way of sleep.

So certainly there are benefits to naps if you're taking them regularly and you're building them into your sleep structure, which leads to a more fundamental question, which I think is you're elegantly hinting at how were we designed to sleep as a species? And maybe we were never designed to sleep in the way that we currently sleep now in modernity, which is what we call monophasic sleep, where we try to get this long eight hour bout throughout the night. Because as I said, if you study those hunteratherer tribes, they don't sleep in the way that we do in many different ways. Some of that is timing, that they're usually going to bed somewhere around, on average, about 9 p.m., and they're waking up just before dawn. And they wake up not as light

is emerging. As we've said, what triggers them to wake up is the rise in temperature, which comes before the emergence of light, it turns out. But the other thing that we notice is that they do frequently nap during the hotter summer months. Now, you can also then say, well, but that's hunter-gatherer tribes. What about us in modern society? Well, we can see it in all of us because somewhere between about 1 to 4 PM in the afternoon, if I place electrodes on top of your head, I will see a genetically pre-programmed drop in the electrical alertness of your brainwave activity. And it's this sort of after lunch thing, you're in meetings in the office after lunch,

and all of a sudden you start to see those telltale head nods where people... And it's not that they're listening to good music with the head bobs. They're actually falling prey to this, what we call the postprandial drop in alertness, which means usually post-meal drop. Now, by the way, it's got nothing to do with food. You can prevent people from having lunch and they still have this drop in their alertness. Oh, yeah. I mean, haven't you heard people say it's something in turkey, it's some chemical in turkey that makes you fall asleep?

Yeah, tryptophan. It has nothing to do with that. Okay. I can have it. No, it turns out that it's very difficult for tryptophan to actually cross the blood-brain barrier, which is this protective sort of filter that some chemicals will get into your brain, some won't. When you digest that tryptophan, if you look at the data, it's really very equivocal as to whether or not that tryptophan actually gets into your brain. What's usually happening during Thanksgiving where people mistake, they say, oh, it's because I had a big turkey dinner that I'm falling asleep. No, it's that everyone usually then goes through to the living room. Everyone is coming into

Thanksgiving with a chronic sleep debt. Everyone is feeling full. No one wants to move. So you just sit down. And what happens? Finally, you give way on a Thursday when you normally would be at work to your sleep debt and you're lying there still. What's going to happen? You're going to fall asleep. Well, there's one other thing. So normally at Thanksgiving dinner, people will have a glass of wine or maybe they had a glass of champagne and alcohol we must discuss as well because I'm trying to remember how you put it. It's not a sleep aid. It's a depressant. It basically knocks you out. And then you wake up at two in the morning and you don't feel restored. You didn't get good sleep and your whole night is off.

Alcohol is not good for sleep. No, it's really not. And alcohol is probably the most misunderstood sleep aids that there is out there. It's not a sleep aid at all. It's desperately damaging to your sleep. But it's very natural that people, once they've tried over-the-counter medications, things like melatonin, which won't work, or valerian root or magnesium, these things that really don't have any significant science behind them, they turn to alcohol. And alcohol will harm your sleep in three ways. The first is that alcohol is in a class of drugs called the sedatives or a depressant. And what we mean by that is not necessarily a depressant in terms of your mood, although sometimes it can be. Alcohol, many people think, no, it actually makes me more alive and sort of alert. What's happening

there is that it's the depressant, the brain cell depressant effects, that it actually shuts down what's called your frontal cortex or your prefrontal cortex, which is what usually helps keep us with our inhibitions. And so we become disinhibited by way of alcohol. That's why people become the life of the party because alcohol is depressing the brain activity in that part of the brain that normally makes you more reserved, especially if you're British. But let's come back to sleep. One of the problems with alcohol, as I said, is it's a class of drugs that we call the sedatives and sedation is not sleep. But when you have a couple of nightcaps

in the evening, what you mistake is sedation for sleep, that it just knocks out your cortex. It just sedates your brain cells. And so you think, well, I fell asleep so much more quickly when I had a couple of drinks in the evening. It's not. You're just knocking your cortex out. You're losing consciousness more quickly. But to argue that you're in naturalistic sleep is really a fallacy. If I were to show you the electrical signature of your brainwave activity with versus without alcohol, they're not the same. They're quite different. So that's the first issue with alcohol. The second issue with alcohol is that it fragments your sleep. So you wake up many more times throughout the night. It litters your sleep with these

awakenings. The problem is those awakenings are usually so brief that you typically don't commit them to memory. So you wake up the next morning, you feel unrefreshed, you feel unrestored by your sleep, but you don't remember having a hard time falling asleep and you don't remember waking up throughout the night. You think it's just a hangover, but it's much more than just a hangover. It could be one glass of wine and you're still getting a bad night's sleep because of this that you don't even remember. Precisely that.

