Dr Michael Mosley on the importance of sleep
Read the full transcript of our Science Focus Podcast interview with Dr Michael Mosley on sleep – listen to the full episode at the bottom of the page.
Amy Barrett: Tell me about your new book, Fast Asleep
Michael Mosley: Sure. So, the book is about sleep. It's about how we know what we know now. The stages of sleep. And then critically, it's about how you actually improve the quality of your sleep. And they're being quite good books out there already, looking at the science of sleep.
But very few which have addressed the question of how you can actually improve your sleep. And unfortunately, a lot of the standard advice is pretty ineffective. I have to say, it's either unbelievably obvious or it doesn't work.
And that's really why I wanted to write the book, because I have been an insomniac for some time and I've managed to, broadly speaking, sort it out. So I kind of wanted to share what I knew with other people.
AB: Why do we need sleep? Why is it so important?
MM: Well, see, it is critical for your mental and your physical health. And there are different stages of sleep. So there is deep sleep, which happens in the early hours of the night or the morning. And then there's REM sleep, rapid eye movements, sleep during deep sleep. We know that you release all sorts of things like hormones.
So an important stage of repair. It is also really important for your immune system because all sorts of components of your immune system, such as cytokines and antibodies, are created during deep sleep. And we know if you don't get enough to eat, sleep, then you are much more vulnerable to bowel infections. Which makes this particularly important now.
And indeed, there are channels in your brain which open up and literally wash out the brain. This is a system called the Glimphatic System, which was only recently discovered. And if you don't get enough deep sleep, that puts you at greater risk of things like dementia.
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Plus, during deep sleep, a lot of memories are consolidated. Moved from a sort of short term into the long term. So that's critical and rapid eye movement sleep, REM sleep where you lie there and your eyes flicker crazily. That is actually linked with vivid dreams. And it seems to be important for your psychological health that it's while you're having these intense dreams, that you are processing a lot of the emotional things that go on during the day. And so if you don't get enough REM sleep, you tend to feel irritable.
REM sleep is also very important for shifting memories around. So those are the two main components. But there are lots of other things. Obesity, diabetes. I could go on for a long time about the list of things and the reasons why you might want to make sure you're getting a decent night's sleep.
AB: So how long should we be sleeping?
MM: Hugely variable, depending very much on your age. So, as a baby, you'll be sleeping 14 hours a day. When you're a teenager, you probably need at least nine hours, eight to nine hours. You often don't get it. And when you're an adult, it's probably somewhere in the region of seven hours.
And there's a sort of myth that as you get older, you need less sleep. In fact, you need just as much. You just don't get it. And so that's kind of one of the things I write about as well. And there are some people who can get by on very short periods of sleep. They call them sleep mutants, their own family. They found recently, which have a particular genetic profile and they get by quite comfortably on four to five hours. But most people can't. It's very much a sort of bell shaped curve.
And the evidence is pretty strong that broadly speaking, we need around seven hours. But again, one of the things I address in the book is a concept known as sleep efficiency, because people tend to think ‘I go to bed at eleven, I get up at seven. That's eight hours sleep. In fact, you're probably awake for about an hour of that time. So you're only actually getting six hours and the evidence is pretty strong that the benefits come from having a good sleep efficiency, which means somewhere around 80 to 85 percent of the time in bed you should be asleep and not just kind of lying there worrying about sleep or other things all your life or whatever is keeping you awake.
AB: You’ve written in your book about going to bed and we shouldn't stay in bed if we're struggling to sleep. What should we do if we're lying in bed, staring at the ceiling, wishing we could get to sleep, but not being able to?
MM: Yes so one of the problems about reading about books, is you start worrying how much sleep you're getting and that keeps you awake. So the advice from the psychologists is that what you absolutely need to do is associate sleep in bed with sleep and sex and nothing else.
