Feel Better, Live More with Dr Rangan Chatterjee - How Separate Beds Can Boost Your Relationship, The Truth About Sleep Supplements & Naps, Reducing Night Time Peeing & The New Science Of The Body Clock with Professor Russell Foster #424

Episode Date: February 7, 2024

Prepare to learn everything you wanted to know about sleep (but were too tired to ask). For today’s episode I’m welcoming back Professor Russell Foster, one of the world’s foremost experts on circadian rhythms and sleep. Russell is Professor of Circadian Neuroscience at the University of Oxford and author of the fantastic Life Time: The New Science Of The Body Clock And How It Can Revolutionise Your Sleep and Health.   The last time I spoke with Russell (on episode 292), we took a deep dive into circadian rhythms, chronotypes, and how best to live in sync with our body clocks. This conversation picks up where we left off and takes in some of the very latest evidence on using circadian science to optimise sleep.   Among many topics, we cover whether you should share a bed with your partner, whether sleep trackers are useful or not, and why routine is key. We discuss the vital importance of daytime light, minimising evening light, helping kids avoid screen time, and how our body temperature cycle affects sleep.   Russell shares the latest research on sleeping pills, magnesium and melatonin and the best ways to use them. We also cover the issue of waking to pee in the night, the importance of rest and relaxation, naps, sound frequency therapy, and weighted blankets.   It’s easy to think that good sleep is something you ‘get’ or miss out on. But Russell wants all of us to know that sleep is dynamic, flexible, and within our control.   This really is a wonderful conversation, jam-packed with practical insights that you can use immediately to improve how you sleep, wake and live. 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. Find out more about my NEW Journal here https://drchatterjee.com/journal and click here https://drchatterjee.com/events to join me at an exclusive event on 29th February. Thanks to our sponsors: https://boncharge.com/livemore https://drinkag1.com/livemore https://zoe.com Show notes https://drchatterjee.com/424 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 qualified healthcare provider. Never disregard professional medical advice or delay in seeking it because of something you have heard on the podcast or on my website.

One fascinating study compared depression and light, and they compared placebo, Prozac, and 10,000 lux for 30 minutes in the morning. Light was more effective than placebo at two weeks. Prozac was only statistically significant at eight weeks. And then light was more effective than Prozac. So light seems to be very powerful for both non-seasonal and seasonal depression. very powerful for both non-seasonal and seasonal depression. I think it's about tuning in to those incredibly powerful environmental drivers of our biology. Hey guys, how you doing? Hope you're having a good week so far. My name is Dr. Rangan Chatterjee and this is my podcast, Feel Better, Live More.

Feel better, live more. This week, I'm welcoming back Professor Russell Foster, one of the world's foremost experts on circadian rhythms and sleep. Now, Russell is Professor of Circadian Neuroscience at the University of Oxford and author of the fantastic book, Lifetime, the new science of the body clock and how it can revolutionize your sleep and health. Now, the last time I spoke with Russell on episode 292 of my podcast, we took a deep dive into circadian rhythms, sleep chronotypes, and how we can best live in sync with our body clocks. This conversation very much picks up where we left off and takes in some of the very latest evidence on how we can use

circadian science to optimize our sleep. And in this conversation, we cover so many different topics. The potential downsides of sharing a bed with your partner, whether sleep trackers are useful or not, why routine is key when it comes to sleep and health, the vital importance of daytime light, why we should try our best to avoid evening light, how we can help our kids reduce their screen time, and how our body temperature can affect our sleep. Russell also shares the latest research on sleeping pills, magnesium, melatonin, and the best ways to use them. We also cover the issue of waking up to pee at night, the importance of rest and relaxation, naps, sound frequency therapy, weighted blankets, and so much more. This really is a wonderful conversation, jam-packed with practical insights that you can use immediately to improve how you

sleep, wake, and live. I wanted to start off by talking about something that is often not discussed, I think, when it comes to sleep, and that's the issue of partners sleeping in the same bed. Yeah, do you know, it's interesting, I was talking about this fairly recently, and I've talked about it, I think, in the book too. And I'm saying that, look, if you find it difficult to sleep with your partner, then, and if you can it difficult to sleep with your partner, then, and if you can, find an alternative sleeping space. Because it's no reflection upon your relationship. If your partner snores, for example, or the bed is too hot, or if they wriggle around

a lot, find an alternative space. And in fact, it's not the end of a relationship. And so many people have come up and said, oh, no, I couldn't possibly sleep in a separate bed. It marks the end of a marriage. It doesn't. It marks the beginning of a new, wonderful phase in your relationship because you both get decent sleep. You don't resent somebody sort of jabbing you in the ribs because you're snoring or whatever.

And you can have nice little rituals of getting together in the morning to have a cup of tea or whatever. So I don't see the problem at all. But there is that psychology that, oh, you know, it's you've got to sleep together. Don't agree with it. If I think about the UK or the US, I would imagine that in these countries and cultures, there may be a bit of pushback. Oh, yes. And go, no, no, if you're in a couple, you sleep in the same bed. But I imagine there's many cultures around the world where this is not the case. That's true. And there's a whole spectrum. So I remember when I first went to Germany

with my wife, and we were given this fantastic room, huge bed, but separate duvets, which is a really smart thing because often the temperature ranges for couples will change. So separate duvets is a really easy solution to that. Snoring is, of course, a lot more problematic. But also in cultures like Japan, it's very frequent that the children sleep with the mother and the father sleeps separately. So there's every sort of relationship. And of course, the aristocrats, it was always, you know, they always had separate bedrooms.

Yeah, it's interesting. I was chatting to one of my best mates about this recently, and he's a spinal surgeon on the south coast of England. And he said to me, mate, no way, that's the start of the end. If you don't sleep in the same bed as your partner, that's how ingrained it is. But I guess let's look at the flip side.

In our first conversation, we discussed together how poor sleep has so many impacts on our short-term and long-term health. And if we just think about the short-term, on our short-term and long-term health. And if we just think about the short-term, poor sleep leads to less compassion, less empathy. Reduced sense of humor. You need humor in a relationship. Yeah, so by that logic,

of course, if sleeping in the same bed is resulting in one or both parties not getting enough sleep, which means you have less empathy, less sense of humour, less tolerance to a whole host of different things. It kind of sounds to me as if you have the space, and of course not everyone does. That's the issue. If you have the space and the capability, it might actually improve your relationship.

That's how I would argue it. Absolutely. Yes. Now you have to be slightly careful because what you want to make sure that your partner doesn't have obstructive sleep apnea. So this is where the musculature of the neck will collapse and block the airway. And so they'll be sort of snoring away and then they'll just stop. And then they'll wake themselves up. The brain realizes it's been deprived of oxygen. And so the individual wakes up and splutters and snores and all the rest of it. And now that's serious.

And that needs to be looked at by a GP. And there are easy ways to fix it. So, you know, just make sure that your partner doesn't have obstructive sleep apnea. So when you're giving us that warning, are you essentially saying, let's look after our partner? If you think there's an issue before you move into the spare room, just have a look and at least ask the question, could this be sleep apnea? Is that what you're getting at? Exactly, yes. And of course, you can get apps which you can download and actually listen to your snoring pattern. And people have done that. And they're pretty accurate too. So yes, just be

careful that it's not obstructive sleep apnea. Snoring is one issue. And of course, snoring can be enhanced by increased weight gain. Rather sadly, as we get older, we deposit more fat in the tongue. And so that can also restrict the airway. Alcohol, of course, will relax the musculature and you're much more prone to snore if you've had too much alcohol. Yeah, it's interesting. I spoke to the US physician, Dr. William Lee, last year on this podcast. And he's done a lot of research into food, but also visceral fats. And he said one of the first places we store visceral fat in the body is in the tongue. I know, isn't it extraordinary?

Who would have thought it? It's bad enough getting old without having a fat tongue. You mentioned snoring and you mentioned obstructive sleep apnea. Just so we're bringing everyone along and no one's getting confused, they're different things, aren't they? Yeah, they can be overlap. Exactly, yes. So snoring would be just the vibration of the tissues in the back of the throat.

Anything to be worried about snoring? I don't know. I mean, if it's very loud, I'd sort of think about some corrective measures, such as making sure that you're not drinking too much, that you may want to sort of prop yourself up a bit. But broadly speaking, straight snoring is nothing to be particularly worried about. But obstructive sleep apnea is, because what you're doing is you're having periods of oxygen deprivation to the brain. And then when the brain wakes itself up, you're getting surges in blood pressure. And that can be very bad for the small vasculature in the eye, for example,

and of course in the brain. So that really does need to be looked at. And so there's a correlation between our higher rates of obstructive sleep apnea and dementia, for example. If someone is listening to this and they do snore or their partner snores and they're not sure, is this just a bit of mild snoring or is this something more serious?

What would you advise them to do? Well, ideally, you go to your GP and they'll recommend you go to a clinic and, well, you'll spend a night and then they'll look at you in some detail and they'll monitor the breathing and the snoring and potentially the obstructive sleep apnea. But there are so few sleep clinics like that, it's tricky. And I mentioned that there are apps you can download.

And so what I would recommend is talking to the GP, seeing what the options are. And if there's a waiting list of two years or whatever it is to get to the sleep clinic, ask specifically about what NHS recommends in terms of downloadable apps to monitor your snoring and potential sleep apnea. Now, in our first conversation, Russell,

I asked you what your views on sleep trackers were. And you were quite clear that there's very few uses you thought they were good for. You were sort of saying that, sure, for some people, they might be okay. But you were saying that no sleep federation actually endorses the use of them. Yeah, that's still the case. So that's still the case. Still the case. so so none and then and also none are fda approved at the moment which means what for an individual who's thinking you know what i see all these adverts yeah for sleep trackers maybe a ring or maybe a bracelet that i wear 24 7 why should they be concerned or why should they proceed with caution over the fact that you've

just said they're not approved by the sleep federation? Yeah, well, so for example, you'll often read medically validated. And that can mean just about anything. And so for example, what it often means, and excuse me for being cynical, is that it's been tested on eight Californian undergraduates for a couple of nights in the sleep lab. If you're lucky, sometimes it's only one night in the sleep lab, and that's just not good enough. And also, because sleep is so dynamic, as we discussed last time, a single algorithm is simply not going to work across the variety of sleep patterns that we see and as sleep changes as we age. Now, I'm down on them now.

And as I said before, they can be useful in terms of telling you roughly what time you went to sleep and what time you woke up and that's can be and if you woke up in the middle of the night. But anything more sophisticated than that, I would be very uneasy about. And indeed, there are now instances of people using these devices and getting sleep anxiety. It's now a recognized condition. People get so worried about the sleep information they're getting from these apps. And they're, in large measure, inaccurate. So don't take them too seriously.

