Feel Better, Live More with Dr Rangan Chatterjee - The New Science Of The Body Clock And How It Can Revolutionise Your Sleep and Health with Professor Russell Foster #292

Episode Date: September 6, 2022

The tired brain remembers negative experiences but forgets the positive ones. Is there a more powerful statement in favour of going to bed earlier and prioritising our sleep? Modern life has seen us push into the night, staying up later and extending our social and work lives around the clock. But this, says today’s guest, goes against what our bodies are wired to do.   Russell Foster is Professor of Circadian Neuroscience at Oxford University and author of the fantastic new book, Life Time: The New Science Of The Body Clock And How It Can Revolutionise Your Sleep and Health. Russell explains that living out of sync with our circadian rhythms doesn’t just lead to sleep disruption and tiredness. The further we stray from them, the more we become vulnerable to chronic conditions such as obesity, type 2 diabetes, heart disease, cancer, suppressed immunity, dementia and mental illness. But he’s not here to scare us – rather share the strategies that we can all use to get back on track.   During this compelling conversation, we cover the science behind exposure to natural daylight at the right times. We talk chronotypes – and if there’s anything you can do to change being a lark or an owl. Russell explains the dangerous phenomenon of ‘microsleeps’ and why 4am is the most dangerous time to be on the roads. And we cover the unique problems faced by night-shift workers and new parents, including what they, their families and employers can do to mitigate their health and safety.   We also chat about the value of sleep trackers and blue-blocking glasses. Russell busts the myth that we all need eight hours’ sleep or that you mustn’t read a Kindle before bed. And he reveals the best time of day for sex (clue: it’s different depending on whether you want to conceive or relax). And for all those insomniacs who go to sleep fine but wake during the night? There’s some wisdom towards the end of our conversation that you’ll want to hear!   This is a fact-filled episode, full of fascinating insights. I hope you enjoy listening. Support the podcast and enjoy Ad-Free episodes. Try FREE for 7 days on Apple Podcasts https://apple.co/feelbetterlivemore. For other podcast platforms go to https://fblm.supercast.com. If you're a healthcare professional, come and see me and Professor Russell Foster speak live in November. https://bit.ly/3RD1DSq Show notes https://drchatterjee.com/292 DISCLAIMER: The content in the podcast and on this webpage is not intended to be a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your doctor or other qualified health care provider with any questions you may have regarding a medical condition. Never disregard professional medical advice or delay in seeking it because of something you have heard on the podcast or on my website.

Sleep loss is so much more than feeling tired at an inappropriate time. It's associated with an impact upon our health at every level. Things like obesity, type 2 diabetes, and indeed, because of the suppression of the immune system, higher rates of infection and indeed cancers. Hey guys, how are you doing? So we are back with a brand new season of the podcast. My name is Dr. Rangan Chatterjee, and this is my podcast, Feel Better, Live More. I hope you've had a good summer. I hope you found some time to switch off and relax. I am really, really excited about this

new season. I've already recorded some absolutely fantastic conversations, which I cannot wait to share with you. If you are brand new to my show, welcome. And if you're a longtime listener, welcome back. So I want to start off today with a surprising fact. The tired brain remembers negative experiences, but forgets the positive ones. Now, is there a more powerful statement in favour of us going to bed earlier and prioritising our sleep? You see, modern life has seen us push into the night, staying up later and extending our social and work lives around the clock. But today's guest says that this goes against what our bodies are innately wired to do. Russell Foster is Professor of Circadian Neuroscience at Oxford University

and author of the fantastic new book, Lifetime, The New Science of the Body Clock and How It Can Revolutionize Your Sleep and Health. In our conversation, Russell explains that living out of sync with our circadian rhythms doesn't just lead to sleep disruption and tiredness. The further we stray away from them, the more we become vulnerable to chronic conditions such as obesity, type 2 diabetes, heart disease, cancer, suppressed immunity, dementia, and even mental illness. Now, I want to be really clear. Russell is one of the world's leading authorities on sleep and circadian rhythms, but he is not here to scare us.

Rather, he wants to share the practical strategies that we can all use to get back on track. We talk about the science behind exposure to natural daylight at the right times. We talk about chronotypes and if there's anything you can do to change being a lark or an owl. And we also discuss the dangerous phenomenon of micro-sleeps and why 4am is the most dangerous time to be on the roads. We also cover the unique problems faced by night shift workers and new parents. We talk about sleep trackers and blue blocking glasses. And Russell is keen to bust the myth that we all need eight hours sleep or that we mustn't read on a Kindle before bed. He also reveals the best time of day to have sex. And a little clue, it's different depending on whether you want to

conceive or relax. And if you are someone who goes to sleep fine, but wakes up during the night, there's some wisdom towards the end of our conversation that I am certain you will want to hear. This really is a fun filled conversation full of facts and fascinating insights. I hope you enjoyed listening. And now, my conversation with Professor Russell Foster. There's a lot of things that I hope we get a chance to talk about in our conversation today. I thought one of the nice places to start would be with a phrase I've heard you say in one of your talks before, which is that alarm clocks stop the single most important behavioral experience we have. Yeah, and that's sleep, of course. And we've so undervalued sleep. You know, it's been treated

as almost an illness that needs a cure or an indulgence. And of course, in the 80s, those of us that remember the 80s, you know, people used to come and say, oh, I've done another all-nighter. And then people used to clap them on the back. And in fact, you don't want people like that in the workplace. I mean, essentially, what we've discovered over the past sort of 20 years or so is that sleep consolidates our memory,

but it's not just the retention of facts. We're actually problem-solving. So if you want to come up with innovative solutions to complex problems, a night of sleep achieves that. We're also discovering that the elimination of beta amyloid, this misfolded protein that's been associated with dementia, is packaged up and got rid of whilst we sleep. So much of the stuff going on within the brain and the body

whilst we sleep defines our ability to function during the day. And, you know, it's really, we've got to start embracing sleep. You know, as I read through your book, and as I think about the literature literature the work you're putting out there I think about the impact that sleep deprivation has on our entire physiology you know this idea that's been sitting with me the last few days is that number one a lot of us don't realize how sleep deprived we are yeah and I think in many ways, the way we experience the world is influenced by our levels of sleep. Yeah, I think that's,

during the research for the book, the realization that the tired brain remembers negative experiences, but forgets the positive ones. So tired individuals' entire worldview is influenced by a negative salience. You know, we're making decisions, remembering the negative stuff and not the positive stuff. That's just one example, I think. Yeah. That's really profound, Russell, because if as a doctor I look around and I see how many problems we have these days with excessive negative thoughts

that people struggle with yeah and then if you look at the data in terms of how sleep deprived we are yeah potentially this is the smoking gun that's sitting there that if all of us started to pay a little bit more attention to perhaps that would have a profound impact on the way we feel, and as you say, these negative thoughts. And across the whole demographic, from youngsters and young youngsters, all the way through to the elderly. I think it could make a huge difference.

Yeah. So we're recording this late morning. It has just passed midday. So I know from your book now that we've just passed the danger zone, the most dangerous part of the day, right? So I feel good that we should celebrate with a glass. It's 12.01. So can you explain a little bit about what is so dangerous about mornings and in particular this 6am to 12pm time period? Yeah, well, the biggie, of course, is stroke and heart attacks. Between 6

a.m. and 12 noon, there's almost a 50% greater chance of having a stroke or a heart attack. And of course, it represents the sort of the biological switch from the sleep resting state to the active state. So, what our internal clocks are doing is anticipating increased activity. So, even before we wake, blood pressure is going up, the mobilization of glucose is going up. Interestingly, the stickiness of platelets is going up, presumably anticipating an increased risk of damage and therefore the need to clot.

And so, cortisol is all going up, mobilizing our bodies for activity. Now, if you're healthy, it's not an issue. In fact, it's a wonderful adaptive response. So you can get out into the new environment and exploit it to the full. But if you have health problems, then that surge in blood pressure, that increased stickiness of the blood, is going to predispose to things like heart attack and stroke.

And what's become very clear is that when you take your anti-stroke medication, your antihypertensives, really matters. So, for example, taking them before you go to sleep, before bedtime, rather than first thing in the morning, over a sort of four or five-year window, can actually halve your chances of having a stroke or a heart attack. Now, that information isn't widely known. And I think we've got to try and get this sort of knowledge more widely accepted. Yeah, a couple of things came up for me there, Russell.

I remember, I'm going to guess seven or eight years ago, I was getting quite frustrated as a medical doctor with my lack of awareness over all kinds of things to do with our lifestyle and how it influences health. And I was thinking, if I knew a bit more about this and how to manipulate it, I'm sure I could help my patients more. So I would go on my holidays around the world to various conferences. I remember in America sitting at a conference and there was a cardiologist called Dr. Mark Houston. I remember him saying exactly this to me years ago. He was saying something like, most blood pressure medications should be taken in

the evening. And I'm thinking, wait a minute, we're giving them all that in the morning and people are just taking them in the morning because it's easy. It's with breakfast, I'll just take it. So I think that was the first time that that lodged in my head that, oh, the timing of these medications is important. The other thing, Russell, that came up for me as you were speaking there, on the show, we've spoken a lot about stress in the past and what happens when the stress response gets activated. And what you just described happening then in the early hours just before we wake up those are the those are the things that the stress response blood being more prone to clotting blood pressure going up cortisol going up so it's almost like a mini stress response first thing in the morning indeed it is, absolutely. Stress gets a bad rap. I mean, you know, it's a shame.

I mean, I liken stress as the sort of the first gear in a car. You know, it gives you that wonderful acceleration. So it's great, you know. But if you keep the engine in first gear, of course, you'll destroy it. And that's the problem with so much of our stress these days. It's not that it's an acute quick shift where for example night shift workers they're running on stress to keep awake and to keep functional during the night shift and so no wonder there's all those health problems associated with that group yeah you mentioned the clock and there's there's a lot in your book about our body clock, our body clocks, I should say, and what they all do, what influences them. One thing I've felt and experienced when people, when my patients,

when members of the public are thinking about sleep, they're often thinking about the evening. They're thinking about what do I do just before bed? What do I do in those hours preceding me going to my bedroom? And of course, that's important. We're definitely going to get to that. But I thought it would be useful, particularly through the lens of the clock, I guess, to talk about the morning. Why is what we do first thing in the morning so important for our ability to sleep at night? Yeah. So we have this circadian system, this sort of internal representation of a biological day. And what it does is anticipate the very demands of the rest activity, the sleep-wake cycle.

Now, for it to be of any use, the internal day needs to be set to the real day, the astronomical day. And the classic mismatch between biological time and environmental time is jet lag. And we eventually get over jet lag as a result of exposure to the light-dark cycle in the new time zone. But what we require in any time zone is daily exposure to the light-dark cycle, and particularly morning light, for 90% of us. Most of us have either a long body clock or a body clock that's slightly longer. And so it will naturally drift a little bit later and later and later each day.