Yep. And we know the reason why. Alcohol will spike the fight or flight branch of the nervous system, which will jag the brain awake at night. Alcohol will also release alerting chemicals, which normally are lowering during sleep, chemicals such as cortisol, for example, a stress-related chemical, alcohol will jack that back up during sleep, hence increasing the likelihood of you waking up and the fragility of your sleep. The third and final issue with alcohol is that it seems to be very good at blocking your dream sleep or your rapid eye movement sleep. And as we've discussed, rapid eye movement sleep is critical for many things, for things like learning and memory and rebalancing your emotions and steering you away from things like depression and anxiety, because we've learned that dream sleep, particularly REM sleep, is a form of emotional

first aid. It's overnight therapy. And if you're not getting that dream sleep because you're suppressing with alcohol, then you can have these next day consequences. Also, by the way, REM sleep is the time when we release many of our peak hormones, including growth hormone. Once that he looked at giving people a dose of alcohol in the evening. It sort of got them tipsy. And as a consequence, they had a 50% reduction in the release of growth hormone during the night, which is critical for the restoration of our body. It's one of the other main functions of sleep. We also know it's during REM sleep that males release their peak levels of testosterone.

We don't release testosterone across the day in a constant amount. We release it during sleep and particularly during dream sleep. And if you're not getting that dream sleep, you're going to be testosterone deficient. This is another thing I showed Doug. So something about having the testosterone of somebody who is 10 years older if you're not getting enough sleep, right? Is that, I'm trying to remember exactly how you put it, but basically a 50-year-old man can look more like a 60-year-old man when it comes to testosterone if he is not getting enough sleep and enough quality sleep. That's right. That's what we found. And this brings us onto a topic that actually is fascinating. And enough quality sleep. But one of the problems when it comes to insufficient sleep is that a lack of sleep will decrease

the levels of these, what we call these sex-related hormones. So if you take a group of healthy, young, virile men, and you limit them to just four or five hours of sleep for a night, for one week, their levels of testosterone will be that of someone 10 years their senior. So just as you said, a lack of sleep will age a man by almost a decade in terms of that critical aspect of wellness and virility. And I should note, by the way, that we see equivalent impairments in female reproductive health caused by a lack of sleep. A lack of sleep in a woman will decrease things such as estrogen, luteinizing hormone, follicle stimulating hormone. All of these things are essential for a healthy and

vibrant reproductive system and also a vibrant reproductive and sex life. So, I mean, if we do all these tips, we're going to be so healthy because we're not going to be really boozing it up and we're not going to be on drugs and we're going to be limiting caffeine. And the other pieces of it are we are going to be ideally having sex more before we go to sleep and then not eating, not overeating the next day. Because if you don't get enough sleep, you tend to overeat. I think most people can understand that anecdotally. And if you're having sex before you go to bed, your odds of having a good night's sleep and of falling to sleep relatively easily are good news. For the most part, I'm a bit of a downer when it comes to caffeine and alcohol and sleep. I'm desperately unpopular. So coming back to it, what we have found is that when you are getting sufficient sleep, firstly, your relationship is

better because when you're not getting enough sleep, you have firstly more conflict in your relationship with your partner. Second, and this was a study done here at UC Berkeley. Second, your ability to resolve that conflict is nowhere near as effective. You can't move past those arguments. And what we discovered is the reason why, because when you're not getting sufficient sleep, you lose what's called your empathetic sensitivity, your ability to understand someone else, particularly your partner. And that's the why that we have more conflict. We've also known, however, more physiologically at a basic level, that when women are getting sufficient sleep, firstly, the sensitivity of their bodies to sexual interaction is actually heightened.

And furthermore, what we found is that one hour of extra sleep for a woman will increase her desire, her likelihood to want to be intimate with her partner by 14%. That's just one hour. I showed that to Doug on the plane too. So if he's thinking, look, can we not just go out tonight and stay up a little bit late? You can say one hour of extra sleep and I'll, I'll leave it and you can take your bedroom chit chat all you want after that. But, um, but then, you know, conversely, what we know is that it's not just that sleep improves your sex life, but sex improves your sleep life.

