#131 Matthew Walker: The Power of Sleep｜The Knowledge Project

I've thought about this quite deeply.

It sounds a stupid thing to spend cognitive energy on thinking about, but why does the snooze button exist?

I actually think it's quite profound.

The snooze button existed because we are always as a first world society carrying some form of a sleep debt, because the alarm goes off and your instant urge is, let me sleep longer.

And the snooze button I think is the perennial expression of the human frustration of this thing called a chronic lingering sleep debt.

Welcome to the Knowledge Project Podcast.

I'm your host, Shane Parrish.

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Check out the show notes for a link.

Dr. Matt Walker, professor of neuroscience and psychology and the founder and director of the Center for Human Sleep Science at the University of California Berkeley joins me today.

Matt is the author of the best selling book Why We Sleep.

Like many of you, I'm interested in improving my sleep.

To that end, this is one of the first of a few episodes that will explore sleep through different lenses.

We discuss sleep stages, how we know we're getting enough sleep, caffeine, alcohol, the different types of insomnia, including the one that seems to affect a lot of people I know where they wake up in the middle of the night and they can't get back to sleep, the controversy around some of his work and which parts

of the critique he agrees with and so much more.

One thing to note is that Dr.

Walker is not a medical doctor and anything in here is just opinion.

So before you do anything or make major changes to your sleep or your routines, it's wise to consult with your physician.

It's time to listen and learn.

Let's start with the basics.

What is sleep? What are sleep stages?

How do we sleep? How does it play out across the night?

Yeah, sleep is a funny thing in that way.

Sleep, at least in humans and in fact, in all mammalian species, is broadly separated into two main types.

On the one hand, we have non -rapid eye movement sleep or what we call non -REM sleep for short and non -REM sleep has been further subdivided into four separate stages and they've been sleep.

So stages three and four, that's the really deep phase of non -rapid eye movement sleep.

And then stages one and two, that's what we considered to be light non -REM sleep.

And then on the other side, we have rapid eye movement sleep or REM sleep, which is named not after the popular Michael Stipe 1990s indie pop band, but because of these bizarre horizontal shuttling eye movements that occur during the stage of sleep, these rapid eye movements.

And we're, by the way, we're yet to really understand why the eyes dart back and forward, left and right, left and right during rapid eye movement sleep.

But rapid eye movement sleep is principally the stage within which we dream.

Now that depends a little bit on your definition of dreaming.

If you have a very lax definition, then you probably dream in almost all stages of sleep.

But when most of us say, oh, I had this strange dream last night, you're really talking about a dream that came from this thing called REM sleep.

So these are the two types of sleep that we have non -REM and REM.

And those two types of sleep are going to almost play out in this incredible battle for brain domination throughout the night.

And that cerebral war is going to be won and lost every 90 minutes, and then replayed every 90 minutes, at least in humans.

And that creates a 90 minute sleep cycle.

So we will, so when tonight, Shane, when you fall asleep, you will go into the light stages of non -REM, then you'll go down into the deeper stages of non -REM stages three and four.

And then after about 70 or 80 minutes, you'll start to rise back up, and then you'll pop up and have a short REM sleep period.

And then down you go again, down into non -REM sleep, up into REM sleep.

And as I said, you cycle every 90 minutes like that.

The final kind of piece of this puzzle though, is that the ratio of non -REM to REM within those 90 minute cycles will change as we move across the night.

So that in the first half of the night, the majority of those 90 minute cycles is going to be comprised of mostly deep non -REM sleep stages three and four.

But as we push through to the second half of the night, now that seesaw balance actually shifts over.

And the majority of those 90 minute cycles are comprised of much more rapid eye movement sleep.

And it's not just sort of intellectually fulfilling.

Well, it is for me, I'm a sleep scientist to sort of discover this.

It also has practical implications for most people.

So let's say that tomorrow, Shane, you have an early morning flight and you would normally wake up at, let's say, eight o 'clock in the morning, but you have to wake up at six a .m.

to catch your morning flight.

And you normally go to bed at, let's say, you know, midnight.

So typically you're going to bed from midnight to eight a .m.

And you wake up at six a .m.

How much sleep have you lost?

Well, you've lost two hours from your eight hour night of sleep.

So you've lost 25 % of all of your sleep.

Well, yes and no, you may have lost 25 % of your total sleep, but you may have lost 50, 60, even 70 % of all of your rapid eye movement sleep because rapid eye movement sleep comes in those last couple of hours of the night.

So there are, I don't mean to sort of just offer this as some, you know, intellectual sort of hand waving.

There are real ramifications day to day practical for understanding how we all sleep.

Does that sort of help, Shane?

Oh, it does totally.

Do we prioritize the different types of sleep based on benefits to us?

Like is the REM sleep, which might comprise half of our total sort of sleep time, is that as valuable as what's happening in the first part of the night?

Like does the body have an evolutionary sort of like process by which it's like, okay, this is the most important type of sleep.

We'll give you that first.

That's a, it's a very astute question.

So for most of us, we should spend probably about 20 to 25 % of the night in REM sleep, about 20 to maybe 30 % of the night in deep non REM sleep and the rest is light non REM sleep.

But people have asked that question to say, well, from an evolutionary standpoint, if deep non REM sleep is biased in the first part of the night and REM sleep comes in the second half of the night, does that mean that deep sleep is the best type of sleep, the most important type of sleep?

And what we've discovered is that no one stage of sleep is more important than the other.

Different stages of sleep do different things for your brain and your body at different times of the night.

So when people come to me and they'll say, look, how do I get more REM sleep?

Or how do I get more deep sleep?

I'll ask them, why do you want more of that deep sleep?

And they'll say, well, isn't that the good stuff?

Or they say the same thing about REM sleep.

And it's actually not true.

It's just that they all perform some different functions.

And from an evolutionary standpoint, that makes a lot of sense.

Why would Mother Nature lie you so vulnerable and unconscious?

If only one type of sleep was important, she would have excised the other type of sleep during the evolutionary course of development long ago.

The fact that they still remain with us, all of them to this day, suggests that they probably all serve some functional evolutionary fundamental importance.

And that's exactly what we've been discovering.

How do we know we're getting enough sleep?

Aren't we all different?

Like has the amount of sleep we need changed across time?

Does it change across even our life?

I'll come back to the how we know that we're getting enough sleep in just a second.

To your point, though, on the second question, we are all different.

There is a wonderful array, a wonderful variability in what we call sleep need across the population.

So if you hear idiots like me saying, okay, you know, it's eight hours.

That's in some ways that sort of nonsense.

What we recommend is somewhere between seven to nine hours will cover the vast majority, the vast distribution of human sleep need.

And that's echoed not by just my inane British dulcet tones, but by the CDC.

They stipulate after reviewing the data a minimum of seven hours of sleep for the average adult.

So we are all different.

And there are people at the tail ends of that distribution, which brings us on to probably the more important question, which is, short sleep and how little sleep can I get away with?

What we found is that once you drop below seven hours of sleep for most people, we can measure objective impairments in either your brain and your body.

And I'll come back to that nuance, because there is beautiful nuance nested in that.

I should also note, there are genetic short sleepers.

And those genetic short sleepers seem to be able to get away and quote unquote survive with as little as six to six hours and 15 minutes of sleep.

And they seem to perform normally relative to those in the general population.

And we understand why because they have certain genetic differences.

And we're starting to understand what those short sleep genetic differences are.

Some people listening to this at this point may think, ah, I think I'm I think I'm one of those people.

I think I'm a short because I can I'm pretty sure I can survive on six hours of sleep.

And many people, if you look at the data, maybe almost 50 % of most people in development patients is trying to survive on six hours of sleep or less during the week.

But your chances statistically of being one of those genetic short sleepers is quite low.

And statistically, you're far more likely to be, for example, struck by lightning in your lifetime, than you are to be one of those genetic short sleepers.

The the lifetime odds of being struck by lightning is one in 12 ,000.

Just if any, if anyone's interested, I love myself.

And let's just come back to those people who say, no, I actually sleep just five or six hours and I'm I'm fine.

So I'm sorry, what you're saying doesn't resonate with me.

Well, what we've discovered here, once again comes back to variability, because you can bring people into the laboratory and put them on a diet of six hours of sleep for let's say a week.

And some of them just fall apart in terms of their cognitive, their neurocognitive ability, let's say their ability to focus and concentrate and attend to certain things on the screen.

But what's also interesting is that if you look at the distribution, there are some people who seem to be utterly invulnerable to that short sleep, as though they are resilient, as though they truly seem to be just fine on six hours of sleep.

But then scientists like myself and others started to noodle that question a little bit deeper, because that was just one test of brain function, which was concentration and attention.

If you then start to assess in a person and you assess the cognitive abilities that learning and memory function, their decision making, their mood, their emotion, and then downstairs in their body, that things like their blood pressure, their insulin response, and their glucose regulation, their immune

system, the thermoregulation, their sex hormones, such as testosterone.

When you take a holistic view, what you find is that there is almost nobody who is completely resilient to that diet of six hours of sleep on all of those different measures.

So some people are resilient to a lack of sleep in some domains, but they will be vulnerable in other domains.

So you have to be careful.

You have to think, well, just because I can focus on the specific work task that I do on a day -to -day basis in a job with six hours of sleep, that means I'm fine.

Well, that's possible, but it could be that you're suffering severe hypertension because of your insufficient sleep, and you're not aware of or your immune system is deficient.

So that's sort of the, probably a far longer answer than you wanted in terms of are we all different and how little sleep do we actually need?

And I promise I will come back to the question of how you're not getting enough sleep, but was that clear, Shane, or did that give you enough information?

This is perfect, man.

I love the detail. Keep going deep.

Okay. Okay. So I love, okay, someone else who's willing to go this far with me.

The question on how do you know if you're getting enough sleep is probably simpler in terms of its answer.