And the effects of light are not the same. Morning light advances the clock, makes us get up earlier and go to bed earlier. Whereas dusk light delays the clock. It makes us go to bed later and get up later. And so what morning light does to us is take this drifting clock and shoves it forward a bit in time so it's beautifully aligned. Now, of course, this is important at every level. I mean, we did a study a few years ago on teenagers, and we found that all over the world, and found that the later the chronotype, the eveningness versus morningness, the greater the evening light these young people got. So they were getting up after morning. So

not getting the morning light, which would advance the clock, but they were getting evening light, which would delay the clock. So part of their going to bed late and getting up late is when they were actually seeing light. And so morning light for most of us is really important to set the biological clock, which then aligns all of our activity, including the sleep-wake cycle, to the appropriate time of day.

Yeah, so this is fascinating. There's so much there. So we live according to 24 hour days yeah okay but one thing i'm aware of from your book and other research is that our internal clocks are not set to exactly 24 hours so i want to i want to talk about that and why you think that might be because we certainly i guess didn't evolve for plane travel in the future. Do you know what I mean? So when we go on a 12-hour flight to LA from London,

we can adapt straight away, right? So that presumably wasn't evolution's goal. So I'm interested as to why it's not 24 hours in your view, but also you say morning light. So does it matter what time of morning light that is you know can people get it at lunchtime are we talking as soon as people wake up and of course that changes in the seasons right so can you help us put all those things together okay so why isn't the human body clock exactly 24 hours well now here's some hand-waving.

Because the modelers say that if you want two oscillators to align to each other, two rhythms, one is fixed, obviously the rotation of the Earth is fractionally under 24 hours. And if you want to fit a body clock to that, it helps if it's slightly different from 24 hours, because then it can align more easily. Now, I don't pretend to understand the mathematics behind it, but that's why it is. But there's an even... So Mother Nature knew what she was doing.

Of course, as always. But the really interesting question, I think, for me is, why is there such diversity in the human chronotype? So, you know, the fact that we have some people, you know, are really early larks, and some people really late owls, there's a huge diversity, you know, to the extent that you can almost bed share in some extremes. Whereas if you look at the mice or any other animal you want to study, it's all very, very similar. And I think this is something that's puzzled me for ages. And it may well be that in our society, you know, and we've only moved very rapidly from sort of essentially small groups, tribes, interacting. It may have been useful under those circumstances to have vigilance across the 24-hour day.

And having some people that were sort of awake early and could perhaps alert the group that there was danger from another tribe, for example, or some sort of animal. And that may be why we've retained this extraordinary diversity. We're very weird as a species in that regard. Yeah, I mean, that makes a lot of sense, doesn't it? You mentioned the word chronotype. I wonder if you could just elaborate exactly what does chronotype mean? And then you also mentioned owls and larks. And I'm really interested in this because, A, me and my wife appear to have slightly different body clocks.

But many people, I feel, certainly if I look at my clinical experience, Russell, and this also, I think, speaks to this idea that the body clock isn't quite 24 hours that we can manipulate it depending on what we need it to do or what the tribe needs or what the weather is right a lot of the time i think well are we evening types really evening types or are they evening types because of the modern light environment yes um so yeah quite a lot there yeah yeah okay so what defines your chronotype whether you're evening types or are they evening types because of the modern light environment? Yes. So yeah, quite a lot there. Yeah. Okay. So what defines your chronotype, whether you're a morning person or an evening person? And there are a number of factors. The first of all is one's genetics.

We now know that the clock genes and the proteins that they make, subtle changes, subtle polymorphisms in those genes are associated with morningness and eveningness. So by their contribution to our genes, our parents are still telling us what time to get up and go to bed at some level. So that's the first thing. Through development, our chronotype changes. So from about the age of 10, we want to start to go to bed a bit later and a bit later. Our lateness peaks in males at around about 21, 21 and a half, in females about 19, 19 and a half. And males peak later, they have a later chronotype than females. Then from those late teens, early 20s, we start to move to a more morning chronotype. So by the time we're in our late 50s early 60s we're getting up and going to bed on

average when we got up and went to bed when we were 10. And that sort of basically maps the changes in some of the sex steroids, testosterone and estrogen. So it's thought that there's a very important hormonal modification of the clock. So that's within individuals. So whatever I'm born with, let's say I was born a morning type, and I think I'm a morning type, then when I'm 10, in my teenage years, that's going to be pushed, it's going to be later and later. As you say, for most males, a peak at 21, and then it's going to start going back again. But what about between individuals? There's variation there as well, right? Yeah, a huge individual variation. I think that's a really important point because,

you know, in terms of our sleep weight patterns, among our chronotype, there's massive individual variation. And, you know, there's on average about a two-hour difference from somebody in their late 50s, early 60s, to somebody in their late teens. So asking a teenager to get up at seven o'clock in the morning is like asking a 60-year-old to get up at five o'clock in the morning. Now, does that matter? I guess there's a real interest here for me, given that my son's 12 and about to enter these teenage years yes and as a family we prioritize sleep or we certainly have done but i'm already noticing with him a change yep in terms of his desire to do what he has done in the past let's put it like that okay i think they call it testosterone poisoning don't

they and what i'm interested in is when we say teenagers want to go to bed later and wake up later, and we think about their chronotype, what if that teenager still went to bed early? So what's driving the change? Is it the fact that they're going to bed late, therefore they're having to stay in bed later? Could that be environmental, school pressure, that sort of stuff? Do you know what I'm getting absolutely well of course the the other factor the sort of as it were the the the biological factor would be when you see light as we as we just discussed sort of morning light advances the clock evening light delays the clock and teenagers particularly over the weekend will miss the

morning light making them get up earlier but they'll get the evening light so they're or the afternoon evening light and so they'll go to bed later. So those are the three sort of biological factors. But then we have to add a couple of other things. One is, of course, the use of social media. It's very interesting. Many teenagers appreciate that they shouldn't be using social media into the early hours of the morning, but they feel that sense of being connected to their group overrides that knowledge about why it's important to be asleep. So there's that element. And in fact, it's really fascinating. Some studies have shown that that lateness can be hugely late. So what happens, of course, is that they have very shortened sleep.

They're driven out of bed by an alarm clock or a parent. They struggle through the school day. Often, and when you talk to many teachers, kids are actually falling asleep at the desks. So then they finish school, and then they have not just a short nap, but it can be a nap of two hours or so, which then pushes back the pressure to sleep that night. And so, you know, the desire to use social media and the fact that they're not as

tired because they had to sleep in the late afternoon means that they can function later at night and they get that shortened sleep. And in fact, you have to be very careful because it can lead to increasingly shortened sleep at night and longer naps after school, which, you know, and you can fall into this sort of feedback loop of really disrupting the sleep. If that teenager could go to sleep, let's say, on time, at a more suitable time, given what time they have to get up for school

or the school bus or whatever that's the sort of fixing that they can't move does the later chronotype still matter i.e if they shift their environment so actually i'm still going i'm going to go to bed earlier i'm not going to expose myself to evening lights but this may sound optimal and hypothetical as something that's practically impossible but in theory would that then normalize things do you think yeah you can shift teenagers to an earlier chronotype because of light exposure absolutely uh practically it's it's very difficult um but it's it's in theory possible yeah and this light exposure whereas in the morning it advances the clock and in the evening it delays the clock so pushes it back what light exposure are we talking about here because

let's say in the evening or at dusk you saw natural natural lights, not artificial lights. Does that still do the same thing at pushing it back? Or does that have a different wavelength that doesn't affect us in the same way? Well, you're sort of impinging upon what I've been working on for a long time, which is how does light interact with the body clock? And the first sort of extraordinary finding was that the visual cells within the eye, the rods and the cones, are not required to detect that dawn-dusk cycle. There's a third photoreceptor within the eye. And we've been working out most recently how those receptors interact with this sort of master clock within the brain. So that's one thing. The second thing is that these photoreceptors need quite a

bit of light. So we don't really appreciate because our visual system is so good, but we live our lives in dim, dark caves. So shortly after dawn, natural light is some 50 to 100 times brighter than average domestic light conditions. And so, really, what the clock is looking for is a bright light signal. And so, we're talking in the hundreds to thousands of lux range. So, if you think of natural light, okay, moonlight will be 0.01 lux. And a bright sunny day, lux and a bright sunny day even in the UK can just about get up to a hundred thousand lux and those weird amazing photoreceptors need as I say this sort of hundred to thousand lux range. Now it's complicated because it depends upon how long you're exposed to that light. So you can compensate to some extent for a lower light intensity by

increasing the duration. And it's worth bearing in mind, until the late 80s, it was thought that the human circadian clock was not regulated by light at all. Because when people use sort of relatively low levels of light that would shift the biological clock, or entrain the biological clock of a mouse, it had no effect at all. This is in the 1980s, right? I read that this morning in your book and that shocked me because 1987, I was just finishing primary school. Maybe it is, but it doesn't seem that long ago to me. And I thought, when I read that, I had to reread it. This idea that back then, which wasn't that long ago, we didn't think light

hugely influenced our circadian rhythm and now that's considered fact and i think well what else is going on that we don't know at the moment well that's what's so exciting about this field but i remember you know doing doing my my phd um and i i got my phd in in 84 and uh you know when you did public talks or anything people say well how is it regulated and so it's primarily social cues and food and I remember being actually at that first presentation in in 1987 and you know it was an audible gasp around me oh my god you know you just need a lot of light and of course now we know light is incredibly important for the regulation of human circadian rhythms but you need quite a bit of it.

And this is where we fall into some problems, because there's a lot of stuff out there saying you shouldn't look at a Kindle immediately before you go to bed, because it'll shift the biological clock. So the most detailed study, which was from a group at Harvard, asked people to look at a Kindle on its brightest intensity four hours before bedtime. And they asked them to do this on five consecutive nights. And after that, on the fifth day, sleep was delayed by an average of 10 minutes. And it was just statistical. And as one of my colleagues said, well, it may be statistically significant, but it's biologically meaningless. And so, but we do know that light in the evening can delay the clock. But how much and what

intensity and for how long is still being resolved? Clearly, the brighter the light and the longer you see it before bedtime could shift the clock. But what we do know that light is doing is increasing alertness and therefore delaying sleep onset. So it's probably not the light from the devices changing the clock, but it's the light from the devices changing alertness and therefore delaying sleep. Yeah, super, super interesting. So if we just stick to what that study showed, that was on a Kindle. If we just stick to what that study showed, that was on a Kindle. I know when I've heard you speak before that you regard Kindles as quite different from smartphones or looking at social media. Perhaps you could explain why that is. Well, because a Kindle is fairly, you know, you're just reading it, basically.