However, what I think is on the horizon with AI is a much more interactive device, which means that it can pick up biometric signals, accurate biometric signals. And what does that mean? Well, it can tell, you know, roughly what your breathing rate is, your pulse rate, and of your activity accurately, and integrate that into a dynamic algorithm, which can say, oh, yeah, I understand, I can tweak the algorithm that fits this sort of person's sleep habits. And so I think that they might, as time goes on, I would imagine in 10 years time, they will be more useful, and they probably give a much greater accuracy for the sleep that we actually experience. Yeah, I guess so like many things,

it's early technology. It's rapidly evolving. And maybe in the future, there'll be a lot more accurate. It's really interesting. I don't think I shared this with you last time we spoke. In fact, I don't think I'd had the conversation at that point. Just over a year ago, I spoke to the Kenyan elite marathon runner, Elie Kipchoge, who's the only marathon runner to have run under two hours, a marathon under two hours, which is just staggering, basically. It's absolutely extraordinary. And he does wear an aura ring to track his sleep. And I asked him, on the morning of a big race, you know, what happens? Do you look at it? You know, what if you're ready to score a save? He

goes, I never look at it on the morning of a race. Because he knows that he doesn't sleep well, like all of us the night before something big, or like many of us, I should say. And he knows for his optimal performance, in order to be confident, go into that race, perform at his best, he doesn't need to see a poor sleep score or a poor readiness score. Absolutely. And I think that- Which is quite telling. Yeah, it is. Absolutely. And of course, it's very interesting that we feel as though we need to be told by some inaccurate device how we feel. And we're in the best position to determine how we're

feeling, whether we're firing all cylinders, whether we're feeling, you know, able to perform. So what are the best questions that one can ask themselves to determine if their sleep is adequate or they're sleeping enough? Oh, and that's straightforward, you know. I suppose the first would be, do you feel that you can function optimally during the day? Are you firing all cylinders? Do you rely on an alarm clock to wake you up in the morning

or a partner to wake you up in the morning if you're staying in the same bed? Do you feel tired and sleepy during the day? Critically, do you oversleep on free days at the weekend, for example? And what does that mean? Well, basically, normally, you know, you've got to get up at a particular time during the week,

and then you're sleeping in for two or three hours at the weekend. And that's telling you you're not getting enough sleep during the week. And so you need to go to bed earlier and get the sleep that you need. And it's worth bearing in mind that many people think, oh, I can just completely catch up by oversleeping at the weekend. You can partially, but not fully. Some really interesting experiments have shown is you don't fully catch up after a weekend of oversleeping. You're still starting Monday with a sleep debt.

So you've got to really get that stability. The other problem, of course, about oversleeping is that you're not getting the morning light, which is so important for setting the body clock and the sleep-wake cycle. To make it really practical though, Russell, some people will say, I get what you're saying, but my life is tough in the week with my children, with my work demands. I just can't go to bed at a time that would be optimal and I do need an alarm clock because my job is what feeds me and my family. In that situation, at the weekend, let's say on a conventional Monday to Friday job, is there a downside to sleeping in? And the second part to this question

is, what about catch-up naps on a Saturday afternoon or a Sunday afternoon? Yeah. Okay. So, yes, it is difficult. But it's all about prioritizing. Because we can cut our sleep, we think that we can squeeze other sorts of activities into the time that we would normally sleep.

So we've got to take our sleep seriously. And if we need eight hours or seven hours, we need to go to bed at a time that will deliver that duration of sleep that we need. So it is about prioritizing. Oversleeping, as we touched on, is you won't catch up fully and you can delude yourself that you can, I can oversleep at the weekends, I'll be fine for Monday. The data suggests that that is not the case. You can certainly, it can certainly reduce the sleep debt, but not fully. The other key thing, of course, is you're not getting that morning light, you're not getting that important time giver to set the clock and the sleep-wake cycle accordingly. So, you know, all of the data that we've got

suggests that it's regularity, which is the key thing that we have to achieve for our sleep-wake cycle. You mentioned morning light. I know we covered it in our first conversation, but for anyone who's not heard that, perhaps give us an overview. You know, what is morning light?

Why is it so important? And how much do we need? Yeah. So we have this internal clock, which is fine-tuning our biology to the very demands of the 24-hour day. And what is it? You say internal clock. Many of us picture a clock on our desk, right? So when you say we have an internal clock, what does that look like? Well, actually, there is a master clock within the brain. And it's called the suprachiasmatic nuclei. So essentially, you can think about where this is. As the optic nerves go into the brain and fuse, sitting above there is a small paired structure of about 50,000 cells. And each one of those cells is capable of generating an endogenous

24-hour rhythm. I mean, it's just extraordinary. And it's based upon a molecular feedback loop. So, clock genes are turned on, they make their proteins, those proteins then form a complex, they then go into the nucleus and turn off their own genes. The protein complex is then degraded, and then the whole thing can start again. And so, it's a biological oscillation of about 24 hours, but it's not exactly 24 hours. And so it needs to be set to the real day. So the internal day needs to be aligned to the external day. And the most important thing for that, it's not the only thing, but the most important thing is light. Now, light does different things to the clock at different times. So morning light

makes us get up early. It advances the clock. Evening light delays the clock, makes us get up later. Now, because most of us, 90% of us, have a body clock that is slightly longer than 24 hours, we, under constant conditions, would drift later and later and later. So what we need to be entrained to get that internal clock aligned to the external world is a daily nudge, an advance. That's why morning light is so important because it gives us that advance, which is what we need on a daily basis. So interestingly, we did some studies on some students all over the world.

And of course, students are notoriously late types. But we found that the later the chronotype, and I know we touched on chronotypes last time, the more evening light they got, which would delay the clock at the expense of morning light. So they were sleeping through, not getting the advancing morning light, but they're out in the late afternoon, early evening,

getting the dusk light, which is delaying the clock even further. So when we see light, it's so important. So we want to get light exposure, ideally natural light outside, as close to our wake-up time as possible. Yeah, exactly. Yeah. Now, a couple of things to elaborate on there. We're recording this conversation in January in the UK. So we're at the height of the British winter. Which means it doesn't often, depends whether it's clouds in the sky or clear, but it can often be 8am until you're getting morning light. Well, it was, it is at the moment about 8am.

So many children, many adults are having to get up let's say at 6 30 am to get ready for their day's activities yeah so they get up at 6 30 let's say with an alarm clock which may not be ideal but maybe in reality what's happening for a lot of people your advice is you need to get morning light as soon as possible. Now, morning light may not be available from the outside until 90 minutes after that. In the summer, I get it, easy. Everyone wants to go outside and get their feet on the grass if they have gone or whatever it is, right? On the wet, damp conditions at the moment, people don't want to do that. So watch for advice with respect to that. And also, what does indoor lighting do? And these kind of sad lamps, I guess, you know, are they useful?

Well, they're certainly useful. And I think we could learn something from our Scandinavian cousins here. So in Tromso, which I visited, it was the most extraordinary place. Where's Tromso? Tromso, northern Norway. And it's in the Arctic Circle. And of course, it's dark for two months of the year. And what the families do there is that they will have a lightbox. And it's set to produce more than 2,000 lux. And we can talk about lux levels in a moment. For 30 minutes, so 2,000 plus lux, perhaps as high as 10,000 lux in some cases. And they have their breakfast in a room where there's artificial light

and they use that to set the clock to the external world. Of course, there's not much of a light-dark cycle, but of course, they're stabilizing it, in a sense, for social reasons. And have they done that on the basis of scientific experiments or has it been something that they've figured out over time, we need to do this for our physical and mental well-being? I think it's a bit of both.

I mean, we've got good data showing that morning light is really important for stabilising sleep-wake. And also, you mentioned seasonal affective disorder. The treatment, I mean, some data for SAD and light is really interesting. Many of us were very skeptical when this first emerged. You know, say, oh, well, you know, sit in front of a light box. What's the control? You know, you sit in front of a light box and you don't turn the lights on. You can, you know, you work out that it's not going to work. So, is it just a placebo effect? And then a range of much more sophisticated experiments

showed that it really was the light. And one fascinating study compared non-seasonal depression and light, and they compared placebo, Prozac, and 10,000 lux for 30 minutes in the morning. And light was more effective than placebo at two weeks. Prozac was only statistically significant at eight weeks. And then light was more effective than Prozac. So light seems to be very powerful for both non-seasonal and seasonal depression. This is a really interesting point, something I wanted to discuss with you today. This idea that light is medicine, this idea that light is a drug. But we as a

society don't see light as a drug. We just think, well, we can expose ourselves to whatever light we want, whenever we want. Light is separate to our lives. We get on with our lives. We do our work. We go on social media. We see our friends. We do whatever, but we don't give attention to light. But your trial that you just mentioned there, or certainly the trial you're citing,

is really comparing light to a drug. Yes, yes, absolutely. So in your view, should we consider light as powerful as drugs? I think we absolutely can. And it would be naive not to think that for the following reason. You know, all life on Earth has evolved on a planet that rotates once every 24 hours.

We're exposed to a light-dark cycle. The light-dark cycle has dominated our evolution and our biology. And because from, what, the 1950s, we could produce cheap, affordable, efficient light, we've invaded the night. And we've thrown away this incredible part of our biology as a result. And it's fascinating that, you know, the humans are wonderful. I mean, we're remarkably arrogant. We think we can do whatever we want, whatever time we choose. I mean, you know, it's part of the success story.

But actually, we do it at some considerable cost. And I think it's about tuning in to those incredibly powerful biological drivers, environmental drivers of our biology. You say it's part of our success story. And again, this is something I've been reflecting on recently, on long walks, Russell, this idea that we say that humans are really evolved and look at what we've achieved with our skyscrapers and our phones and our technology. But you could also make the case that we have epidemic rates of chronic disease. We have epidemic rates of mental health dysfunction.

And so I guess sometimes we need to challenge the narrative that this is a success story. Do you know what I mean? I know that's slightly controversial and I'm not pushing back at what you're saying. I just think as a general point, it's like worth considering that there are some cultures and some parts in the world where, yes, it's worth considering that there are some cultures and

some parts in the world where, yes, let's say they've got other issues to contend with, but their chronic disease rates are much lower. They don't have mental health dysfunction. Like a lot of hunter-gatherer tribes, yes, they may have threats from predators. And we regard our lives as better, many of us, which speaks to this arrogance I think many modern humans have. But I think we could also make a case to go, well, is it necessarily better? I'm certainly arguing for a bit more humility. It's all about its understanding. And of course, what we haven't had is out there the education that allows us to make sensible decisions about our lives.

And that's the thing that's changing. And I think people are thinking, hang on, I do need to reconnect a bit. I do need to get that balance into balance. And so, yeah, it's all about education for me. And it's trying to have the information to make the best decisions about our lives. It's trying to have the information to make the best decisions about our lives. And so that we can embrace the extraordinary successes of our species, but also not get kicked in the teeth by them. Yeah, I agree.

I think it's possible to have the best of modern humanity if we just remember some of the evolutionary principles, as it were. If we can remember those and apply them in the context of the modern world, we can possibly have our cake and eat it. Yeah, but I mean, we can't do everything that we want to do at any time of the day. There's a balance we've got to prioritise

and we've got to structure our days so that we can achieve what we need to achieve, but also not at the expense of fundamental biology like sleep. You mentioned that it was in the 1950s that we discovered ways to make light and our use of light much more cheap and more accessible. It kind of reminds me a little bit about what happened in the 1970s and 80s with food.

We found ways to make energy-dense, calorie-rich, super tasty foods that we can't resist. And now I think many of us are aware of this junk food problem that exists in society. You could kind of make the same case with light. I think it's a good analogy. We have a junk light problem. Yeah, absolutely, yes. I mean, it's very interesting because there was a House of Lords

Science and Technology Select Committee on the impact of light and noise pollution on human health, and particularly how it affects our sleep-wake cycle. And it was really interesting to see how Parliament is now beginning to take these sorts of issues seriously. And I urge people to go onto the website, House of Lords website, and look at the Select Committee report. It's really interesting. Let's just go back to partners for a minute sleeping in separate beds.