Short of coming into the my laboratory and us doing all of these tests, you firstly can ask yourself if you set an alarm clock to wake yourself up every morning, if that alarm clock didn't go past that time of the morning.

And if the answer is yes, then it's clear that your body's not done with sleep yet, that you're clearly not getting enough sleep.

Your body doesn't seem to be able to get too much sleep.

And it's something that we can speak about too.

It has its sleep need, and it wants that sleep need to be met.

So if you would sleep past your alarm, if it didn't go off, then that's probably one indication.

Also, by the way, we should ask ourselves, why does the snooze button exist?

And I've thought about this quite deeply.

It sounds a stupid thing to spend cognitive energy on thinking about, but I actually think it's quite profound that the snooze button existed because we are always as a first world society carrying some form of a sleep debt because the alarm goes off and your instant urge is, let me sleep longer.

Let me sleep longer.

And the snooze button, I think, is the perennial expression of the human frustration of this thing called a chronic lingering sleep debt.

There was a great study, by the way, that addressed this a little bit.

They studied it, granted it was a small group of subjects.

And firstly, in the week before the experiment, they just measured the typical amount of sleep, what we call your habitual amount of sleep.

And surprisingly, for these folks, and I'll come on to why it's surprising in a second, they were sleeping a decent amount.

They were sleeping about 7 .3 hours every night.

And they said subjectively, I feel fine.

I feel well rested.

So then they brought them into the laboratory for eight nights straight.

And then they gave them an extended amount of time in bed.

I think it was almost 12 hours time in bed.

It could be a little wrong on that number.

But more importantly, what they found was that despite arriving into the laboratory for that eight day experiment, on already a very solid average of getting consistently 7 .3 hours a night on average, the first night when they had that extended sleep opportunity, they slept for a total of almost 10

.5 hours. And then on the second night and on the third night, they were sleeping 9 .5 hours a night.

And then finally, by the eighth day, they bottomed out at what seemed to be their true sleep need, which was about eight and a half hours.

So in other words, even though they came into the experiment, saying that they slept 7 .3 hours a night, and I feel completely fine, they were still carrying a lingering debt of over one hour of sleep loss.

So that I find fascinating.

And I say it was remarkable that they were sleeping 7 .3 hours a night, because to your question, how has sleep changed over time?

It's changed dramatically.

There was a Gallup poll that was performed back in 1941, or 1940, I think it was 1942, sorry.

And what they found was that on average, the human adults in that survey reported sleeping 7 .9 hours a night on average.

But now based on data from the National Sleep Foundation a couple of years ago, that number is down to just 6 ,031 minutes in the United States.

It's 6 ,049 minutes in my home country of the United Kingdom, and Japan for at worst, they were down to 6 ,022 minutes on average.

So there's been a remarkable change in how much we're sleeping over the past century.

And I think many of us do feel the need that to sort of try to get back that sleep at the weekend, it's what we call social jet lag, or what I almost call sleep bulimia, which is where we sort of binge at the weekend, and then we sort of purge during the week.

And then we try to binge again and get back those sleep calories that we've been absent of during the week.

I just want to clarify when we talk about sleep time, when you're talking about sleep time, you mean actual time of sleep, not time in bed.

Correct. And that's a profoundly important point.

Is there a danger to trying to force more sleep?

Like what if you wake up in the morning naturally and you're like, oh no, I only slept five hours, like should I?

And I can't go back to sleep, should I just lie there until...

That's a hard question to answer without sort of taking more of a clinical history.

And by the way, just right up front, I am not a medical doctor, I'm not a clinician, I'm just a scientist.

And so I could say what the science would speak to on that point.

If you are getting just five hours of sleep a night, typically we would think about that being insufficient amounts of sleep.

If you were to say, look, I'm getting six and a half hours of sleep each and every night, and I feel well rested during the day, I don't feel as though, and this is probably another way to ask the question, am I getting enough sleep?

Do you feel as though you need caffeine to function in the morning?

Because if you do, you're probably self -medicating a chronic sleep debt.

So if you can say to me, look, I wake up naturally, I've had six and a half hours of sleep, I don't feel sleepy during the day, I function perfectly fine, I don't drink caffeine, I don't need caffeine to function, then I would say, okay.

You're superhuman if you don't need caffeine.

Yeah. Well, we can come on to that too.

And I've changed, I think that's one of the things that we may get onto, which is, how have I changed my views on sleep over the years since being, unfortunately, and surprised in being a public figure in sleep?

And caffeine is one of those areas, but not to derail our question here, I would say at that point, six and a half hours of sleep, no caffeine needed, feel rested during the day, then I think you're okay.

Five hours of sleep, I would say something is probably a miss there, or at least a clinician would say, because I'm just a scientist, they would say, we should take a deeper look into that.

Is it that you're using extensive amounts of caffeine that forces your brain to not be able to get more than five hours of sleep?

And if we were to bring you off, whatever stimulant that you're using, your brain would actually acquiesce to its natural sleep need and you would be getting more sleep.

That's one answer. But I think perhaps an even more salient point is if you're lying there in bed awake, separate from this question of are you getting the sleep that you need?

And that's sort of what we were discussing prior to this.

I would say it's very dangerous to stay in bed awake for long periods of time.

And it's especially dangerous to do that and force yourself to try and sleep and become frustrated with not being able to sleep.

And the reason is the following.

We are very Pavlovian like as a brain in terms of our learning capacity.

And very quickly, if you're lying in bed for long stretches of time awake, your brain associates this thing called your bedroom and this thing called the bed as this place of always being awake and never being able to sleep.

And people will say to me, you know, look, it's so strange, I'm falling asleep watching television at night on the couch.

And then I get into bed and I'm wide awake and I don't know why.

And in part, it's because your brain has learned that negative association and bonded that negative association of being awake with this thing called the bed.

And you need to break that association.

So typically the advice that a clinician would say is get up, get out of bed, go to a different room and in dim light just read a book or do something relaxing, stretch, meditate, and only return to bed when you're sleepy.

And that way, and there's no time limit for that.

And that way your brain will relearn the association that this thing called my bed is this thing called, you know, safe and sound sleep.

And I guess the analogy here would be, you know, you would never sit at the dinner table waiting to get hungry.

So why would you lie in bed waiting to get sleepy?

And the answer is that you shouldn't.

The other thing I would note, Shane, about trying to force sleep and sort of brutalize yourself to stay in bed is that sleep, unlike the gym where you could say, look, I'm going to mentally, you know, deliberately force myself to work harder and I'm going to go harder and I'm going to exercise harder,

or I'm willfully going to restrain from eating those bad foods for me.

The other third domain of health, speaking about which is sleep is not like that.

Sleep is not deliberative in that sense.

You can't consciously just turn sleep on and say, right, I'm going to sleep.

I'm going to force myself to sleep.

I'm thinking about sleeping and it's happening right now.

If only that were the case.

It's in fact the opposite, which is that the harder you try to fall asleep, the further that sleep gets pushed away from you.

And it's a little bit like trying to remember someone's name, you know, that feeling where you're trying and the harder you try the worse it gets, the further you push that name away from you.

And when you stop trying and all of a sudden the name just pops back into mind, sleep is very much like that.

And we can speak about techniques for trying to take your mind off itself and allow that version of that analogy of trying to remember a word to happen with sleep too.

But let me pause there because I'm so sorry.

I go on. I love this thing called sleep.

Let's talk about the two most common stimulants, which are caffeine and alcohol, but let's break them into two so we don't come mingle them.

How does caffeine interact with your sleep?

And should I still drink coffee?

Like you're scaring me here.

So this is something that I think I've very much changed my tune on when I first came out with the book and started to become a little bit more public as a communicator of sleep's story and my love affair with sleep.

I was probably heavy handed in lots of things and wrongfully so.

And caffeine was one of them.

I sort of almost, you know, vilified caffeine.

I've changed my tune firstly because if you look at the data, it's very clear that drinking coffee is rather good for you.

But here, when it comes to coffee and when it comes to sleep and when it comes to health, the dose and the timing make the poison.

Just as an aside, by the way, the reason that coffee has those remarkable health benefits that it does, and in fact, paradoxically, the benefits that you get from drinking coffee are very similar to the benefits that you get from getting sufficient sleep.

And people have said to me, how can you square that circle?

How can you resolve that tension?

It doesn't make sense from what you're saying.

Well, the reason that coffee provides those health benefits is not because of the caffeine.

It's because the coffee bean provides for most people because our diets are not really very good.

The standard American diets, for example, isn't ideal in its nutritional profile.

The coffee bean provides the majority of people's daily dose of things called antioxidants.

And because of our deficient diet, the humble coffee bean has been asked to carry almost the entire burden, weight of supplying everyone's antioxidant dose each and every day.

Case in point, you get very similar health benefits from decaffeinated coffee.

So you can remove the caffeine from the equation and the benefits of the coffee bean remain.

So it's the coffee bean and the antioxidants rather than the caffeine itself that's giving the benefit.

But in terms of coffee, again, dose and timing make the poison.

Caffeine is stimulant and it's in a class of drugs that we call the psychoactive stimulants.

As an aside, it's probably the only psychoactive stimulant that we or some people will readily give to children without necessary concern.

And I think it's probably there is necessary concern there, but caffeine can harm your sleep in at least three ways.

Firstly, caffeine obviously will just keep you awake more so at night.

And part of the reason of that stimulant property of making it harder to fall asleep and making it harder to stay asleep is because of the duration of action.

So caffeine has a half life of probably around five to six hours.

In other words, after five to six hours, 50 % of that caffeine is still in your system, half of that caffeine, hence half life, which means that after 10 to 12 hours, there's about a quarter of that caffeine still in your system.

So in other words, if you have a cup of coffee at midday, a quarter of that caffeine is still in your brain at midnight, which would be the equivalent of sort of took yourself into bed.