Whereas a smartphone, you're checking your emails, you're looking at social media, you're checking the news, you might even be listening to music at the same time. And so these are really interactive devices, and they will be increasing alertness and therefore delaying sleep onset. Yeah, super interesting. In terms of light, just to finish off in the evening then, we talked about the complexities of light, know how much how long for all these kinds of things some people who are promoting health and well-being are talking about the importance of morning lights morning natural light i know there's one neuroscientist in america who talks about getting 10 to 30 minutes if you can yeah within half an hour of waking up okay so

that's very clear guidance. I want to know your view on that. The data are good for that. I mean, really, really. So, for example, the Ken Wright studies have shown beautifully that bright morning light, real light, not artificial light, can advance the clock and really shift individuals two hours earlier. So, there's no question about it.

And you can mimic this in the lab as well. So for example, 10,000 lux for 30 minutes from a light box will also set the clock. So the data there are pretty solid. So we say advance the clock. What if someone doesn't want to advance their clock and they wake up and they're like, you know what, I've got a late work night out tonight

and I won't be back for my normal time. I've never thought of this question before, but I'm just intrigued. Might one then think, hey, for tonight, I'm actually going to not expose myself to light for a couple of hours, because I want to delay that? Or is that hard to say? It probably will have a small effect. I mean, the tricky thing is for those 10% of individuals who are really morning types, and it's a shame really because most of their colleagues will be intermediate to late types.

And of course, they will be then forced on a Friday and a Saturday evening to stay up way beyond where they want to be. And they sort of complain bitterly that, you know, God, all my friends want me to stay up. Of course, for the work environment, it's great. They can get up, you know, go to the gym early and then go on to work. Whereas most of us who are late types find that a struggle.

So you're happy with that 10 to 30 minutes natural light recommendation? Would you ideally have people do that as soon as they can after waking? Yes, certainly. The earlier, the bigger the effect yes and it's and it's very important um across the spectrum so for example in the nursing home environment up until fairly recently the light in those nursing homes was really low i mean terribly low some cases in the television room it would be just sort of 10 20 20 lux. I mean, crazy low.

Now people are realizing that if you increase the light in the day spaces, then you can actually improve the sleep-wake behavior of individuals in a nursing home. And where it's been looked at in individuals showing mild dementia, you could actually improve cognition by 10% simply by increasing the light with inside. And also using other tricks like having breakfast by a window where there's a lot of light coming through. Wow, that's fascinating. And then in terms of evening,

I want to draw a distinction between natural light and artificial light. So let's say you live in a country where you have long light evenings at particular times of the year, like the UK for example. You want to get your morning light in the morning, which is clearly a lot easier in a UK summer than it is in the winter. What happens if you want to be outside in the evening? So it's still natural. It's not your screen. It's not's still natural it's not your screen it's not social media it's not the news it's not all that attention stimulating information is there something going on in natural light where actually you know the evening light perhaps doesn't shift the clock as much or or or does that still do it well course, when we're all agricultural workers, we got symmetrical exposure to dawn and dusk.

And so, you know, the morning light would advance us, but then that was counteracted by the dusk light, which would delay us. And so it was fine. And the problem that many of us face now is that we get asymmetrical exposure to the dawn-dusk cycle, which invariably means most of us will miss morning but get lots of dusk light and therefore get up later. We'll delay the clock. Now, in terms

of the quality, we've talked about the intensity, we've talked about the duration, but we should also touch about the colour, the wavelength of light. Now, those specialised photoreceptors are maximally sensitive in the blue part of the spectrum. In fact, intriguingly, if you look at the blue of a really beautiful blue sky, that's where they're maximally sensitive. So, there's been a suggestion that actually only blue light is important. But again, it's more complicated than that because the response is like a bell-shaped curve. It's maximally sensitive in the blue, but of course it doesn't mean that the receptors won't detect shorter wavelength

or indeed longer wavelength light. Again, it's how long you're exposed to it. We also now know, which has turned out to be really confusing, that the rods and cones, which we know are not required for the regulation of the clock, talk to those specialized photoreceptors so they can modulate their activity. Some of the rods and cones seem to add sensitivity and others seem to inhibit the responses. So it's turning out to be really complicated and we don't fully understand why. So the best advice would be,

let's say someone is trying to get on top of their circadian rhythm and their sleep, and they feel, either for work reasons or for other reasons, they're going to bed too late. The best advice at the moment would be to try and limit light exposure in the evening, even if it's natural light, you still want to be a bit careful. Yeah. And if you are an extreme late type and you really are struggling, then what you need to do is set the alarm and either get outside first thing in the morning or get a light box, which will advance the clock and make it easy for you to get up for job or whatever reason. Yeah. I know you're on the Chris Evans

Breakfast Show recently talking about your book. And I remember in that conversation, Chris said, because he for many years is presenting on live radio, I think at the moment at 6.30am. And I think he said to you that he goes to bed at 7pm, or he at least puts an eye mask on at 7pm. So it's reducing how much light is coming through his eyes. I think he said in that conversation with you, it had a massive difference. And then when he wakes up at 4am, he puts all the lights on in his bedroom as bright as possible. And that's really interesting. And I know he was saying it's had a huge difference for him. And of course, it maps onto exactly what we know about the system. He's doing exactly the right thing for what his requirements are,

which is to get up early and then perform early. And this is where I feel it's very empowering for people, even if they were to find out their chronotype, and then to find out that, man, my job is actually in disharmony with my natural chronotype. You can do things, can't you, to manipulate it so you're maybe not as vulnerable as you might have been. That's right. And I think we tend to feel as though our body clock is this fixed thing, just like our sleep-wake cycle. And it's not. It's dynamic and influenced by a whole range of different factors that can

be tweaked to our advantage. Yeah. So interesting. You know, Russell, one of the things that's helped my sleep a lot over the past years, quite a few things recently, one is to avoid any sort of emotional stimulation in the evening. So I've, this is probably been going on for six or seven years now, I've had to educate the people around me, particularly my family, that I go to bed early, I wake up early. It suits me. I don't know if I am actually a morning type. I certainly live like a morning type, but then I set everything up around that because ever since my kids were born, they've always got up really early. And I know for me, I'm a much better human being when I've had time to myself in the morning before anyone else is there. So I would shift it back so that I could have an hour

to myself before they wake up. So I'm now in a position where I usually go to bed by nine o'clock at the latest, and I'm up by 5am at the latest. When I can stick to that consistently, I feel fantastic. Yeah. And that's exactly what we should all be doing. We I can stick to that consistently, I feel fantastic. Yeah. And that's exactly what we should all be doing. We should be defining, you know, what our biological needs are, and also, of course, what our social needs are, societal needs are, and particularly our work, and try and tune ourselves accordingly. You know, it's so important. Yeah. And so that process required me to help people around me understand that, look, after seven, half seven, I really do not want to be contacted with anything

unless it's an emergency. I know. And of course, it's very difficult because, of course, towards bedtime is the only time when many couples get a chance to talk about stuff. Yeah. But of course, it can be charged. And so, for example, I have banned any discussion of family finances before we go to bed or anything like that. You have to carve out time at a different time. The other thing that's interesting

about your earlier bedtimes, of course, is you'll be eating much earlier. Yeah. And that can be very important. And the data now are very clear that trying to concentrate one's calorie intake during breakfast and lunchtime and a very light supper or an earlier supper that you can possibly manage is better for metabolic health and reduces the chances of weight gain, obesity, and type 2 diabetes. So you have a double advantage there by going to bed earlier. Yeah, we'll come back to that because I think that's a really important point. And that really speaks, I think, to this wider issue, which is a lot of the things that we

would optimally do to optimize our circadian rhythms optimize our sleep optimize all these different functions in our bodies sometimes have to be done in conflict with what society is driving us to and i think there's a much wider piece there just to finish off on light at least for the for the moment because i think it will keep coming back and it's so important one of the things that has really helped me over the last years is, you know, I try my best not to be on my screen before bed. Usually I'm good with that, although I'm human and, you know, I fall prey to the temptation like anyone else might do. I try and read before bed. And in my bedside lamp, I've now changed maybe for a couple of years, bedside lamp I've now changed maybe for a couple years maybe not even quite that long but certainly recently I put these low lux bulbs in so I've got this like amber low lux bulb now I really feel

it's made a massive difference the way I feel it just feels softer and whenever if I'm in another room or staying somewhere where they've got a usual bulb and i think wow this is quite obnoxiously bright so are these things helpful in your view they are indeed um it it sort of maps on again to the to the biology this is what you you'd certainly recommend um because the lower the light uh you'll reduce alertness and it'll be easier to get to sleep and of course if it's bright light then of course you will shift the clock but but um you know most most artificial light is not going to have much of an effect just taking a quick break to give a shout out to AG1, one of the sponsors of today's show. Now, if you're looking for something at this time of year to kickstart your health, I'd highly recommend that you consider

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biochemistry. I talk to them regularly and I'm really impressed with their commitment to making a top quality product. Until the end of January, AG1 are giving a limited time offer. Usually, they offer my listeners a one-year supply of vitamin D and K2 and five free travel packs with their first order. But until the end of January, they are doubling the five free travel packs to 10. And these packs are perfect for keeping in your backpack, office or car. or car. If you want to take advantage of this limited time offer, all you have to do is go to drinkag1.com forward slash live more. That's drinkag1.com forward slash live more. But the other thing, of course, is that what you're doing is defining the sleeping space. And so, for example, you know, we need to sort of reinforce the fact that the bedroom or the sleeping space is what you do when you want to go to sleep.

So you have a lovely mattress, you have great pillows. a lovely mattress, you have great pillows, you might even have a distinctive smell, like lavender or something else, because you associate that distinctive smell with the sleep state. And I know people who, when they go and they travel and they're staying in a hotel room, they'll take a partner's perfume or aftershave, because that defines the sleeping space for them. So, the extent to which those are almost placebo effects, it doesn't matter. If they work, then you should embrace them. When it comes to blue light blocking glasses,

I'm interested what your views are. Before you answer that, I will say as a clinician, what I have found is for some people, they appear to have been transformative. Now, what does the science say? What is your view based upon all your years of research? Yeah, I mean, blue light blocking glasses were sort of originally introduced

because it was thought that blue light would promote age-related macular degeneration. And the evidence for that is a bit mixed. Certainly, you'll get more damage with blue light in a laboratory setting. So, sort of, if you expose cells to blue light, there's a greater chance of those cells undergoing apoptosis, you know, those cells dying, as it were. But when that's translated to the natural realm, it's not clear that blue light is having much of an effect on age-related macular degeneration. This has also been studied in the context of cataracts.

So, for example, blue blocking lenses have been introduced to reduce the blue light getting in and therefore age-related macular degeneration. The evidence for that is not great. There was a lot of concern that these blue blocking lenses were also going to disrupt the clock, because after all, the clock is maximally sensitive to blue light. We've done some studies showing that it doesn't matter whether you use a blue blocking or a UV blocking. It doesn't. And in fact, it's quite interesting.