What we found is that people who have sex, as long as it results in orgasm, which is a big caveat, and maybe I could be stereotypical and say, guys, please do listen to that part of the equation. Sex, as long as it accomplishes orgasmm is associated with a faster ability to fall asleep and also a higher quality of sleep at night. Some of the reasons are because of the release of critical hormones, things like oxytocin for women and vasopressin for men. Both of those things will actually, uh, will bring about the engagement of the quieting branch of the nervous system and shift you away from the fight or flight branch of the nervous system, which is what has to happen for good sleep. Is that true if it's sex with yourself too? Ah, wonderful question. And it turns out,

yes, it's not quite as effective. It's about 15% less effective. But what we're talking about here is that masturbation is also an effective tool for helping you fall asleep and get better quality of sleep. And if you survey people anonymously, because obviously it's somewhat of a taboo topic, unfortunately, even in this day and age, nevertheless, some people will use it as a sleep aid when they're struggling with sleep. So that's the story with sleep and sex. But yeah, I think we can then come on to maybe sleep and weight gain. And I'm happy to sort of dive into that too. Well, I mean, I've noticed that myself because I can be, I'm pretty good about my willpower when it comes to eating. I've always found TV to be a good regulator. It's like, oh, you can see it if you gain it. So I'm usually pretty good,

but not if I'm not well-rested. I can't control it. I need to eat. It feels like the only thing that will make me feel better when I'm under-rested is food. Yeah. And this relationship we've known for now almost two decades is that when you're not getting sufficient sleep, you may find yourself to be more hungry and have a higher hunger and want to eat more. And it's no coincidence. First, what we know is that there are two appetite regulating hormones in your body and they are called leptin and ghrelin. Now, leptin is a hormone that when it's released, signals to your brain that you're full, that you're satisfied with your food, and you don't want to eat anymore. It's what we call the satiety hormone. Ghrelin does the opposite.

Ghrelin is the hunger hormone. And when ghrelin levels are high, you don't feel satisfied with the meal that you've eaten. Even if it's a big meal, you still feel hungry and you want to eat more. How are these two things related to sleep? Well, what we find is that if you limit people to, let's say, four or five hours of sleep for one week, or even just for several nights, those two hormones go in opposite directions. Firstly, what we find is that the signal of leptin, which is the signal that says you're no longer hungry, you're satisfied, you don't want to eat anymore, that signal of satiety is lost. It decreases by 18%. If that wasn't bad enough, the signal of ghrelin, which is the hunger hormone, that

increases. In fact, it increases by almost 28 percent. So I almost think of it like it's double jeopardy, that you're getting punished twice for the same crime of a lack of sleep. Once in the sense that you're losing the signal of being full and being satiated by a food. And once by the increase in ghrelin, which is the revving up of your hunger, and therefore you can eat the same food that you would normally eat, but you won't feel satisfied. You'll continue to feel hungry. And as a consequence, people will eat when they're not getting sufficient sleep, somewhere between an extra 250 to 400 calories each and every day. So maybe it doesn't sound so much, it's one extra chocolate bar every day. But if you add that up, even just across the five days during the week when most people

are short sleeping, and you do that week after week, month after month, year after year. It's like compounding interest on a loan. And that's why we see very strong relationships between short sleep duration and the risk for being obese. We also discovered more recently that it's not just about these two hunger hormones called leptin and ghrelin. Something else comes into play and it's called the endocannabinoid system. Now, many people have heard of cannabis, of course, and they may have also heard that when people take cannabis, they get the munchies, they get hungry. And we know why, because those cannabis chemicals increase your appetite. But what many people don't realize is that we have our own naturally occurring cannabinoids inside of us. They're called endocannabinoids, and they're critical for many functions within the brain. And what we've learned is that when you're not

getting sufficient sleep, those naturally occurring cannabinoid chemicals also start to increase. They increase by somewhere between about 30% when you're not getting sufficient sleep. So you get that almost munchy feeling, but without having had the cannabis itself. Think about it. If you are taking in an extra 400 calories a day, as you say, let's just say Monday through Friday, that's 2000 calories a week. There's 3500 calories in a pound. So call it one pound every two weeks to be nice to you, right? Because it could be more if you do the actual math. So let's say one pound every two weeks. And that's, well, I mean, there's 52 weeks in a year, so let's call it 26. You're looking at upwards of 20 pounds that you could gain in one year just because you didn't get enough sleep.