And the problem is that once you get into a bad pattern where you're looking at your smartphone or you're watching telly or you are simply awake worrying, then you've broken that link between sleep and bed and you have to reassert it. So the advice is, broadly speaking, that if you wake up in the middle of the night, 3:00 AM, which is the classic form of insomnia, then after about 10 or 15 minutes, you kind of and you feel you're not going to drift off, then you should get out of bed. You find a sort of nice warm space, which you set up earlier with some really boring books or perhaps some music with the sort of rhythm of about 60 or 70 beats a minute. Jazz seems to be particularly good. And you can just sit there and chill out until you feel relaxed and you feel sleepy and then you go back to bed. This seems to be a very effective way. And just lying there, worrying about it and worrying about how bad you're going to feel the next morning is one of the worst things you can do.
AB: It's hard to keep those boundaries, especially now, isn't it? I am in a flat where there's only of a few rooms, one them being the bedroom, it's hard to kind of keep that as separate. Just for sleeping.
MM: It is. It's very hard indeed. I'm fortunate at the moment that I have a house where I can find the space. I sometimes when I'm travelling and if I'm travelling with my wife and we're in a hotel room, I'll go into the bathroom and just kind of hide under the floor in the bathroom with a pillow. Not comfortable, I have to say. But that's one way of coping.
But I do appreciate it is tricky. But it does seem to be very effective. There is another approach to it which some people try. I personally find it quite challenging, which is called accepted theory. And I write a bit about that. And that's what you kind of just learn to accept the fact your weight, you challenge the thoughts you are having.
So if you're thinking, gosh, I'm awake again, I'm gonna feel terrible tomorrow and this all thoughts give me a fine. I generally find I go back to sleep again and there is also some breathing exercises you can practise. One of them that I like is called four-two-four. And what you do there is you breathe in through your nose to a count of four. Hold it for two and then out again through your mouth to a count of four.
In. Hold it and then out. Then you just do that for a minute or two. And what you'll find is your heart rate will drop and the drop in the heart rate is one that triggers for sleep. It's very kind of calming. It's best to practise it during the day as well. Any time you feel stressed that these sort of breathing exercises are unbelievably effective and they just kind of distract you as well. And another approach is to do something like mindfulness meditation. And I try to do that during the day. Again, some people find that's brilliant at nighttime. They just kind of start listening to their breath.
But it's tricky if you haven't already got into the habit of just taking up something in the middle of the night is never a good idea. It used to be something that you've already kind of incorporated into your life. Mindfulness is very effective as well.
AB: I for one know that I've been spending a lot more time in my bed, now because of the lockdown, than I ever was before. Is that going to be causing me some sleep problems?
MM: Have you been having sleep problems?
AB: I mean, I think everybody I've spoken to has sleep problems. It's just a difficult time to know what causes them.
MM: Absolutely. And it's obviously about stress and things like that. But it is also about the breakdown of routine. And as you said, spending a lot more time in your bedroom. Now you can try and allocate bits of your bedroom to different tasks.
So you have a bit of the bedroom where perhaps you work or you do whatever you do, and then the bed, the right side of the bed, whatever, to the bed. Where do you sleep, though? You do not take your laptop to bed with you. You do not take your phone to bed with you. The only things, maybe a boring book which you read and that's kind of it to one part of the bedroom is work, play, other stuff. And the other side is this is where I sleep.
It's really about establishing habits. That is hugely important. And beyond that, another component which is not widely recognised is the importance of the impact of food on sleep. And I write quite a bit about that because there's been a lot of research which emerge on the way the eating a Mediterranean style diet and the benefits that has in terms of inducing more deep sleep than what you eat really does have a big impact.
And it's partly because of its effect on mood, but also because of its effect on the microbiome, on the, you know, the microbes that live in your gut. And they in turn, if you feed them right, seemed to produce sort of sleep inducing chemicals. So it's about what you eat. It's badly team and it's bad a number of other things as well.
