How to Sleep Smarter & The Bad Habits That Are Ruining Your Sleep w/Dr. Matthew Walker EP 1155

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This is episode number 1155 with Dr. Matthew Walker, part two. Welcome to the School of Greatness. My name is Lewis Howes, a former.

Pro athlete turned lifestyle entrepreneur. and each week we bring you an inspiring person or message to help you discover how to unlock your inner greatness. Thanks for spending some time with me today. Now let the class begin.

Joseph Costman said, the best bridge between despair and hope is a good night's sleep. And Eleanor Roosevelt said, the future belongs to those who believe in the beauty of their dreams. My guest today is Dr. Matthew Walker, who earned his degree in neuroscience from Nottingham University, UK, and his PhD in neurophysiology from the Medical Research Council in London. He also became a professor of psychiatry at Harvard Medical School, but he's now the professor of neuroscience and psychology at the University of California, Berkeley, and he is the go-to expert on all things sleep. And in case you didn't know, this is part two of my conversation with Dr. Walker. You can find part one by going to lewishowes.com/111 In this episode, we discuss how sleep affects your intimate relationships, why naps are actually good for you but can also be bad for you if you do them wrong, how caffeine, smoking and alcohol affects your sleep and when you can do them, the wrong ways people try to fix their sleeping habits, the simple hacks you can start doing today to improve your sleep and so much more. And a big thank you for being here. If you're a new listener, thank the person that sent you here. Also, big shout out to some of the fans of the week who have left reviews over on Apple Podcasts. This one's from Sylvia over in Australia who School of Greatness is one of my favorite by far. Lewis is humble and has had such a great personality. Thank you. There have been many interviews he's conducted that have given me the tools I need to move forward during difficult times in my life. And I'm forever grateful for the work that they are doing. Big thank you, Sylvia from Australia. And if you wanna be shouted out as a fan of the week, make sure to go to Apple Podcast, leave us a review, and let us know your favorite part of these episodes or the part that you enjoyed the most. Okay, in just a moment, the one and only Dr. Matthew Walker. I want to ask you about the impact of love and sleep. When someone feels an overwhelming feeling of love, connection, intimacy with a partner, does that support their sleep and improve the quality of their sleep? Does it hurt the quality of their sleep? And is there a difference if they're actually hugging and feeling love and connection to their partner, feeling that heartbeat or that warmth or whatever it might be that they're feeling, is there a difference if they're just feeling it but they're not next to them in the same bed? What's your thoughts on this topic?

I think the best answer is it's complicated. Let me pick it apart. Firstly, what we know is that couples who have a strong, loving relationship typically have overall significantly better sleep, both quantity as well as quality. When that relationship deteriorates and there is conflict, typically sleep is worse. We also know that there's just a very strong relationship between sleep and sex for the following reasons. Firstly, we know that your sex hormones are powerfully affected by sleep. So if I take a healthy young man, and I put them on four hours of sleep for one week, they will have a level of testosterone, which is that of someone 10 years their senior. So a lack of sleep will age a man by a decade in terms of that critical aspect of wellness and virility. You see exactly the same profile in women. We see that insufficient sleep is linked to a reduction in estrogen, in luteinizing hormone, and also in follicle-stimulating hormone, all of which are critical for female sexual health and reproductive health as well. What we've also found is that when, for example, a woman gets an extra hour of sleep, her desire to be physically intimate with her partner increases by 14%.

Guys need to listen to this.

So, you know, and certainly when it comes to testosterone as well.

Right, right.

What we've then found at the psychological relationship level is also interesting. When couples aren't sleeping well, firstly, they have more conflict. Secondly, not only do they have more conflict, they don't resolve that conflict as well. And part of the reason that they don't is because they lose empathy. They can't empathize. They become more self-centered and less compassionate towards the other. So for all of those reasons, you can see this bi-directional relationship regarding sleeping together in the sense of physical sleeping in the same bed. The data is very interesting. What we know is that about 30% depends on what survey you look at, but about 30% of people surveyed anonymously, and it usually has to be done this way, will report not sleeping in the same bed. Of those who do sleep in the same bed, a significant proportion of them, up to 40% of them, will report waking up in a different location for whatever reason. And this is what we've then, because the stigma at first is that if you're not sleeping together, then you're not sleeping. together. But the opposite seems to be true for those specific couples for whom it works. When they start to sleep apart, firstly because their sex hormones improve and the desire for each other increases, typically the physical intimate relationship is improved by way of what we call that sleep divorce. So, a sleep divorce can actually help you prevent a real one in that sense. But it's not a one size fits all. I'm not suggesting that by any means. For some people, sleeping together works very well. That overall, what we know is that when people sleep together, objectively, the quantity and the quality of their sleep is worse. On average, it's worse.

When people sleep in the same bed, objectively, the quality and the quantity of.

Their sleep is worse. However, if you ask them what they felt their sleep was like in terms of their satisfaction with sleep, on average, they will say that they felt more satisfied by their sleep when they were sleeping together. Now, that could just be because of this sort of stigma and this bias towards how we think we should sleep as couples. But I want to give people the permission to undergo at least this exploration with your partner, because there are many reasons sleep disorders such as sleep apnea, snoring, tossing and turning. We know that when one partner starts to toss and turn, it has a knock-on effect, like a domino, causes the other to have a bad night of sleep. So there are several ways that you can think about this. Firstly, have a conversation, and you don't have to admit it to the outside world if you don't want. I've admitted to this before having a sleep divorce. I would say that it's fine to tell people I love you, I care for you, I don't sleep well when we're together often, and I think I would be a better partner if I could try to sleep in a separate location. However, the funny thing is most of us, for the majority of that nighttime period, we're non-conscious. So we're actually not aware of the other partner. What we miss, I think, is the bookends of sleep.

It's going to sleep.

Getting into bed, saying goodnight, having a cuddle.

And waking up.