Most artificial lenses allow less blue light through than a natural lens. So we would be naturally exposed to more blue light anyway. So I think that's where the origins of these blue blocking glasses and things are used. Now, in terms of the circadian system and the arousal systems, we do know that blue light is the most effective wavelength, and Christian Kirchhoff has done this from Switzerland, in increasing alertness. So if you want to reduce alertness in the evening, it's likely that a blue blocking set of glasses will be useful. Will it be useful in terms of the clock? Well, possibly. But it depends again, how long, how bright the environmental light is.

I guess this speaks to a much wider point, which I think comes through in all the work, all the talks I've seen of yours, everything I've read in your book, is this idea that sleep is highly individual. Yeah. And I know there's many myths out there that you're keen to bust, one of them being that we all need eight hours. Yeah, yeah. I mean, that was part of the motivation for writing Lifetime, because I think there's been a tendency to feel that, you know, we have to have a certain, we've got to get eight hours. And I remember one person came up to me and they said, I don't get eight hours of sleep.

Am I going to die? And I sort of said, well, I can assure you, you will die. But it may not be anything to do with not getting eight hours of sleep. And, you know, of course, I'm being a bit flippant, but actually the natural sort of span for humans is six hours to maybe ten, ten and a half hours. And so that's in the natural range. And I think people get very anxious that if they're not getting eight hours, you know, they're going to, it's going to be a disaster.

Now, I think you have to be careful because the tired brain is very good at fooling itself that it's going to be a disaster. Now, I think you have to be careful because the tired brain is very good at fooling itself that it's okay. So, you need to really be tough about assessing what your sleep needs are. And if you can function optimally during the day, if you're feeling fine, then chances are you've had a good night of sleep. If you need an alarm clock to drive you out of bed in the morning, if it takes a long time to wake up, if you crave caffeinated drinks, if your family, friends, work colleagues say, oh, you're being a bit, you know, where's your sense of humor?

You know, you're a bit more irritable. And critically, if given the opportunity to sleep longer on free days or indeed on holiday, you sleep much longer. That's all telling you you're not getting enough sleep. So what we all have to do as individuals is define how much sleep that we need for optimal daytime performance. And I guess that would also depend on what we're doing, right? Because let's say, I don't know, that you have defined that, hey, you know what, I keep hearing about the six hours, but I think I sleep for, I don't know, that you have defined that, hey, you know what, I keep hearing about the six hours, but I think I sleep for, I don't know, six hours 30 each night or six hours 45. And I'm fine. And I wake up without an alarm clock and I've got energy and I feel emotionally

quite with it, you know. But then let's say you start, I don't know, training for a half marathon, or maybe at the weekends you go on long runs or something. It's also having that awareness to go, well, yeah, in the week I may be okay with this amount, but actually if I'm really exerting myself physically and I have a desk job Monday to Friday, maybe I need more at the weekend. And I guess the reason, I don't know what your view would be on that. One of the reasons I asked that is because I think Roger Federer is well known to, is it 10 hours or 12 hours a night? I think he talks a lot about how much sleep he has and how important that is to his optimal performance as a tennis player. A few little subtleties there do you think physical activity

levels um make a difference in terms of how much we need and i guess how would you put all that together well of course the the famous long sleeper was albert einstein um who basically sat at his desk for for every day um and he needed he he craved 10 hours of sleep. So I think that it's probably influenced by athletic performance. And certainly, there are some data suggesting that really strong training is associated with slightly longer sleep. But it's not an overwhelmingly increased amount of sleep. And I think Federer just needs that amount of sleep and for his optimal performance, same way that Einstein did. And in the book, I compare Einstein to Salvador Dali. You do.

And it's great, undergraduate lectures, they say, well, Einstein, a classic, slept 10, 10 and a half hours, perfect example of long sleep genius. And then, you know, one of the students said, well, what about Salvador Dali? You know, he only, he didn't sleep at all, really. And his trick was, of course, to hold a metal spoon in his hand and sit in a chair. And when the spoon dropped from his hand, when he fell asleep, it hit a metal plate on the floor and woke him up.

But, of course, Dali was the first to recognize that his altered state of mind because of his chronic lack of sleep gave him the sort of surreal vision to generate the art that he generated um yeah so it depends what's the goal it depends what the goal is the goal is to hallucinate and have an altered state of consciousness and you need that for your job you know what sleep deprive yourself all you want yeah that's true it may make you impossible to live with um as uh dali of course was so yeah but but if you want an altered state of consciousness then decide you know deprive yourself of sleep well maybe now's a good point in the conversation

to make the case for sleep, right? First of all, how sleep deprived are we as a society? And then secondly, what are those consequences? Yes, sleep deprivation varies a lot because, of course, sleep need varies a lot. But I think on average, people are saying that we're sleeping one, maybe two hours less than we were in the 1950s. And I think those data are pretty robust. And certainly that's the case in adolescence, big time. And so what are the consequences? Well, short-term sleep loss, we see changes in our emotions and our cognitive performance. So we increase levels of irritability. The failure to process information accurately. We do stupid and unreflective things. We are less empathetic. I mean, it's really fascinating. We fail to pick up the social signals of friends and family.

We're less socially connected. We have reduced capacity to remember things. We are less creative. So all the things, reduced sense of humor. I mean, you know, all the things that make us this extraordinary creature, you know, these amazing humans, you know, all this creativity and wonderful interconnectedness goes as a result of even short-term sleep loss. Longer term, as many individuals are experiencing at the moment, is associated with this falling asleep uncontrollably, so microsleeps. And it's estimated in the States that 100,000 crashes on the American freeway are as a result of people falling asleep at the wheel. The American Automobile Association suggests it's much greater than that,

perhaps as high as 300,000. And of course, if you're falling asleep at the wheel, you can't stop yourself. So those crashes tend to be really bad crashes. We also see that there's changes in immune responses. So it's likely because we're chronically tired, we're activating in a sustained way the stress axis. And that's going to push up blood pressure, it's going to throw glucose into the circulation. So it pre then disposes to things like obesity, type 2 diabetes. And indeed, because of the suppression of the immune system, higher rates of infection and indeed cancer.

Some very convincing studies showing that night shift work, for example, night shift nurses have higher rates of colorectal cancer and breast cancer. In fact, those data are now so good that the World Health Organization has listed night shift work as a probable carcinogen. So I think the really key point is that chronic sleep loss is so much more than feeling tired at an inappropriate time. It's associated with an impact upon our health at every level. Yeah, I mean, what you just went through there, it impacts negatively our day-to-day lives. You mentioned empathy. I mean, what do we need for good quality relationships with partners, children, work colleagues, family? We need empathy. Yeah, and invariably in the

workplace. You need creativity. You need people to be able to work together. You want to reduce irritability. You need, after, a good sense of humor. And so, really, we should be really promoting good sleep to improve productivity. Yeah. It speaks to something you said earlier on in our conversation, that when we are sleep-deprived, we forget all the positive experiences and remember the negative ones, which, of course, completely alters your view and perception of the world it feels like this dark scary place

rather than an uplifting hopeful joyful place you mentioned yes these short-term consequences but also these pretty scary long-term consequences. Now, one thing I really appreciate about the messages you try and put out there into the public is you really seem to be trying to help promote health without scaring people. Now, of course, these statistics are scary. And there's two groups of people I want to keep at the forefront of our mind now, as we think about these negative side effects. We mentioned shift work, and I want to talk about shift work, because what I read in your book is that one in eight UK workers currently are shift workers. That's probably only going to increase. That's a lot of people. And I can't imagine what it's like for a shift worker to just hear what you said the WHO say, which is a probable carcinogen. That's not a nice thing to hear if you work shifts, if you're a,

whatever, if you're a nurse looking after people to help their health and you think, yeah, but at the same time, I'm wrecking mine in the process. So shift work is something I want to talk about. But also the other thing I've noticed as I've been trying to raise awareness to sleep now in books and podcasts for maybe five years unwittingly we can often end up scaring people and making them feel worse and more anxious now young parents often will get in touch and say look wrong you know uh love what you love what you said, I understand about sleep, but I'm really worried. My three month old doesn't sleep through the night, or whatever's going on. So many parents get really scared when they hear this sort of stuff. So if we address parents, first of all,

short-term sleep deprivation, long-term, is it okay for a few years of a parent sleep deprived you know help us sort of get less scared about that if you can well i think there's two issues here and one thing that that our society or the in the developed nations at least uh has shifted very rapidly from the extended family to the nuclear family, where the parents become the sole providers for their children. And it's usually the mother. And what's happened up until fairly recently is that childcare was a distributed activity. And so when the mum got tired,

there was an aunt or a sister or a friend who would take over so that the mum can get some sleep. And if you look at the primate societies, you see that care is distributed across the group. We have never evolved to be the sole parents, as it were, of our children. to be the sole parents, as it were, of our children. And I think the first point to make is that young mums in particular, but both parents, should not be afraid to reach out. And I think there's this sort of terrible guilt that I can't cope because I'm feeling tired. Well, no surprise.

We never evolved to look after our children in this manner. So before babies are born, it's really important to think about the support network that you can put in place to try and mitigate some of the chronic sleep loss. Now, what are the long-term consequences of this? It's not clear. I suspect that there are probably buffers that kick in that actually prevent some of the

damaging effects of chronic sleep loss during those sort of few months. I don't know. And in fact, I think it's a really important area of study. Yeah. I think, you know, what you said there, I think is really helpful. First of all, just recognize that the way we're bringing kids up now is tough. We never had to do it like this. You know, recently, Russell, my wife's father has been away in Kenya for a couple of months to see his family. And my mother-in-law has been staying with us on and off for a couple of months. And let me tell you the difference. It's little things,

but just having a third adult in the house when it comes to childcare, it's not just one more person. It seems to have changed everything. The whole dynamic changes. The whole dynamic changes. I was like, this is incredible. This is what humans have always done. Yet many of us have moved away for work, for opportunity. We

don't have those support systems. So I thought that hopefully takes the pressure off people to at least go, yes, I know it's hard, but yes, it is hard. It really is hard. You're not broken. It's not that you can't cope. None of us can cope with that. So I think that's a really nice message. But also that message, you can reach out, you know. Maybe you need to phone a friend and say, hey, listen, I'm knackered. Could I just have a nap? Could you come while I have a nap?