When you have spoken about this at live talks or in the media before, you know, what kind of comments have you had from people? Has there been a lot of pushback? Are some people saying, no, my husband and I have been doing this for 30 years and it's the best thing we ever did? Or are you mostly getting pushback against that idea? getting pushback against that idea. 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 AG1. AG1 has been in my own life for over five years now. It's a science-driven daily health drink with over 70 essential nutrients to support your overall health. It contains vitamin C and zinc, which helps support a healthy immune system,

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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. 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. That's drinkag1.com, forward slash live more. I'm not getting pushback. In fact, what's happened is that a bunch of celebrities,

you know, then came out saying, oh yeah, well, of course, you'd be sleeping in separate beds. And actually, of course, endorsement by a celebrity means it's kind of okay to many people. Forget an endorsement by a celebrity means it's kind of okay to many people forget an endorsement by you yeah um and so uh i know i i it's been the reverse people i think actually people have felt phew i'm so relieved i don't have to feel guilty about it

any longer and i think initially people probably push back because they think, yeah, but what about intimacy? But I don't think sleeping in the same bedroom equals intimacy. Because you could, let's say, I mean, it's not an extreme example at all. I think it's happening in many bedrooms around the world where you're in a double bed with your partner and each of you are on your own devices. Right? You're physically in the same space but mentally you could be tens of thousands of miles away one of you is in your curated world of entertainment the other one is in their curated world so yeah sure you're in the same beds yeah but is that intimacy well no no no absolutely and of course you know if you want to promote intimacy you have to have empathy.

You have to be responsive to the behaviour of your partner. You have to have a sense of humour often. You have to enjoy other people. And you'll enjoy other people a lot more if you've had a good night of sleep. So one option is separate rooms. The other option which you have touched on, which you first came across in Germany,

is you're still in the same beds but you have a separate duvet are there any other options you can think of when it comes to couples potentially sort of dealing with this issue I mean of course the default is earplugs but a lot of people just can't cope with those to block out any snoring noise, for example.

But temperature, I think, is also an important factor. Males and females have different temperature preferences on average. So men prefer a slightly lower temperature compared to females, compared to women. And what's the basis for that? Well, we don't fully know. But one argument is that men tend to be larger. Therefore, they have a reduced surface area to volume. So they're not going to lose heat as readily. Also, men tend to have more muscle than fat compared to women.

And muscle is metabolically more active, and they're therefore producing more heat. So that might be part of the difference, and why, you know, the Germans have, you know, used separate duvets. But there are now mattresses which also take the heat away from the sleeper. And, you know, I think it started as a bit of a sort of a selling issue, but there are data suggesting

that actually they do improve sleep. I mean, we should talk about temperature and the importance of temperature for sleep generally. Yeah, let's see that. It's interesting as you say that. So it's a friend of mine yesterday and I told them that you were coming back to the studio today.

And she said to me, I don't know if this is a bit weird or not, but, you know, my husband and I like different temperatures. He likes to sleep completely naked and I've got loads and loads of clothes on and the duvets wrapped around me. That works for us. So I thought I'd put it to you. That kind of speaks to what we're talking about, right? It's presumably there's a temperature regulation difference or a temperature preference difference between the two of them. And the way they're managing that is by the clothes

that they're wearing. Fantastic. Yes, absolutely. Yeah. Have you heard that from others? Oh, absolutely. Yes. And the sorts of things you can wear in bed, you know, some people just wear a t-shirt. I think night shirts are becoming more, are replacing pajamas in certain sectors. Maybe it's because I'm just dealing with an older demographic, but you know, yes. And so I think it's finding, as long as the material is cotton or linen and absorbent and comfortable, then I think there's lots of different options, yeah. At the end of our first conversation, Russell, you briefly touched on biphasic and polyphasic sleep. I wonder if we could retouch on that, but then linked to that, I'm wondering, you know,

has any of your work studied tribes, you know, hunter-gatherer tribes or, you know, tribes in different parts of the world? How do they sleep? If there is a couple there, for example, a man and a woman, do they sleep in the same bed or are they in different places? Yeah. Okay. We need to go back to a wonderful chap called Roger Earcook. And he looked at the sleep habits of pre-industrial Europeans from the writings, the diaries, and kept on finding references to a first and a second sleep. And so went through and there were records that go way, way back to

a polyphasic sleep. So not sleep in a single consolidated eight hours, as we're all told we've got to have, but people would wake up, they'd interact, then they go back to sleep again. And this was common. This was just the norm. And then it seems that as we've developed a more industrial society and we've compressed our opportunity to sleep, the polyphasic sleep pattern is not as clearly pronounced as it was. You know, in the pre-industrial societies, light was incredibly expensive. I mean, the cost of a candle in the 19th century was almost equivalent to a working man's daily wage. You couldn't afford, and also they were made of fat, and you couldn't afford to burn fat because you know you most people were were food poor and

so you so we would so the sleep-wake cycle was was dictated to a large extent by the the the natural light environment so anyway um roger's work then stimulated a chap called tom weir to do some experiments and and he got young people into the lab, exposed them to 12 hours of light, 12 hours of darkness. So, you know, expanded the nighttime opportunities to sleep. And what he found was they became biphasic. So they then sort of would go to sleep, they'd be asleep for a few hours, wake up, and then they go back to sleep again. And so you see this also in societies now without electric light. So people have studied, to Renneberg, for example, societies in South America,

and shown very nicely that sleep isn't a single consolidated block. And that's so important because we're told, eight hours, consolidated, this is the perfect sleep pattern. And when people wake up, they think, oh my God, never going to get back to sleep. I might as well start doing emails and drinking coffee. And of course, if you know that the biology is like it is, and so if you stay calm, you stay relaxed, you keep the lights low, your chances are you will go back to sleep. So potentially, we could make the case that a biphasic sleep pattern is the kind of natural human way to sleep?

Can we say that? Well, I think that's fair under those sorts of circumstances. So, for example, you would expect that biphasic, polyphasic sleep would be the dominant sleep type during the long nights of winter. I think perhaps by the time we get to the short nights in the summer, we might find that the sleep patterns will change. So I think it'll depend upon changing light-dark signals. But yeah, it's perfectly normal to have biphasic or polyphasic sleep at certain times of the year, I would say. And on that, something I've often felt,

which kind of speaks to your work really, Russell, is that society has really lost its relationship with rhythm. You know, everything in nature, in life, operates with rhythm. Absolutely. Whether it be a heartbeat, whether it be electrical activity, whether it be the sleep-wake cycle. And even if we think about, let's say, a seven-day rhythm, and we think about the fact that certainly when I was a kid, supermarkets in the UK were closed on Sundays. Oh, yes. Now, what's really interesting, if we really reflect on that, and of course, many religions have a Sabbath or some sort of day of rest ingrained within them.

Pre-internet, pre-supermarket's been open seven days a week and having online shopping seven days a week, you would naturally have rest on a seventh day. Right? So we have a rhythm there. And I kind of feel modern society tries to make us feel that every day is the same. Now, I get that we want similar wake-up times and bedtimes to help us with our circadian rhythm, but you mentioned winter and summer. And for many years, it's felt quite natural to me that in the winter, let's say in a Northern Hemisphere country like the UK, where you do have short days in the winter and it's not light till 8am, it's dark at 4.30pm, and it's even more pronounced than that in places

like Scandinavia, it kind of makes sense that you would spend longer in bed and potentially sleep more in december and january as compared to the light months of june and july yeah what does the research say well studies have been done uh we're suggesting that we do increase our sleep duration a little bit during the winter it's not huge but but it does occur historically i suspect it was very marked. But because we can manipulate our environment in terms of light and temperature, I think it's become less pronounced. But it certainly occurs in many people.

So it's reasonable to think that your sleep need might be different in the winter than the summer. Yeah, I think that's fair too. Yes. We don't have huge amounts of studies underpinning that statement, but I think it's a perfectly reasonable assumption. But then we could go to what you said before, which is we don't need fancy tech to tell us about our sleep. We need to ask ourselves some simple questions. And therefore, if in the winter and the summer, whatever your sleep amount is, if you're functioning well,

if you have empathy, if no one's calling you moody, if you can concentrate all day, you know, you may well be sleeping enough for you. Exactly. And it's also worth bearing in mind, we're not unique. We are just like every other kind of mammal. And all mammals have some form of biphasic or polyphasic sleep. They don't sleep in a single block, and their sleep-wake patterns expand and contract over the seasons. So it's not surprising that we show those trends as well. Temperature, right? What's the relationship between temperature and sleep?

Yeah, it's really interesting. So if we start with the circadian changes in temperature, so we're told that temperature is about 37 degrees C. But actually, if we go to the early morning, to four o'clock in the morning, it's at its lowest point. And it might be as much as one degree below 37 degrees. So this is our body temperature.

Our core body temperature, yeah. And then in anticipation of increased metabolic rate, increased activity, our temperature is driven by the clock to start rising. And it rises and rises throughout the day. And then about six, seven o'clock in the evening, it begins to decline to that low point in the early hours of the morning. Now, what's critical is that that circadian driven rhythm in temperature also impacts upon the sleep-wake cycle. Because that evening drop in core body temperature seems to be a signal to initiate sleep. So, part of the physiology of going to sleep involves a drop in core body temperature. And if you block that drop

in core body temperature, it's much more difficult to go to sleep. So it's a really important part of our biology. And this, of course, is why hot showers and hot baths can be helpful before bed. I know, it's ironic, isn't it? You've got to promote cooling, but you're doing it with a hot bath, a warm bath. And the reason, of course, is that what the warming of the bath water does is to vasodilate, to expand the blood vessels in the hands and the arms and the legs and the feet, which means that blood is being shunted from the core, where it's hot, to the periphery, and that heat is being lost to the outside.

So that's why a warm bath can actually promote going to sleep. Relaxing, of course, but also it's helping produce that subtle drop in core body temperature. And again, that makes sense if we think about our evolution. We were living on the equator and presumably in the day it would be hot and presumably at night the sun would go in,

it would be dropping temperature, right? So we've evolved under those conditions. And so I guess these modern temperature controlled houses, again, I can speak about Britain because that's where I live in the winter with heating on. I think a lot of people don't realize that having the heating on in the bedroom, there's a balance of course, but you can make it too hot. Oh, absolutely, yes. And there's some discussion about

what's the optimum temperature for a bedroom. I suppose the consensus is about 18 degrees. Personally, I like it much cooler. I turn the heating off and sometimes even open the window, so I like it nice and cool. But a recent study showed that in elderly people, 65, 70 and older, that the optimum

temperature for sleep was closer to 22 degrees. So it's a big change. Yes. And I have to say the data surprised me. So, you know, everybody's different. You'll have to find, you know, what works for you. But of course, it's not simply the temperature in the room. It's the sort of bedding you're using. And of course, whether it's an effective duvet with layers, which are keeping you warm, or it's something much lighter, and therefore you're going to lose heat. And certainly, if it's too cold, you're more likely to wake up. So yeah, you've got to get the balance right, again, as with everything. But yes, but ideally a slightly cooler bedroom temperature would be the best for promoting sleep.