And just before you turn the light out, you swig a quarter of a cup of Starbucks and you hope for a good night of sleep.

And you know, and it's probably, it's probably unlikely to happen in that way.

So be mindful of caffeine, I would say try to cut yourself off, you know, somewhere around about 10 hours before you're expecting to go to bed if you can do it even earlier than that.

That's great, too. So that's the timing part of the equation.

And that if you keep stacking on the dose, then more and more caffeine will accrue in your system.

And the longer and longer it's going to be and the more intensive it's going to be in terms of its impact on your sleep.

Also, by the way, for those health benefits separate from sleep, once you get past about three or four cups of coffee a day, then the health benefits start to go in the opposite direction, it starts to become a negative trending direction in terms of health, but also in terms of sleep, too.

The other concern with caffeine that I hear from people is to say, well, look, I'm one of those people who can have an espresso with dinner, and I fall asleep just fine.

So I don't have that problem.

And furthermore, I stay asleep, which is the other thing that you just told me that caffeine can do, which is caffeine can both prevent you from falling asleep and mimic something called sleep onset insomnia, or it can have you waking up and you find it hard to fall back asleep, which is mimicking something

that we call sleep maintenance insomnia, can't stay asleep.

The final issue is that even if you're someone who says, I don't have either of those two problems, and I can have an espresso with dinner, what you don't realize is that caffeine can actually decrease the amount of deep sleep that you're getting stages three and four.

And in fact, what we found is that even just one to two cups of coffee in the early or late evening can decrease the amount of your deep sleep anywhere between 20 to 40%.

Now for a spot of context, I'd have to age a healthy adult by probably somewhere between 10 to 15 years to produce that kind of a reduction in deep sleep.

And we've seen that with just 100 milligrams of caffeine, which is essentially a standard single cup of dripped healthy brewed coffee that can blunt the electrical quality of your deep sleep and strip away almost 30 % of those electrical deep sleep brainwaves in the first cycle of your sleep at night.

I love the amount of detail we're getting into and I really want to come back to sleep maintenance insomnia because that is the number one thing when I told people I was talking to you, they were like, Oh my God, we need to talk about this thing.

But before we get there, let's talk about alcohol.

Alcohol is probably the most misunderstood quote unquote sleep AIDS that there is out there.

It is anything but a sleep aid.

Alcohol is actually in a class of drugs that we call the sedatives.

And this is the first problem with alcohol.

People will have a couple of glasses in the evening.

They'll have a couple of night caps and they say, you know, I just, it helps me fall asleep.

That's not really quite true.

What you're doing with alcohol is sedating your brain and sedation is not sleep.

But when we have a couple of drinks in the evening, we mistake the former for the latter.

And if I were to show you the, the electrical brainwave signature of your sleep with and without alcohol, it's not the same.

It really looks quite different because of that sedation impact.

The second problem with alcohol is that even though it is a sedative on your brain, throughout the night, it can be an activator of the fight or flight branch of the nervous system within your body.

And as a consequence, it can spike your body's nervous system and cause you to wake up many more times throughout the night.

And as a consequence, it produces what we call sleep fragmentation.

And here again, it can mimic that terrible thing that we are going to talk about, which is sleep maintenance insomnia.

I fall asleep fine.

I, I've sedated myself with alcohol, but I wake up many more times throughout the night because of sleep fragmentation.

The third of the four problems with alcohol and sleep is that it will block your rapid eye movement sleep or your dream sleep.

And we have discovered, for example, at my sleep center, lots of different benefits of REM sleep.

For example, it seems to provide forms of emotional therapy, overnight therapy or emotional first aid.

It's profoundly important for stabilizing our mental health.

REM sleep is also essential for creativity, learning and memory.

But also REM sleep is key for your body.

In fact, we produce peak levels of many of our key hormones during REM sleep.

A good example is testosterone.

Both men and women, by the way, require testosterone at different levels, but we all need it.

And we produce our peak levels of testosterone release, not during the day or even after the gym or just as we're working out during the gym.

We produce our peak levels during REM sleep just before and throughout that period of REM sleep.

And if you're blocking that REM sleep, you have hormonal consequences.

Another good example, which is the fourth problem, is that by blocking perhaps that sleep, particularly REM sleep, you can also get a deficit in what's called growth hormone.

Now, we often think of growth hormone as essential for kids developing, but we all need it as adults and we continue to release it.

And we release it during sleep and alcohol will block that.

In fact, there was a frightening study that demonstrated that a couple of doses of alcohol in the evening, sort of getting you not really tipsy, but kind of close to that, resulted in a 50 percent, five zero decrease in growth hormone at night.

And to give some context there, for every decade of aging that we go through, we have a 15, one, five percent reduction in growth hormone.

But take a couple of glasses in the evening of alcohol and you can drop that by 50 percent.

I think two points here again.

One is, come on, let's all just enjoy life at a time.

There are times when we should just cut loose and have a good time.

And we'll all know, look, my sleep is going to be a disaster that night.

And one bad night of sleep, it's not the worst thing in the world, even based on all of the things that we're going to discuss or have discussed.

Don't get me wrong.

One bad night, it's not the end of the world.

And then I think the second piece of advice that I would never offer publicly on especially something as popular as your podcast would be the following, that we should all go to the pub in the morning.

And that way the alcohol is out of our system by the evening and there's no harm, no foul.

So everything's just fine with your sleep.

But I would never recommend advocating for alcohol consumption early in the morning, of course.

But that's maybe one way to placate the effect.

If we're going to have it at night, is there like...

I'm going to lose my job right here, by the way.

Is there like a half life to it in the same way that there was with caffeine?

Is there something like, hey, if you're going to have a couple of glasses of wine, like, you know, maybe cut it off four hours before bedtime.

Is there a heuristic around this?

There's a little bit of heuristic and it's probably earlier in the day.

So, you know, probably, you know, having a glass or two with lunch is less likely to impact your sleep.

But we found that even just one glass of wine in the evening can have, you know, significant and measurable impacts on your sleep at night, which I know...

All of this makes me...

I'm desperately unpopular as a person, just firstly out there in the public.

And secondly, even to my close social circles based on personality and nationality, but saying this type of stuff makes me even sort of less popular and interesting.

But best to be truthful about the science.

No, totally. Okay, let's come to sleep maintenance insomnia.

Because when I was talking to my friends about interviewing you, they were like, man, I have no problem falling asleep.

I fall asleep right away.

But sometimes like I'll wake up at three, four am and then I just can't get back to sleep.

And this seems common.

Like when I surveyed my friends, this has got to be at least 50 to 60 % of them, if not more.

So insomnia is... Again, you know, not a medical doctor, not a clinician, but insomnia, the way that we currently establish the criteria for the diagnosis of clinical grade insomnia.

It's actually very stringent.

And some people in the sleep field have tried to push back against this arguing that it's too stringent a threshold, that it's so difficult to receive, and I'll come on to the criteria as I understand them, to receive that diagnosis, that it leaves many people out in the cold, many people like those,

your friends, who perhaps would not meet that very high bar of of clinical grade insomnia, and therefore would not receive medical attention and treatment.

And I think that's a desperate problem in a very sad and unfortunate circumstance.

But in terms of insomnia, just as kind of ground rules, insomnia right now is defined as at least probably one of four different things, and they're not mutually exclusive.

The first is what we call sleep onset insomnia.

So problems falling asleep.

The second is what you and I have just been discussing, which is sleep maintenance insomnia.

I can fall asleep fine.

I can't stay asleep.

The third, which is a little bit separate than sleep maintenance insomnia, but it sounds very similar, which is waking up too early in that last hour or two before your alarm goes off and just not being able to get back to sleep.

And then the fourth is a very important one.

And it came later in the historical arc of insomnia diagnosis.

You can fall asleep fine.

You can stay asleep.

You don't wake up and you sleep what seems to be a reasonable amount.

And despite all of that, you still tell me in the morning, I don't feel restored by my sleep.

I don't feel as though I can function well during the day because I'm still tired.

So that has been what we call unrestorative sleep.

So you can have any one of those four things, and that can put you into the consideration category of potential insomnia.

But then to have what we call chronic grade insomnia, you actually have to be having one or some of these symptoms for several times a week for consistently for three months.

Now there are some criteria that have brought it down to just one month, but that's quite a long time to have that degree of impairment that consistently week after week after week, month after month after month.

And many people don't meet that criteria.

And that's I think a problem.

So that's the sort of the ground rules for what we think of as insomnia.

What are the causes of that?

Well, there are many current causes that we've identified.

Firstly, there is some genetic heritability to it.

It seems to be that insomnia is about 30 % heritable.

So if your parents have always struggled with sleep and are chronic insomniacs, then there is a substantive chance that you too will be not 100%.

It's not deterministic.

It's probabilistic.

But then there are other things too.

And I would say that probably the greatest thing that I know of, and that we commonly hear of at the sleep center is stress and anxiety.

That seems to be the number one culprit.

Now there are many other potential culprits, excessive use of caffeine.

There can be other physical constraints, such as I'm in pain.

And that would actually be not classified as insomnia, because that would be secondary insomnia secondary to the primary diagnosis if you have in chronic pain.

And it's the chronic pain at night that keeps waking you up.

And when we address the pain, you start to sleep just fine.

In other words, you don't have insomnia.

So there's lots of things to exclude, but I think one of the standout things is mental distress and anxiety and that degree of stress.

And if you look at the underlying biological basis of insomnia, the principle model that we have is something called, and it's poorly named because of where people's minds will go, but it's called the hyper arousal model.

Now, I don't mean arousal in the sense of, you know, kind of just keep your bedroom chit chat to yourself.

If you're out to dinner with that couple, that's kind of sharing a little too much about those activities.

That's not the type of arousal I'm talking about here.

In more common speak, it's that you're jacked, you're wired in terms of your nervous system that it's jacked up in terms of its activity.