And it's not a sign of weakness. It's actually, you know, embracing our biology in a sense. And it's tragic that I think that young parents don't know that and feel guilty about it. It's simply wrong. And it's, you know, so many unintended consequences that we're facing at the moment. And sort of with increased wealth and independence, you know, we think, right, you know, we don't have to live with our parents anymore, or we can move a long way away from them. And yet we've lost something in the process. I mean, I was very close to my grandparents who looked after me while my mother was working. And it was, as you say,

it was a big thing. So, mommy's coming home. And it was all excitement. And you have that dynamic environment. And clearly, we are where we are. but people shouldn't be afraid to reach out i think that's so important let's talk about shift work um there's all kinds of things there's a huge section on shift work in the book which i think will be very helpful for anyone we mentioned how many people of course are shift workers we mentioned the potential health problems off that yes you know something i read in your book, which I found fascinating, was that over 90% of night shift workers, was it even 97%? 97, yeah.

They don't adapt. No. And so that's going back to light again. So you've got relatively dim light within the workplace, within the office or the factory. And then, of course, on the journey home or on the journey in, you're going to, or during the day, you're going to experience bright natural light. And the clock always defers to the brighter light signal as being daytime.

So the assumption by employers... The clock always defers to the brighter light signal. I think that's a really powerful thing. That's why we don't shift. And in fact, there's one group, there's a lovely study from the university of surrey josephina rent and we know that that three percent some of them are north sea oil workers because what happens is they're out on the rig at night under these great arc lights and then they're in windowless metal boxes during the day and they do switch and so they become nocturnal, as it were.

Then, of course, it's really tough for them, because then they have two weeks of shore leave, completely maladapted to their friends and family. But the serious issue is you don't adapt. And so I remember chatting to the chairman of the CBI many years ago now, and giving a speech saying, we're going to cure the problems of British industry by running it on a 24-7 basis. No need to build lots of offices in London, the rush hour, et cetera, et cetera. Deeply well-meaning individual, no idea of the biological consequences and the assumption that the clock will adapt to the demands of working at night. And for 97% of people, it doesn't. We're not machines.

We're human beings, right? Absolutely, yes. And I think you could apply that across all kinds of different things in society. It is fascinating because we've achieved so much. I mean, it's phenomenal what we've achieved as a species. But we are, it comes with some massive arrogance. And what we've assumed is that we can do whatever we like, whenever we choose.

And because we've invaded the night cheaply with electricity since the 1950s onwards, we've invaded the night and have thrown away that really important part of our biology, which is sleep. That's interesting. It was only in the 1950s when we've... Big acceleration. When we've really aggressively invaded the night. That's not long. No. Through an evolution lens, that's just a blink. Yeah. And clearly, you know, we've been creeping in. The aristocrats are using candles. And in

fact, a sign of wealth was you would eat later in the evening and you'd light your... But remember, a candle, you know, in the early 19th century was the equivalent of a working man's daily wage. So only the rich could have light. And of course, why would you burn fat, which is what candles were made of, when this is food? And of course, food was incredibly scarce for so many people, working people, 200 years, 150 years ago. We'll stay on shift work for the minute, but this doesn't just apply to shift work. Driving. Driving tired. And a pretty alarming statistic in your book about what it means to drive at 4am for most people.

Yeah. Well, Drew Dawson has done a wonderful study. Drew Dawson's based in Australia. And he compared the cognitive performance, the loss of one's ability to process information across the day, and found a very poor cognition around about four o'clock in the morning, where it got to its lowest point. And he compared that with the loss of cognitive ability with consuming sufficient alcohol to make you legally drunk. And on the scale, it was about a minus 15 dropping cognition when you were legally drunk. But at four o'clock in the morning, it was minus 20. So if listeners take nothing from this at all, other than the fact that you are driving at four o'clock in the morning, your ability to process information is worse

than if you were legally drunk. Okay, this is big, right? Because we've touched a few times on this whole societal condition, what we're being asked to do now, what we think we have to do to fit in with society versus what's biologically optimal some people of course have to get up early for work yeah some people now drive through the night yes lorry drivers you know big big cargo in the back um now i'm sure they've got certain regulations certain things that they do in order to be less tired at that time. But you know, driving at 4am, for most of us being worse than when we might be legally drunk, that's pretty alarming. It's extraordinary. Because also then let's think about, look, I don't really do this anymore. But if I think

about my social culture in my 20s and 30s, You know, you go to a mate's wedding, right? There'll be some late nights, a few drinks. I think you drive home on the Sunday. You know, yeah, you're, you know, just to be super clear, you know, you're fully sober, you know, but culturally it's okay. Oh yeah, I'm knackered. I've just got to drive now for four hours.

But we're putting people's lives at risk. Not just our own. We're putting other people's lives at risk. are just our own we're putting other people's lives at risk so culturally this idea of driving one side i think is something we all need to face well i think it's like smoking we're not only um endangering our own health but um the collateral damage is that we're harming uh other people people will do this yes and i think it's again it's it's a matter of education and a failure to appreciate. You know, junior doctors, a study published fairly recently showed that 57% had either had a crash or a near miss on the drive after the night shift.

So, now, again, we're going into scary territory. But the key point is there's stuff we can do about it. We're not going to put the 24-7 society, you know, genie back in its bottle. So what can we do to mitigate some of these problems? Well, knowing that we're going to be vulnerable to having a crash on the drive home, then we, or employers, and I think there's a serious duty of care here, is they should make available or subsidize the use of devices you can put on the dashboard that measure head nod or the fact that the car is veering and alert you to that.

And, you know, an alarm goes off and make sure, you know, you're woken up. And of course, many high-end German cars now have this technology built in. Yeah. But that's something that could be done. Knowing that night shift workers have higher rates of cancer, coronary heart disease, diabetes 2, etc., etc., why don't we institute higher frequency health checks every six months for these individuals to catch these conditions before they become chronic? What food do we provide for our night shift workers?

You know, higher rates of cancer, coronary heart disease, all the rest of it, high fat, high sugar. Nobody, to my knowledge, is actually supplying easy to digest, high protein snacks to their workforce throughout the night. Now, it's tricky because if you're tired, you're programmed to eat more sugar. But at least we should make that option available. But why high protein? Because it doesn't have the same impact as carbohydrates and fats on coronary heart disease and in decancer.

But that would be quite easy, right? Let's say for a hospital, which is staffed at night, it would be quite easy either to have those snacks or to work with a nutritionist and make in bulk protein shakes full of phytonutrient rich foods that are easy to digest that are tasty that they could give people it's not that hard and in fact i think there's a phenomenal commercial opportunity here somebody

should develop this and make it available to know, a very significant percentage of the workforce. And the other area, I think, is education. In some sectors, the divorce rate is six times higher in the night shift compared to the day shift. And six times. So, what we should be providing is education, not only for the individual who's doing the night shift, so they're aware of some of the consequences, but so that the people they live with also understand that they're not turning into monsters. But this is a kind of the biological consequence of driving your biology outside of its normal range. Before we get back to this week's episode, I just wanted to let you know that I am doing my very first national UK theatre tour. I am planning a really special evening where I share how you can

break free from the habits that are holding you back and make meaningful changes in your life that truly last. It is called the Thrive Tour. Be the architect of your health and happiness. So many people tell me that health feels really complicated, but it really doesn't need to be. In my live event, I'm going to simplify health and together we're going to learn the skill of happiness, the secrets to optimal health, how to break free from the habits that are holding you back in your life, and I'm going to teach you how to make changes that actually last. Sound good? All you have to do is go to drchatterjee.com forward slash tour. I can't wait to see you there.

This episode is also brought to you by the Three Question Journal, the journal that I designed and created in partnership with Intelligent Change. Now journaling is something that I've been recommending to my patients for years. It can help improve sleep, lead to better decision making and reduce symptoms of anxiety and depression. It's also been shown to decrease emotional stress, make it easier to turn new behaviours into long-term habits and improve our relationships. There are of course many different ways to journal and as with most things it's important that you find the method that works best for you. One method that you may want to consider is the one that I outline in the three question journal. In it, you will find a really simple and structured way

of answering the three most impactful questions I believe that we can all ask ourselves every morning and every evening. Answering these questions will take you less than five minutes, but the practice of answering them regularly will be transformative. Since the journal was published in January, I have received hundreds of messages from people telling me how much it has helped them and how much more in control of their lives they now feel. Now, if you already have a journal or you don't actually want to buy a journal, that is completely fine. I go through in detail all of the questions within the three-question journal completely free on episode 413 of this podcast. But if you are keen to check it out,

all you have to do is go to drchatterjee.com forward slash journal or click on the link in your podcast app. And one other area which I think is worth trying is that we talked about this great diversity of chronotype, whether you're a morning type or an evening type across the population. Well, wouldn't it be smart to chronotype your workforce so that, for example, the late types did the later shift and the morning types did the morning shift? What you want to avoid, of course, is putting a late type onto a morning shift, which is a really bad idea.

So, you know, as I say, we've got to be pragmatic. But I think there are things that we can do now to mitigate some of these problems. We don't want to be too scary, but I can't stop thinking about that. As a doctor myself, that 57% figure. I have told this story, I think at least twice on this podcast, where when I was a SHO, a senior house officer,

so I think second or third year after qualifying, after a, what would it have been? Probably a 36-hour shift, certainly between 30 and 36 hours, I probably fell asleep on the M60 in traffic. Thankfully, I think I fell asleep in a traffic jam and then I was only woken up by horns because the jam had moved on. It could have been a lot worse.

This is scary because there are people around the country, around the world right now, who are vulnerable of dying as a consequence of their jobs. That sounds extreme. I don't think what I've just said is extreme based upon what I'm reading. And you mentioned duty of care for employers. Surely this should have been put in place yesterday. Is it justifiable for people in shift work to be getting in a car now? Where does the culpability lie? What if they have an accident? Is that personal responsibility?

Or is it, no, but my employer didn't do anything? Or, and of course, this comes into finance and expenses, but providing taxis. Well, that's what the Royal Perth Hospital, at least when I was visiting Western Australia, would actually do. They would actually provide taxis to get people home. Yeah. And I know there's an expense thing here, but we're talking about lives here, not just that individual's life. So, yeah, that really hits home, big time. And, you know, there's a very poignant description in the book of a police officer um who contacted me actually several years ago saying what can we do you know i just had a friend who after the night shift fell asleep at the wheel and drove his car into a tree

and was killed outright um and nobody's warning us that this is going on and that's part of the educational piece because i think if people realized of the danger of doing this, they'd think twice about it and try and get something else in place. I mean, maybe we should be making sure that there's, I don't know, somewhere to sleep after the night shift so you weren't driving home chronically tired. You know, it's these sorts of things that we need to think about. There are, are again we're not going to cure it but we can mitigate some of the problems and it's not rocket science it's it's low-hanging fruit that we could institute now across the workforce and make a difference i don't know when my behavior around this started to change but i'm pretty diligent these days over when i'll drive

now i don't need to drive much anymore yeah for work i remember in one of the practices i used to work at you know there was a probably 45 minutes to an hour commute each way on a motorway and depending on traffic conditions etc etc and i appreciate not everyone is in a position to make active decisions depends on work, all kinds of things. But when I'm weighing up how to get somewhere, and whether to take my car or not, how tied I'm going to be absolutely plays in my decision making. And I think, you know, as I think about it, Russell,

I think one of the first times it really struck me, it was probably 2015, 2016, I was making a documentary for bbc one i don't think this bit actually aired in the program in the ends but is it in gilford where is the driving simulators i think so yes i think what what happened i can't remember the exact ins and outs but one of the participants yeah we put them in the simulator and we watched them drive and then we compared it with one night sleep deprivation and then alcohol yeah and it was noticeable after sleep deprivation it's just like you said with that research it was worse

than when they'd been drinking yeah i was like wait a minute that's just fatigue and their their reaction time to things popping up in the simulator to when they press the brake was significantly increased. So I think that possibly has played into my head for many years about that. Number two, I think a point here is that you bring up this to micro-sleeps, right? Number one, what is a micro-sleep?