You mentioned lux before, which of course is a unit of light. Could you expand on lux? What exactly is it? And maybe give us some examples of the amount of lux we're often exposed to when we're either inside or outside. Yeah, so lux is an old measure of environmental brightness. And it's essentially calibrated to give you a sense of brightness as it would appear to a human observer. So, the response of the detector is not flat, meaning that it doesn't absorb all wavelengths equally. It actually has a bell-shaped response, which peaks in the sort of greeny part of the spectrum at 555 nanometers,

which is where humans are maximally sensitive to their daylight vision. So, lux comes in values. So, if we think about the sort of light that we'd see outside, so shortly after dawn on a clear day, you would have about 10,000 lux. By noon, that could get to 100,000 lux, even in Britain. Now, you know, it's not common. And do we just measure it as a static measurement, or is it more if you are outside on a sunny day in July in the UK for 10 minutes,

you get X amount of lux. If you're there for 20 minutes, you get Y amount of lux. Is it like that? Yeah, it's certainly additive. And, of course, it's constantly fluctuating because of cloud cover and whether you're moving inside or under a tree or whatever. But if you just took your lux meter out and you pointed it skyward, you could get up to 100,000 lux on a bright, bright sunny day. Most of the time, it's going to be something around 50,000, 60,000 lux. But as we go inside, this is where the big changes are occurring. So if you stand on a

reasonable sunny day, and you point the meter at the window, you could get between 3,000 lux and 1,000 lux. Walk two to three meters into the middle of the room, and it's dropped to maybe as little as 100 lux. And why is that a problem? Or a potential problem? Well, yeah. And of course, the sorts of levels of light you're seeing in the evening would be something like 90 lux

in most domestic settings. Even with bright kitchen LED lights on? It varies, of course, a lot. And kitchens now are very well illuminated. So that would be more, that would be 400, 500, maybe even 600 lux. So the sort of light you get from a Kindle, for example, on maximum setting would be 30 lux. So very low. So low, yeah. And so what does it all mean? Well, the circadian system requires relatively bright light over an extended period of time. And so there's a lot of controversy at the moment because sort of people have said,

okay, well, in fact, domestic light setting, let's say 100 lux, will actually shift the clock. But you have to have seven and a half hours of light exposure to get any effects. So it's a good example of where intensity and duration are being titrated and integrated by the circadian system. However, other more recent studies have shown that actually those low levels of light, even for seven hours or so, are completely abolished if you've seen relatively bright light during the day. So we said that dawn and dusk is sort of the most important times for shifting the clock, but the clock sensitivity is being gated by the sort of light exposure that you get during the

day. So what these studies showed is that 500 lux or more during the day for four or five hours would actually abolish even subtle effects of dim light in the evening, which I think is really interesting. Okay, let me just try and summarize that to check I've got it right. So, you're initially saying that essentially that essentially, the lux you will expose your eye to outside dramatically outweighs anything you could get inside. Broadly speaking, yeah. Broadly speaking, which is why getting outside, particularly in the morning, is so important to set the circadian rhythm.

Exactly. Unless you use a light box, which is in the 2,000 to 10,000 range. Like you mentioned before in northern norway yeah they're using exactly okay then you were saying there was some research and i know you touched on this last time i think it was the harvard research showing that actually light exposure in the evening will delay the clock but it was seven hours plus it was it was a longer well well the particular experiment um individuals were exposed to a Kindle,

brightest intensity for five consecutive nights for four hours before bedtime. And that delayed sleep onset just statistically significantly by 10 minutes. Okay. So it had an effect, but it was a small effect. But what's so important is that the latest study is showing that if you had reasonable levels of light during the day, abolished small effects of reading a light emitting ebook. Yeah and this is something

I became aware of maybe five six years ago I was reading some research that indicated that if you get a lot of light exposure in the day it mitigates and insulates you from some of the negative impacts of light at night. And you're saying more research is now supporting that. Exactly, yes. So if you work outdoor, for whatever reason, or you're able to get out, you know, for, I don't know, a one-hour walk at lunchtime. I know many people in offices probably can't do that, but if you can walk to work, walk back from work, assuming it's light outside. Yeah, get off the tube a bit earlier so you can extend that walk. It's cumulative. The more light exposure you get in the day, the more it insulates you from nighttime light exposure. That's, I think, very empowering because there is a lot of concern

over nighttime light exposure. You also mentioned in our first conversation that light exposure in the evening may not delay the clock so much, but it increases alertness. I really want to unpick that because a lot of people will report to me that when they're not looking at screens for, let's say, an hour before bed, and I've seen this in my own life, when I'm not, my sleep is much better. I fall asleep quicker and I'm more rested when I wake up. Yet some of this research is saying it may not be to do with the clock. That's right.

Can you help us understand that? So, of course, light is critically important for regulating the circadian system, but light can have a direct alerting effect upon the brain. And so, it looks like lower levels of light can have an alerting effect that won't have such an effect upon the circadian system. So, it still could keep you up? Yes, but it's not by shifting the clock. But it's very difficult to disentangle because there's the light alerting effect. But if you're working on a computer screen and you're, let's say, doing social media

and you're being energized by emails and you're doing all that sort of stuff, that will also have an alerting effect. So, in fact, relatively low levels of light and other activities that have an alerting effect on the brain could act synergistically. So, I think the rule of thumb would be, And other activities that have an alerting effect on the brain could act synergistically. So I think the rule of thumb would be ideally don't use devices for 30 minutes and maybe an hour before bedtime for two reasons. One, it could have an alerting effect upon the brain, but also because of the sorts of alerting effects that social media, emails and all that, and just thinking does if you're sitting in front of a computer screen. And it's all part of the process of winding down. As we discussed last time, most people don't have a sleep problem. They have an anxiety or a sleep issue. And the more you can

do to relax and wind down before that transition into sleep, the easier sleep will become. the easier sleep will become. You mentioned the Kindle, which seems to have a very limited effect on the clock. Might have an alerting effect, but limiting effects on the clock. What does TV do? And of course, there's a difference between the TVs of the 1980s

and the big LED mega screens of today. Interestingly, we don't have any really good studies on that. That's incredible, isn't it? It's extraordinary. And a lot of it is extrapolation from other sorts of studies. So what would a television screen produce? Well, the old tellies were producing something, again, in the order of, what, 50, 60, 70 lux, but then you're further away. And so actually the amount of light would be relatively low. What you're getting from a big LED screen, it's interesting. We should try our lux apps that we've loaded onto our phones earlier today and see what the LED screens are.

Although I don't have one, unfortunately, so we can't do it. But we don't have any really good studies. And I think it's a very interesting question. I think there's a great citizen science project there. What about, you know, your iPhone? Or let's broaden it out, your smartphone, all these modern laptops, which are really bright, have got very high contrast colours,

which is often a selling point for these companies, right? Do we know what Deluxe is doing there? 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 and 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 the problem that we have is that the circadian system response to light depends upon the intensity, the duration, the color, the wavelength, your light history, how old you are. And we don't have a really clear model about how this is integrated. So recommendations have been sort of kind of come to, but they're based upon many lab-based experiments. So, for example, one suggestion is that you shouldn't see more than 40 lux, which is really dim, for two hours before you go to bed. Now, that's extracted from lab-based studies

where people were not exposed to a natural light-dark cycle during the day, but kept in a lab under dim light and then exposed to dim light in the evening. Furthermore, it would have been on youngish people. And it looks like the clock of younger people is more sensitive than older people. And so I think we need to be really careful, because I don't think we should recommend elderly people should be wandering around in their homes under 40 lux. The chances of tripping and falling under those levels of light, I think, outweigh any potential benefit, particularly as the potential benefit

isn't well founded in science. You mentioned there that children, they are more sensitive to the effects of light. It seems so, yes. In the evening. Do we know the age category there? Not really, no. I mean,

usually what's happened is that teenagers have been compared to 65-year-olds and 65-year-olds. So we think teenagers are more susceptible. Yeah, and that might also be why the sleep-wake cycles are more easily disturbed, because they are more sensitive to light. So again, the key experiments need to be done. So I want to come on to nighttime exposure in the evening. I'm very passionate about what's going on in schools at the moment. We'll get to that. But perhaps a way of getting into this part of the conversation is this paper that was published in October 2023 in Nature.

It's called Day and Night Light Exposure are Associated with Psychiatric Disorders, an Objective Light Study in Greater than 85,000 People. day and night light exposure are associated with psychiatric disorders, an objective light study in greater than 85,000 people. Now, can I just read a couple of lines from the abstract? Greater nighttime light exposure was associated with increased risk for major depressive disorder, generalized anxiety disorder, PTSD, psychosis, bipolar disorder, and self-harm behavior. Okay, so greater nighttime light exposure is associated with all of those things. And then it says, independent of nighttime light exposure, greater daytime light exposure was

associated with reduced risk for major depressive disorder, PTSD, psychosis, and self-harm behavior, which speaks to some of the things you've just been mentioning. And one of the conclusion lines was, avoiding light at night and seeking light during the day may be a simple and effective non-pharmacological means of broadly improving mental health. Now that's really, really interesting. You know this paper very well. Perhaps you could comment on some of your thoughts about it. Yeah, I mean, over a decade ago, we were talking about the influence

of sleep and circadian rhythm disruption on mental health and mental illness. And we showed that, led by Dan Freeman, a psychiatrist in Oxford, that if you could even partially stabilize the sleep-wake profile of individuals with insomnia and showing paranoia and hallucinatory experiences, partial stabilization of the sleep-wake profile using cognitive behavioral therapy, which of course is going to bed and getting up at the same time, eating at the same time, and of course that involves light exposure, would reduce paranoia and hallucinatory experiences. And so what this

paper has gone on, I think, really very elegantly to show is that, yeah, a stable, robust, light-dark cycle almost certainly improves circadian health, and therefore sleep health, and therefore mental health. So it's all part of the same package. And it's great. And I think this is another really important way of showing that the sleep-wake cycle is a therapeutic target for mental illness. We should just, you should just use it much more effectively than we are at the moment. Now, also on a personal level, in my capacity as a medical doctor, I have seen at least twice, actually more,

but two very clear cases, one I've spoken about before on this podcast, one I haven't, where adolescents who were suicidal significantly improved their wellbeing. And I mean significantly by reducing light exposure in the evening, right? One of them in particular, it was two hours before bed. I said, look, let's really try, get off everything. Phone off, laptop off. The difference in mental wellbeing was marked.

Yes, yes. And studies would support that. And even what I've just read out there would kind of support that, where the increased nighttime light exposure was associated with, in this case, suicidal ideation. So really quite striking. And so I then think about the school system in this country. And before I go into it, when I was reading your book yesterday,

on page 314, you say, it is perplexing that while there is raised awareness about the importance of sleep and the consequences of sleep disruption in the media, decision makers across all sectors of society have not done much about it. Right? So obviously, yeah, this was published maybe a couple of years ago yeah um

2022 so 2022 yeah and so you would have you would have written it probably in 2021 right so what's interesting to me if i think about schools and i'm very passionate about this because my kids are 13 and 11 and what i noticed, not just in my children's schools, but when I talk to other parents, is that there has been, since COVID, where homeschooling came in and Google Classroom came in on a huge scale, now lots of schools are giving homework to their kids, sometimes quite a significant amount of homework, all on screens. Now, in medicine, I've always adopted the precautionary principle, which is when something new comes in, let's just be very cautious before we start introducing it. We've already mentioned that light could be considered as powerful as a drug.