Even if it's just 200 calories, that's 10 pounds of extra weight gain. Or maybe you're just getting six and a half hours of sleep, so maybe it's just 100 calories. Well, that could still be five pounds of extra know extra um added and that's just that's just this first year that you're dealing with that what about the year after that now you have a five pound heavier base to start from right and then you've got another five on top of that that's why my my primary care physician who i always talk about he was such a character but he that's why he's very um he's just strict when it comes to weight gain because he's like gotta understand especially now that you're in your 50s you gain you gain two pounds this year. It's going to be there next year when you

come back. And then you're going to gain two on top of that. Now, you know, that's how people get to a problem, you know, where it's just spun out of control. Yeah. And I, you know, it is a, it's a really interesting problem too, because it's born not just out of the fact that you want to eat more, but you also change your desire for food preferences. So you start to want to eat different things when you're sleep deprived. That's true. Speaking of the cannaboid. Right. The first issue is that you lose control. We did a brain imaging study where we sleep deprived people and we looked at how they started to make their food choices and they started to become much more impulsive and a deep emotional brain center, sort of a hedonic based emotional center started to erupt in its activity.

I believe that. I feel like we've all had that. You feel deprived. You feel like sad because you haven't your sleep, and you're looking for a substitute, hi. Yes, that's right. And you self-medicate in part by way of food. And so when we look at what people, it's not just that they start to eat an extra 200 or 300 additional calories or 400 calories, it's that they change what they want to eat. They start to try to eat about 30 to 35% more of what we call the obesogenic type foods. So sugary treats, simple sugars, such as ice cream and cookies, as well as chocolate. And then they also have a 30% increased desire for the heavy hitting carbohydrate foods, such as bread and pasta. All of these things are foods that we know lean you more towards what's called the obesogenic profile of food intake.

That's what they ought to put on wrappers from now on, the obesogenic. You see that on your food, you're not going to select it. Yeah. It's almost like the lung that they used to put on cigarette packets. It would be the equivalent for food. And speaking actually of different organs, we also know that there's a 45% increased desire for salty snacks when you're not sufficient sleep. And we know that salt can significantly increase your blood pressure and set you on a path towards hypertension. That's right. And it just makes you look bad. It makes you look bloated and unattractive. And you retain water because of that sodium concentration. So you're not just eating more food. You're starting to eat the foods that will increase your desire to actually gain

obese mass. And then finally, let's just say that you're trying to be careful and you're trying to diet, but you're not getting sufficient sleep. What we've learned is that dieting becomes far less effective because 60% of all of the weight that you lose when you're dieting, but when you're not getting sleep will come from lean muscle mass and not fat. So in other words, when you're not getting sufficient sleep, your body will become stingy in giving up its fat. So you retain what you want to lose, which is the fat, and you give away what you want to keep, which is the muscle. And so the way that your body starts to partition the calories that you're taking on board also changes when

you're not getting sufficient sleep. And this is why we see these links between a lack of sleep and quite significant weight gain. I'm just thinking about partners out there who, you know, when you get married, you sleep with your spouse and a lot of people, especially when they get older, they have that sleep apnea, you know, where you, you wake up, you know, you haven't been breathing or you snore, what, what have you, would you, would you sleep in a different room from your, you know, you're the sleep master. So like, would you say, I love you, honey, but we're going to have to have separate bedrooms because I need, you know, you're on your own. I need my sleep. It seems to be happening. And it's certainly, Iously, what you find is that one out of

every four people will complain that their bed partner causes some form of sleep disruption. And based on some of those surveys, it seems to be that almost 30% of people will actually sleep in separate beds or separate locations in couples. And it's what we've called the sleep divorce. Now, some people have argued that that's not an ideal phrase, but sometimes you need a sleep divorce to prevent you from having a real one. And what we've also found is that of those people who do at least go to sleep together in the same bed, almost 40% of them will end up waking up in a different location. So it does seem to be a non-trivial problem. And part of the issue here is the stigma that's associated with it, which is that as a couple, if you admit to not sleeping together, then are you actually

sleeping together? People are like, oh, you get marital problems. Right. And if you come back to what we just described regarding sleep and sex, it's quite the opposite. That when two couples, sorry, when two people are in a couple are sleeping well, their sex hormones are increased, their desire to be physically intimate with each other increases, and the quality of their sex increases, and the quality of their sex increases and the quality of their relationship is improved. So if anything, it's an investment in that you could argue. Now, one of the other aspects of the reason that it has stigma or that people don't like the idea, and by the way, I'm not suggesting that this is for everyone. This is not a one size fits all.

