Sleep: Dr Michael Mosley on what it is, why we need it and how to get more

In June 2020, Dr Michael Mosley joined Science Focus Book Club on Facebook for an online Q&A about his recent book, Fast Asleep (£9.99, Short Books). He gave his tips for good sleep and health, as well as answering your questions about coronavirus.

You can watch a preview of the interview below and in full on Facebook, or read on for the highlights.

This month, the book club is reading Angela Saini'sSuperior, so make sure to sign up to the newsletter below to join in or find out more here. Head to the BBC Science Focus magazine Facebook page to send in your questions for Angela ahead of our Q&A event with her 12:00 BST, Thursday 2 July.

Why did you decide to write Fast Asleep?

There have been some quite good books out there already, looking at the science of sleep. But very few have addressed the question of how you can actually improve your sleep.

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 wanted to share what I knew with other people.

Why do we need sleep?

It turns out that sleep is absolutely critical for your mental and your physical health, and also your immune system, which is particularly important now, during the coronavirus pandemic.

We know there are different phases of sleep. There is deep sleep, and during deep sleep, for example, an awful lot of repair goes on, your body produces growth hormone and other things. All sorts of components of your immune system, such as cytokines and antibodies, are also created during deep sleep.

We know that if you don't get enough sleep, it makes you much more vulnerable to infections.

In deep sleep you actually get brainwashing going on. There is a system only recently discovered, called the glymphatic system, which literally opens up during the night, during deep sleep, and fluid wishes and washes through your brain and clears out the gunk.

Plus, during deep sleep, a lot of memories are consolidated and moved from short term into the long term.

If you don't get enough deep sleep, that puts you at increased risk of things like dementia.

And then there's another component of sleep, which is REM sleep, rapid eye movement sleep. That is associated particularly with intense dreams. And it turns out that dreaming is very therapeutic.

Read more about dreaming:

It's this weird stage, REM, where you are sort of paralysed, where you're having these sort of intense reenactments of the day where a lot of emotional processing goes on.

If you don't get enough REM sleep, you feel perfectly grouchy and out of sorts. And again, a lot of people reporting some pretty weird dreams during these COVID times. So those are just some of the things that a good night's sleep does for you.

How much sleep do we actually need?

It’s hugely variable, depending on your age. So when you're a baby, you probably need more like 14 to 15 hours a day – you get a lot of sleep. And then as a teenager, they probably need around nine to 10 hours, but get an awful lot less. When you're an adult, it's probably somewhere in the region of seven hours.

And there is a myth that as you get older, you need less sleep. In fact, you need just as much, but you just don't get it.

There are some people who can get by on very short periods of sleep. They call them ‘sleep mutants’. There is a family they found recently, who have a particular genetic profile and they get by quite comfortably on four to five hours. But most people can't. The evidence is pretty strong that broadly speaking, we need around seven hours.

In the book, I talk about sleep efficiency, because people talk about sleep by which they generally mean the time they spent in bed, because one of the ways you work out how much sleep you're getting, is you say, "I went to bed eleven o'clock. I got up at seven o'clock. I had eight hours sleep."

In fact, for a considerable chunk of that, you're probably awake. So maybe 10 or 15 per cent of that time, maybe an hour, sometimes more. You're actually awake.

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What's really important is this concept of sleep efficiency, which is a measure of the amount of time you spend in bed asleep as opposed to in bed. Because the classic sign of an insomniac is they are in bed, but they're awake, and they’re worrying about stuff. And sleep deficiency is linked to all sorts of mental health issues as well.

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?

Yes, well that’s one of the problems about reading books about sleep is you start worrying about how much sleep you're getting and that keeps you awake.

The advice from psychologists is that what you absolutely need to do is associate bed with sleep and sex and nothing else. 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, 3am, which is the classic form of insomnia, and you feel you're not going to drift off, then after about 10 or 15 minutes you should get out of bed.

You should find a nice warm space, which you set up earlier with some really boring books or perhaps some music with a rhythm of about 60 or 70 beats a minute. Jazz seems to be particularly good. And you 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. 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.

It's hard to keep those boundaries, especially now, isn't it?

It is. It's very hard indeed. I'm fortunate at the moment that I have a house where I can find the space.