I've mentioned how I've seen two suicidal adolescents dramatically improve their mental well-being by reducing nighttime light exposure. So I have a concern with this widespread adoption of homework in the evenings on screens. And actually, Russell, there was a question from somebody who heard our first conversation. They emailed my website to say, if you have Russell Foster on again, please can you ask them what I can do? This is a GCSE and A-level biology teacher. What can I do to help my children live and exist better in harmony with their circadian rhythm? So I think this is kind of related to this. Do you think we should be this blasé about widespread use of children being on screens doing homework in the evening, or do you

think we should be a little bit more cautious? I think we should absolutely be more cautious. It strikes me that the educational sector is what happened to the business sector, you know, 20 years ago, or more, which is you squeeze more and more and more into an overpacked day, and therefore you invade the night. And of course, the demands, the educational demands on our young people is extraordinary, you know, pressurized by metrics of schools, and they've got to do well and all the rest of it. And it's, I think, at some degree, that personal well-being is being sacrificed as a result. We should allow, I mean, the one thing we know about sleep is that it enhances our ability to not only memorize facts, but actually come up with innovative solutions to complex problems.

And by packing masses and masses into the evening and reducing the opportunity to relax and sleep, we're actually impeding the one thing that we want to enhance, which is our ability of our brains to function. And I don't think that message has got clearly into the educational sector. And I really feel passionately about this. And look, I'm not a teacher, right? So I want to reiterate what I always say, which is I really have so much respect for teachers. I'm sure like all professions, they're trying to do the best that they can. But sometimes what happens is that you just get swept in the tide

of what's happening around you. And often you find no one's actually given this any thoughts. And I actually would like to start maybe a national campaign on this in some way to go, listen, guys, let's just be cautious. Sure, technology is coming into the workplace. You may feel that it's important to teach kids about technology. Okay, maybe do that in the day. Maybe do that in the mornings at school. Let's not get our kids having loads of light exposure in the evenings, because also, Russell, what happens, and I give talks at schools.

So often when I go and present all this research, a lot of it your research, I present the guidelines from these organizations. And then they contact me afterwards or send me DMs on Instagram and they say, Dr. Chachy, I get all that, but the school is making it impossible because Johnny goes to football practice after school. School's half an hour away. By the time he comes back and has had dinner, he's going to be on his screen all the way until bedtime or he can't get his homework done. I don't mean to sound like a broken record, but I actually think we could be setting off a ticking time bomb here. I'm biased because I've seen two suicidal patients in the past

in this teenage adolescent age group. And I really would love schools to go, okay, look, I get it. We're bringing in technology, but what do we want from our kids? We want concentration, focus, empathy, problem solving. We want all those things. To get all those things, you need good quality sleep. Yeah. And the duration of sleep, of course, in young people, you know, I know I don't like averages, but it is certainly longer than the eight hours that adults are recommended to have. It's not possible in the school day.

If you measure it out, I've done this with parents. Actually, unless some schools change their approach to technology in the evening, I think it's impossible for some children to not be on their screens in the lead up to bedtime. Yeah, we do need to think about ways in which we can mitigate some of these issues. Yeah, look, every industry, and I guess we could call education an industry, although it doesn't sit that well with me, has got its own metrics, right?

it doesn't sit that well with me, has got its own metrics, right? It's got its own levels. It's got its own performance metrics, which it is assessing. Now, let's argue, let's say that a teacher or a school thinks that, look, it's very important that our children are up to speed with technology because all the jobs require it. Let's say that's the case they're making. Then we need the wider question, which is, okay, if the cost of meeting those metrics is that some of our children now suffer with severe mental health problems. And let me just read out that line again. Greater nighttime light exposure was associated with increased risk of all of these kind of psychiatric problems.

Including self-harm. Including self-harm. I mean, I don't think it's a difficult answer to me at least, and I'm a doctor, so I'm biased as well, which is if the cost is poor mental health, well, I would say that price is too high to pay. So what I would love, and I'm going to try and do this with some schools, is to actually have a really open discussion and go, okay, what are your challenges? What are you trying to do? How can we mitigate this? Maybe it's,

we give the homework on screens, but we also give guidance and say, listen, guys, do what you can, but really 60, 90 minutes before bed, we'd encourage you to reduce it. Or when you're doing this, turn the light down on your screens or give an option because if you are a proactive family who want to reduce light exposure in the evening for an alertness standpoint and a circadian clock standpoint well you're kind of taking the option away from me by giving my children homework on their screens yeah yeah when should be the cut off and i think the debate has to involve an engagement with the students, with the teachers, and of course the parents. So a few years ago, we developed some educational materials for schools. And part of that was a leaflet, which was sort of trying to give guidelines for parents about how they should prioritize sleep.

And what was on that leaflet? Oh, it was basically, you know, trying to restrict social media use, regular bedtimes. One of the things that emerged rather chillingly from that discussion is that we asked the, these are early teens, do you share your sleeping space?

Do you share your bedroom with anybody else? What we didn't ask is, do you have a bed? And what emerged from this group who were socioeconomically deprived was that a chunk of them didn't have a bed. They didn't have a bedroom, of course. And their sleep consisted of trying to sleep on the family sofa while the family were watching TV. So I think this raises a very important point in the educational sector, because these kids were then going to school the next day, chronically sleep deprived, they can't then take advantage of their educational opportunities, and are already

being socially marginalized, because they're being deprived of a decent education, because they're being deprived of a good night of sleep at night. And I think that's so, poor sleep is the hallmark of poverty, I think, in many sectors, but not least our young people. And we see, as we've discussed, the spectrum from terrible sleep, because there's no bedroom, there's no bed, to essentially overstimulating, overpressurizing our young people to get the grades. And as I say, I think the analogy with the business sector 20, 30 years ago is squeezing more and more and more into an already overpacked day, overpacked syllabus. And maybe the debate should be, okay, let's step back. What do we really want to prioritize? And when do we want to prioritize it? And the problem is,

the easy thing is you cut out music, or you cut out you know non-maths non-english non-science and that also i i find offensive um because you know we live in a glorious civilization which has contributed to every human endeavor and whilst i clearly see the value of the sciences and maths and English, we can't ignore those other things. So it's a really difficult discussion. I don't know how we do it, but it's a debate that we really need to have. I guess business deals with adults. Why I'm so passionate about this is because it's about children. And children are more sensitive to light, the mental health rates in children. And children are more sensitive to light. The mental health rates in children. I mean, you cover it in your book, you know,

that I think it was US research you quoted that the increasing rates of mental health dysfunction in adolescents in US, it has been shown to be a cause of great concern. I know when I'm at my son's bus stop in the morning, most kids are yawning, right? Again, you can yawn for a variety of reasons, but we know that sleep is going down. I think also something for schools to consider is that

for many kids, their downtime these days is on screens as well, whether it be on an Xbox, a PlayStation. So therefore, if light exposure is cumulative, and the more you have off it, the more impact it may have on your clock, it's going to have an impact on your alertness, but it may also push your clock back. It's like, well, should schools, of course, parents have to do what they feel

is right for their children. But at the same time, I kind of feel homework going into screens is just increasing that accumulation of light exposure at a time when our biology actually doesn't want it. Yes. Well, somewhat tangentially, of course, there's some very interesting studies emerging, particularly from Asian countries like Singapore,

which has shown that myopia, short-sightedness, is hugely on the rise. And now there's a very clear correlation between levels of outside light exposure and the incidence of myopia. And these children in particular don't see much natural light. The pressure that's on them to succeed means that they're inside working on their television, they're inside working on their computer screens, essentially every free moment. And so there are other consequences than just circadian rhythm disruption. I read some research suggesting there was a correlation between if you get under two hours of natural light exposure a day your your risk of myopia goes up significantly is that absolutely yes i was at a meeting just recently i've talked for just

recently and some fascinating studies this is a real real tension in australia because um you know you need to get the kids outside into the light but of course in australia and in new zealand where the ozone layer is somewhat depleted, particularly in the South, there's greater incidence of ultraviolet light and the risk of skin cancer. And one of these studies showed that the lower rates of myopia were noted in individuals with skin cancer. So, yeah, get the the kids outside but make sure that they're um they're they're suitably protected with hats and and sunscreen let's play devil's advocate for a minute what if someone's hearing that and going okay

so the downside of not having enough natural light exposure or one of the downsides is myopia, short-sightedness. So my kid has to wear glasses. So what? Yeah, I suppose, so what? I'm not saying that. I'm just putting it there. Like, why is that a problem? I mean, as someone who's worn glasses and contact lenses their whole life,

I really wish I didn't have to. Let's put it like that. Well, I think it's suggesting that our biology has evolved to actually need suitable light exposure, natural light exposure. And so what those data, what those observations are showing us is that we're not getting the light that we need. That's impacting upon eye health at some level. And of course, these changes in one's ability to focus can have other sorts of effect. So, for example, retinal detachment and other implications. So, I don't think it's just a matter of wearing glasses, but it's other stuff as well.

And things that we're probably really just becoming aware of. So, it's probably more of a shot across the bow saying, hang on, team. You know, let's just step back and think about what we're doing here. Because this parameter has been affected, chances are other parameters will be too. To finish off the children's part of this discussion, in terms of teachers who are thinking about practical things they can maybe introduce straight away, I imagine one conclusion from what you're saying is that encouraging your kids to get outside

during the day at lunchtime at break not keeping in inverted commas naughty kids inside as a punishment to make them naughtier to make them naughtier it might be counterproductive maybe because I know in a lot of secondary schools, a lot of high schools, I know this from chatting to a lot of these children, that there's such a pressure of homework that at lunchtime they go to the library so that they get ahead. And then what's that doing? It's eroding light exposure in the day. So I guess schools could immediately start to go, okay, we need to, at least in assemblies, we need across all the lessons,

be encouraging our kids. Even if schools start to educate their kids, say, we're giving you all this stuff, but look, get outside in the day, get outside at lunchtime. Even that may make a difference. And have a cutoff of computer use in the evenings. Yeah.

And you need to wind down two hours before your bedtime. Okay. And whatever that is, and maybe that's the time that you could listen to some music that you love. You could read the novels that you love, or whatever it takes, whatever young people like to do before they go to sleep. I'm too old to remember. But, you know, it's about, it's not about squeezing more and more and more into this overpacked day. It's about stepping back. It's about, I don't know, embracing the broader values of life. The teacher who wrote into me also wanted to know what your chronotype is. Are you happy to share it? Yeah, I, of course, chronotype changes as you age,

but I was a very late chronotype. So you like to lie in in the mornings. I would go to bed late and get up late where at all possible. As you age, of course, you get up earlier. So it's quite noticeable. I mean, this week I've had to get up early twice. And if I'd have had to have done that even 10 years ago, I feel utterly wretched.

But so, but by, yeah, I'm by default a later chronotype. But, and did struggle a bit when I was younger. But now it's become easier. So that's something for late chronotypes to look forward to as you age, along with a fat tongue. This is wonderful. Yeah, you'll get an earlier chronotype. Let's move on to sleep aids. Okay. So let's talk about sleeping pills. Let's talk about magnesium. Let's talk about melatonin. These are things that people commonly use either by themselves or they're prescribed by their doctor. What's your take on them? If we look at the biology, first of all,

then these sleep aids, largely speaking, hit the GABA system. So GABA-aminobutyric acid, it's a neurotransmitter which acts to inhibit the actions of the central nervous system. So we've got all of these excitatory neurotransmitters which increase alertness, increase the stress axis and all the rest of it. And what GABA does is turn that down. So you mentioned the word neurotransmitter.