AB: So what should we be eating then to help us sleep better, especially during this time?
MM: Lots of fibre. Fibre seems to be particularly good for your microbiome. I bang on about the Mediterranean diet because it has so many benefits. There's a lot of research now showing that Mediterranean diet.
One of the ways it seems to be beneficial is because it also feeds your microbiome. It's rich in fibre to the Mediterranean diet. I'm talking about is one which is oily fish, not legumes, plenty of veg and things like that. And a glass of red wine in the evening, but preferably not much more than that. And olive oil seems to be a key component as well.
And if you have all these things, then that seems to be a broadly antiinflammatory diet. And that means there's mounting evidence that depression, anxiety, or at least in part induced by inflammation in the brain. And so antiinflammatory diet seems to be good at reducing your risk of all sorts of things heart disease, cancer, diabetes, but also sleeplessness. And that seems to be really important.
So if you can kind of shift into that sort of got more nuts and more olive oil, more bleeding humans, then that seems to be a really good way to go in terms of sleep, but also all the other things, because one of the other critical things for a good night's sleep is to ensure that you are relatively slim because unfortunately, obesity is linked with lots of fat random neck and around the gut. And that leads to snoring. It leads to sleep apnoea. And again, a Mediterranean diet, particularly a kind of calorie controlled one, seems to be a good way of reducing central obesity. And that's one of the other things I bang on a lot in this book and other books. But I do think it's a very important message.
AB: Jason has picked up on your routine of getting up every single day at seven a.m. He says does a weekend lie-in help? Can he keep his weekend lie-ins?
MM: Unfortunately, weekend lie-ins, although lovely, are probably not terribly good. It's almost like jet lag because if you get up a couple of hours late to say three hours later, then that would be the equivalent, say, of travelling to Athens for the weekend.
And your body really doesn't like jet lag. So it feels quite good at the time. But unfortunately, when you come to Sunday evening, if you've been getting up on Saturday and Sunday morning at 10 a.m. rather than seven a.m., then it means you're going to struggle to sleep that night. It's probably fine when you're young, you're much more adaptable. But unfortunately, when people get older, that's when they need routine more than ever. So I'm afraid the line is for most of us, it's not a great idea.
AB: David Hawkins has noticed that during the lockdown, most of us are having sleep issues, why do you think that is?
MM: I think it's in part because we've broken with our routine, a lot of people are not going into work. And that means they are sort of lying in there possibly watching boxset late at night and eating junk food. And we know the impact to diet of what you eat on your gut, on your microbiome, on your weight, on your weight and on your sleep is very profound.
So I think it's largely a product of that, the fact the routines have been broken and also that people are obviously much more anxious. And there's a study out from the Institute of Fiscal Studies today showing that racial anxiety have shot up during lockdown. And that's not surprising. But it just means you're going to have to kind of prioritise routine.
Be very mindful of what you're eating. And this might be a good moment also to take up mindfulness. There are lots of apps out there, but that would be one way of coping with stress, because these are undoubtedly difficult times when you're sleepless. That unfortunately adds to all the other stuff.
Lack of sleep, poor quality sleep means you're going to feel less like exercise, more like eating junk food, and you're going to stop snoring a lot because when you pile on, you know, the weight around your neck, that's when you start to really, really snore. So this is the moment to try and take your health into your hands. And yeah, good luck is difficult.
AB: It's a vicious cycle sometimes, isn't it? I mean, Ali and Emily – Emily comments about dreams making them more tired, but the more tired you are, the more stressed you are, so perhaps the less good sleep you're getting.
MM: Yes, and it's interesting that there have been a number of websites recently which are dedicated, in fact, to asking people to kind of describe their dreams and some of the dreams are helpful. Some are not. I came across one the other day where somebody was dreaming about sort of a writhing snake, which this rabbit leapt on and devoured. And he interpreted that as being COVID-19 being eaten by a white rabbit. I’m not sure of the meaning.