Recent research has shown that eating a Mediterranean-style diet – oily fish, nuts, legumes and plenty of veg – can induce more deep sleep, says Mosley © Getty Images

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 lie down on 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.

Teenagers’ sleep patterns seem to be more nocturnal. Should they be encouraged out of that?

It's a reality. The truth is that when you're a teenager, your waking time shifts by about two hours. 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. Plus, it is hugely useful for the tribe that some people are awake late at night in case there are predators around.

All of these are actually powerful biological reasons why teenagers time shift. I'm a big fan of shifting the time at which teenagers have to go to school to later, because I think it would fit in with their chronobiology better, and there have been studies particularly in the states which have shown a remarkable impact to them starting the school day just 40 minutes later.

Read more about teenagers:

But having said that, I would try to encourage your teenagers to at least get up by 9am or 10am. Not necessarily 7 a.m., have some sympathy, but it would be reasonable for them to have a pattern and for that pattern to include 9am starts.

So how can I improve my sleep efficiency?

Well, there are lots of things, and that's kind of why I wrote the book.

The main thing you can do is to keep to a sleep window. That means waking up at the same time every day, 7am, 7:30am, whatever the time is, and try to stick to that time rigorously.

When I get out of bed, I open the curtains and I get a good old dose of light because we know that's really important for resetting the internal clock.

When it comes to meals, meals seem to be quite important, particularly towards the end of the day. You should try to avoid eating within about three hours of bedtime. You need to have good wind-down routine.

Some people like to have a nap. But I don't because I find that reduces my sleep drive. So when I go to bed, I want to make sure that I'm going to go to sleep pretty fast.

Beyond that, if you wake up in the middle of night, there are also some breathing exercises you can practise. One of them that I like is called four, two, four.

Unfortunately, weekend lie-ins, although lovely, are probably not terribly good. It's almost like jet lag. If you get up say three hours later, then that would be the equivalent of travelling to Athens for the weekend

What you do there is you breathe in through your nose to a count of four. Hold it for two and then out again for your mouth to the count of four. You just do that for a minute or two.

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. These sort of breathing exercises are unbelievably effective and they just kind of distract you as well.

There is another approach to it which some people try, though I personally find it quite challenging, which is called acceptance theory. And I write a bit about that. And that's what you kind of just learn to accept the fact you’re awake, you challenge the thoughts you are having, so if you're thinking, gosh, I'm awake again, I'm gonna feel terrible tomorrow and those sort of thoughts, but then think, “okay, it’s fine”, you’ll generally find you go back to sleep again.

Another approach is to do something like meditation. I try to do that during the day, but again, some people find that's brilliant at nighttime.

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 ought to be something that you've already kind of incorporated into your life. Mindfulness is very effective as well.

More on meditation and mindfulness:

Because of the lockdown we may be spending more time in our homes and bedrooms, not sleeping, than ever was before. Is that causing sleep problems?

Have you been having sleep problems? It can be 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 to 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 is the bit where you sleep. You do not take your laptop to bed with you. You do not take your phone to bed with you.

The only thing is maybe a boring book which you read and that's kind of it. So 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.

Beyond that, another component, which is not widely recognised, is the importance of the impact of food on sleep. I write quite a bit about that because there's been a lot of research which has recently emerged on the way that eating a Mediterranean style diet has benefits in terms of inducing more deep sleep.

What you eat really does have a big impact, 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 about routine and it's a number of other things as well.

So what should we be eating to help us sleep better?

A lot 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 seems to be beneficial because it also feeds your microbiome.

What is the Mediterranean diet?

The Mediterranean diet I'm talking about is one which is oily fish, nuts, legumes, plenty of veg and things like that. Maybe a glass of red wine in the evening, but preferably not much more than that. Olive oil seems to be a key component as well.

If you have all these things, then that seems to be a broadly anti-inflammatory diet. And there's mounting evidence that depression, anxiety, are at least in part induced by inflammation in the brain, and so an anti-inflammatory diet seems to be good at reducing your risk of all sorts of things heart disease, cancer, diabetes, but also sleeplessness.

So if you can kind of shift into that sort of diet, then that seems to be a really good way to go in terms of sleep, but also all the other things.