For anyone who doesn't understand that, can you just put that in layman's terms? So we have neurons and they talk to each other via synapses and chemical synapses involve the release of a neurotransmitter at those junctions, which then stimulate the next neuron down the chain. So chemicals in the brain to send messages between nerve cells. And GABA is one example. Can you give us examples of others? And GABA is one of the ones which actually reduces that transmission. So it calms things down. Yeah.

And so, for example, the benzodiazepines, Valium, or the Z drugs, Zopiclone, they actually act by promoting, increasing the sensitivity of the GABA systems, which means that you're sort of turned down. So you're reducing excitatory neurotransmitter release. Okay, so GABA is a calming neurotransmitter. What are examples of neurotransmitters that do the opposite, that excite us? Oh, just about everything else. I mean, so yeah, the elements of the sympathetic nervous system.

Some adrenaline, cortisol. Adrenaline, cortisol, yeah, exactly, yes. So they would be all excitatory. And of course, we have those projections from the hindbrain called the excitatory arousal system, which is this whole system that is bathing the cortex, that bit of the brain for consciousness, in excitatory

neurotransmitters. Okay, so GABA calms things down. So if we can enhance GABA, we can help to switch things off in the brain, which in theory is going to help promote sleep. So sedation is not the same as sleep. So although it's working on a similar pathway, so sleep does involve an increase in the GABA systems and a winding down of the excitatory systems, but it's a whole bunch of other stuff as well. And you can think of benzos and Zed drugs as being a hammer hitting the conscious centers of the brain. So you're not providing a biological,

a complete biological mimic for sleep. And in fact, some of these drugs can, benzos in particular, can actually reduce memory consolidation and the formation of new ideas in response to complex sort of questions. And of course, the sedative that we've used since time immemorial is alcohol. So, one of the reasons people love alcohol is because it has a calming

effect. And so, you think, yeah, great, that's fantastic. But of course, alcohol, when it's broken down, produces a whole bunch of sort of aldehydes. And of course, they're extremely toxic. And of course, that's associated with all the metabolic failure that you get associated with excessive alcohol consumption. So people have developed a sort of mimics of alcohol, which give you the GABA effects, the calming effects, but it's not converted into some of these acetaldehydes. Okay. So in terms of prescription medications,

you mentioned benzos and Zed drugs. So some people may know examples like Tamazepam or Zopiclone. These are things that are commonly prescribed by physicians to help their patients sleep. Yeah, and short-term use, of course, as you'll know, can be very useful. Okay. Let's say someone's listening to this and they take Zopiclone each night and it helps them nod off, whatever that means. If you were to put them in a sleep lab, right, and you were to compare what goes on in their brain when they've taken a pharmaceutical

like Zopiclone compared to when they've fallen asleep naturally without that, would you see a difference? You would see a difference, yes. Not a huge difference, but you would see a difference. The problem is that our metrics of sleep using EEG are pretty crude. I mean, think about it. It's a cumulative changes in the brain's electrical activity.

Frankly, it's extraordinary that we can identify any different states of non-REM-123 and REM sleep. So, you will see some subtle differences, but not huge differences. But the use of these drugs is correlated with deficits in cognitive performance the following day. And long-term use has an increase of dementia, right? Absolutely. And in fact, in individuals with dementia, it's not recommended that these drugs are used because it causes excessive daytime sleepiness, and that can be a real problem as well. So I think my position would be, and I'm not a clinician, but on the basis of the papers that I've read, short-term use, yes, yes that's fine let's say a week or so to correct let's say a really difficult time

let's say you're struggling with emotional issues there's been some bereavement in the family then you might want to just have a short-term correct but then either ease out or try and then use the cognitive behavioral therapies for sleep, light exposure, winding down, all those sorts of things that we talked about last time. And they're in lifetime. Just to, I guess, stand up for clinicians for a moment. What often happens is the clinician's desire is to give it as a short-term tool. That's my understanding too. Yeah. But then what you'll often see is a patient found it useful. And then seven days later, when they're there for their repeat consultation, it can be quite a difficult discussion because often, not always, of course, every situation

is unique, but often the patient's like, well, listen, I just, it was so good. It really helped me. I just want it for a bit more. And I think clinicians can, especially if the consultation is time limited. And I've been in many of these tricky consultations before where it's just really hard and a patient can often feel hard done by if you don't re-prescribe it. And then they become anxious and they don't sleep. Yeah, so it is quite complex. Let's talk about magnesium. Magnesium is seen as a natural sleep aid. What happens... Yeah, and the data are emerging which suggests that magnesium may indeed be useful as a sleep aid. It's still not absolutely solid, but there are some studies,

some correlation studies, which have given additional magnesium and there's been a statistical difference, a statistical improvement of sleep. And interestingly, magnesium is thought to act on those GABA receptors in enhancing GABA responsiveness. And of course, anything that reduces anxiety and produces more of a relaxed state can be useful in getting up to sleep. And magnesium, of course, many of us call it the relaxation mineral. And so I have used it effectively with many, many patients when you get that sense from them that, yeah, everything's a bit tight, right? They're wound up, like even the bowel is tight, right? They're constipated.

All these things, you start to build up a picture, oh, maybe magnesium might be helpful. And of course, I don't know if you're familiar with the research on different forms of magnesium or not. Well, I know that depending upon the rates of absorbance can be, so the formulation is quite important as I understand. For sure, because some work particularly well on the guts and can help with constipation. Others are more helpful for sleep. But you're basically saying that, yes, the data seems to support that magnesium, for some people, can be useful. I think that's a very fair statement, yes.

And I have to say, I was suspicious to begin with. And then I looked at the published papers and I became convinced that, yes, I think it's an interesting avenue. So yes, I think magnesium could be very useful under certain circumstances. Yes. Melatonin. Oh, dear. Here we go. All right. What is melatonin? Melatonin is this neurohormone produced from the pineal gland, which is a pea-sized structure right in the middle of the brain. Descartes said the pineal was the source of the soul.

It was the seat of the soul. Because it's one of the only unpaired structures within the brain. Most bits of the brain have a twin, as it were. What's your take on that? Is it the seat of the soul? Well, I think it would be fair to say that the pineal has no soul function. Sorry about that. Not just a scientist, a comedian as well, Russell. So the circadian system and the light-dark cycle regulates via the sympathetic nervous system

the release of melatonin from the pineal. And the release of melatonin from the pineal. And the release of melatonin is confined to the dark period of the light-dark cycle. So, as dusk approaches, melatonin levels will rise. They'll peak at around about four o'clock in the morning, on average, and then they'll decline in anticipation of dawn. So, there's a circadian-driven rhythm in melatonin, and it's modified by the light-dark cycle directly. So if you turn the lights on in the middle of the night, you can acutely suppress melatonin as well. Which is why it's problematic to do so. Let's say you're going to biphasic sleep, you're up at 3am, is that a problem to have bright light exposure? Well, it'll increase alertness, but the alerting effects occur before you change the melatonin.

So it is not the melatonin that is driving those changes in alertness. And so that's the biology of melatonin. Let's discuss its role, where we know it's important. And so that's in seasonally breeding mammals. So, as the day lengths expand and contract for a small mammal, let's say a hamster, then the increasing day lengths trigger the reproductive system and you trigger reproduction. And that's associated and is driven by a decreased profile of melatonin release. Now, for sheep and deer and animals like that, they use the expanding night lengths during the autumn to trigger their reproduction because, of course, they have a long

gestation, which means that they mate and then the offspring are produced the next spring when there's lots of new production. So, the expanding and contracting melatonin profile is a beautiful reflection of the seasons. And that signal is used by seasonal mammals to regulate their reproduction and other processes as well. That's clear. That's beautiful biology, which has been well, well documented. What's it doing in humans? It's often called a sleep hormone, and it is most emphatically not a sleep hormone. So individuals who are on beta blockers, for example, produce very little melatonin. Individuals who are quadriplegic and have severed those connections from the brain into the pineal have poor sleep, but it's no worse than paraplegic individuals

who have that pathway intact. So the evidence suggests that yes, you can have a perfectly reasonable sleep-wake profile in the absence of melatonin. What melatonin does is probably have a mild modulatory effect. The most efficacious study showed that taking three milligrams of melatonin before bedtime could reduce the time it takes to get to sleep by around about 20 minutes or so. So yes, it can have a mild, moderate effect. It won't keep you asleep. So we shouldn't be thinking of it as a sleep home at all. It's a biological marker of the dark.

And it's also probably enhancing the effects of light on the clock. So light comes in, sets the clock, then melatonin is produced at night, and it's reinforcing a light signal. And so it's also been used, for example, in jet lag. So there's some evidence that taking melatonin at local bedtime in the new time zone can speed up the rate at which you can lock on to the new time zone. So it has an effect on the clock. It's having an effect on the clock and it also seems to be having an effect upon the sleep-wake systems, but a mild effect. One area of action which is really

interesting, and we go back to sleep, and we talked about that drop in core body temperature. One idea is that melatonin released at night is actually causing that vasodilation, that expansion of the blood vessels in the hands and the feet and the arms, and promoting that loss of heat. And so that may be one way that melatonin is making it easier to get off to sleep. But it's still, I mean, I'm fairly much persuaded by those data, but we do need a bit more. So a mild modulator of sleep, it is not a sleep hormone. I've also heard melatonin has antioxidant effects. Well, yes, it does.

But it's no more effective than vitamin C. And so, you know, 20 years ago, people were saying, ah, the reason why children are using nightlights, we've seen a doubling of childhood leukemia since the 1950s, is because everybody's turning nightlights on, and that's suppressing melatonin at night and that's taking away an antioxidant and all that. Nonsense, absolute nonsense, because the level of light you get from a nightlight is too low to suppress melatonin. Just to take a quick aside there from melatonin. Children's nightlights, many kids want to

have a light on at night. In your view, should we be careful? Of course, you probably don't want it as bright. You want it as dim as possible. What about different colours, like a red light? I know when my children were young, we put a red light there that seemed to make a pretty marked difference compared to a white light so perhaps you could speak to that yeah i think low levels of light and night light if it's comforting for the child is perfectly fine um and and and these lights are really low i mean the old um night lights would produce one or two lux which is terribly low and is is enough it's a good good illustration that is enough to sort of be aware for the visual system to sort of kind of function

but it's not going to have an effect upon the clock melatonin is often used in pediatric clinics uh for children what's your sort of there's nothing else that's the problem um and melatonin has also been used uh in the case of the blind so if you have no eyes or no functioning eyes, you've lost those specialized cells within the eye that are regulating the clock. You've lost your eyes. Then you're drifting through time constantly. So you're not only visually blind, but you're time blind as well. And so melatonin has been used to try and stabilize the sleep-wake profile. So yeah, been used to try and stabilize the sleep-wake profile. So yeah, we don't have anything else. It's been the only drug. What's your take on the idea that we set the clock through our exposure to light, not just through the eye? Some people say that

you can also set it, or there was some talk in the past, I think, from light on the skin and light in other areas. I believe there was one trial that was then not replicated again. Oh, yes. What's the latest with that? Because some of these myths kind of stick around. Yeah, absolutely. So there was a paper published in Science in about, I think it was 1998,

suggesting that light behind the knee could be used to set the body clock. And this was published, as I say, in leading journal, peer-reviewed, and it could not be replicated by any other lab. And we don't quite know what happened, and I don't want to speculate, but basically the experiment was profoundly flawed. So there is currently no way you can set the clock with light exposure outside the eyes. So in theory, if one could sleep in a room full of lights, but you had an eye mask on that we could measure stopped all light coming into your eyes, in theory, you could have a sound night's sleep.