And then it's waking up. and so you can kind of hack the system. So whoever goes to bed first, depending on chronotype, morning type, evening type, somewhere in between, and we can speak about that too, whoever goes to bed first, it's the job of the other person to come through and as they can send them a text and say, look, I'm about to turn the light off, can you come through? And you go through and you give them a kiss and a cuddle and you have your little sort of bedtime minutes of the front end. lovely. And then on the back end, whoever wakes up first, they, you know, get to the kitchen and they start making their tea or coffee, whatever it is. And then the other person as they're waking up, they text them and say, I'm just waking up, come through. And you can go through to the bedroom and you can have your back end bedtime, sort of union, when they wake up. It sounds like a lot of work, but the cost benefit that you get in terms of healthy sleep and how good you will feel and how much better the statistics tellers relationships are when couples are well slept, I think is worthwhile at least exploring that. So it's not a one size fits all. I'm not suggesting that different people find different. Some people find it very safe to sleep with another partner because there is a degree of threat for whatever, you know, historical psychological reasons or They just feel better about having someone else there from a threat perspective, which I totally understand too. So just explore it with your partner.

What does the data say about animals, pets in the bed with you? You're going to ruin every animal, dog lover, cat lover.

I often say I'm not a particularly popular person just by personality and maybe nationality, but This makes me even more unpopular, which is sadly, pets are not a good outcome. They're not a good impact on your sleep. Human beings will typically sleep worse when pets are in the bed. So the advice is, you know, again, but what if there's so much love.

You have this love in your heart, you feel this connection, and it allows you to peacefully, restfully go to sleep.

As a pet person as well, dogs and cats, and other species.

Is that, is that animals in bed? Is that animals in the room next to your bed? Is it mammals?

Animals in the room, as long as they are trained not to wake you up for whatever reason.

They don't bark, they don't poke you, they don't, yeah.

Right, exactly. Not so bad, but if they're in the bed, not so good. But all I can tell you is the data, and if we speak about, alcohol, caffeine, drugs. It is not my responsibility as a sleep scientist to tell anyone how to live their life. And I'm not going to tell anyone that they should or should not sleep in the same bed with their partner or have their animal, their pet in the bed. You should live life on your own terms. And all I'm here to do is try to empower you with the science and the knowledge of sleep so then you can make an informed choice as to how you want to live your life. I have no business telling anyone how to live their life, let alone try to fix my own.

What does the science say about the people that live the longest, the people that live in the blue zones? How are they sleeping? What is the quality of sleep they get? Is there research around that?

It is interesting that when you look at some of the blue zone areas, in some of those communities, what we typically see is that they will have two bouts of sleep. They will have a long bout of sleep at night, and then they have a siesta-like nap in the afternoon. And there is some evidence physiologically that maybe we were designed as a species to be napping during the day, and we can speak about that in detail too. But to your question, there's a great island, I don't know if it falls into one of the blue zones, but it certainly should. It's a Greek island called Ikaria. and there the people have a wonderfully healthy lifestyle, but they also take naps during the day. And I think males there are almost, I could be getting this statistic wrong, but they're almost twice as likely to reach the age of 80 as any male American in America. And in fact, the island has often been described as the place where people forget to die. Isn't that lovely?

Wow. When out, now also, I mean, there's probably other factors. They're probably outside in the sun more. They're eating a certain lifestyle of food. Right.

The food, they're probably more physically active.

Social connections.

Social connections. And so all of those factors, is sleep a missing piece in the explanatory puzzle of the blue zone equation? It's actually never been studied. I should speak to Dan Buettner and sort of see if we can get some statistics on that. My guess is that it's if you add up all of the factors that they have right now, which is nutrition.

Social connection, physical activity, moving physical activity. Where that I think, yeah, isn't it part of like the amount of sunlight or how close it is to the equator.

Light exposure.

Yeah, yeah.

Sort of those things and having purpose in life and that sort of community. If you were to add up all of those factors and then say, of when you combine them all, how much of the variance in lifespan do you explain? Maybe you can explain 80%. So you can predict with 80% accuracy, you know, the lifespan of an individual when you know all of these five things, the blue zone things, let's call them. That means that there's 20% left on the table. Now, is sleep going to accommodate and absorb some of that additional variance that we can't yet explain? My guess is probably yes.

Yeah, and I'm guessing they're not sleeping three hours a night. You know, they're probably sleeping- no. Seven, eight hours a night.

Usually sleeping- Plus a nap, right? Right, yep. Six to seven hours of sleep at night, and then they will have that siesta-like activity in the afternoon, making up exactly what we typically predict, which is.

Somewhere between seven to nine hours of sleep. Now, is five hours of sleep plus a two or three hour nap acceptable? Is it six hours of sleep plus a one hour nap acceptable? Does it still transfer over or do you really need that seven hours minimum of kind of deeper sleep at night? And then if you get an extra 30 to 60 to 90 minutes in the afternoon, that's a bonus. How does that work?

It's certainly probably not as large as the first example you gave sort of, you know, five hours at night, then a three hour nap during the day. That doesn't seem to be biologically, physiologically how we were designed to sleep. But if you look at some of the cultures that have been untouched by sort of modernity, they, especially during the warm summer months, they can have a period where they'll have, you know, six and a half to seven hours of sleep at night and then a short siesta-like nap in the afternoon. So certainly it seems to be for the full 24-hour period, a minimum of seven hours is required. usually in one large about of sleep at night, and then perhaps one short sort of soups on little sampling of sleep in the afternoon in that nap-like behavior. I would say with naps, though, they can be a double-edged sword, and you have to be a little careful. We and others have shown time and again that naps can have very powerful benefits for the brain and for the body. They can improve your mood, your emotions, enhance your learning and memory. They can lower blood pressure. They can boost the immune system.

Right.

But naps are potentially dangerous because during the day from the moment that you and I both 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 you will feel. And after about 16 hours of being awake, you should feel heavy enough with that sleep pressure to fall asleep and stay asleep. And then when we sleep, what's beautiful is that sleep gives the brain the chance to evacuate all of that sleepiness, all of that adenosine, out of the brain. So after about eight hours, you have jettisoned 16 hours of sleepiness chemical of adenosine, and you wake up naturally. Why is this related to naps? It's related to naps because if you take a nap that's too long, or a nap that's too late into the day, it's a little bit like a valve on a steam cooker that you remove some of that healthy sleepiness, that sleep pressure, so that when it comes time to fall asleep at night or try to stay asleep, it's not as easy anymore because you've removed some of that burden. So I think, you know, napping late in the day or napping for too long, it's a little bit like snacking before your main meal. It just takes the edge off your sleep appetite and hunger, if that makes any sense.