Many people find incredible comfort sleeping together one size fits all. Many people find incredible comfort sleeping together in the same bed. Some people find that there is safety in it. Some people find that there is warmth and emotional bonding. What I would say though, is that if you are finding that your sleep is markedly disrupted or even modestly disrupted by your partner, have a conversation and then build in a clever routine. Because when you think about what sleep is, and as a couple, it's the front and the back end, it's the bookends of sleep that you miss. You miss getting into bed and sort of cuddling and saying goodnight. And then you miss waking up in the morning and saying good morning and having a kiss and a cuddle. So what you can do if you have a sleep divorce is that the person who goes to bed a little bit earlier, the person who's, let's say more of the morning type who's

going into bed earlier, they get into bed. And then the person who is more of the evening type, they get a text from their partner saying, look, I'm in bed. I'm ready to go to sleep. Come on in and give me a cuddle. Give me a kiss and say goodnight. And then on the reverse end, when the morning type will have woken up before the evening type, the evening type is obviously sleeping in a different location. Then it's the time for the evening type to send a text and say, darling, I'm just waking up. Come on in, say good morning to me. And so you can essentially get, you know, 80, 90% of the way there of all of the benefits because the rest of the middle part, most of us are not conscious. We're not really consciously aware of- We're having our REM stage, our deep sleep and our REM stage. And can I just ask you a question?

Because I meant to ask you this when we were talking about the REM stage and the dreaming. My kids, they often have scary dreams. And I've just said to them without really knowing whether it's true, I just believe it, that that's your, your brain is working out your fears. You know, like that's, it's good to have a scary dream because that's your brain working out something that's scaring you. And the next day you'll be a little bit less afraid of it, whether you, whether you know it or not. Now, I'm really kind of just making this up based on life experience, Matt, but is there any truth to that? You should be a sleep scientist, Megan. There's absolute truth to it. And this is a part of sleep science that we've been doing a lot of

work in over the past 20 years, which is sleep and your emotions, your moods, and also sleep and mental health. I'll start with the latter and come back to your good advice on the former. Firstly, when it comes to psychiatric disorders, we have not in the past 20 years been able to discover a single psychiatric condition in which sleep is normal. And I think that tells us a profound story about the intimacy with which these two things go hand in hand, sleep disruption and mental illness. What we've also started to learn, however, is that when you sleep deprive people who don't have psychiatric conditions, you can produce a pattern of brain activity that is very similar to anxiety disorders

as well as depression. And we've done some of these studies too. What happens is that when you are sleep deprived, the deep emotional centers of your brain, particularly the regions that are involved in the generation of strong negative emotional reactions, those become hyperreactive and irrational in terms of their emotional sensitivity. And that deep emotional reactions, those become hyperreactive and irrational in terms of their emotional sensitivity. And that deep emotional center, it's a structure called the amygdala, is 60% more reactive when you are not well slept. And that's the reason that we become so unbuckled in terms of our emotional stability and our emotional integrity when we're not getting sufficient sleep. That notion of I just snapped, dot, dot, dot, it's often the sentence that comes after a

bad night of sleep. Now, we can turn the tables on that and say, what's the bad that happens when we're not getting sufficient sleep? What's the good that happens when we do get sleep, which comes on to your sort of wise advice to your children? What we've discovered is that there is a very intimate relationship between your sleep health and your mental health, that it's during sleep and specifically during dream sleep that we receive a form of emotional first aid. And I've described this as overnight therapy. And it's dream sleep that will take these difficult, painful experiences, sometimes even traumatic experiences that we've been having during the day. And dream sleep acts almost like a nocturnal soothing balm. And it just takes the sharp edges off those difficult, painful, sometimes even fearful events and experiences

that we've had so that we come back the next day and they don't feel as emotional anymore. So in other words, it's not time that heals all wounds, but it's time during dream sleep that provides that form of emotional convalescence, as it were. And it's as though dream sleep and the act of dreaming itself acts almost like it strips away the bitter emotional rind from the informational orange of the experience. And it divorces the emotion from the memory. And that's why we feel better. And there's a wonderful quote by an American entrepreneur called E. Joseph Kossman. And he once said