Well, yeah. I mean, but of course, in theory, we don't have to talk about theory. I mean, if you're given a light-dark cycle and your eyes are covered, you won't entrain to that light-dark cycle. You'll drift through time. So you have to have light exposure via the eye. Now, I'm not saying that there may well be in the future some receptor somewhere. But at the moment, we know that eye loss or covering the eyes means you can't entrain.

I get it. Things may change in the future. And of course, I'm not sure any of us want to wear an eye mask and have a brightly lit room just to try and prove a point. Unless they're in one of your experiments. But it's been done. Yeah. But it has been done. And therefore, would you say... But I should say, I mean, when we were, I remember when we had a grant into one of the funding bodies, and these are the early days, we were looking for these novel receptors within the eye, these non-rod, non-cone, photosensitive retinal ganglion cells.

And I remember the grant went down. It was just blitzed. And one of the comments is, why is Foster looking for a novel receptor in the eye when we know it's behind the knee? So I'm not bitter. But I was completely shocked. know it's behind the knee so i'm not bitter well but but i was completely shocked and it's still there i mean it's it's still it's still in some text yeah and and that i think you know we mentioned humility before in this conversation i think we all need

to adopt a bit of humility in terms of what we know and what we might know in the future, because I remember so well in our first conversation, you basically saying that in 1987, you were at a conference talking about light being one of the main ways to entrain our circadian rhythm, and it was almost laughed off. Oh, well, because I was saying that it's not the visual system. It's not the rods and cones detecting this light. There's something else in the eye. And as I may saying that it's not the visual system, it's not the rods and cones detecting this light, there's something else in the eye.

And as I may have said last time, you know, the comments were, we've been studying the eye for 150 years. Are you seriously telling us, you young pup, that we've missed an entire class of photoreceptor? Of course, I was young, full of vigor. I said, yes, and these are the data. It really does help to be young,

if you want to say something new. Yeah, so we all need a bit of humility about what we may not know yet. Oh, absolutely. are the data. It really does help to be young, if you want to say something new. Yeah, and it's, so we all need a bit of humility about what we may not know yet. Oh, absolutely. That's important. Yeah, and how things might change. But, you know, the data is the data. And what we accumulated was 10 years

of absolutely, you know, solid data showing it's got to be something else in the eye. Just to finish off melatonin, there is a concern often being expressed that if you are taking melatonin long term, it will suppress your body's own natural endogenous production. Is that within your expertise? Do you know much about that? It's not really within my expertise, but I don't think that's likely to be the case. I don't think, I think it would be additive rather than suppressive. Unlike, you know, most other systems

which have a feedback loop and they would turn it off. I think it's because of the way melatonin works is that it's not secreted, it's released. So the pineal is generating melatonin and because it's so lipid permeable, it just spreads, you know, into the brain, into the cerebral spinal fluid and everywhere. So it may well, there may well be a feedback loop, but I'm not aware of it, actually. Something that often affects people as they get older,

it affects their sleep, is the need to pee at night. Oh Oh yeah, I'm so often asked about this. Yeah, so what are your initial thoughts about that? Well, there's a couple of things going on here. One is that as we age, the amplitude, the strength, if you like, of the circadian drive becomes diminished. So sleep-wake cycle becomes less robust. It's a bit more wobbly. But that's also true for the release of many hormones which are under circadian regulation. Can I just pause you there a second, Russell? Do we know that that sleep-wake cycle becomes less robust as we get older, because that's how we're programmed, or because of what we do? Is it environmental? You know, as we get older, are we going out less? Are we getting less of those environmental inputs? Yes. And it's a very

good point because, of course, it may well be that because the circadian response to light diminishes as we age, then light that we could normally drive the circadian system earlier in our lives is not as effective. And so if you increase the amount of light, for example, in the nursing home environment, you can increase the stability of the sleep-wake. And what Asvan Samaran showed is that when you do increase the light in a nursing home, you not only improve sleep, but you can improve cognition in those individuals showing mild dementia. I think that's a really important point, Russell, and one we should just pause on because

whether we have parents in nursing homes or they're living by themselves in the house or whatever it might be, paying attention to light exposure in the day, even if they're not going outside, you're basically saying, put the lights on, get it really bright in the day. That's going to help sleep and cognition. Yes, absolutely. Well, what's interesting is that architects are getting this.

It's really, then they're responding beautifully. So the people designing modern nursing homes and buildings generally are not relying on artificial light to light, but is actually as much as possible letting natural light in. And in fact, there's now an award called the Daylight Award for architects who've actually shown that in their building design,

they've enhanced the exposure to natural light. I love that. It's brilliant. It's fantastic. And I'm on actually the jury to select these prizes. And so I've learned so much about what architects are doing and how they value light. In fact, there's an architect called Ian Ritchie, and he says the first principle of architecture is natural light. Isn't that brilliant? I love that. You can almost retire now and go, my work is done.

That's wonderful, isn't it? Because that actually is such a serious and such an important point. If more and more buildings, work buildings, home buildings, blocks of flats, nursing homes, hospitals, whatever it might be, were designed with natural light at the heart of them, you're probably immediately going to have an improvement in physical health, mental health, cognition, all kinds of things without even having to do anything. So there's a very interesting set of studies done about 20 years ago which looked at different schools and measured the amount of light

that the pupils were being exposed to and then correlated that with grades. And the greater the light in the classroom, the higher the success in terms of grades. I love that. And then I think about all the research on exposure to nature and what that does to lowering cortisol and our wellbeing. And you think, well, you know, when you're in nature, you've been exposed to light, right? So it's hard to pass out what's the difference between looking at a tree in a dark place versus in a in a light uh park let's say but all the data is supporting it's all kind of saying the same thing get outside as much as you can again yes light okay let's go back to peeing at night yes so yes we got deflected there yes as usual so we were talking about the circadian system um and that

the circadian drive the amplitude becomes flatter so that means that the sleep-wake cycle is less robust it's less strongly driven but we also said that of course if you can increase light exposure you can sort of kick it in and you can increase the drive um but but it's still going to diminish to some extent. And that's also true for the hormones that are under circadian regulation. And the hormones regulating urine production are under circadian regulation. Of course, they're high during the day when we're moving around and we want to pee, and they're low at night when we're asleep and we ideally shouldn't pee. And that difference becomes slightly blurred. So, the hormonal drive underlying urine production is not as precise as we age. So, we're more likely to want

to pee at night. The other thing, of course, if we're on antihypertensives, they can also make you want to pee at night more readily. But another thing that is so fascinating, particularly in elderly individuals who are sedentary, you know, they're sitting in a chair all day. And at the end of the day, you look down, there's puffy ankles, swollen lower limbs. And of course, fluid blood has collected in the lower limbs. Now, when you lie flat, that is then reintegrated into the body. That increases blood pressure. The heart detects that increase in blood pressure

and triggers the production of urine. And so, actually, just by lying down after a day of sitting, and you know you're probably slightly hypertensive you can generate a liter of urine so that's why it's so important for the elderly not to sit in day and to move around as they as much as they possibly can to prevent that sort of settling of fluid in the lower limbs yeah it's it's super interesting. I think for many years, we would often put down, particularly in men, if they were having problems,

we would often say, after doing investigations and tests and examinations, that it was down to the prostate getting bigger, something called BPH, benign prostatic hyperplasia. So not cancer, it's a benign mechanism. You can't void as much as you need to. Yeah. And so the pressure of that would cause that urge. I think you're also saying that the sleep, the depth of sleep might be lower as you're older. So you're going to be aware of that more.

That's right. I mean, you might become sort of conscious and then you sense that your bladder's full, and then you go and pee. But it's not necessarily the bladder waking you up. It's just that you have lighter sleep, and then you become more aware that you need to pee. There was a nice paper, I think it was 2018, called Circadian Rhythms in the Kidney. And it was one of the first times I came across this idea that,

you know, I knew about circadian clocks and that every organ system is running on its own clock. And that paper, I think, was saying that for the first 10 hours after waking, that kidneys are filtering fluid at a really rapid rate. then after 10 hours, it goes down dramatically. And when you think about that, and I was actually chatting about this literally a few days ago, a friend of mine, who's I think in the mid fifties, he has to get up at 4am for his work. And he's really struggling with his sleep and getting up multiple times in the night. And he's been to see his doctor. I think all kinds of investigations have been done, but I don't think there's anything that's come up. And I was rereading this paper recently. And so I said to him, hey, listen,

you get up at 4am. So that means if we're to believe that your filtration system in your kidneys is working as per this paper on the circadian system, that actually that means by 2 p.m., right, things are starting to shut down. How much fluid are you drinking after 2 p.m.? Turns out a load of fluids, cups of tea, maybe at the evening meal with his family at about five five thirty he would also go to bed early at seven half seven because he had to be up yep so i said listen you might want to try really being mindful after 2 p.m he goes that early i said well it's worth a try yes i think it's going to make a difference i think you're absolutely right i think it's going to make a massive difference because this the circadian system, right?

Yeah. And of course, we talked about changes in those hormones underpinning urine production, so vasopressin being one. Now, there are synthetic analogues of vasopressin, because I think it's called desmopressin. Is that right? Yeah. And that can be used to actually reduce nighttime peeing as well,

because it's sort of compensating for that drop in amplitude. So yeah, that's one thought. Talking about humility, Russell. Yes. Do you ever think... Don't know where this is going. Do you ever think... This idea that every organ system in the body is running on its own clock,

and we're learning with all this modern science how incredible that is, and how the liver has its own clock, the bladder, the kidneys, all these things have their own clock. To my knowledge, traditional Chinese medicine has been saying this for, I don't know, Chinese medicine has been saying this for, I don't know, two, three thousand years. I find that really fascinating that there was in that culture an understanding and knowing. Of rhythmicity. Of rhythmicity. Yes, yes.

I don't know, do you ever reflect on that? Well, yes, I do. And every time I sort of give a sort of a public talk, somebody says, what about Chinese medicine? Do they? Oh, yeah. People are very sensitive and aware of it. And of course, in the West, we've rather sort of rejected it as being something a bit weird. But they did get the bigger picture that biology follows a rhythm

and that one needs to think about medicines and one's activities that enhance that rhythm. Yeah, it's fascinating. It is absolutely fascinating, yeah. I want to talk about rest for a moment. Oh, yes. It's something I've been thinking a lot about recently, rest. And one of the reasons this has come up for me

is that you talk a lot about sleep. I talk a lot about sleep. And what I would notice for quite a few years now is that some people who are apparently sleeping well are waking up feeling unrested. And in particular, when I dive deep here, what I've noticed is a lot of people these days, they are staying stimulated in the one hour before bed. Whether on a device or anything else, they're staying stimulated, so they're not winding down. And they say, yeah, I sleep fine, but I wake up feeling exhausted. And I found that with those individuals,

when I can help them realize the importance of winding down for an hour, ideally 90 minutes, well, let's say an hour, they're actually having the same amount of sleep, apparently, they're not measuring it or tracking it, but they're waking up feeling refreshed. I don't know if you have any data to support that or you have any thoughts on that.