But I think the thing about dreams is we are certainly reporting more vivid ones. But that is at least in part because people are lying in more. When you're being woken, you know, abruptly by the alarm clock, you're less likely to recall your dreams. So the fact that you're recalling your dreams is probably as much a product of the fact that you're having a lion as anything else. I don't think the dreams themselves are likely to be making me feel more tired. I just had it just a by-product of the fact that your life is now disrupted.
AB: And you were talking about deep sleep and REM sleep. Is it that we dream in REM sleep only?
MM: You dream in both REM sleep and a deep sleep. But in REM sleep, it seems to be particularly intense. And REM sleep is weird. If you've never seen anybody, then kind of google it or watch your partner do it or your child do it. It's very, very strange. You see these eyes, the flickering to and fro. And the thing we know about REM sleep is that during it you are totally paralysed. Apart from your eyes and your breathing. And that seems to be because during REM sleep you have these intense primps.
If you weren't paralysed, you'd be thrashing around the place and jump out of bed and sort of hitting your partner or things like that. So it's seems to be a really important part of sleep for humans. And and as you said, you do sleep as well. You do have dreams during deep sleep, but not as intense. And the intensity seems to be a big part of the way in which you kind of process the emotions of the day.
Because we know during REM sleep you also don't produce anything like the same levels of adrenaline. I mean, my personal dream I have over and over again is the one where I'm kind of running to catch a ride. It's a sort of aspiration dream as much as anything else. I'm either being chased or I'm chasing something. I never quite catching it. One I had last night with a suitcase and pack it to go on holiday. But every time I put on me and it falls out, then I just I know the is going to go and it's fairly obvious interpretation of its frustration that it kind of killing him did. I want to go to holiday. So whether that is actually helping me process or not. But there are like seven classic games you can have, and that is one of the most common ones that either chase or being chased.
AB: And Katasina has asked what's the best percentage of REM and deep sleep during the night?
MM: Broadly speaking, demand to REM sleep you get is on average something like 17 to 20 per cent. Your only way of really telling is to have a sleep activity monitor. And I recently got hold of one because it got a lot better. Do you if you're going to get one, get one that also measures your heart rate, because one of the things that happens when you're falling asleep is your heart rate goes right down. That's kind of the thing that puts you to sleep.
It's also a reason why you really don't want to be doing exercise very close to bed because your heart rate's up to one of the triggers for sleep is the heart rate dropping, breathing, exercise, reduce your heart rate. That's another reason why they help you fall asleep. But the other thing about your heart rate and stuff like that is with the activity monitors is during REM sleep. Your heart rate shoots up, though, although you are paralysed, although you appear to be in deep sleep, your heart rate is actually racing. These are things that the activity monitor measure. So based on that and there are a number of them, I use a Fitbit.
Broadly speaking, REM sleep occupies something like 17 percent of the sleep and deep sleep, anywhere between eight and 20 percent. And the rest of it is kind of like sleep. And it's kind of interesting looking at the stats, though, as you get older, the amount of deep sleep you have kind of drops off. It's broadly around an hour when you're in your teens and then it falls to much less as you get older and deep.
Sleep onset tends to be particularly refreshing optically for the older brain and changing what you eat. The fibre seems to be a good way of inducing deep sleep. There've been a number of smaller studies which have shown broadly that eating the sugary carby stuff is very bad , whereas eating fibre-rich foods is good. So it's it's the likes of legumes and stuff like that. You should be eating certainly at nighttime rather than perhaps the milky drink.
AB: Don't eat cheese before bed either.
MM: There are a number of myths, and I have to say cheese. The idea of cheese gives you nightmares seems to be one of them. They actually did a study at the University of Surrey some years ago, which they got 200 people to keep a record of their dreams. And then they had to eat cheese every night for a month.