And number two, I've heard you say before, I think about these micro-sleeps, that you don't know they're going to happen. Yeah, yeah. So can you speak to that a little bit? So micro-sleep is essentially an uncontrollable and an unpredictable episode of sleep. And so you can be going along and you will just fall asleep.

And of course, that's extremely dangerous if you're driving. And so people think they're okay, and then they can just sort of have a micro-sleep and then a crash or whatever. And it's frightening because so many people say, oh yeah, you know, I've had one of those. I was sort of nodding, and then I realized I was sort of in the next lane. But for the grace of God you know you would be killed or you'd have killed somebody else you mentioned in your book all these things what Chinook the Chernobyl nuclear disaster was a Selby crash and Air India like you've mentioned all this stuff can you maybe speak to some of those one of the one of the really interesting

ones I think was the the Air India flight where where the pilot was landing the aircraft and then fell uncontrollably asleep. And the plane hit the deck with a huge loss of life. Now, how do we know he fell asleep? Because you could hear snoring in the cockpit recorder. And, you know, this is not something that he would have wanted to do. And it sort of really illustrates the fact that you have no control over these microsleeps. But if you're chronically tired, that's what's going to do. And it sort of really illustrates the sort of the fact that you have no control over these microsleeps. But if you're chronically tired, that's what's going to happen. And you know, the Exxon Valdez oil tanker that hit the reef off the coast of Alaska. Now,

everybody says, oh, it's because the captain was drunk. Well, yes, he was drunk. And he was asleep in his cabin. And it was a chronically tired, inexperienced individual. And they were telling him, turn the ship, you're going to hit the reef but he couldn't process the information because he was so tired and it's a really good illustration again of one's chronic tiredness prevents you from processing information accurately and you know we've sort of touched on this but this is what's so dangerous because the tired brain is so tired it can't detect how tired it is and we can fall and we can fool ourselves that we're okay whereas we're not russell i want to just ask you your view on my interpretation of my dad's working life

i know from research you've written a beautiful section on it in your new book, about the impacts that sleep deprivation has on the immune system. Yeah. And all kinds of other biological processes in the body. my dad's at the age of 57 got lupus now it's very unusual for an asian man an asian man who's slim it's it's not the profile that's normally caucasian women 30s or 40s but typically of course there's always variation here now for many years i cared for my dad until he died nine and a half years ago. And I didn't know then what I know now since his death. But I am convinced, I have a deep knowing that my dad's lifestyle gave him lupus.

Now I'm not asking you to say yes or no on that. I just want to share with you certain aspects of his lifestyle. And I'd be interested in your perspective. My dad slept three nights a week for 30 years. So he'd work his day job as a consultant at Manchester Royal Infirmary. But he'd come home, he'd get ready. And then for four nights a week, Carl would pick him up and he'd be doing cheap GP house calls all night.

So he'd be out all night. He'd arrive again at 7, 7.15 in the morning, get ready and then drive through Trafford into Manchester and work. So for 30 years, he only slept for three nights a week. So that is sleep deprivation, I would say at a hyper extreme level.

He was chronically stressed, of course. I hear what you say about empathy and i think about mom and dad's rows yeah um and yes you need a genetic susceptibility for autoimmune disease but i believe my dad had that genetic susceptibility i know he did because i've i've done my genetic i've done some of my testing and I know I have a predisposition as well to certain things if the environmental conditions are right. My dad had chronic sleep deprivation, chronic stress. Something maybe out with your expertise perhaps is I think my dad was very unhappy and had a lot of unexpressed emotions and anger about the state of his life. I've spoken to Dr. Gabor Mate, a physician,

about the link between unexpressed emotion and also immune disease. So I'm not necessarily asking you to comment on that, but from what I've shared and from what you know about the immune system and sleep deprivation's impact, do you have any comments at all? Yeah, I mean, I think it's worth bearing in mind that for our biology to work, you need the right stuff, the right concentration delivered to the right tissues and organs at the right time of day. And of course, our circadian and sleep-wake systems do that. So if you disrupt them, you have a whole bunch of vulnerable points where things could fall apart. And so if you have a genetic susceptibility,

then the disrupted biology will play to that problem. And so I wouldn't be at all surprised if there was an element of sleep disruption. Did your father show any signs of dementia later in life? It's really hard because his dad was on dialysis for 15 years and all kinds of medications but yeah i'd probably say so little bits yeah no formal diagnosis but if i think back now possibly probably yeah and some very interesting uh data is showing that massive sleep weight disruption in the middle years can increase your risk of dementia in later years. What do middle years mean?

So in your sort of 40s, 50s, your peak working period, where we think of our businessmen having incredibly shortened sleep periods. And it's been well known, it's been documented, but a mechanism has not been clear until relatively recently, or a potential mechanism. And that's this newly discovered thing, which is the glymphatic system, this sort of clearance system within the brain. And whilst we're asleep,

there's a whole bunch of toxic stuff that is wrapped up and disposed of, not least beta amyloid. And just one night of no sleep has been shown to increase beta amyloid deposition within the brain and increase the concentration in the cerebral spinal fluid. So, you know, there's a very tangible link between sleep disruption in the middle years and a mechanism that could predispose to dementia in later years. And I think we're going to find increasingly these sorts of connections. I mean, what we know about the immune system is that it's turned up, or at least the adaptive immune system is turned up during the day

when we're most likely to encounter people with bugs or bugs in the environment, and then turned down at night. And again, a really interesting question is, why? Why do you have the immune system on full kilter all the time? And that's, of course, because if you did, you increase the chances of an autoimmune response. And so, you know, disruption of these systems leads to lots of different ripple-through effects.

Yeah, there was something in the book I found fascinating about our skin permeability changes throughout the day. Could you speak to that perhaps? Yeah, I mean, so at night, it's a bit more porous. And we're losing, as a result, we're losing water. And so also it becomes itchier.

And so we're more likely to scratch our skin at night, exacerbated by psoriasis and dermatitis and things. And so, the skin is an incredibly effective barrier at keeping bugs out. And that's why the main root of infection is the lungs. But the skin is, again, trying to slough off these old cells and presumably the bacteria with them and, in a sense, sort of cleanse itself,

but it increases the vulnerability to infection. Does it at that time of day, of course, because we're far less likely to encounter bugs at that particular time. Yeah, there was also this fascinating bit of research you shared where I think if we get cut or have a a scar how well it will heal or how quickly it will heal depends on whether it was done in the morning or the evening yeah i found that fascinating yes it is you know and of course um uh more effective healing during the day than than at night yeah yeah this relationship between midlife sleep depri, so in our 40s and 50s, and dementia later on, is really something just to pause on.

Perhaps because I'm in my early 40s, perhaps because I know many listeners and viewers are. But there is this tendency, I think, across society, to think we can keep pushing. We can keep pushing. We'll get away with it. We'll be okay. Now, I've seen first time with my dad. Yes, it was quite extreme,

but nonetheless, I see that pattern. I've seen it in myself before. I've seen it in a lot of my patients and a lot of my friends. You can't keep pushing your biology and not expect a consequence at some point so i just wanted to highlight that point and then i want to you know you mentioned sleep and dementia i know you've done a lot of research on the relationship between sleep and mental health problems yes and i'd love to just talk about this a little bit you know is it sleep deprivation that's causing mental health problems is it mental health

problems that's causing sleep deprivation or like most things is it a bit of both well i think this is really important and i got into this because i was um in a elevator with a psychiatrist. And he said to me, oh, yeah, you work on sleep and stuff. I said, yeah, kind of. And he said, well, of course, my patients with schizophrenia, they have terrible sleep patterns. That's because they don't have a job. So they get up late, miss my clinic,

and are socially isolated and so don't have friends. And I just thought at the time, that doesn't make any sense at all to me. And so we started, and Katarina Wolf was one of my colleagues who was very much involved in this, to look at sleep-wake patterns in individuals with a diagnosis of schizophrenia,

same number of individuals age-matched who are unemployed, and working healthy controls. And the patterns you saw in schizophrenia were some of the most extraordinary observations I've ever made in my career. These weren't just sort of kindly, mildly disrupted. These rhythms were absolutely smashed in everyone we have looked at. And so that stuck in my mind. And then with an increasing understanding of the mechanisms that generate sleep and circadian rhythms. So essentially, the consciousness sleep flip involves a realignment of every brain neurotransmitter system and an interaction between multiple brain structures. So with these two sort

of observations, we thought, well, hang on, why do you always find sleep-wake disruption and mental health associated? And of course, you see it in bipolar, you see it in depression, you see it everywhere. And we came up with a model, which was perhaps at the core within the brain there are overlapping neural circuits and neurotransmitter pathways between stable sleep and stable mental health so if you're predisposed to mental health problems let's say there's a change in a neurotransmitter dopamine serotonin that nudges you towards a mental health crisis but it's going to have a parallel impact upon the sleep-wake systems at some level, because they also draw from those neurotransmitter systems. And so we then tested that hypothesis. And so genes which have been linked to human schizophrenia, when

mutated in a mouse, not only showed weird behavioral patterns, but also smashed sleep-wake cycles. So now there's an incredible body of evidence for that mechanistic overlap between mental health circuits and sleep circuits. But it's, of course, much more complicated than that, because the disrupted sleep, via its impact upon psychosocial health, one's ability to process information, that negative salience, and of course, the sort of physiological disruption could exacerbate the extent to which you're experiencing mental health problems. And of course, the mental health problems will feed back and make the sleep worse. And so you can very rapidly go from sort of this sort of overlap at

the middle, we know there's a genetic predisposition to certain mental health conditions, but it can then amplify massively as a result of these positive feedback loops, the mental health making the sleep worse, the sleep making the mental health worse. So you can exaggerate it completely. So we then thought, well, hang on, if we try to stabilize sleep-wake in individuals exhibiting mental health problems, will we reduce the severity of those mental health problems? So working with Dan Freeman and Colin Espy, a big paper was published a few years ago in The Lancet, which showed that if you can even partially stabilize the sleep-wake in individuals, you can reduce levels of paranoia

and hallucinatory experiences. So I think we can think of the sleep-wake systems as being a new therapeutic target for mental health. Now, what's fascinating for me is that we've known about the association between mental health problems and sleep disruption back at, you know, and sleep disruption back at, you know, Kraepelin's time in the 1880s. He talked about it way before the introduction of antipsychotics and all of the other sort of issues. And so it has a long history.