What's the latest we should be napping and what's the longest we should be napping?

I would usually say cut naps off after about 2:00 p.m. And assuming a standard prototypical bedtime of which, you know, it varies. And then I would say try to limit your naps to probably no more than 20 to 25 minutes at max. And the reason is because if you go longer than that, you can start to go into the deeper phases of sleep. And if you wake up after an hour, your brain is in the deep stages. And then when you come out of that nap, you can typically feel worse. You almost have what we call a sleep hangover.

Right.

Or this technical term is sleep inertia, where it takes you then about another hour and a half to kind of wake back up because you went too deep, as it were. So the best advice is the following. if you are struggling with sleep at night, do not nap during the day. Build up all of that healthy sleepiness. Give yourself the best chance to get to sleep and stay asleep. But if you can nap regularly and you're not struggling with sleep, naps can be just fine. Maybe cut them off, you know, depending on your bedtime, 2 to 3 p.m. and try to keep them to around 20 minutes.

I'm curious about diet and nutrition and food choices and how it impacts sleep and also alcohol. I would put caffeine, smoking cigarettes as another category. And maybe there's three categories, but if someone is drinking a cup of coffee a day or multiple cups, or they're having a few cigarettes or drinking alcohol, any of those categories, how does that affect the quality and the depth of the sleep that you have?

So, this is where I become even more unpopular, Louis. So, let's start with caffeine first, of which I've changed my tune actually over the years. I will tell you, drink coffee, which sounds strange coming from, you know, a sleep scientist.

But just only drink it before a certain time, I'm assuming, right?

So, the dose and the timing make the poison. If there is a tagline for coffee, that would be it with regards to sleep. And the reason is this. Firstly, coffee has been associated with some wonderful health benefits. And in fact, people have often reached out to me, and I'll soon release one of my podcast episodes on this explaining this in more detail, but they would say, look, coffee is associated with lots of health benefits. In fact, many of the same health benefits that sleep is associated with. And we know that caffeine is not great for sleep. how do you reconcile that paradox? It seems to be counterintuitive. And there's a very simple one word answer, antioxidants, right? Because the it turns out that the humble coffee bean has now had to carry the weight of infusing most people who eat a poor diet with their major source of antioxidants each day. And in fact, if you look at the American population, and the same is true in many European countries, because we don't eat in a holistic way in whole foods and get all of our nutrients and antioxidants. The coffee bean is the principal source.

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So it's not the caffeine that causes the association between coffee being good for you, It's the antioxidants. And a good demonstration of this is decaffeinated coffee, which still contains the antioxidants and is still associated with many of the same health benefits.

Interesting.

So certainly most of us, you know, many people will like to wake up, they will enjoy, you know, a coffee or two in the morning, and that's great. Definitely do that, no problem. Be mindful of whether you're sensitive or not, and it depends on your genes and a certain type of liver gene that dictates an enzyme, they're called cytochrome P450 enzymes that degrade certain compounds. And there is a gene that if you have one variant of it, the gene is called CYP1A2, if I'm getting my nerd genes correct. If you have one version of that, you metabolize caffeine very quickly. If you have a different version of it, you metabolize caffeine very slowly. Unfortunately, I am one of those individuals who has a slow caffeine metabolizer, and I can have one cup of... I drink decaf, but if I have one cup of coffee in the morning, for the most part, it won't impact my sleep at night. But let me come back to the dose and the poison part. One of the problems with caffeine is that it has a half-life in the average adult of 5 to 6 hours, which means that it has a quarter-life of about 10 to 12 hours. So, in other words, if you have a cup of coffee at midday, then a quarter of that caffeine is still circulating in your brain. At midnight.

No way.

So, it would be the equivalent of a cup of coffee at midday would be the equivalent of getting into bed. I sometimes sort of note it. And before you turn the light out, you swig a quarter of a cup of Starbucks and you hope for a good night of sleep. And it's probably not going to happen. So, the first issue is, the duration of its action. The second concern with caffeine, though, is some people will say, look, I can have an espresso with dinner, and I fall asleep fine, and I stay asleep. So it's no problem. Even if that's true, what we've discovered is that caffeine can decrease the amount of deep sleep that you get. And so that you wake up the next morning and you don't remember having a hard time falling asleep, and you don't remember waking up, and finding it hard to fall back asleep, but you don't feel refreshed by your sleep. And so, you're now reaching for two cups of coffee rather than one in the morning. And just to give you a context, drop your deep sleep by 20%, which is what caffeine can do at night. I would have to age you by about 15 years, or you can do it every night with a cup of coffee.

So, if you're going to have coffee, drink it before, what, 10:00 a.m.?

Well, I would say, you know, see how your sensitivity is. Certainly, I would wish for most people, assuming a typical bedtime again, of cutting it off before midday, try to limit yourself to maximum three cups, two cups if you can. What we do find, by the way, those health associations with cups of coffee, once you get past sort of three or four cups, it starts to go in the opposite direction. It actually has, you know, it doesn't.

Have those health benefits. and if you're gonna do a cappuccino at night, just do decaf.

Just do decaf. It's actually doesn't taste too bad in the end, and it will save your sleep.

Yeah. Oh, yeah.

And then I can come on to alcohol if you want and. Yes, please. Put the nail in my.

Well, I've never actually, I. Most people know in my, my, my life and also on my show that I've never been drunk. I've never, I've had sips of alcohol in my life. I, you know, I didn't. have a sip in four years of college because I just made a commitment to be a better athlete and have better performance when all my teammates were drinking on the weekends. And, I could see that they were sluggish the next day in practice. I was like, this is my way. And, I just kind of was like, why start after college? I maybe have like a Bailey's on ice once or twice a year. It's just like sip on and that's-- you- rebel, Lewis. Listen to you. I know, right? And, it's just like a little sweet milk or something. But, I've always felt like, man, people just don't seem to make good decisions or they don't wake up better after they have alcohol. So, it just, you know, I knew I needed advantages in my life somewhere when my vice is sugar, which is probably going to be the next thing you talk about. But how does alcohol affect sleep? And does it matter the portion and the potion of when?