Yeah, I mean, where we have some interesting data is that during the day, if you could go into a state of quiet restfulness, then you actually do benefit. You do feel more restored and your productivity during the second half of the day can improve. And that's without sleep. That's just with quiet, you know, quiet relaxation. And it helps you sleep at night? And it helps you sleep at night. So, napping is a very interesting issue. So, the agreed sort of metric for napping is 20 minutes,

ideally no longer than 30 minutes, around the middle of the day, can enhance your ability to function later in the day. And that's going into sleep. Longer than that, it can be counterproductive. And of course, the danger for napping is, of course, if it becomes very long, because then, and it's close to bedtime, because then it'll push back the pressure for sleep,

and you'll find it very difficult to get off to sleep. But short naps, fine. And I don't see anything wrong with that on the basis of the data that we know. That quiet relaxation before bed, I think, is really interesting. We know that relaxation will allow you to get to sleep easier. Whether it produces more restful sleep, and what do we mean by restful sleep? And it's essentially restful sleep. And what do we mean by restful sleep? And it's essentially restful sleep is regular sleep. I don't know. And whether the structure of the REM, non-REM cycle is influenced in some way. And maybe if you're waking from REM sleep naturally, you will feel more rested because that's how we naturally wake up. So if you've used that relaxation and it's changed the timing of sleep in some way so

that you then ultimately wake up in REM sleep rather than non-REM sleep, you probably will feel more rested. But we don't have any studies. I've seen it in enough people to know there's something going on. Sort of my clinical acumen tells me there's something going on here and I haven't measured it but I've seen that if you apparently for the same amount of sleep in the same way if you relax for an hour before that compared to being stimulated subjectively at least people are saying oh I feel much more rested I felt that myself yeah there's some also some really interesting stuff emerging on using sound frequencies to induce slow-wave sleep while you're asleep. BMDR? and that has been, there's one or two papers suggesting that your memory formation and problem solving might be enhanced by that, but it's a very tiny effect. Trouble is, it's now,

you know, commercial companies are now jumping on it, saying, all right, you can enhance your sleep, you know, with these sound frequencies, and I don't know how beneficial it will ultimately turn out to be. I guess it comes down to what we've repeated on many occasions. If you use sound therapy and you're waking up feeling better and you answer those questions and subjectively you have more energy, your relationships are better, your patience is better, great. If it isn't and it's making you feel more obsessed about measuring all these metrics, it's possibly not. Yes, yes. I mean, the bottom line is, anything that relaxes you before you go to sleep is going to be good for sleep. And, you know, I was unconvinced by mindfulness when it first started, you know, rumbling around 20 years or so ago.

Were you an Oxford neuroscientist with a healthy dose of skepticism about something called myopornos? In fact, it's worse than that. You talked about arrogance. And I abjectly apologise because the data are now clear that that type of relaxation technique can be very useful for enhancing,

for reducing insomnia in some people. Ideally, before you go to sleep, you know, so it's in that sort of few hours running up to sleep. But yeah, I think it's anything that de-stresses, relaxes towards the second half of the day is going to be helpful. And I think just picking up on the point

you mentioned a few minutes ago, that lunchtime break, you know, I talk a lot about stress thresholds and that we accumulate micro stress doses throughout the day. I call a micro stress dose, a dose of stress, a little dose of stress. In isolation, you can handle just fine. But when they accumulate one after the other, they get you closer and closer to your stress threshold. And what I find these days is that people, they're just accumulating these micro stress doses

continuously they feel pressure I'm not going to take my lunch break I've got too much to do so they're just accumulating accumulating accumulating so in the evening they're just wound up they're past their threshold they can't sleep they need to stay up late to binge watch but a little lunchtime reset a 20 minute walk yes it can just reduce how how much that threshold you know how much that dosage is as it were yeah and connected to that i think it's very interesting that poor sleep is associated with the reduced ability to multitask because what we're having to do is make lots of decisions from a cloud of stuff that we're being exposed to. And so good sleep will actually help with teasing out what's needed to be done

from the massive information that we're being inputted and so reduce, to some extent, that feeling of being overwhelmed during the day. Weighted blankets, do you know much about that? Yeah, I did look into this in the book. And because individuals, parents with children with autism, swear by them. Absolutely. And they absolutely say they're fantastic. Sadly, the data doesn't support that. And so the studies that I've seen, and when I published Lifetime, the data was that it makes no difference. I've looked it up

for other reasons recently. And one of the Royal Colleges, Royal College of Occupational Health, their conclusion also was that weighted blankets have probably little or no effect. have probably little or no effect. So people like them. They feel more relaxed with them, but it's not having a big impact upon sleep. That's the consensus. I mean, I find that slightly awkward because anything that relaxes you and de-stresses you

is probably going to enhance your sleep. So I think it's teasing apart those things. Let me put this to you. You're a very well-respected scientist, right? So you do studies, you assess what works, what doesn't work, and a host of other things. If we just take weight of blankets for a moment, you and I both know plenty of mothers who say

that was game-changing for their child. So in that individual case, it's working. Something's working, right? And then could we say, to play devil's advocate, that sometimes, could we say one of the downsides sometimes to scientific studies which lead to these singular conclusions, and you're the world respected scientist here, not me, right? So I'd love your perspective on this.

Let's say that study had a hundred people in it, right? And let's say 20 kids did improve their sleep, but 20 didn't and 60 you couldn't tell or whatever it might be, when you're then averaging this out to say, does it work or does it not work? Might we sometimes miss out the individuals who do get benefits when we give these broad conclusions? Were you in my home last night? I was not to my knowledge. Because that is exactly the conversation I was having with our youngest daughter, Victoria, who's in second year of medical school. And I was saying that by taking an average, we're losing the variation. And what I want to see is ideally longitudinal studies where you look at individual responses over time to a particular stimulus. And the larger the cohort,

often the averaging loses that variation. And I think that's an incredibly important point because we might be missing those individuals who do respond to that sort of thing by taking an average. And I wouldn't want any mother listening to this who is finding benefit to stop using it. No, no, I completely agree. And if it works for you, use it. There's no downside either, right? Let's look at side effects. There's no downside. And let's not be rude about placebo because, you know, placebo has an effect. If it's a placebo

effect, well, that's fine. It's working. And I think there is, you raise a really important point and something that I find increasingly frustrating is that we take an average and therefore we set that as a standard for everybody. And it's completely wrong. And it goes back to, you must get eight hours of sleep. Well, that's the average, but it ranges between six and ten and a half hours. And so an average can be deeply misleading and very harmful under certain circumstances. It's a guide. It's kind of an indicator, but it shouldn't be used as a metric for everybody.

Russell, you know how much I love your work. You know how much I love your book, Lifetime. It was published two years ago. If you were publishing it today, what would you add to it? Well, I think there's been progress in the past two years, almost in every field. And so our understanding of fundamental mechanisms, and it's not a mechanisms heavy book. It's more of sort of, you know, consequences. But I'd like to have a bit more mechanisms because it's turned out to be so fascinating. It's very well written. And one thing I really enjoy about it is I think you have a certain style as a writer, you bring a lot of historical perspective, a bit of humour

that you've, you know, you've touched a bit on in this conversation today. I think that really adds to it that there is the science in there, but there's also some really nice human stories. Thank you. Well, and I didn't have the courage to do that originally. I mean, I threw in an anecdote and Tom Killingbeck, who was my editor at the time, said, oh, that's great. Don't be afraid. And so it was like a champagne cork going off. I could then add in all these sorts of things I'd love to add in. And people have said that it's very much helped. Just the equip has helped them sort of get through some of the tougher bits of the science was there not a bit about the song yesterday being oh maybe tell the story yesterday well i mean it's incredible we're talking about you know the importance of sleep and and actually

coming up with novel solutions to complex problems and you, what our grandparents said was sleep on it. And there are loads of anecdotal examples whereby people have slept on an issue. And so, Paul McCartney woke with the entire song, as I understand it, of yesterday formed in his brain. His brain had been ticking over and constructing. I think it's right. The chap that worked out that the benzene molecule is a ring. He had a dream about a snake biting his tail. So he woke up and thought, ah, it's a ring structure. That's how the carbon atoms are organized. And I think we all have had those sorts of anecdotal experiences. Oh, gosh, yes, that's what I need to do.

I love it. Yeah. It's a great illustration. Our grandparents knew. Our grandparents, as always, tended to know. gosh yes that's that's what i need to do i love it yeah it's a great illustration our grandparents knew our grandparents as as always tended to know to finish off our conversation russell we've covered so much in our first one and in this one there's plenty more in the book that we've not spoken about for people who want to dive deeper just Just to finish off though, the importance of sleep, I would say has grown significantly

in the public sphere over the last 10 years or so. There's much more awareness now that sleep is really important. Are there any downsides to raising awareness of sleep? Yes, I think there are. I mean, I think if we raise awareness without providing the educational underpinning, we can generate anxiety. And you do have a condition now called sleep anxiety,

because people are now bombarded with conflicting advice. The six hours, the waking up in the middle of the night, what you should and what you shouldn't do, whether you should wear an app, and all of the other sorts of things. And I think what we must do is embed knowledge about sleep and circadian biology within our curriculum. Let's get our young people understanding the value of sleep and have that voice that's authoritative. And I think that would be really useful. And I've sort of argued that what we need is perhaps the government should sponsor an authoritative website

where different questions are addressed about sleep and circadian rhythms. And it's not simply a, you know, melatonin as a sleep hormone, you know, all these sorts of shorthands, which are confusing people. If I take melatonin, I'm going to sleep. Well, no, you're not necessarily. Yeah. Thank you. And I want to make sure we did cover this in the first conversation. Shift workers, we did a deep dive on that in conversation one. We, you know, we recognize that it can't be easy to hear all this if you are a shift worker. Also, we covered young parents who often get really anxious when they hear about some of the consequences of poor sleep. And what we said in the first

conversation, what you said was, don't be afraid to ask for help if you're feeling tired. Get a friend around whilst you have a nap, you know, recognize that it's hard and don't worry too much no and get that structure in place i mean you know as we've shifted from the extended family to the nuclear family you know we've got to reach out to our friends and family to get that additional support we did not evolve without that support you know a single you know a mother on her own is would have hoped to do that support. So we must, and get rid of the guilt. And final words, Russell, for someone who feels inspired by what they've heard and is thinking, you know what?

I've not given sleep enough of a priority. I've heard some new things today. I'm going to go and try and get it sorted in my own life. What are your final words of wisdom for them? Well, I think that everybody thinks that sleep is what you get rather than having any control over it. And so I think understanding that the quality of our sleep defines the quality of our wake, but it's an incredibly dynamic and flexible behavior. We just need to find the ways that work for us and then embrace it. It shouldn't be too difficult. And so that was the key message in Lifetime, which is that,

you know, we have control to a greater extent than we think over our sleep by using simple modifications of behavior. Russell, you have been doing incredible work all throughout your career. It's helping individuals. It's helping wider society. Thank you for coming back on the show. Thank you so much. It's been a great privilege. Really hope you enjoyed that conversation. Do think about one thing that you can take away and apply into your own life. And also have a think about one thing from this conversation that you can teach to somebody else. Remember, when you teach someone, it not only helps them, it also helps you learn and retain the information. Now, before you go, just wanted to let you know about Friday Five. It's my free weekly email containing five simple ideas to improve your health and

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