And, of course, the life expectancy of individuals with severe mental health is hugely reduced. And they all report, you report, what do they report? Sort of coronary heart disease, obesity, type 2 diabetes, all of these major health issues dismissed as a byproduct of the antipsychotics. But actually, a major contributing factor to that will be the poor sleep. And it's never addressed. Yeah. And so, I'm hoping that this will will also

provide a change in our mindset to these extraordinarily vulnerable individuals and to take their sleep weight disruption seriously because we have empirical evidence that even partial stabilization can reduce the severity of those symptoms You're effectively saying bipolar or depression or anxiety, right? Instead of just accepting it as, oh yes, people with these conditions don't sleep well. It's like, well, hold on a minute. What if we go straight in and give sleep education or sleep CBC or whatever therapy we might deem appropriate? And then if you think about research, I mean, I remember reading a paper, Russell, where it showed that maybe if you go from eight hours a night to five hours a night, your amygdala, the emotional part of your brain, may be up to 50% more reactive. I think, well,

that's kind of anxiety. You know, if your amygdala is on high alert you're anxious yes and sleep deprivation by itself will make you anxious so before we go to anti-anxiety medications or exactly it's like why don't we tackle the sleep why don't we at least try to and and it's because the failure to educate our general practitioners and indeed our the entire um you entire doctor and nurse community. It's just not part of the curriculum. And in fairness, it's only fairly recently that this stuff has become really clear. And again, that was part of the reason for writing Lifetime, because wanting to make it accessible to not only medical practitioners, but everybody, so we can take some ownership of this field, this critically important field. I mean, this is really quite profound,

because what we're talking about here is sleep as therapy. Yes. I mean, this was really sort of shown to me when we were working on a project with Guy Goodwin, who's a psychiatrist at Oxford. And he was able to identify individuals as a result of family history and questionnaires, whether they were at high risk or low risk of developing bipolar. So these are young individuals in their teens usually. And what was absolutely fascinating is the sleep-wake patterns of those at low risk were perfectly normal. But all of those who were at high risk were already showing a disrupted sleep-wake pattern prior to any clinical diagnosis of bipolar. Now, if we can use this as an early marker, and then, of course, in therapy, the earlier we know something's going to go wrong, the earlier the chance of an intervention. So, wouldn't it be amazing if we could identify

those individuals at risk? We could institute sleep-wake stabilization protocols that may either delay the onset of these conditions or knock the brain into a different developmental trajectory whereby it won't necessarily go inevitably towards that condition. So again, I think there's, you know, we're just sort of unmasking all this incredibly important stuff that could have a major impact upon health and well-being in the coming decades. Let's talk about sex and sleep. You write a little bit about it, of course, it's a topic of huge interest to many people. And I guess there's two facets to it the way I see it. One is to do with fertility, right? There is an ideal time to have sex from a fertility standpoint. So I think it'd be great to talk about that. But then I think also the relationship between sex and sleep, the of sleep i think is also really interesting so um in whatever way you want to maybe start to unpack that i mean again this was something that

i wasn't particularly familiar with until i did the research for the book because i'm going to often ask these questions in public lectures what was absolutely striking is that every element in the regulation of the female menstrual cycle involves a circadian clock, whether it's the timed release of hormones, of the neurohormones in the hypothalamus, whether it's the pituitary gland, or whether it's the receptors in the ovary, for example, responding to those hormones. And so you've got, for example, very strong evidence that disruption of the menstrual cycle is much worse in night shift workers. The chances of miscarriage is higher in night shift workers. It's not hugely significant, but it is significant. And you find that in the airline industry, either pilots or flight

attendants have fertility problems. So there's clearly a relationship between the circadian system and the menstrual cycle to produce this extraordinary, exquisitely timed ovulation and the release of the egg. And it's been shown that sperm needs to be in the reproductive tract, in the fallopian tube, around about two to three days prior to ovulation to have the greatest chances of success. So, there's that, there's the circadian system interacting with the hormones that drive the menstrual cycle, and that precise window. And that was really fascinating. And then you've got this study suggesting, well, it doesn't really matter. You know, humans don't have any real discrimination. They'll just do it whenever they want to do it. And then there's this whole literature on the fact that, in fact, our behavior is subtly altered.

So that actually during that sort of pre-ovulatory window, men are less discriminating of women and are much more likely to seek out, you know, copulatory experiences. And females are much more discriminated. They're far more likely to have an affair during that window. And they look for male, they're more interested in male features. So, for example, a deeper voice, a stronger jawline, all that sort of thing. I mean, stuff that we never really think about, but there is that still biology, you know, underpinning it. Wow.

So, yeah. But also, male fertility seems to peak in the morning testosterone rises and has a you know morning peak and that's where sperm motility is uh at its peak and anyway i mentioned this i think on the chris evans uh breakfast show and i got this email uh several a month or so later, from a couple of young medics who said, you know, we've been trying for the last two years to conceive. And, you know, as medics, we thought we tried everything, but we've forgotten circadian rhythms. So we started, and their words, not mine, started doing it in the morning and the first and the

first time we did it you know my partner got pregnant um now i mean an n of one is an n of one so you can make of it what you will but i was actually thrilled that that that bit of biology had been translated congratulations yes. Even that line, we forgot about circadian rhythms. I'm not surprised. We didn't learn anything about circadian rhythms in medical school. I don't think they still do.

Right? This is a massive, massive issue. So, regarding fertility, super, super interesting. I'm sure that's very relevant to many people listening who are actively trying to conceive.

It could be something that has practical value for them or people could share it with people who they also know who are struggling. That might be helpful. In terms of, we mentioned the problems with sleep deprivation and you've written a section in the book how the timing of sex could potentially help people with sleep. Yeah, I mean, I think anecdotally, there were reports that sex relaxes individuals and they're more likely to fall asleep. And there are now some studies suggesting that there are hormones that are released which actually promote sleepiness.

And so, yes, consensual sex of course um it has been shown to promote sleep yeah and also masturbation as well you have once said that many people don't have a sleep problem they've got a stress problem yep and i guess sex intimacy you, you know, switching off, it all kind of feeds into that a little bit, doesn't it? Absolutely, yes. And the bonding, following sex, you know, relaxes individuals and brings them closer together. I think that one thing that's very important to distinguish

is fatigue from sleepiness. Sleepiness is cured by sleep. Fatigue is this overwhelming chronic tiredness that even given the ability to sleep longer, it doesn't go away. And it's very important that people distinguish between the two because fatigue, as you know, is indicative of some underlying health problem. And I spoke to somebody fairly recently, really fascinating, and this is a really high-powered individual, very, very active, but she has an immune issue and so is chronically fatigued. And so she can't get done what she wants to do during the day.

So she'll fall asleep fine, and then she'll wake up in the middle of the night, and we should talk about that, because that's perfectly she'll wake up in the middle of the night. And we should talk about that because that's perfectly normal to wake up in the middle of the night. And most of us fall back to sleep again, or are awake for a short time and then fall back to sleep again. But because of her stress, because she couldn't do what she wanted to do, she couldn't fall back to sleep again. And so this is a really interesting, so the fatigue was not allowing her to do what she wanted to do, which meant that she was immensely stressed, which meant that it was screwing up her sleep problems.

And so, yeah, I think that so many instances of, I think stress is one of the major issues in poor sleep. And as we've just said, it's not a sleep problem, it's a stress problem. And that's why sort of winding down towards the end of the day, leaving work at home, if you possibly can, and doing something different, whether it's going to the gym, whether it's doing whatever, is so important.

And that's, of course, been the huge problem during the COVID epidemic, where people's workspace and home space were the same. And that's probably part of the reason why sleep has been reported to be worse in certain sectors. Yeah, I mean, you spoke before about various scents and what people associate with sleep. And, you know, we know the brain is an associative organ. and we know the brain is an associative organ. And so if you are sitting with your laptop doing your work emails in bed, what does your brain associate with bed and the bedroom?

Precisely. And of course, so many bedrooms became studies. Yeah, and I understand that depends on your space and it's not a criticism, it's just more a... An explanation. It's more an explanation. This can be problematic. I think, you know, that the the low lux amber bulbs

that i have in my bedside lamps and i think there's a biological explanation it's as if the lower lux it's not pushing my circadian rhythm back my clocks back sure but actually and critically i'm reducing your alertness which is probably the main main factor okay so it's reducing my alertness yeah because of the lower light exactly higher the light greater the alertness and the more more difficult it is to get off to sleep okay so that's fascinating and i guess speaks to well so many bathroom mirrors are yes like bathrooms are full of these bright LEDs, right? So what do people do before bed?

Well, I know. I mean, I think it's absolutely spectacularly ironic that what's the last thing we do before we go to bed? We stand in the most brightly lit room of the house, which is the bathroom, and then we look into an illuminated mirror as we clean our teeth. And, you know, we talked about an investment opportunity in developing night shift food.

Another perfect investment opportunity is developing night shift food. Another perfect investment opportunity is developing a bathroom mirror, which has bright, alerting light in the morning, and you switch it to the evening, which is dimmer, less alerting light in the evening. I mean, it's simple. The technology is there to do it. Absolutely. Yeah. So that's something else we can think about what how you know what sort of light are we exposed to there but speaking about these bedside lamps i think also as well as the biological explanation i think there's also i guess something behavioral about them for me in terms of it's it signals to me oh it's now evening time it's rest time it's now evening time, it's rest time, it's not stimulation time.

Do you know what I mean? So I think sometimes... Winding down. We assume that we can go from a fully conscious state, you know, the gear analogy, you know, going from first gear to fifth gear. You can't do it. You have to do it through stages. And again, winding down from the wake state to the sleep state requires an adjustment.

And whether that's, as you were saying, you enjoy reading some novel under relatively dim light before going to bed. Some people listen to music or something else that they find relaxing. And it's adopting those behaviours that make the transition easier. And again, it's, as you were saying, it's the brain knows what's coming next and what's coming next is sleep and so it can prepare itself it's what we do with our kids right we give them a routine you know we don't read a story we read a story we we don't as i often say in talks we don't give them a ton of sugar put the lights on bright speak loudly no no we do the opposite of

all those things but as adults we kind of think we can somehow... Until their favorite uncle visits. Exactly. We think we can override them, but we can't. Oh, Russell, I could speak to you for hours. As we come towards the end of this conversation, a few things I wanted to briefly cover, if possible. Sleep trackers. Yeah.