And you have a nervous system within the body.

And one separation of some of those branches is the separation of what we call the sympathetic from the parasympathetic nervous system.

Sympathetic nervous system is terribly named.

It's nothing sympathetic.

There's nothing sympathetic about it.

It is very agitating, very aggravating, and it is the fight or flight branch of your nervous system.

When that branch of the nervous system is switched on, it is very difficult, nigh impossible for you to fall asleep.

Because that branch of the nervous system has to disengage for you to fall asleep easily, and then stay asleep across the night.

And this is the sort of the phenomenon that I will often hear about, which is the tired and wired phenotype, which is people saying to me, look, and maybe this covers some of your friends, look, I'm so tired, I'm so desperately tired, but I'm so wired that I'll wake up in the middle of the night and I

just can't fall back asleep.

And this is because of this stress or anxiety biologically due to or founded upon the fight or flight branch of the nervous system being switched on too much, which caffeine, by the way, will also do.

And so what to do then about that situation?

Again, I'm not a clinician, so I can't really offer any sort of clinical advice, but often the recommendations are one of the techniques for anyone suffering from insomnia.

I would suggest not trying to seek out necessarily medication.

That's not, and this is not me making this recommendation.

I'm not trying to play doctor.

In 2016, the American College of Physicians made a landmark statement.

They said, based on reviewing the evidence from sleeping pills and their minimal effective use for insomnia, the first line recommended treatment for all people with chronic insomnia should actually be something called cognitive behavioral therapy for insomnia or CBTI for short.

And you work with a therapist and you do about six or seven, eight sessions, and it's a whole set of different techniques that focus on the cognitive part of your problem, the thinking, mentalizing problem, and then the behavioral things that you're doing.

And those two things together can cause you insomnia.

That's the first line treatment.

And one of the recommendations firstly is that if you are awake, lying in bed, as we've said, get up, get out of bed, do something different.

But some people will say, and I think rightly so, and I've, by the way, I've, I'm no poster child for good sleep.

I have had my own struggles with sleep throughout my life.

I've had two really bad bouts of insomnia and I'm very sympathetic and empathetic to those people.

But some people just don't like the idea of getting up.

It's dark. It's cold.

You know, why do I want to get up?

I'm a good person. And, and I think the other thing to do is if you're going to stay in bed, which is not the recommendation, try and not force sleep and do something that we call cognitive reappraisal or re contextualizing.

Those are just fancy nonsense words for the following.

You're going to lie in bed there and you're going to think fine tonight is just not my night.

It's angry and start to get anxious looking at the clock thinking, oh my goodness, my day tomorrow is toast.

It's going to be a mess.

I need to sleep. That's only going to make matters worse.

Instead just say, I'm going to rest.

I'm just going to lie here in bed.

I'm just going to rest.

Because if someone said to you, look, Shane, in the middle of your day, don't worry about all of this work.

Just set it aside for a second and just go get into bed and just have a nice rest.

Just lie in bed and just kind of think and just enjoy resting for an hour or so.

Does that sound nice?

I would think, ah, that sounds lovely.

Well, think that when you're in bed.

And usually once you start thinking, I'm just going to relax.

I'm just going to not stress, don't catastrophize, don't ruminate.

I'm just going to maybe do a meditation, just going to hang out in bed and relax.

Usually the next thing that you remember is your alarm clock going off.

Because as soon as you stop trying, it's usually when sleep returns back to you boomerang -like.

Right. So the other thing to do for people who have that sleep maintenance insomnia is just keep an eye out on your caffeine intake.

The final thing, if you really want to get aggressive, and it seems to be, I mentioned that technique called, that therapy called cognitive behavioral therapy for insomnia.

And it is just as effective as sleeping pills in the short term, but what's better is that once you stop working with your therapist, once you stop engaging with that treatment, you then continue to sleep well because you've been armed with all of the tools and the knowledge for how to control your

sleep. In other words, you've shifted from a place where your sleep controlled you to now you control your sleep.

That's the confidence that that therapy gives you.

And it lasts even when you start working with your therapist, unlike sleeping pills, where if you stop using sleeping pills, not only do you go back to the bad sleep that you were having before, but even worse, you have what's called rebound insomnia.

Now, I should say that there is a time and a place for those sleeping pills.

I'm not, this is something I've changed my tune on and through helpful advice from medical doctor colleagues in the sleep medicine field.

You know, if you're going through in a period of what's called acute insomnia or reactive insomnia, let's say that you're going through a really bad breakup, a very painful divorce or a bereavement, there is a time and a place where you can combine that medication with cognitive behavioral therapy.

And then that medication should at least not be seen as a long -term treatment solution for insomnia.

Acute short -term use, potentially viable.

Long -term use, not so much.

But the final tool I should come into in the box of cognitive behavioral therapy, and it's probably if you look at the scientific studies, it's probably the most effective of all of these tools that they have that they'll pull out and help you with, is something that has been re -termed as bedtime rescheduling

or bedtime regulation.

It used to be called sleep restriction therapy, which sounds kind of scary.

So Shane, you or one of your friends comes to me and says, look, I don't think I'm not getting enough sleep waking up in the middle of the night.

I can't get back to sleep.

And my response to you is, okay, I understand that.

I'm going to have you in bed for less time.

And you think, hang on a second, you're supposed to help me get more sleep, and you're telling me to stay in bed for less, you're going to kind of constrain my bedtime.

And what we do, what we do, quote unquote, that's the royal we, what clinicians will do, is that they'll take that, let's say seven hours of time that you're in bed, and maybe for an hour and a half of that, you're tossing and turning and you're wide awake.

So in other words, you're only getting an average of five and a half hours of sleep out of that seven hours of time in bed.

That's what we call a very poor sleep efficiency.

Sleep efficiency, by the way, is defined by the amount of time that you're asleep relative to the amount of time that you're in bed.

So if you're in bed eight hours and you sleep for all of that eight hours, that's a 100 % sleep efficiency.

Whereas if you're in bed for eight hours and you sleep for six of those eight hours, that's a 75 % sleep efficiency, and that's not a good sleep efficiency number.

And that's what's happening to many of your friends here.

They probably have sleep maintenance issues and they're spending a lot of time awake in bed.

So their sleep efficiency is low.

So what's recommended is that we limit your bedtime and we say, you normally go to bed, let's say 11 p .m.

and you wake up at 7 a .m.

and you're having all of these problems.

Well, now I'm going to have you go to bed at midnight instead of 11 p .m.

And I'm going to have you wake up at 6 a .m.

rather than 7 a .m. So I take your sleep window of eight hours and I constrain it down to just six hours.

And gradually what will happen is that you're awake for longer periods of time and you build up something called sleep pressure.

You're building up all of that healthy sleepiness.

And the more of that sleepiness that you build up, the heavier the weight of your sleep drive, your sleep pressure is when you fall asleep.

And after some time period, what we're trying to do is teach the brain to become a little bit excessively hungry for this thing called sleep.

Whereas before it's been a little bit lazy.

Actually, that's not a good analogy.

Maybe a better analogy would be, let's say that, Shane, you normally go to the gym every day and you go to the gym for one hour.

But when you go to the gym, you know, you're using, and this is, I'm just using you as the example here.

You're not, you know, I'm sure you're very good at doing, not doing what I'm about to suggest, which is that you see people who kind of do the 11th rep, this was a friend, Andy Huberman at Stanford, to the top of this time, the 11th rep were you kind of, you know, you do your 10 reps and then you immediately

go to your phone and you pick it up and that's your 11th rep.

And it always happens at the end of every set.

And so you're on Twitter, you're on Facebook, you're on whatever different apps.

And then you start chatting to people in the gym and you kind of really are only working for about 35 minutes of that one hour.

It's very inefficient.

And now I say to you, look, I'm sorry, Shane, for the rest of the next four months or three months, and it's usually not this long for sleep restriction therapy, let's say the next month, you're only allowed to be in the gym for 40 minutes.

And as soon as that 40 minutes is up, those huge trainers in the gym that weigh kind of 220 pounds and they're cut, they're going to come over and they're going to remove you forcefully if you don't get out of the gym.

So all of a sudden you get into the gym and the first day you're in there, you kind of do the same thing.

You're messing around, you're not very efficient.

And you only get half a workout in because you have to get out of the gym, just like you have to get out of bed early in the morning with sleep restriction therapy.

But then gradually your brain and your system learn, I can't mess about anymore.

I have got to be ultra efficient.

And your brain starts to forget or it starts to abandon this idea of waking up and then just staying awake for long periods of time.

It builds up such a pressure, such a demand that the efficiency now is incredible.

So you're in the gym for 40 minutes and now you're spending maybe almost 37 out of that 40 minutes working out.

And that's what we try to do with sleep restriction therapy.

So it sounds very paradoxical that you tell me, I don't get enough sleep.

And I say, I'm going to try and have you sleep less.

But by doing that, you create this hunger, this demand for sleep and your brain starts to become much more efficient.

And your brain relearns the capacity for continuous sleep throughout the night.

And then once we feel comfortable with your brain's return of its true, what was always present, ability to sleep soundly without waking up and staying awake, we gradually back it out.

So now I'll say, okay, now you can finally go to bed at 11, 30 PM and you wake up at 6, 30 AM.

And then if that's working and you're still sleeping well, let's go back to 11 PM to 7 AM.

But if at any moment your system, you start to be waking up and you're spending more time in bed, whoosh, we'll go right back to constraining it and we'll kind of wrestle it right back under control and bring it back down.

You mentioned temperature a while back.

Is there a relationship to temperature and sleep?

And does that change during the night, during our four phases?

Very much so. I think many of us underestimate temperature as one of the key regulators of sleep.

And I've got so many ways that I could show you as to why temperature is so impactful for your sleep at night.