So, I should admit, right up front, too. I'm like you, I'm not a big drinker, which means I probably should have had my British passport taken away from me long ago. I think it's a birthright of many. But what we know is that alcohol will hurt your sleep in at least four different ways, or it has four consequences, I should say. The first is that when people say, Look, I have a couple of drinks in the evening and it helps me fall asleep, The problem is that alcohol is in a class of drugs that we call the sedatives. And sedation is not sleep. But when you've had a couple of drinks in the evening, you mistake the former for the latter. And sedation is where the brain simply, the brain cells are switched off, and they essentially, you're not knocking out your cortex. But when you go into deep sleep, it's very different. Deep sleep is a time when hundreds of thousands of brain cells, all of a sudden they coordinate in their firing. And it's unlike any other time we see during the 24-hour period. All of these brain cells fire together, and then they all fall silent. And then they all fire together, and then they all fall silent. It is this spectacular physiological ballet. And that type of sleep is very different to sedation. So that's the first issue. The second issue is that alcohol will fragment your sleep so that you will wake up many more times throughout the night. It will litter your sleep with many awakenings. And lots of people sort of, you know, I wear the Oura Ring and I'm related to the company too, but a lot of people will say with their Oura data, you know, after I've had a night of some drinking, I just see my sleep is decimated. I'm very punctuated with all of these awakenings, and that's what we call sleep fragmentation. that's poor quality of sleep. And sleep quality is just as important as sleep quantity. The third problem with alcohol is that it's very good at suppressing your REM sleep or your dream sleep, which is what we've spoken about, has many benefits, by the way, including other benefits down in the body. We know that it's during dream sleep when the body releases in both men and women highest amounts of testosterone. so if you're blocking your dream sleep and you're drinking particularly in athletic context, you need that testosterone for recovery and restitution of muscle mass and muscle growth. So, and then the final thing coming back to muscle growth is that if you lace people with alcohol at night and the sleep disruption as a consequence at certain phases of sleep, it can cause a 50% impairment in the amount of growth hormone that's released, five zero. at night. So again, I want to back up though here and I really think this is important. I don't want to be puritanical and I don't want to wag my finger. You know, life is to be lived to a certain degree. Of course, live your life and don't let anyone tell you how you want to sort of live your life. As long as you're not hurting anyone, doing anything wrong, live your life as you As you wish.

But I understand the consequences that the data speaks to, that people who do certain things tend to not live as long or tend to have worse quality sleep or age faster based on the data. Maybe some people can get away with certain things or live a little longer and have a glass of wine every night, but they have everything else in their life going for them in, you know, or something, you know.

And maybe the choice is that you say, you know, I would prefer to live a shorter life with less sleep. Right. And you know, that's your- I live.

It on my terms.

Right. And then what I wouldn't wish you to do, right, exactly, is do it that way unwittingly or unknowingly. Once you're imbued with that knowledge and you still want to make that choice, then if that's the flag that you're hoisting, I'll salute it every single day. But I just want you to at least have the evidence so that you can then do whatever you want with it. That's all my job is. I'm not here to tell.

What is the, based on the data, what would you say would be a suitable amount of alcohol someone could drink on a weekly basis where it wouldn't affect too badly their sleep but it wouldn't be the best thing? But it'd be like, okay, this is doable. Is that a couple glasses a week? Is that a glass a night? Is that one glass a week? Like, is that five shots at a time?

What is this? We've even seen that one glass of wine at night will have an impact.

One glass of wine every night will have an impact. What if it's one glass?

We haven't actually done the studies where we repeat across multiple nights.

Just one glass.

Just one glass will change the composition of your sleep that night.

And if you do it every night, one glass, that's probably going to have... Compounds.

It may have deleterious consequences is the suspicion. And I think the politically incorrect advice that I never give on podcasts would be the following, that you should go to the pub in the morning and that way the alcohol is out your system by the evening. But I would never suggest that, you know, to it's just you and me here, isn't it? There's no one else.

Exactly.

So if someone did want to have a glass of wine over lunch, let's say between 12 and 3 p.m. and they went to bed at, you know, 10 or midnight, how would that affect their sleep?

It's possible, depending on how successful your liver and your kidneys are and what the strength of that alcohol is, that it may have been metabolized and cleared from the system sufficiently that it wouldn't have an impact on sleep. But I don't know anyone who's tried to really do the dose response curves of that question, which is, you know, let's start with this proof of alcohol, you know, 10% or spirits, whatever it is, 40% or beer, seven, whatever it is. And then let's do that and see the impact. And then let's bring, let's march that dose from the afternoon, closer and closer and closer to sleep and see if the detriment to sleep is a linear relationship that the closer you get, the worse the consequence of your sleep. Or is it more of an exponential, a sort of a ramping up curve where it doesn't have too much effect in the afternoon, but then it's really in the last two hours, and especially in the last hour, the last three hours when it climbs, that's when you have a monumental impact on sleep and then it I don't know if that makes sense, but I don't know. That would be the city that I would want to do. It's just immensely costly and probably no one wants to fund that city.

Right. And what about the impact of cigarettes, cigars, or mushrooms or other types of drugs that are now becoming more popularized, the mushroom kind of community, the, yeah, not ayahuasca, but whatever's in between mushrooms and ayahuasca, kind of like those types of drugs. how do those impact or even marijuana? How does that impact sleep quality?