Any view on sleep trackers? Well, I think we should define where they could be useful. So most sleep trackers, if you use them to determine roughly when you went to sleep, how many times you woke up in the night, for example, and when you finally woke up. So your sleep timing, your sleep duration, and your sleep fragmentation. That's a tried and tested technology, and it's what we use in the lab. The problem is that most of the trackers that people wear these days try and do more than that. They say, oh, you've had lots of good deep

sleep, or you haven't had enough REM sleep. And for that, they're completely useless. And they can generate huge anxiety. So I spoke to an individual, again, before lockdown, who said, I'm not getting enough slow-wave sleep. I'm really anxious about it. In fact, what I do, I set my alarm clock for four o'clock in the morning, wake myself up to find out how much slow-wave sleep I've had. I mean, that's the kind of level of anxiety that these things are developing. And in fact, so what does it really tell us if we've had lots of slow-wave or lots of REM sleep?

We don't really know. And the algorithms, first of all, are not very good at detecting that. And they've been largely worked out for a bunch of 20-year-olds in California. And, of course, our sleep changes hugely as we age. And they're not going to work for somebody in their 70s or indeed, you know, somebody younger. So, until we got, you know, really sophisticated artificial intelligence, you know, plotting, extracting information to get sleep phase, they're not accurate.

And the other problem I have is, so what? Do we really know what slow-wave sleep is all about? Well, sort of. I mean, we know that if people are selectively deprived of slow-wave sleep, their memory isn't as good and their problem-solving isn't as good. And if people are selectively deprived of REM sleep, then their emotional process, they can show a bit more anxiety during the day. But in a sense, we don't really know.

And so I do get very frustrated because we become, as a society, finally more sensitive to the importance of sleep. But what's happened is that a large sector have become very anxious about their sleep. And, you know, there's this sort of sergeant majors screaming, you've got to get eight hours. You've got to do this. You can't do that. And we have to define what works for us.

And in fact, so many people think the sleep is what you get, but actually it's a highly dynamic bit of our biology. And we have the ability to work with it and optimize it. And I think that's something that I, and the sleep apps, you know, drive us in the opposite direction. So I get a bit worried. I mean, you know, in principle, good idea, because it's like losing weight. If you weigh yourself every morning and you see you've lost weight, that'll reinforce your changed eating behavior. And if you wanted to get longer sleep or different timing of sleep, as we've kind of touched on, it would be useful metric to say,

yes, well, that changed behavior has worked. So, you know, getting that more morning light meant I did go to bed earlier and I've got up earlier. So in principle, they could be useful. But it's worth bearing in mind, none of the sleep federations endorse any of the commercially available devices. And none of them are FDA approved. So we're a long way from them being, I would say, useful.

Yeah, thank you for that. That was very, very clear. I mean, that weight loss analogy, if we take it one step further, yes, if you see every day your weight is going down, let's say you are tracking that and you think that's the reason all things are tracked, sure, it can motivate behavior.

But on that one day where it goes up, and I read a study once which said that actually our weights can vary, I think three to 10 pounds in any given day, I think it said, maybe three to five pounds, but just from fluid and all kinds of other stuff. But I thought, well, actually it can have a really toxic effect when you're making

all the right changes for your health and maybe for excess weight, but actually one day it happens to go the wrong way. good point what's the point yeah what's the point well i think it could be problematic and i have a real concern over trackers in general i'm not at all saying they can't be useful for some people i understand it probably depends on personality type a little bit and says what you do with that data i do have a sleep tracker i don't think i've used it for about six months um it was considered one of the good ones and i have no problem with it you know it was useful there were certain things that i felt it helped me understand which is if i eat late it appears to really have an impact on various things but i

kind of learned what i needed to learn from it. And one day, Russell, I remember waking up feeling pretty good. And I looked at my sleep score, and it was rubbish. And then my mind starts to play tricks on me. I was like, oh, and then I thought, God, am I starting to feel tired? Like, because I'm tired or because what I've just seen? I thought, you know what, screw this. I'm not not i don't need to use this anymore i need to tune into myself and i personally i've seen even with blood pressure monitors i've seen patients over the years tie themselves up in knots and have health anxiety so i guess i would just urge a note of caution as well for people i think that's absolutely right and we've talked about it how do you know if you're getting enough sleep what what the factors are. That's the most important thing.

And these are questions we can answer for ourselves without the need of a health tracker. A good friend of mine, Ken Wright, who's University of Colorado, he starts his class, and it's a large number of students, with who here has ever used a sleep tracker? And essentially the whole class sort of put their hand up. And they said, who now is using one routinely? And about three hand they go up. And, you know, these are smart people. They learn pretty quickly that these devices just don't work.

And as you've discovered, you embrace the knowledge from your own personal experiences. Yes, yeah. To be a human and to really experience what that means. Just very quickly, a lot of people will often say about light exposure. Well, what about, let's say Scandinavia, for example. I guess that's top of mind because I've been recently. The hotel in which I stayed had pretty poor blackout blinds.

And so I woke up in the night and then I thought it was morning and I looked at my watch, it was 3am. It was bright at 3am. How have people in Northern Hemisphere countries or other countries where there are these wildly different day and night cycles, have they evolved to that? Have they adapted to that? Do we know? Well, the short answer is no. But let me tell you about a group of animals that have. And from the University of Tromso, they've looked at Arctic reindeer. And during the two months of constant light, they turn their biological clocks off. And during the two months of constant dark, they turn their clocks off.

They have no adaptive value. There is no day-night cycle. And in fact, during the winter months, these reindeer feed whenever the weather conditions permit. And during the summer, of course, they have to feed constantly to put on enough fat to survive the winter. So there are instances where clocks have been turned off

because they have no adaptive value. What about humans? Well, we've, of course, been there for a very long time. The Europeans who've moved into those places have shown no signs of adaptation. In fact, in Tromso, a family will get up and then they'll go in winter, for example, into a room where there's artificial light. So they'll get that morning photon shower.

And so they can try and stabilize. And they use very effective blackout curtains. Now, what's going on with those peoples, the native peoples who've been there for 30 40 000 years isn't clear yeah um and it may well be that there has been some adaptation but we're we don't know russell my brain is going so fast in so many different directions um out of respect to your time i'm going to stop firing questions at you and i hope i can persuade you at some point in the future for a part two. To finish off this conversation on an upbeat note, for people who feel inspired to prioritize their sleep, to get on top of their sleep, to basically go, you know what, maybe it was a bit about being in your 40s to 50s and not pushing it whatever

it might have been that connected with them this podcast is called feel better live more when we feel better in ourselves we get more out of our lives of course when we're going to sleep better we're going to get more out of every aspect of our lives so do you have any final words of wisdom advice practical whatever it might be to leave my listeners with? I mean, I think the key thing for me is that, you know, sleep is like shoe size. One size does not fit all. And we as individuals need to work out what's best for us. Because there's huge individual variation and our sleep will change. So good example would be waking up in the middle of the night. So, what's happened is that our sleep episode has been compressed. And so, we tend to not wake up in the middle of the night. But in societies where

there's no electric light, and indeed from the literature, we know our sleep patterns in the recent past were very different. So, literature from the pre-industrial age talks about, I had a wonderful first sleep. And sleep was biphasic, going to sleep, waking up, then going back to sleep again, or indeed polyphasic, which is several periods of waking up. And because we don't know that, when people wake up in the middle of the night, they think, oh my goodness, that's it. I'm never going to get back to sleep again. I'm going to start doing my emails now and start drinking coffee. And the key thing is that waking up in the middle of the night need not mean the end of sleep. In fact, that polyphasic

or biphasic sleep pattern is what all mammals experience. And so this, again, single block of consolidated one block of sleep is not the natural state. That is such an important message, isn't it? The amount of people who feel bad that they wake up. I know the amount of questions that get fired at me about this. Is it okay? And you're clearly're clearly saying no this is not only okay it's very very normal i guess this speaks to the problems with having our smartphones in our room just looping back i don't know you mentioned and not in this conversation i've heard you say about your relationship with your blackberry when you're in australia and actually had to ultimately leave it in your lab yes i i have i i'm just sort of i think it used to be called

crackberries um and and yeah i was in australia and so i would do my australian uh emails on the in your lab. Yes, I have. I'm just sort of, I think it used to be called Crackberries. And yeah, I was in Australia. And so I would do my Australian emails on the BlackBerry. Then, of course, the European ones would come in. And then the North American. So if you're jet lagged, and I remember, you know, this red blinking light, those who had a BlackBerry. And I was so weak. I could not, first of all, it was by the bed and of course i then moved it very quickly to the room next door and that was hopeless because i'd wake up and then i'd go next door and so um i left it in the lab and of course as a result i got much better sleep yeah because when you wake up if you're not getting your mind actively engaged back into work you a lot of us

probably don't realize that we may well have fallen asleep again had we not done that. And that's what most of us do. In fact, you know, we go through cycles of REM and non-REM and we naturally wake from REM sleep. And then we fall back to sleep again without even noticing it. Now that wake up period can be, you know, a few seconds, so you don't notice it, or it may be 30 minutes. But the chances are you will go back to sleep as long as you stay relaxed, you keep the lights low, and you do something that is not alerting the brain. And as I say, because we haven't ever passed this information on, you know, people don't know when they think, oh my goodness, that's the end of sleep,

I'm sleeping terribly. And in fact, if you stay calm, it's fine. The other thing, another tip, I guess, would be illuminated alarm clocks. Because many people clock watch, they'll wake up and then they think, oh my God, I've only got two hours before the alarm goes off. It doesn't matter. You know, if you go back to sleep, you know, and you have that additional two hours or half an hour, again, it doesn't matter. So if you have an illuminated clock, put some tape over the front of it. The only thing that matters, I guess, is the alarm, not how long you've got before the alarm goes off. Which brings us back to the start of the conversation,

which is alarm clocks stop the single most behavioural, single most important behavioural experience we have. Russell, it has been such a joy talking to you. Honestly, this book, Lifetime, The New Science of the Body Clock and How It Can Revolutionize Your Sleep and Health, it's frankly brilliant. It's so, so good.

I hope everyone goes out and gets a copy. And look, it's been a great chat. I really appreciate all the work, all the research over the years. And as I say, I hope I can persuade you for a part two at some point. It's been great, Roman the research over the years. And as I say, I hope I can persuade you for a part two at some point. It's been great, Roman. Thank you so much.

Really hope you enjoyed that conversation. As always, do have a think about one thing that you can take away and start applying into your own life. Now, before you go, just want to let you know about Friday Five. It's my free weekly email containing five simple ideas to improve your health and happiness. I share exclusive insights

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