that the best bridge between despair and hope is a good night of sleep. That's exactly what we're finding in science. I believe that. So we have to wrap it up because we're almost out of time. But the number of sleep benefits, I mean, you really have to read Matt's book and you'll see them all. But I mean, immunity to disease goes up. Chances of contracting diseases go down. The I mean, there are the number of things that they now think can be potentially prevented just by you getting steady sleep night after night throughout your life, it seems significantly long to take us back to where you started this, like on maybe Alzheimer's or Parkinson's. You tell me, just to sum up, how important is it to your health, your well-being? You can think of sleep essentially like the Swiss army

knife of health. There is almost no ailment in your brain and your body that sleep doesn't have a tool for. Sleep is your life support system. And I think it's mother nature's best effort yet at immortality. And if you look, as you said, almost every disease that is killing us in the developed world, from things such as cardiovascular disease, to cancer, to immune deficiencies, and then upstairs in the brain, Alzheimer's disease, stroke, diabetes, obesity, as well as also suicidality, which we've been looking at too. All of these things have significant and many of them causal links to a lack of sleep. It's amazing.

Gosh, when you think about that, they've done studies to see even everything from immunity to other diseases to vaccines. Does it go up with more sleep? They've studied it all. And the bottom line is get your sleep, prioritize it. Ideally eight hours, but you got to figure out what's right for you. Somewhere between seven to nine, but yeah, you can think of sleep. Essentially sleep is the very best health insurance policy that you could ever wish for. And it's there for you

to take and repeat prescription every single night. And it feels so good on so many levels. Dr. Matt Walker, thank you so much. Again, I want to remind everybody that if they want to listen, they can hear you on the Matt Walker podcast, which is about sleep among other things. And you can buy his international bestseller, Why We Sleep, or you can enroll at UCAL Berkeley and take one of his classes in neuroscience and psychology. What a pleasure. Thank you so much. It's been a delight. Thank you so much. And thank you for being a wonderful sleep ambassador. You are wonderful, Megan. So thank you again. All the best. See you soon. Wasn't that fascinating? I want to tell you a little

about what's coming up the rest of this week week because we have good stuff for you as we dig into wellness. First, we've got Oliver Berkman tomorrow who has written several books, but one in particular that we're going to dive into is on time management. It's a wide-ranging discussion on how we can be productive and on the power of limits and frankly on how to build a meaningful life. Let me tell you something funny about this interview with him. When I was reading the packet, getting ready for it, I said to my team, I don't, I'm not gonna be able to talk to this guy for two hours. I don't have like the problems he's outlining. I can't really relate to. These aren't my things. Well, it turned out to be like the funniest, most charming back and forth. Like he had, he was adorable and brought out so many

stories and we started like laughing about the, it's just like, I know you're going to love it. And if you do share these issues of time management and so on, I think you'll find it helpful. And even if you don't, I think you're really going to enjoy it. It was a sort of a sleeper. It was a sleeper on my list of really enjoyable conversations. Uh, and he was terrific. And then on Friday, we're going to be joined by Peter Attia. Now, do you know this guy? He was like a big hit on Joe Rogan and a lot of people in the health circles know and like revere Peter Attia, who talks about exercise and well-being the way Matt Walker talks about sleep and well-being. And that exercise is everything. But he has a great explanation for actionable ways to make exercise

part of your life and why you need to. And not just that, like the device you can put under your arm to help you not get type two diabetes, which he says is at the root of all evil. He calls it type, he calls it the fourth horseman and sort of the four things you really need to worry about and how it's never too late to get started on exercise or some of his eating programs. He's not like a dieter, but he has ways of approaching food that are really helpful. Lots and lots of great tips and the magic of saunas. I could go on. Just listen to it. You'll love it. So join me the rest of the week and let's help each other because I want to hear from you too. Love to know your feedback on any of these interviews or shows. The best way right now to do that is to go to Apple to subscribe and download the show and then leave a note in the

Apple reviews. I read every single one of them. We're over 22,000 now. It works on many levels because it helps us with Apple, which gives us no love because we're not named Oprah or Hillary or Michelle. So it helps us, but it also is a great way for me to get your feedback. And you can also, in the alternative, just email us at questions at devilmaycaremedia.com. We read every single email that comes in. Sometimes they make it on the air and, or it could just be feedback on the shows, right?

What do you want us to focus on? A guest suggestion, what you like, what you didn't like. Uh, we welcome all of it. Thank you guys so much for listening and we'll talk to you again next time. Thanks for listening to the Megyn Kelly show. No BS, no agenda, and no fear.