For example, when we've studied hunter -gatherer tribes, whose way of life hasn't changed for thousands of years and you study their sleep, one of the striking, one of the many striking things that we've learned about their sleep is that they don't go to bed at the moment when light disappears, when the sun

is completely set. They go to bed usually a few hours after that and they don't wake up with the rising of the sun.

They usually wake up a little bit before that with the rising of temperature.

And so it is temperature that seems to dictate when you want to fall asleep and it's temperature that seems to dictate when you will naturally want to wake up.

And we can do these studies.

So for example, if I were to bring you into my sleep laboratory and you come in and you're in a room with no cues as to what time of day it is, there's no windows, there are no clocks on the wall.

And I say to you, all I want you to do and I'm gonna check in with you every 30 minutes or so, I'm just going to say, are you feeling sleepy?

Do you think you're ready for bed?

And just tell me, whenever that wall of sleepiness hits you and you say, yeah, look, I'm ready, I'm ready for bed now, just tell me when that happens.

Now, before that, you and I will have had a very intimate time in a private room where I will have inserted a rectal probe.

And trust me, it's no fun for you, but it's equally no fun for me in terms of application.

But that way I'm going to know your core body temperature.

And here's the reason that's important.

The moment when you say to me, I am sleepy now, I am ready for bed.

The moment when you subjectively feel most sleepy, even though you've got no sense of what your core body temperature is doing, you have no knowledge of that consciously.

The moment when you tell me that subjectively that you are sleepy is the moment when you are on the steepest downward slope of your dropping core body temperature.

So what we know is that for you to fall asleep and for you to stay asleep across the night, your body and your brain need to drop their core temperature by probably almost about one degree Celsius across the entire night from its extremity, from the highest point to the lowest point, for you to fall

asleep and for you to stay asleep.

And this is the reason that you will all feel that it's a lot harder, sorry, it's a lot easier to fall asleep in a room that's too cold than too hot because the room that's too cold is taking you in the right temperature direction for good sleep, which is a drop in your core body temperature.

But there is a little bit of a twist in that initial story of temperature and falling asleep.

And your night to your question is, in my mind, played out in a kind of a stanza, in a three verse stanza, which is that you need to warm up to cool down to fall asleep.

And then you need to stay cool to stay asleep.

And then you need to warm up to wake up.

The funny thing about falling asleep and getting cool at the core of your body is that it requires the opposite to happen in the extremity peripheral parts of your body.

And this is why I say we have to warm up to cool down to fall asleep.

And the reason we need to warm up is because during this sleep onset phase, a strange thing happens where blood starts to swell to our hands and to our feet and to our face.

And what happens is that, and you can actually artificially force rats, force quote, unquote, you can artificially get rats to fall asleep quicker than they would normally if you just warm their paws.

And scientists have done this experiment where they've kind of got these little rats and they're warming these, it's like a spa for rats, they're warming their paws.

And those rats will fall asleep more quickly in the hands of the experiences.

And you could do the same with humans.

So they've done these experiments where they will warm the feet of humans or warm the hands of humans.

And there's some crazy contraption devices that they've come up with to do this.

And what happens is that by warming the hands and the feet, you bring, you charm the heat out of the core of the body and you bring that blood to the surface of the skin.

And what's special about your hands and your feet is that they are made from a very particular type of skin and a set of vessels, and I won't bore you with the name of them, but they are highly vascular.

And in almost all mammals, even mammals that have hair on them, when you look at their feet at their paws, there is no hair there.

And the reason is because it is a special surface of the skin on the hands and the feet that is designed for one purpose in mind, which is to radiate heat out of the body and to regulate heat.

And what happens is that as we warm up the extremities, the surface of the body in these areas in particular, it brings the blood, the very warm blood that is trapped at the core of your body, out of the core of the body to the surface perimeter of the skin.

And it's when it's at the surface perimeter that you can have this massive thermal evacuation of heat from the core of your body.

And this happens as we're sort of getting ready to fall asleep in the evening.

It's the reason by the way that hot baths and hot showers work.

In fact, there's something in sleep science called the warm bath effect.

And most of you think, well, if I have a bath in the evening, I get out of the bath, I'm all nice and toasty.

I get into bed. And that's the reason I fall asleep and have such good sleep when I've had a bath.

It's actually the opposite, that when you get out of the bath, you're all warm and toasty.

You know, you sort of pink hands and feet.

And for me, someone like me of British kind of complexion, you know, very kind of cherubic red face.

And all of a sudden what happens when you get out of the bath because the blood has raced to the surface of the skin, your core body temperature plummets.

And that's the reason that you fall asleep.

And then once we fall asleep, we need to continue to drop our core body temperature to stay asleep and to stay into that deep sleep.

And that's why we recommend a cool bedroom temperature.

And I'll come on to sort of what that is in a second.

But then something strange happens, which is that as we're starting to get closer to our natural time of waking up, if we allowed ourselves to wake up naturally, your core body temperature actually starts to increase once again.

And it's the rise in your core body temperature that helps wake you up and bring you out of sleep.

Hence that three part sort of stanza that you need to warm up to cool down to fall asleep.

You need to stay cool to stay asleep.

And then you need to reverse engineer that trick, which is you need to warm up to wake up.

And that's by the way, the reason that you feel better when you've had your coffee in the morning.

Some people will say, just let me have a couple of sips of coffee.

And after three or four minutes of nursing a coffee or probably doing a lot, most people are probably like gulping that coffee because of their chronic sleep deprivation.

They say within a couple of minutes, five minutes later, oh gosh, I feel so much better.

All right, I'm ready to face the world.

And you think that that's the caffeine, that's nonsense.

The caffeine isn't probably working within your system at peak plasma concentrations until certainly 10 minutes at the earliest.

Instead, what's happening is that you're consuming a hot drink and it's the hot drink and the hot temperature that's warming the core of your body that's having the more immediate thermoregulatory benefit of waking you up.

And then the caffeine kicks in and that also helps wake you up too.

Everybody's got these devices these days like oral rings and stuff.

Is there a danger to the quantified self movement?

Do you think we're sort of like going too far by tracking everything like heart rate when you're sleeping and how long it took you to fall asleep and your heart rate variability?

Yes and no. I am, I'm a gadget freak and I've worn or I've placed on my body.

I've stuffed up my nose, I've strept on my head.

I've jumped on mattress.

I've done every sleep gadget that there is out there for the most part.

And I do track my sleep.

I track my sleep with an aura ring.

And just to full disclosure, I am a scientific advisor to the company and connected to the company.

So take what I say about aura with a grain of salt and I'm happy to sort of come on to once we speak about whether sleep tracking is useful or not.

What I would recommend in terms of sleep trackers and how I think about making the decision of which sleep tracker is the best sleep tracker.

But I think there is a danger and I don't think it's a danger for everyone.

But I think for maybe a modest proportion of the population, I would say, perhaps based on just my survey data, maybe around 10%, it could be as high as 10%.

I think it's potentially damaging for a short period of time for that small 10 % of the population.

And it creates now a condition that we have a label for in sleep science, which is called orthosomnia.

And everyone's heard of this in medicine, orthodontics, orthopedics.

What that means, it's about straightening or getting something right.

So orthodontics, getting your teeth straight, orthopedics, getting your bones straight, getting them right.

And orthosomnia is a condition where you get so anxious and so worried about trying to perfect your sleep and get your sleep right, that it has the opposite impact.

Just as we described earlier, that you get so anxious about perfecting your sleep and you get so concerned about the fact that you're not sleeping enough if you're an insomnia patient.

It then becomes not a useful device, which for the most part, I think it is, and I'll say why I think it is in a second, but it becomes actually a detrimental device from being something that's adaptive in terms of its utility for your sleep, it becomes maladaptive for your sleep.

And so for those people for whom it's just triggering, and that's sort of the psychological term where it becomes a trigger for you and your sleep, I would strongly advocate for taking a break, just taking a vacation holiday from your sleep trackers, just put them away in a box, stop worrying about that.

Don't let that ruin your day or your night and return to the basic principles of good sleep that you can find on the internet or that you can find by working with a sleep professional.

So I do think there is a concern, Shane, that we become hyper focused and hyper attentive.

There's another version of that where people become hyper competitive and they become competitive, less so with other people, they become more competitive for themselves.

And they'll say, well, you know, I got an 87 % sleep efficiency last night.

By the way, anything above 85 % sleep efficiency is sort of where we would think of as good, healthy, very healthy sleep efficiency is usually above 90%.

And they start to game the system, they start to gameify their sleep with themselves, which is dangerous too.

And they think, ah, last night I only got, you know, an 84 % and the night before I got an 87, ah, I'm gonna beat it tonight, I'm gonna do it.

Or it dictates your whole day, right?

You get up and you see your sleep score and then you're like, oh man, you know, I feel great, but now all of a sudden my sleep score says I'm only, you know, a 71, so the day's ruined.

And what's very interesting about that is it sounds like psychological hocus pocus.

Okontra and we've done some studies and other people have done some studies where you'll bring people in and you'll have them sleep in the laboratory and you'll have a group where, you know, they've slept, I don't know, seven and a half, eight hours of sleep.

And you say, you know, before they do a whole set of psychological tests in the morning, which is often what we do after a night of sleep at my sleep center, you wake up and you'll say, look, would you like to know how you slept?

I'll say, yeah, I'd love to know.

And you say, well, you slept pretty well.

You've got a really healthy profile of sleep, you slept about seven and a half hours, your sleep efficiency is, you know, sort of somewhere upwards of 90%, everything looks great.

And then for the other group, you will say, ah, you know what?

I know you think that you slept well, but looking at our data, you really didn't sleep well at all.

You had a really low sleep efficiency and it looks like even though you probably weren't aware of it, you were awake for a lot of the night, even though they've had roughly the same amount of sleep as the other group.

And then you have them perform a set of tests.