And they found there was no correlation whatsoever between the massive sheets they're reading when they eat it and their dreams. But no, I don't think cheese eaten just before you go to bed is a great idea, mainly because your body is switched off the night your gut wants to go to bed.
It's kind of like a busy restaurant. You come in and you shove food down and then your digestive system has to crank up. That will raise your blood pressure, will raise your heart rate kind of just at the time when you want to go to sleep. So certainly a heavy meal eating late at night is a really bad idea. Small nibble of cheese. I suspect it's going to make one a lot of difference one way or the other, and particularly nice smelly cheese. But then you're gonna be shoving a few probiotics down there as well.
AB: And how can you tell if you’re getting good quality sleep?
MM: I think the most reliable indicator of whether you're getting good quality sleep is do you feel terrible when you wake up or not, that there isn't actually a formal test you can do, which is what you do is you go to bed in the afternoon with a quiet sign at the door and you set your alarm for 15 minutes and then you close your eyes.
And the question is, do you fall asleep before the alarm goes off? If you do, then this suggest you are sleep deprived because falling asleep quickly is not actually a terribly good sign. It's a sign that you're actually very sleepy. And if you fall asleep within ten minutes, that means you are seriously sleep deprived. 50 minutes you have a problem within 20 minutes is fine.
There's actually a version of this test which was originally developed by sleep researchers at the University of Pittsburgh, which is quite entertaining, where you get a metal spoon again, you kind of look at your watch, you put a metal tray by the bed, you hang your hand over the side of the bed and close your eyes.
The idea is when you fall asleep, the spoon falls out of your hand. It hits the metal tray, it goes clang, and you wake up and you look at your watch and see how long it's taken. I think that's that I've done it is quite entertaining, but I think just setting your alarm is probably simpler. And obviously, if you're falling asleep during the day, if you're falling asleep, sitting on the sofa, if you're falling asleep in the cinema. Well, we don't go to cinema anymore. But falling asleep during the day is an indication that you are sleep deprived.
AB: Alice has noticed that there are some dreams that are common to all of us. You know, running for a train, flying, your teeth falling out. Why is that? Why is it some people have similar dreams?
MM: Not sure. There are seven archetypal dreams, which everyone has in variants and they are the ones you've described. One of the most common is one that I described, which is the one we are racing to catch something you the frustration dream. Another is falling. I've had quite a few of those. You're clinging to the cliff edge and then you fall. Being naked in the public place. That's common when you teach full and should probably tend to be linked to a fear of ageing.
And they're all variants on anxiety dreams. Why we have these particular seven. I'm not entirely sure. I imagined. Probably a cultural thing, I don't know whether people in other parts of world had the same one again, another common one is going into an exam and being completely unprepared. You have read, you haven't revised, you haven't done anything. I don't know if that continues. That is a very common one.
But whether it is a culturally specific one or not, I don't know. And then beyond that, there are lots and lots crazy dreams. And obviously, Freud and Young made a big thing about, well, young in particular, about archetypal dreams. But statistically speaking, the seven I described are the communist, and they're all variants on anxiety dreams.
AB: Natasha has asked about teenagers who sleep in shifts and seem to be more nocturnal, should they be encouraged out of that?
MM: OK. So it's a reality. The truth is that when you're a teenager, you time shift so that most of us… There are larks and owls. So I am a lark. I like to get up early and I like go to bed late, early as well. About eleven o'clock.
Owls, typically they tend to go to bed late. Get up late. And you are as a teenager, you shift by about two hours. And there is a biological explanation for this, which is that Mother Nature, if you like, wants you to separate from the rest of the clan. You're having to learn to be independent as a teenager. And one way you learn to do that is by hanging around with your peers. And one way you do that is by staying up late at night. So you're with them. You're gang. You learn skills. You do things like that. Plus, it is hugely useful for the tribe that some people are awake late at night in case there are predators threat. So all of these are actually powerful biological reasons why teenagers time shift.