So, there is emerging evidence on CBD and THC. I think the best evidence we have so far is on THC, which is tetrahydrocannabinol, which is the psychoactive component of marijuana. That's the part that gets you high. We know that that unfortunately is not good for sleep. for at least two reasons. Firstly, people will say it does help me fall asleep quicker and it does seem to hasten the onset of sleep. The problem is that you develop a tolerance. You develop a dependency very quickly. And then when you stop using, you have very horrific rebound insomnia, and therefore you have to go right back to it. So you develop a dependency on the drug. So that's the first reason that we don't advise it. the second is that it seems to THC seems to be very good, like alcohol, but through a different mechanistic pathway, it seems to be very good at blocking your dream sleep, your REM sleep. So unfortunately, THC is probably not advised from a scientific perspective. CBD, however, is interesting. I, you know, I'm not a medical doctor, and I'm, you know, none of what I say here or anywhere else is, you know, prescriptive or medical advice. But the scientific data on CBD is starting to become quite interesting. Many people have suggested that they use it and it helps their sleep. If you look in some of the animal studies at higher doses, CBD does seem to improve some aspects of deep sleep, deep quality sleep. The dose also is interesting though, and this has not been spoken about widely in the community, and I think it's a disservice At low doses, CBD may actually be awake promoting, it may keep you awake, whereas at higher doses it may be more soporific, it may be more what we call somnogenic and increase sleep. The question then to me is that if that data is real, I'll start to believe it more if I can come up with a plausible physiological mechanism that underlies it. And after doing a lot of research on in this area and reading, I think there are at least two non-mutually exclusive possibilities as to why CBD may be, and I don't think there's anywhere near enough data to suggest that it does, but it may have an effect. The first is that it seems to be a very powerful, what we call anxiolytic. In other words, it decreases your anxiety. And there's some great science around CBD and anxiety right now, even within the brain. You know, we spoke before about how you become very emotionally irrational without sufficient sleep. And in part, it's because a deep emotional center called the amygdala erupts and becomes at least 60% more reactive when you're not getting sufficient sleep. That same emotional epicenter, the amygdala, is actually quietened down by CBD. Some great studies there. And we know, and we spoke about earlier on, that anxiety is one of the roots to which you get to insomnia. So I think it has an indirect potential benefit, which is that it quiets the nervous system down, it reduces anxiety, and when you remove the roadblock of anxiety, you enter into the richer world of sleep. The second is a more direct mechanism, and this comes onto something called temperature, because your brain and your body need to drop their core temperature by about one degree Celsius or around two to three degrees Fahrenheit, for you to fall asleep and stay asleep soundly across the night. And that's the reason that you will always find it easier to fall asleep in a room that's too cold than too hot.

What's the ideal temperature of the room?

It's different for different people. You know, men typically run hotter than women. But on average, what we found is that a bedroom temperature of somewhere between sort of somewhere between 62 to 65 degrees Fahrenheit. which is actually quite cold, a little over 18 degrees Celsius. So now, if you're worried about that, no problem, you can take a hot water bottle to bed, you can put it at the end of the bed, warm your feet, wear thick socks, but for the ambient temperature, that seems to be ideal for the average adult.

62 to 65.

Yeah.

Wow.

So one of the interesting things coming back to CBD, however, is that it seems to have what we call a hypo- thermic profile to it. In other words, it drops your core body temperature. And by the way, this is the reason that people will think, look, if I have a hot bath or a shower before bed at night, I fall asleep faster and I seem to get a better night of sleep. And part of the reason you think that is because you get out of the bath, you're all warm and toasty, you get under the covers and you fall asleep. It's the exact opposite reason. In fact, what happens is that when you're in the bath or the shower, all of the blood comes to the surface of your skin, rosy cheeks, kind of red hands, red face. And that means that you've charmed all of the blood out of the core of your body to the surface. And when you get out of the bath, that skin surface radiates the heat out of the core of your body. So after a warm bath, your core body temperature plummets. That's the reason why you sleep better. And in fact, it's so reliable that we call it the warm bath effect in sleep science.

Is it better to take a warm bath or a cold shower before bed?

Cold showers, typically not, because what that will do is usually the opposite. Firstly, cold showers will activate you and sort of, you know, create usually a brain response, including a neurochemical called norepinephrine, which is an alerting, activating chemical. The second is that when you have a cold shower, typically your skin will get whiter as a consequence. And what will happen is that the brain is doing what we call vasoconstriction, sorry, the body is doing vasoconstriction. It's locking down all of the blood vessels because it's trying to hold onto its heat. So you withdraw the heat into the core of the body and you trap the heat. So you usually go for a warm bath or a shower when you are trying to get to bed at night. that's usually the best prescription.

And what about nicotine, the effects of nicotine, whether it be vaping or cigarettes, how does that affect sleep?

So nicotine is a very activating chemical. It's a stimulant. It's what we call a psychoactive stimulant. And coffee is a psychoactive stimulant too, but they work through very different mechanisms. So nicotine will bind onto specific receptors in the brain that can activate the brain called nicotinic. receptors. And what we typically find is that smoking and smoking before bedtime will usually create sleep disruption and activate the brain. So it will make it harder to fall asleep. But the hard part is when you're going through abstinence, we also know the same with many drugs, when you're trying to quit, sleep usually is disrupted as a consequence as you go through withdrawal. And in fact, what we found is that in For example, we've done some studies with cocaine addicts. We found that the severity of their sleep disruption during withdrawal predicts their relapse.

Because I need to just feel like I can sleep, relax and sleep again.

Or it's just that when they're not sleeping well, they are predisposed to A, making bad choices. They become more impulsive, and we've seen this in healthy individuals. You sleep deprive them, the dopamine circuits in the brain that are reward seeking, impulsive, risk taking, those circuits of the brain become hyperactive and hypersensitive. So when you are going through abstinence and your sleep is disrupted, what's unfortunate is that you become more reward sensitive and more impulsive. You lack self-control. So no wonder it predicts relapse. But the good thing that tells us is, If that's the case, can we use sleep treatment, sleep therapy as a way to intervene during abstinence to see if we can shore up and bootstrap the system so it doesn't fall prey to relapse because of the abstinence induced sleep disruption. Does that make any sense?

Yeah, of course, yeah it does.

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So is there if someone was vaping or smoking cigarettes would they be a cutoff time they should stop during the day if they wanted to get better sleep or suggest if you're having nicotine at all and anytime during the day it's going to.

Affect you at night the nicotine typically has a shorter half-life in terms of its activity. So unlike caffeine, which has quite a long sort of half-life and alcohol too, nicotine has a shorter half-life. So the sort of proximity to sleep that you may have to cut yourself off may be shorter as a consequence, but just keep an eye out. You know, it usually is going to be an activating thing, and we see it all of the time. It can be a potent e disrupt up.

And what about, a, sugar and the standard American diet, the sad diet. How does this impact our sleep?

Unfortunately, it it's not great, so ha um, what we found um and there's a very there's a very you know, I seem to be like just the the the gom.

Yeah.

I know. I feel like Eeyore in Winnie the Pooh. Everything's terrible.

But.