And lo and behold, despite both groups having on average about the same amount of sleep, the group that was psychologically informed as to having insufficient sleep performs insufficiently on the cognitive tests.

So there is something to what you're saying, which is that it can almost destroy, even though you could feel as though if you didn't know what was happening with your sleep, that it looked bad.

And in that case, you know, those sleep trackers are probably right.

It's not the devious form of the experiment that I just described.

It probably is telling you some degree of ground truth that you didn't sleep well.

But knowing that can make your matters even worse because they reinforce a psychological construct that also has and carries a burden with it, just as the physiological burden of insufficient sleep will have its own impact, separate from the psychological burden that you've just lumbered yourself with,

which you could really do without at that stage, which is knowing how bad my sleep was.

So I think there's cause for concern there, but I'd also like to speak about, you know, if you wanted to, about I think some of the good sides of that and making the right choice for a sleep tracker.

Yeah. I want to know what are the variables that you sort of keep track of and what devices and tools do you use?

So I use right now, my go -to device is the Aura Ring.

And I should note, by the way, that I was using the Aura Ring for about two years before I joined the company.

And it ended up being the only device that really stuck with me.

And that's in part, that was one of the two reasons why I decided to help the company out.

The second was just because of the team and the people there that I'd not met a team like that in the sleep.

And I've been working, I've been working in the sleep tech industry and advising and consulting for probably 15 years.

And that team was very special and they've gone on to do amazing things and they continue to do amazing things.

So that's the reason I went with them rather than some of the other sleep bands or sleep wristwatch devices out there.

And the reason I like Aura Ring is because both of the data that it provides that some of these other companies don't or they're only now catching up in terms of doing.

But it's also the form factor.

And the way I think about sleep trackers, if someone were to say to me, what's the best sleep tracker?

I would say the best sleep tracker is the one that you use most frequently.

The second way that I think about sleep trackers is the accuracy.

And I think looking at the data out there, and again, I'm probably more intimate with Aura than anything else.

I think right now, and it's just released some updates with its algorithm.

I think it's probably the industry leader in terms of its accuracy.

Is it perfect? Is it the quality of accuracy that I get at my sleep center when I make you look like a spaghetti monster with all of these electrode wires coming off your head and your face and your body?

No, it's not that accurate.

And I don't think any of those devices will ever be that clinical grade accurate.

Is it industry leading?

I think it is right now.

So I think about it in one form factor, which is one silo of decision choice, which is accuracy.

The second silo of decision consideration is that form factor.

Because there's no point in creating a device that is even more accurate than the Aura ring, but is something that it's so difficult to wear.

It's this weird headband that is uncomfortable.

It wakes me up at night.

And the adherence rate to those devices just drops off within the first month.

And if you're not using it, it doesn't matter how accurate it is.

It's not very useful to you.

So it has to be a beautiful balance between those two different forces.

It has to be a sort of Fred and Ginger in terms of its dance between form factor and accuracy.

So that's the, I think the issue around which tracker to use and how to think about making that choice.

In terms of the metrics that I focus on, there are several.

I do focus quite a lot on my sleep efficiency.

And I am very mindful of that because I'm very nervous of spending too much time awake in bed.

And I think my sleep efficiency is a pretty good overall health barometer.

In the health industry, we're always trying to look to that single, simple measure that isn't going to be accurate for everything within the body, but is a pretty good proxy.

If all you can measure is just one thing, what would be the thing that you would measure for to assess someone's health?

And some in the field believe that HRV or heart rate variability is a pretty good measure of lots of different sort of systems in your body and maybe also your mental health.

I think there's some probably pretty good data for that too.

In terms of what is that one thing that I would want to know about if it came to my sleep and you really put the metaphorical sort of gun to my head and said, no, you can't have all of the things that you're about to say, you have to have just one of them.

I would probably focus on sleep efficiency, but thankfully I don't have to focus just on sleep efficiency.

I also look at my REM sleep and I look at my non -REM sleep, particularly my deep non -REM sleep and I look to be getting a nice balance of both of those as well.

And then the final thing is I look at my sleep latency.

Now these devices, it's hard to even measure.

Sleep latency, by the way, means how long did it take you to fall asleep?

What was the latency time from the point when you turned off the lights and you tucked yourself into bed to the point where you have stable sleep initiation?

And that's called your sleep onset latency or your SOL for short.

And these trackers will measure that too.

In the laboratory, it's a bit tricky to measure with these devices, it's even harder.

So I take that with a bit more of a grain of salt, but I also am mindful of my sleep latency because it's a Goldilocks phenomenon.

Not too little, not too much, just the right amount.

I don't want to have a sleep latency that is very quick, which may sound strange.

You would think, I really want to be able to get into bed and just fall asleep immediately.

Sleep is not like that, nor should it be like that.

Sleep is not like a light switch.

Sleep is much more like landing a plane that it takes time for you to descend down onto the terra firma of healthy, good sleep at night.

And the reason I'm nervous when people say, look, I get into bed and I, you know, as soon as my head hits the pillow, I'm fast asleep, that probably means that you're carrying maybe too much of a sleep debt.

Because in some ways you shouldn't be falling asleep that quickly if you are really truly well rested and fully slept from the night before, or the nights before, because usually it's an accrued sleep debt.

But also equally, I don't want to be lying there awake for long periods of time, because then that starts to look like sleep onset insomnia.

And the kind of rule of thumb is, you know, some people will say 20 minutes, others 25 minutes, others 30 minutes, but let's call the average of 25 minutes.

If it's been 25 minutes or longer and you still haven't fallen asleep, then it's usually time to get out of bed and try and do something different and just recognize that, you know, you've kind of missed your sleep train and it will come to you, just give it some time.

So I'm mindful of my sleep latency.

I don't want it to be too quick.

I don't want it to be too long.

Focus on my sleep efficiency.

Focus also on what's going on with my REM sleep and my non -REM sleep, including my deep non -REM sleep.

And then make sure that I'm not spending too much time in bed, too much time in bed awake.

Let's switch subjects a little bit since you've wrote the book.

I mean, you faced a lot of controversy since you wrote the book, Why We Sleep.

What would you attribute that to?

I don't know if it would be classified as a lot of controversy, but certainly there's been sort of some controversy.

And I really, you know, I'm really welcoming of that.

And if you were to ask sort of, you know, which parts of the different sort of critiques that have been sort of passed my way that I would agree with, the first thing I would note is that I've actually written an essay that is sort of on WordPress and that really offers a very in -depth exploration of the varied

questions that people have raised.

It also details any errors that were present.

And there were some, absolutely there were some errors in the first edition of the book that have now been corrected in a second print of the book.

I think the first point to make in all of this, and I've spent so much time thinking and journaling and sort of meditating on all of this, the first point to make is that if I'm ever wrong about something, life in general or science specifically, I don't want to be wrong any longer than I have to be.

So that's the first issue.

The second issue is actually one of reflected gratitude to the folks who took the time to actually reach out or to note on their blogs, any errors that they found in the first edition of the book.

And, you know, no matter how those things were expressed whether they were somewhat hyperbolic or click bait -like or sort of sensationalizing or sort of hashtag cancel culture type stuff, that's fine, I get that.

But I genuinely really no matter how it was expressed, I'm really thankful to those people for taking the time and alerting me to those.

I think the third point is that before giving some examples to help sort of concretely respond to your answer, is that I do have a system for self -questioning and it's sort of maybe a three -part system, which is whenever there is something that someone raises as controversial or they say that something

is as an error that I've made, the first step is that I evaluate the issue and I compare and contrast it to objective data and all of the data, not just the data that they're sort of using for their argument, but all of the scientific data.

And then I'll make a decision of two things.

I'll decide whether I embrace the issue that they've raised and actually say, yeah, I was wrong on that point.

I think now looking at the new data that's been published since the book or I actually think that you're absolutely right and I'll change my mind on those things.

And if I don't, if I don't agree with what's been said, then I will describe my evidence and I will offer sort of a data -driven rationalization of why I'm not embracing that position.

And usually I'll just write that and I'll write it sort of dispassionately without being personal or without being derogatory to anyone or being sort of sensational or hyperbolic, just because that's I think the best way to have a scientific discourse is to sort of remove all of those adjectives from one's

lexicon when writing.

So that's the first thing.

I'll just evaluate the issue raised and look at the data and decide, do they have a really good point and I need to change my point and accept that there was an error or do I not embrace it because I feel comfortable in the data?

The second thing is that if I accept and embrace an issue that they've raised, then I will openly admit that error and I will then make good on correcting that in whatever way is required, be it in conversations like this saying, I used to say this about caffeine and coffee and now I say this and make

sure that it's clear I was wrong or I had a change in my mindset because of contrarian data that has now changed my stance.

Or I'll go back and I'll do what I did with the book.

I will collate any errors that were made in the book and I'll change them.

I think the third point is that I take a higher altitude approach and I will try to then look back and say, okay, if I did make an error, let's look at what led, what were the steps that led to that error and then I'll try to formalize a construct that puts in place a practical risk mitigation strategy

so that I don't then make that same mistake again in the future.

And I think in writing the book and noticing that there have been some errors, that was a really hard thing for me because I am a perfectionist and I know everyone says that but it was very hard to realize that I can't be perfect.

And of course I am just human.

We all make mistakes and I will make some mistakes again in the future.

I'm not perfect. And I found it very hard to accept that I'm not perfect.

And that was very difficult.

So I wanted to, and there's a lot of shame that happens when you find that you're not perfect and that there are errors.

And particularly when you're someone who is like myself, people say sometimes say, oh, you kind of sound as though you have false modesty.

I'm not guilty of false modesty.

I'm just guilty of being British.

And with that comes at least for my form of the kind of Hugh Grant gene issue, you're not very secure in yourself.

You have a pretty thin skin.

And so whenever you realize that you made an error yourself, it's kind of painful.