So I'm a big fan of trying to shift the time at which teenagers have to go to school later, because I think it would fit in with their chronobiology better, and there have been studies in the States which have shown a remarkable impact to them starting the school day just 40 minutes later.
But having said that, I would try to coach your teenagers to at least get up by nine or ten. Not necessarily 7:00 a.m.. Have some sympathy, but it would be reasonable for them to have a pattern and for that pattern to include 9am.
AB: Emily has said that her dad always falls asleep to Radio Four. Does the continued noise, once you've fallen asleep, actually affect the sleep quality?
MM: Yeah, I suspect he is probably sleep deprived. Obviously, my dad used to do that and until I lost some weight, I did it as well. My dad used to fall asleep, you know, in cinema theatre, at the dining, you know, during dinner, sometimes pretty much. And if he ever sat down hosing down the sofa, he would fall bang like that, though, I suspect has less to do with radio for more to do with the fact. He's probably quite sleep deprived. I don't know anything about her dad, but I would wonder if perhaps you've got a little bit of a bigger waste going on.
Sleep apnoea is one of the communist codes declared men for disrupted sleep. It's like snoring. But even worse, you kind of get. And then you stop breathing for periods of time and very, very common, massively underdiagnosed. They know, particularly with fire officers, police officers, around a third of them suffer from sleep back there.
And indeed, it is the leading cause of death in people who do particularly shift weight because they're eating unhealthily. They put on the weight and then they have the same sleep apnoea where they stop breathing.
It is immensely curable. You just need to lose weight. If you can lose around five, six kilos, then that will have a major, major impact on the quality of your sleep and on your breathing. Beyond that, there are things like sepak machines. But going back to the original question, I think once you are asleep and the soothing sound of Radio Four has put you to sleep, and to be honest, it doesn't really matter what's going on as long as they know nobody's shouting or doing something disruptive.
There's quite a lot of research into different types of noise, pink noise, white noise, black noise. I go into that as well. And these are different types of noise. So for some people, it's the sound of sort of tinkling waters. Others, it's more there's a more sort of coming and going noise. She's known as pink noise. What seems to be quite effective is more sort of natural noise and others you've just kind of blocking out almost there. So it's worth kind of exploring different types of noise. But I'm not sure Radio Four is any worse or better, nothing else.
AB: For a while I was setting up my phone so it would play music or ocean sounds to get to sleep. But then I’ve been using my phone while I’m in bed. Is that a problem? Because I’ve read things about blue light. Is it a problem to be looking at my phone while I’m in bed?
MM: Well, I think the blue light thing, certainly, as far as phones are concerned, is a myth. Your phone is not going to be emitting anything like enough blue light to wake you up or keep you awake unless it’s really intense.
I think it’s mainly a marketing device so people could sell devices to filter out blue light.
So I think that is a top myth. The thing that mainly is a problem with phones and laptops and stuff like that is not the light, it’s the distraction. The whole point of social media is to grab your attention.
My daughter, for example, who’s 20, when she’s on social media she’s doomed. So she has to leave her phone outside the room, otherwise, when she’s watching something, it doesn’t stop. Once she’s started following something, it just doesn’t stop.
That’s exactly how these things are designed to hook you up, keep you addicted, keep you going. It’s nothing really to do with the light, much more to do with the addictive nature of the material. So if you’ve got it there and if you can ignore your emails and stuff like that, you’re just listening to sound, then that is not a problem.
The risk is that, if it is within hand’s reach, you’ll think, ‘oh, I must just check out the latest on COVID-19’ or whatever it might be. And before you know it, the hours have gone by.
You’ll be delighted to know, of course, that Fast Asleep is available as an audiobook. I’m sure that will put you to sleep.
AB: Is it narrated by you?
MM: It is narrated by me, indeed. My dulcet tones will be very soothing and calming. Sleep, sleep, sleep. Yeah.
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