There is a very strong link between your sleep and what you're eating. And there is an equally strong link between what you're eating and how you sleep. And we can maybe take both of those. There's less evidence, actually, regarding your first question, which is how does what you eat impact your sleep? What we do know for certain is that diets that are high in sugar and low in fibre will typically result in worse sleep. And part of that, especially if you're having sugar intake in the last couple of hours of sleep. And part of the reason I believe this is true, although we don't yet have the evidence, is that sugar is a very good way to release energy and increase your core body temperature. And what we've just spoken about is that when you to go to sleep, you need to drop your core body temperature. And that can be one of the many, I think, consequences.

So, if you're going to have sugar, try to wait, do it two or three hours before at the latest when you sleep.

Would be advise it. Yeah.

And don't have it at midnight and then wait three hours of sleep.

No, that would be ill-advised as well from my scientific that knowledge.

And what about food in general? Is there a time where you should stop eating before you sleep?

Great question. And in fact, that's kind of a bit of a myth when you look at the data that you could bust. People will say you should really cut yourself off three or four hours before bed, and that's the optimal. If you look at the studies, you can go as close as to one hour before bed eating, and it doesn't seem to have an impact. once you get closer than one hour, it does seem to have a negative consequence. Also, just be mindful of acid reflux. That's the other thing. If you have a large meal and then you lie down, a lot of people will get that reflux that will wake them up throughout the night. And that's another reason a cost of eating too big too late.

Interesting. Yeah, a couple nights ago, I hadn't had pizza in a long time, and I'm a big pizza guy. And I had a a pizza. It came like two hours late. It was supposed to come at like eight. And then I had. The delivery got messed up. Anyways, it came like 11 30. I was like, ah, do I eat this now or do I just, you know, eat it tomorrow or something? And I. I kept. I was like, maybe I'll have one piece. And then I ate, like, almost the whole thing. And the next morning I woke up and I felt like this acidy type of feeling. And I was like, huh?

It didn't wake me up in the middle of the night, but I felt it. At least you don't remember. That's the One of the downsides too is that you don't remember waking up, but if we looked at your, you know, if we had a sleep tracking ring on you, it's probably likely that, you know, we would have seen some.

Of that restless sleep. Yeah, that's true. And, but I also felt it the next morning for a couple hours, which was just uncomfortable, you know, feeling that kind of acidy feeling. So that's interesting.

Yeah. So timing, we can sort of bust that myth a little bit. Also, time restricted eating, which has been a big thing of late, the studies there are great. And, you know, intermittent fasting, you mean? Yeah, I would say it's time restricted eating rather than intermittent fasting because to really call it fasting, you have to, you know, not eat probably 36 hours past to say that you're in a fast. But I think time restricted eating, there's some great work, my good colleague Sachin Panda at down in San Diego at the Salk has done some amazing work in animal models. David Sinclair's got some great data on this too. Dr. Jason Fong, Yeah, exactly. These people are great. But what's interesting is that I don't doubt the health benefits. Those health benefits are very clear on multiple metrics of body health and some brain health. But when you look at the sleep data, from what I can tell, there are really only three studies so far that carefully controlled studies. Two out of the three were in obese populations. One out of the three was in healthy weight individuals. And what they found was that time-restricted eating offered no benefits to sleep. Now, it's not that time-restricted eating gave any or caused any detriment to sleep. It just didn't offer any benefit. That doesn't mean that I'm advising against time-restricted eating. In fact, I do time-restricted eating. But in terms of sleep, unfortunately, it.

Doesn'T seem to benefit. It's funny you hear people who intermittent fast or time-restricted eating say, you know, I sleep like amazing, you know, when I I sleep so great when I do it. So, maybe it's just a placebo effect or something.

I think there's inter-individual variability, of course, too. And for some people, I have no doubt that it probably creates objectively good sleep. But, you should also make the point as you did, the placebo effect is the most reliable effect in all of pharmacology.

Right, exactly. Or also, it's maybe you're also not eating later at night because you're not eating in general. and maybe your body just isn't like metabolizing something when you're right about to go to bed and you're, I don't know, maybe it's not working as hard the body and so you're able to get cooler temperature, I don't know. But that's interesting.

Time restricted eating, yeah, but we can turn the tables then. That's sort of the impact of food on your sleep. The impact of sleep on how you eat is incredibly well resolved.

So, if you get a lack of sleep, does that mean you tend to go after the things that want to give you more energy, the sugary, carby type of things, and then it's never enough and you keep eating more of it? That type of stuff.

Did I say you should be a sleep scientist? So, you've nailed it. So, firstly, what we find is that your appetite regulating hormones go in opposite and bad directions when you're not sleeping well. so firstly, so there are two key appetite regulating hormones, leptin and ghrelin that I know I think you've had discussed on the show before. Leptin is the satiety hormone and it signals to your brain that you're full and that you're satiated and therefore you typically don't want to eat more. You're satisfied with what you've eaten. Ghrelin, on the other hand, is the hunger hormone that will say, no, I'm not satisfied with my food. I want to eat more. and when you are insufficiently slept, the levels of leptin, which is the satiety signal, the I'm full, I'm comfortable with my food, that drops away. And if that weren't bad enough, levels of ghrelin actually increase. So you lose the signal of feeling full and you increase the signal of hunger. And no wonder then, as a consequence, insufficiently slept individuals will typically be eating somewhere between two to 300 extra calories each day. And you can add that up, you know, day after day, week after week, month after month. And depending on your, you know, how you calculate it, it could be, you know, 40,000 extra calories every year, which could be somewhere in the region of, you know, four to £7 of obese mass that you add on each year because of insufficient sleep. The second thing that we found is that it's not only that you eat more, but what you want to eat changes just as you described. So your food preferences not only shift to just eating more, but you eat more of the things that are what we call more obesogenic. Right. So when you are underslept, you start to reach out for simple sugars and the stodgy, heavy hitting carbohydrates rather than the sort of the protein rich food. Yeah, yeah.

The vegetables, fruits and nuts Exactly.