But then when it's in public, it's especially painful and it can really, it can really hit you hard.

And so I think that's been very difficult.

And what I learned is that if you've made errors, don't just correct those errors, step back and ask what led to those errors, create a system, a safety net that puts in place, because I've now come to accept that I will always make errors that I'm not perfect, that I'm just human.

That sounds very Spock like, but I think I am just human unfortunately.

We're all human, right?

We're all mistakes.

I know. But I think the key is that what's acceptable is to make an error.

What's not acceptable in my mind still is to make the same mistake twice.

And so that's why I've tried to sort of create that system, but it's been very difficult.

And do you know what?

In fact, Shane, I've got something to thank you for when I was kind of just going through this process of recognizing these errors.

And when all of this sort of criticism comes on and people are sort of, you know, that cancel culture starts to take hold, you had a tweet and it was right around the time that I was sort of going through some of this.

And it was so profound because you said, and I can't remember, I'm going to have to paraphrase it, I apologize, but you said, if you can't handle controversy, you will never outperform.

And you went on to say that if we can't endure controversy rather than give into it and those who instigate it, then you will sabotage yourself.

And what I found to be so refreshing was that it taught me that if you fold in the face of controversy, in response to controversy, you are giving up the opportunity for important self -development and specifically the development of courage and resilience.

And by ourselves enduring through controversy, we emerge anew and we emerge in elevated form of ourself and our being.

And I really read and reread, and in fact, I saved, I took a picture of the screenshot on my phone and I put it in a little folder that I have in my photos called Wisdom.

And I would return to your quote many a time when I was facing that sort of controversy.

So thank you. I think you paraphrased it better than I actually said it, but there is something to that, right?

Where if you won't put yourself out there and you can't endure people sort of saying something about you, maybe it's right, maybe it's not, but if you can't endure it, then you'll never do anything outside of the ordinary and you'll never put yourself out there.

And if you do that, you'll never get any sort of extraordinary results.

I'm wondering if there's any parts of the critique that you particularly agree with.

Yes, there are. Yeah, there's some really, and let me come up with a few examples.

I think a really good example was in the opening chapter where I'd, which sort of the controversy was around risk for cancer and looking back, the opening chapter of the book, which I'm not blaming it on anyone, but I was sort of, that was the chapter that I think I worked with publishers and editors

on. They sort of really wanted it to be a sort of a more generalized high -level introduction to the rest of the book.

And I think what happened is that it became too generalized.

And as a scientist, that's one of the worst things that you can do.

And that through that generalized language, I was rightly criticized.

And so one error in the book, in that first chapter, I said that a lack of sleep can double your risk of cancer.

That is non -specific and it is well worthy of being criticized.

What I should have said and now have revised is that a lack of sleep can double your risk for certain forms of cancer and then name those cancers.

And those, for example, those cancers would be thyroid cancer, lung cancer, ovarian cancer, myeloma, which is a form of a blood cancer linked.

It's in the ilk of sort of lymphoma and leukemia.

So yes, there is evidence there that supports that at the epidemiological level.

So that was a great demonstration of where I should rightly have been pinned to the wall.

It's not that a lack of sleep can double your risk of cancer.

It's that a lack of sleep will double your risk for some forms of cancer, not all forms of cancer.

So that's, I think, one really good example where they were right to criticize me.

I think another one is again, some non -specificity.

What I said later in the book is that every species sleeps.

And again, that's stupidly generalized.

What I should have said and now corrected is that every species that we have carefully studied to date sleep or does something very much like resembling sleep.

And I should have then said what this suggests rather than sort of emphatically saying what this means is that sleep may have evolved with life itself on this planet and it is fought its way through heroically every step along the evolutionary pathway.

Now to counter my self argument against the question of myself, it's like that Austin Powers line, allow myself to introduce myself.

My former Harvard colleague, Stephen Pinker would actually take me to task on the latter.

He very much liked or dislikes in writing, particularly in scientific writing, this notion of hedging.

So what you heard me say is what this suggests is that sleep may have.

So I'm hedging by using the word suggests and using the word may.

And he would say, no, do not do that.

He would push back and say, you should go back to removing suggests and may.

You should just say what this means emphatically is that sleep has not that sleep may have but sleep has.

So you can go back and forth on this.

But I think I acquiesced to being a lot more cautious and as I now write more public prose and do more writing will do and maybe more books to come, I'll be a lot more careful.

And so those are just some of several examples and people can go and find them on the blog where I was absolutely right to be criticized and really enjoy the idea of correcting those errors.

It's still hard because people look at you as a public intellectual and some people, I shouldn't say, or people put you in that category of a politician.

And if a politician changes their mind in the face of contradictory data, they're seen as being wishy -washy.

Which is so weird when you think about it.

Which is so stupid, isn't it?

What we should all do is work like, yeah, an adaptive model of machine learning where you've got your priors and you're constantly updating your priors with new and novel information so that your decisional weights are altered for optimization.

That's how I want to be as a human being and as a science communicator.

And if you're going to do that, you have to firstly be open to controversy and criticism because you have to be brave enough.

It's like sort of Brené Brown has said, you've got to put your armor on because once you stick your head above the public parapet, you're going to get shot at.

And of course it's very easy for people in the crowd to throw stones.

And but too bad, I'm not going to wish for anyone to have sympathy for me.

Someone very wisely once told me that if you're looking for sympathy, it's between shit and syphilis in the dictionary, which technically they're correct on.

And that's the only time I will use profanity, which is in the sense of quoting someone else because otherwise my mother will lambaster me five ways till Tuesday.

So I'm not wishing for looking for sympathy here.

I'm just saying that I'm someone who is very shy and very much of an introvert.

And it's very hard for me to be out in the public arena.

But if you go out there, you're going to get shot at too bad, put your armor on, step up, dust yourself off, if you get knocked down and get right back up there and keep doing what you're doing, just as you said, don't crumble in the face of controversy.

Thank you for that tweet.

Yeah, just let it make you stronger.

Let's switch gears.

I want to get off that for a second.

Let's get practical.

We have like 20 minutes left.

I want to drill into sort of when it comes to sleep, what are the two or three things that virtually ensure we have a bad sleep?

I think caffeine, alcohol, and nicotine are going to be one category of things that will probably guarantee a bad night of sleep.

No, nicotine too. Nicotine too, nicotine is a stimulant and it's a very clear disrupter of sleep.

We've got some really solid data on that.

That's one thing that's probably not going to be so controversial in saying.

I think the other thing that I would very much suggest is getting your mental health straight.

That, and we sort of came onto this when we spoke about insomnia.

If you are in a state of high anxiety or if you're in a state of stress, that is one thing that will just almost guarantee you would have to be very sleep deprived and have a really high amount of sleep pressure to be able to fall asleep easily and stay asleep soundly if you have a high degree of stress

in your life and stress and anxiety.

Those two things will really guarantee a bad night of sleep.

The other probably two things I would note is making sure that you are sleeping at the right phase of the 24 hour clock face.

And this brings us onto something called chronotype.

In other words, are you a morning type?

Are you an evening type or are you somewhere in between?

And you can do a test, it's very easy online.

It's called the MEQ test and it stands for morningness, eveningness questionnaire, MEQ, and it takes less than probably like five minutes.

And if you Google it, it's free versions online and it'll give you a score and it will bucket you into being either a morning type, a morning lock, a neutral or an evening type or a night owl.

Now it turns out there's actually in sleep science we have five categories, extreme morning type, morning type, a neutral, evening type and extreme evening type.

And the reason everyone has a 24 hour, what we call circadian rhythm.

And no matter who you are, your circadian rhythm is going to be 24 hours.

So my rhythm is 24 hours, Shane, your rhythm is 24 hours.

And that's set a little bit by daylight because if you leave your body to its own devices it's a little bit laggy, it runs a little bit longer than 24 hours it turns out.

It's about 24 hours and I think 11 minutes for the average human adult we've calculated as, but things like daylight and food and timing and those different, we'll give, they act as a little set of fingers on a wristwatch.

That's kind of a little bit, you know, it's not quartz like and it just pops the dial out and it resets you to 24 hours.

That's no different from one person to the next.

We all have an unwavering 24 hour rhythm.

What is different, however, across individuals is where the peak and the trough of that circadian rhythm resides on the 24 hour clock face.

That's the difference between your circadian rhythm and your chronotype.

So let me ask you the question Shane, what time would you sort of say that you would normally ideally like, not the time that you have to go to bed or have to wake up, but ideally, what time would you naturally like to go to bed and naturally wake up?

I try to go to bed between 10 and 10 .30 every night and then I wake up usually between, I don't know, 4 .30 and probably six.

Okay, and do you wake up with that?

I haven't used an alarm clock for, Alarm clock, since I had kids.

Well, you're really quite a morning type on that basis.

Now I'm a neutral. I'm desperately vanilla, just like most of the things of my nature in life.

So I'm usually a sort of 11, 11 .30 to sort of 7, 7 .30.

And so what's nice is that you can see the two of us have slightly different chronotypes.

My natural urge to go to sleep is going to be an hour, an hour and a half later than yours.

And my natural urge to wake up is going to be an hour and a half to two hours later than yours.

And I make this point to come back to your question about what guarantees a bad night of sleep.

You can guarantee a bad night of sleep if you are mismatched in terms of your chronotype with your bedtime.

So some people will say to me, look, I get into bed and I just can't fall asleep and I'm lying awake and it's an hour, maybe even two hours before I drift off.

And then I'll ask them the question, let's do a chronotype test.

And again, this is not me being a clinician.

I'm just trying to sort of offer some help to them.

And it turns out that they're an evening type that naturally they would ideally like to be going to sleep around about 11 .30 midnight and waking up 7 .30, 8 a .m.

But they're trying to get in bed because they have to be awake at 6 a .m.

in the morning for whatever they've got to do, get to work or get to the gym or if they have children.

They're getting into bed at 10 a .m.

That's a biological mismatch of an hour and a half to two hours.

And so they think that they're suffering from sleep onset insomnia when they may not have sleep onset insomnia, instead what they have is a mismatch between their innate chronotype and their standard sleep bedtime schedule.

And so that's another thing just to keep in mind in terms of what can cause you problems with your sleep.

The final thing I would say that can guarantee a consistent pattern of bad sleep is spending too much time in bed.

It's sound again paradoxical but it comes back to our bedtime restriction therapy.

Don't spend, if you're struggling with sleep and you're spending a lot of time in bed awake, that's a bad thing.

And if you're doing something even worse which is now I'm lying, I'm going to bed and I'm staying in bed for nine hours a night to try to compensate for the fact that I'm only really sleeping five hours a night.

I understand why you wouldn't actually think that that's the solution.

But in fact, it's the very worst thing that you can do.

So try to be mindful and not spend too much time in bed.

You know, a lot of the common sleeping tips are sort of out there but there's gotta be some unconventional tips out there that help you optimize your sleep.

There are, and I think, you know, for people to trying to get the typical, what we call the sleep hygiene tips that out there and you can hear idiots like me espousing them on different YouTube places.

And those would be, you know, regularity, temperature light, not staying in bed awake and then, you know, minding your alcohol and caffeine.

I think unconventional tips, however, maybe there's probably four, three or four or five of those.

The first thing I would say, and this sounds going to sound unconventional, if you've had a bad night of sleep, here is my following best advice.

Do nothing. And what I mean by that is after a bad night of sleep, firstly, don't try to sleep it off by waking up any later than is natural.

Don't sort of say, I'm going to then sleep in for an extra hour.

The second thing is don't go to bed any earlier than you would do.

The third thing is do not nap during the day to compensate and fourth, don't start drinking more caffeine to try to get you out of that bad night of sleep.

So let me rewind the tape and go through those because me just barking rules at people isn't useful.

I don't think people respond to rules.

People respond to reasons and not rules.

So I'll try to explain the reasons.

Firstly, don't wake up any later.

Don't try to sleep it off after a bad night.

The reason is because if you sleep in later into that following morning, when it comes time for you to go to bed at your normal time and you get into bed at your typical kind of chain, you know, 1030 at night, you're not going to be as sleepy as you naturally would be.

Why? Because you woke up that much later.

So you've been awake for less time.

So you've built up less sleepiness.

And so you're almost guaranteeing a bad night of sleep the next night because you're going to be tossing and turning to fall asleep.

The second thing is don't go to bed any earlier for the same reason.

Don't say, well, I had a bad night of sleep last night.

I'm going to try and make good.

I'm going to try and get into bed at 9 p .m.

tonight rather than 1030.

Well, you're a morning type, but you're not an extreme morning type.

You're naturally going to be tired even if you've had a bad night of sleep at 10 to 1030 p .m.

And by getting into bed at 9 p .m.

with all goodwill and intention, you're setting yourself up for then just twiddling your thumbs lying wide awake for the first hour because you're mismatched with your crone type.

Naps are a double -edged sword, but in this circumstance, they can be a bad thing because if you nap during the day after a bad night of sleep, again, I understand why, but naps in the day are a little bit like snacking before your main meal at night.

They just take the edge off your sleep appetite, off your sleep hunger, and you're not going to be as hungry for sleep when it comes time for it at night.

So try not to nap during the day.

And then the caffeine, the final one of those four things is sort of pretty obvious.

It's just going to jack you up and you're going to have too much caffeine in your system.

The second thing is having a wind down routine, which comes back to this idea of sleep being like a light switch and it's not like that.

I think as, since you are a father, you will probably know this with raising your children, you kind of have a bedtime routine and it's different for different kids, but when you figured out what works, you stick to it.

What you're doing is creating a wind down routine.

Why? Because kids can't just go from 60 down to zero within a short breaking distance, which is you can't just go from lights on of wakefulness to lights off of sleep within a minute or two.

You build in a wind down routine, but somewhere between childhood and adulthood, we abandon the notion that we need a wind down.

Why don't adults need a wind down routine?

Now, it doesn't have to be your significant other coming in and reading you a bedtime story, even though that's actually quite nice.

And in fact, if you look at some of the meditation companies like Calm, for example, and Headspace, they have bedtime stories read by some wonderful characters like Stephen Fry.

Why were they so popular?

Why did they save those companies?

It certainly saved Calm and it gave them a, I think almost a billion dollar valuation.

What saved them was sleep stories.

And the reason is because we all need a wind down routine and being read too is part of a wind down that works for many people.

Well, not only does it work, I mean, it's probably how most of us grew up, right?

It's how we experience going to bed.

And it doesn't have to be reading, by the way.

Find something that works for you if it's having a bath or a shower before bed, if it's meditation, I do usually try to meditate for 10 minutes before I get into bed.

If it's light stretching, something that just helps you disconnect and wind down is a really good piece of advice.

I'm doing a deep dive on naps at some point.

So I've idiotically released my own podcast with a wonderfully creative title.

It's called The Matt Walker Podcast.

And it's very different to your form of podcast.

You're far more elegant and erudite and you can interview people and explore.

My podcast is rather inane in the sense that it's a short form podcast.

It's usually somewhere between five to 10 minutes in length and it's a short form monologue from yours truly.

And it's just a little slice of sleep goodness to accompany your waking day.

And there I'm going to take a deep dive into explaining all of the science behind naps.

But again, I would say that if you are struggling with sleep at night, then the unconventional tip is not to nap during the day.

Or if you're going to nap during the day, make sure that you nap before 1 p .m.

And keep those naps brief, maybe just 10 minutes or 15 minutes in duration and no more.

I think the final two pieces of advice unconventional would be don't count sheep.

It's a myth. And that myth was exploded by another wonderful sleep scientist here in my department, Dr.

Alison Harvey, and she did a great study.

What she found was that not only did counting sheep not make you fall asleep any faster, it actually made people take longer to fall asleep.

What she did find that was exceptional, that worked to help people fall asleep was taking themselves on a mental journey.

So think about a walk that you would take, a hike that you like to do, or a walk on the beach or a bike ride, and just try and move through that with your mind and just take yourself on that mental journey.

And it's all about, once again, taking your mind off itself because in this modern era, we are constantly on reception, and rarely do we do reflection.

And reflection is so critical and it's so powerful, and you've spoken a lot about the power of reflection.

However, I would say that the last time you want to start doing reflection is when your head hits the pillow at night, because then it's just, you start to ruminate, you catastrophize, because there's something weird that happens to our thoughts in the darkness of night.

Our thoughts are not our own at night.

They are darker, just like the absence of light around us.

The bad things feel twice as bad.

The frightening things feel twice as frightening.

The anxious things twice as anxious.

It's just not a good time to be ruminating.

And taking yourself on this mental journey helps you not ruminate and catastrophize and blow things all out of proportion.

My one kryptonite in life, that my one vice is, I love racing motor cars.

This is why our mutual friend, Peter Atiyah and I, we're good friends for many reasons, but one is that we race cars together.

So I'll just put myself on one of my favorite tracks, and I'll try and go around the track and remember what gear I should be in, when I should be braking, my braking distance, left foot right foot brake.

And I can remember, and I'm halfway around the course, and that's it, I'm out like a light, I'm done.

So that's the second thing.

Don't count sheep, but take yourself on a mental journey.

The final silly tip, and it sounds silly, but it is actually effective, if you're struggling with sleep, remove all clock faces from your bedroom.

If you're waking up in the middle of the night and you're staring at the clock and you look and you see, it's 3 .21 in the morning, and then you toss and you turn, then you look at the clock and now it's 4 .38 in the morning.

Knowing what time of night it is, is not your friend.

It's not going to change anything, it's only going to make matters worse.

So if you need an alarm clock, that's fine, but make sure that you can't see clock faces in your bedroom.

That's only going to hurt and harm your sleep rather than help you out during your night of bed sleep.

Matt, this has been an amazing conversation.

I want to thank you so much for taking the time to go into the detail and into the weeds about how we sleep.

I have 50 other questions for you and we'll have to do a part two of this.

I would be, honestly, anytime you would like me back, as you can tell from the unfortunate tenation of my voice, I get far too excited about this stuff, and that's part of the problem.

I think I've been a bit too heavy -handed.

I get so excited about sleep.

People think, God, it's a bit too much and I get that.

So thank you for giving me this opportunity in this forum to speak sleep's message to the public and go all over the map and ask the hard questions too.

I'm so open to those and you do so so elegantly and with such a gift.

So thank you, and if you would wish me back, well, listeners would wish me back, date, time, and I will be right there with you.

Oh yeah, there's so much we didn't talk about.

We'll definitely do a part two.

Thank you. Wonderful, Shane.

Thank you very much.

The Knowledge Project is produced by the team at Farnham Street.

I'd love to get your advice on how to make this the most valuable podcast you listen to.

Email me at shane at fs .blog.

You can learn more about the show and find past episodes at fs .blog .podcast.

To get a transcript of this episode, go to fs .blog .tribe or check out the show notes.

Can you do me a small favor?

Go online right now and share this episode with one friend who you think would love it.

Thanks for listening and learning with us.

Till next time. Thank you.

[수면의 과학: 수면 단계, 불면증, 그리고 최적의 휴식을 위한 전략]-[#131 Matthew Walker: The Power of Sleep]

📋 Summary

수면의 과학과 현대 사회의 수면 부채

수면의 두 가지 핵심 단계

충분한 수면을 판단하는 기준

카페인과 알코올의 함정

불면증과 '수면 유지 장애'

온도의 마법: 체온 조절 전략

결론: 수면은 훈련이 아니라 자연스러운 과정

🎯Key Sentences

📝Key Phrases

📖 Transcript