So now you're reaching for this sort of ice cream and the cookies rather than the leafy greens and the handful of nuts. So that's a second problem with insufficient sleep. The third problem that we've discovered is dieting. It's really fascinating. If I take an individual who is not sleeping enough and they're dieting, they're trying to lose weight and manage what they eat, unfortunately, 70% of the weight that they lose will come from lean muscle mass and not fat. So in other words, when you are- Without sleeping properly. Without sleeping properly. So when you are short sleeping a set of individuals, this is what we see. In other words, when you are not getting sufficient sleep but you are dieting, you hold on to what you want to lose, which is the fat, and you lose what you want to keep, which is the muscle. Does that make sense?

It makes sense. It makes me sad.

I know, I'm bloody depressing aren't I? This is why I tell you I'm just so unpopular. I'm a nightmare.

We need this information.

The way you put it.

Yeah, exactly. We need this information to help us improve the quality of our life. And that's my mission to serve people with the right information, with the right data, with the right science that can help them if they could do one thing better to improve, you know, even just a little bit, that'll help them overall. maybe they're not going to be able to apply all these strategies, but it's like, what would you say if there were three things someone could do to improve their sleep tonight? Only three things. What would those three things be for you?

I think beyond what we've spoken about, which is sort of the alcohol and the caffeine and being mindful of that, I would say, firstly, regularity. If there's one thing that you take from this this podcast regarding sleep, its regularity, go to bed at the same time and wake up at the same time, no matter whether it's the weekday or the weekend.

Really?

Regularity is king. And I don't like giving rules. People don't respond to rules. People respond to reasons, not rules. And so, I'll try and explain the rule as it were. The reason is because your brain has a master 24-hour clock inside of it. It sits right in the middle of your brain. It's called called the suprachiasmatic nucleus. And it expects regularity and thrives best under conditions of regularity, including regularity of your wake sleep schedule. And if you give it regularity, regularity is king, and it will anchor your sleep and improve the quantity and the quality of your sleep. Okay. I think the second piece of advice I would have is have a wind down routine. You know, many of us think of sleep almost like a light switch, that we are racing around during the day, we're desperately busy, we jump into bed, we switch the light out, and we think that sleep should be like that same light switch. Sleep is much more like landing a plane. It takes time for your brain to descend down onto the terra firma that we call good sleep. sleep at night. And we do this with kids, of course. We have to go through the routine. We sort of give them a bath and then we sort of get them out and then put them into bed. Then we read to them and then gradually, and if you deviate from that routine, from that wind-down routine, bad things are gonna usually transpire. Why don't we do that for humans?

Yeah, how long should that routine be? Is that, can that be 10 minutes? Can be an hour? I mean, what's, does it matter?

I would say find what works for you. I would say usually try to think about some kind of a 30 to 20 minute routine, whether that's taking a bath. I found meditation to be incredibly powerful. I really enjoy the app Headspace. And I know you've had Andy on the show before too. Fantastic, wonderful individual doing great things. So meditation before bed, you know, stretching, some kind of a wind down routine. The other thing you can do is have a worry journal. Just sit down and usually two hours before bed, don't do it right before bed, with a pad of paper and a pencil, write down everything that's on your mind. And it's catharsis. And it's just like vomiting out all of your anxiety onto the page. And that's something you can sleep with. You can sleep with it. So you don't sleep with it. So you can have that as part of your wind down routine. Find something that works for you, but a wind down routine is critical. The last piece of advice I would give, the third piece, is that after a bad night of sleep, or if you're struggling with a bout of insomnia, the very best advice that I can give you is do nothing. And what I mean by that is don't wake up any later, don't go to bed any earlier, don't nap during the day, and don't drink more coffee. And I'll explain each of them. Yeah. So, if you wake up later in the day because you think, well, I had such a bad night of sleep, I need to sleep in a little bit to compensate. because you're waking up later when it comes time to your normal bedtime later that evening, because you've only been awake for less time, you've been awake for less time than you would do normally. You're not as tired. So, what happens? You get into bed because you think, I had a bad night of sleep and I want to sort of make this one a good one. And now you're tossing and turning and you have another bad night because you woke up too late in the morning. The same is true for going to bed too early. You think, well, My bedtime is normally, you know, let's say it's 11:00 in the evening. I'm going to get to bed at 10:00 tonight because I had such a bad night of sleep. Resist. Don't do that because your circadian rhythm, your natural 24-hour rhythm, will not typically want you to go to bed until 11:00. But you get into bed at 10:00 and then you're wide awake and now you have another bad night of sleep. Napping, we've already spoken about, just takes that edge off your sleep desire. And then don't obviously try to compensate with caffeine because you'll just have more caffeine in the system which means that following night you're going to be more alert and more awake. So it sounds strange to say, but after a bad night of sleep, stay the course. Just do what you normally do. And by the way, the other tip as a strange one, many of us have a wake up alarm. Why don't we have a to bed alarm?

Hmm. You mean like an alarm that tells us time to go to bed?

Yeah, just, you know, set it for You know, 30 minutes before bed and.

It just- and that's your wind down time. Yeah.

And that's your wind down routine. And even if it just means that two out of the seven nights a week, you end up just being nudged to go to bed a little bit earlier or on time, I should say, then that is a great hack. The other thing too is, I would say remove all clock faces in your bedroom. Because if you wake up and you're having a bad night of sleep, knowing what time of night it is, is not going to help at all. It's not going to change anything. So, remove all clock faces, have a to bed alarm. The other thing you can do, by the way, is get ready for bed. You know, most people finish up their Netflix and then they start brushing their teeth, take their makeup off, get changed. Instead, before you sit down for television, brush your teeth, floss, get changed, get ready for bed, And then what's great is that when you feel sleepy on the couch and you turn the television off, you go straight to bed and you've already hacked back 10 or 15 minutes of extra sleep. Add that up night after night, month after month. It's like compounding interest on a loan. So even just small sort of nibbles of extra sleep can have a compounding benefit long term. Does that make some sense?

Makes a lot of sense. And I'm assuming also, What about light? If there's any light in the room, making sure you have blackout shades, how does that impact you?

Great question. Yeah, another tip that I would usually give is darkness. We are a dark, deprived society in this modern era, and we need darkness at night to trigger the release of a hormone called melatonin.

Yes.

So in the last hour before bed, dim down half of the lights in your house. And you will be surprised at how sleepy that actually makes you feel. And you can go even further. You can dim, you know, three quarters of those lights and try and stay away from screens. The data on screens has actually taken a twist of late. If you look at it, at first we thought, you know, the blue light from those LEDs was bad, and it is bad. It's the worst form of light. in terms of blocking melatonin. You know, the yellows and the red wavelength of light, that isn't as harsh on blocking melatonin. The cool blue light, that's the lower sort of wavelength spectrum of light, that's especially harmful to melatonin. But what we've started to realize, some great studies coming out of Australia have found that perhaps it's not so much the light, it's that these devices are activating. those devices are designed for attention capture. Correct.

Gamification.

Gamification, you know, get me on there, activate my brain. So you are perfectly sleepy and you would be fine to get into bed and fall asleep. But because you're using the device, the device acts as a masking agent and it stimulates you awake despite you underlying having a strong desire to sleep. and that's one of the reasons why those devices can have such a deleterious impact. But again, unlike some sleep folks, you know, that genie of technology is out the bottle, and it's not going back in any time soon.

It's not.

So there's no point in me saying, you know, has sleep become an enemy of, you know, has the invasion of sleep into the, sorry, technology into the bedroom hurt our sleep. I think it has. However, I actually think that technology can become a salvation to bring us back in line with our sleep. And, you know, there's a whole separate episode we could do on sleep and technology. But so to come back to your point though, darkness at night is key and then keeping it dark at night, try to block out any of those small little lights in your bedroom. Blackout curtains are great. If you can't accomplish that, wear an eye mask. Earplugs are great to help dissipate sound and noise interruption from a noisy environment. All of those things are great.

Okay. I love this. This is powerful. I've got a couple final questions for you. I could continue for a long time on this because I think this is fascinating. But when you're in LA next, we'll have to do another one in person. But, I would love to.

I'd love to sit down.

For those that want more, you've got a new podcast, the Matt Walker podcast, and you've got an amazing book, why We Sleep: Unlocking the Power of Sleep and Dreams. And, I highly recommend people subscribe to your show and follow you over on social media and get the book for yourself, for your friends. You're also sleeppdiplomat.com and Dr. Matt Walker.

Yeah, you can find me at sleeppdiplomat and on Instagram, which is usually the best place to connect with me. Dr. Matt Walker, D-R-M-A-T-T-W-A-L-K-E-R.

Perfect, yes. A couple of final questions for you before we wrap things up. This is called the three truths question. Hypothetical scenario. I'd love for you to imagine it's your last day on earth, many years away from now. You've slept your way to 200 years young and done all the right things and you have accomplished all your greatest dreams in life. you've seen everything come true that you want to have come true, Matt. And for whatever reason, all of the content you've created and put out into the world, it has to go with you or it goes to another place. But no one has access to the information anymore. It's a hypothetical scenario. But you have a piece of paper and a pen and you get to write down three things you know to be true, the big lessons you learned in your life that you would leave behind. And this is all we would have as information. that you would leave behind? What would you say would be those three truths for you?

I would say acceptance over denial. I would say questions over advice. And I would say self-compassion over self-brutalization.

Those are powerful ones. Very powerful.

And I've probably been guilty of all of those.

I think we probably all have been.

I think we all have been.

We've probably all been guilty and I think that's why it's so important to see the other side of the coin and how important it is to let go of those things and be more aware. So, those are great truths.

It's still not perfect in any way, shape or form on those, but those would be it.

But you're aware and you're practicing it, so that's beautiful. I would acknowledge you, Matt, for showing up and being obsessed with this science and this data and making this a mission of yours to learn how we can heal, learn how we can live better, longer, healthier lives, and giving us the data, giving us the science, and making this a part of your life's mission to help people live better. I think it's, you know, you're the one who's saying sleep, except for oxygen, sleep is the key factor towards productivity, towards health, towards mood, towards happiness, towards longevity. So I appreciate you constantly in the the research constantly looking for more ways that we can optimize, especially as technology advances and more challenges and complications and distractions and poor food, nutrition and drugs come into play, giving us the research and the science to help us hopefully make better choices with our life. So, I really acknowledge you for everything you're up to.

And, I stand on the shoulders of some wonderful past all of my colleagues and sleep scientists and I'm just trying to do a tiny little to hopefully reunite humanity with the sleep that it's so desperately bereft of.

Absolutely. Again, I want to make sure people subscribe, get the book, check you out on social media, make sure to let Dr. Walker know what your thoughts are about this. Leave a comment below over on YouTube or message him over on Instagram and Twitter if you're listening to the audio. And, my final question for you is what's your definition of greatness?

Astonishing service to others. There you have it.

Dr. Matthew Walker, thank you so much for being here. I appreciate it.

Thank you so much for having me. It's just privilege and a delight to speak with you, Louis. Thank you.

Thanks so much for listening to this episode. Hope you enjoyed it. If you've got some value out of it, please spread the message forward and help some of your friends post it over on social media, text a few friends right now and say, hey, you got to check out this two-part episode. on sleep. I think it'll really help you optimize different areas of your life. And again, this is all about learning and sharing. So if you've got some value from this, please share it anywhere you think people would enjoy it as well. And if this is your first time here, welcome to the School of Greatness. Please click the Subscribe button right now over on Apple podcast. Leave us a review. Let us know what part of this episode you enjoyed the most. Was there something you learned about sleep that you want to try and start applying in your nighttime routine? And I'll leave you with this quote. from Roy T. Bennett, who said, do not let the memories of your past limit the potential of your future. There are no limits to what you can achieve on your journey through life, except in your mind. I'm a big fan of sleep and the importance of sleep, because when we don't have the necessary rest, it's hard to think clearly. It's hard to think with abundance and with expansion. And we are much more in survival mode, in reaction mode, when we don't. So if you want to live great life, you got to make sure you optimize and maximize your sleep. And I want to remind you of no one's told you lately that you are loved, you're worthy, and you matter. And you know what time it is, it's time to go out there and do something great.

Hey, everybody, it's Rob Lowe here. If you haven't heard, I have a podcast that's called Literally. with Rob Lowe. And basically it's conversations I've had that really make you feel like you're pulling up a chair at an intimate dinner between myself and people that I admire, like Aaron Sorkin or Tiffany Haddish, Demi Moore, Chris Pratt, Michael J.

Fox.

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