The worry about the impact of blue light from a mobile phone is a myth, says Mosley. It's much more to do with the addictive nature of social media © Getty Images — The worry about the impact of blue light from a mobile phone is a bit of a myth, says Mosley. It's much more to do with the addictive nature of social media © Getty Images

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 around the neck and around the gut. That leads to snoring, it leads to sleep apnoea. And again, the Mediterranean diet, particularly a 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 about in this book and other books, but I do think it's a very important message.

There've been a number of smaller studies which have shown, broadly, that eating sugary or carby stuff is very bad for deep sleep, whereas eating fibre-rich foods is good for deep sleep. So it's the likes of legumes and stuff like that, you should be eating certainly at nighttime, rather than perhaps the milky drink.

I’m guessing you shouldn’t eat cheese before bed, either?

There are a number of myths, and I have to say the idea that cheese gives you nightmares seems to be one of them.

They actually did a study at the University of Surrey some years ago, in which they got 200 people to keep a record of their dreams. Then they had to eat cheese every night for a month, and they found there was no correlation whatsoever between the amount of cheese they were eating and when they ate it, and having nightmares.

Read more about getting a good night's sleep:

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. 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 eaten late at night is a really bad idea. A small nibble of cheese, I suspect, isn't going to make a lot of difference one way or the other, and particularly nice smelly cheese, then you're gonna be shoving a few probiotics down there as well.

Do we really have to get up every single day at the same time, even on weekends?

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 later, say three hours later, then that would be the equivalent of travelling to Athens for the weekend.

Your body really doesn't like jet lag. 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 10am rather than 7am, 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.

How can you tell if your sleep is good quality?

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?

Obviously, 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.

You shouldn't be eating too close to your bedtime. Your gut is a bit like a motorway: you can't repair it while there's still traffic going down it

There is actually a test you can do, which is what you do is you go to bed in the afternoon with a quiet sign on the door. 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 a terribly good sign. It's a sign that you're actually very sleepy. If you fall asleep within ten minutes, that means you are seriously sleep deprived. 15 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. You hold a metal spoon in your hand and hang your hand over the side of the bed. Just below, beside the bed, you put a metal tray. You check the time, and then close your eyes.

The idea is when you fall asleep, the spoon falls out of your hand and hits the metal tray. It goes clang, and you wake up and you look at your watch and see how long it's taken.

Does anything special happen in the gut while we’re sleeping?

Well, one of the main things that happens in your gut when you're sleeping is it closes down for the night.

One of the parallels I use is the idea of a busy motorway. Your gut takes a tremendous amount of bashing during the day. It does a lot of processing, a lot of cells need to be renewed. So, it's a bit like a motorway: you can't repair it while there's still traffic going down it.

If you're shovelling food into your gut late at night and you get up at 3:00am and you have a snack and stuff like that, then your body is unable to get on with the central repairs. So that tends to lead to things like dysbiosis [a microbial imbalance in the body], it also leads to acid reflux and a lot of gut related problems. So, it is important to have a long-ish period without food.

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There is a thing called time restricted eating (TRE). There's a lot of science around it, and I've written about TRE before. There’s a man named Satchidananda Panda, based in the States, and he's kind of the guru of this. He started doing animal studies in 2012.

The idea of time restricted eating is you try to extend the period within which you're not eating. So, for example, you might aim for 12 hours. That would mean you would stop eating by 8pm, and you wouldn't eat again until 8am the next morning.

Or, you might extend it to 14 hours by not eating again until 10am. And that's known as 14:10. And that's kind of probably the most doable. Some people do 16:8. But that’s more challenging, where you go without food 16 hours and you eat within an eight hour window.

Again, in the book, I go to some lengths of describing TRE and the benefits thereof. And there are benefits which extend to type two diabetes, losing weight and stuff like that.

But it is also good for sleep patterns. At least one of the benefits comes from the fact that it's giving your gut more time to get on with essential repairs.

I’ve been using my phone while I’m in bed at night. Is that is that a problem? Because I've read things that say blue light disrupts sleep.

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.

Read more about social media:

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.

Is it narrated by you?

It is narrated by me, indeed. My dulcet tones will be very soothing and calming. Sleep, sleep, sleep.

Fast Asleep by Dr Michael Mosley is out now (£9.99, Short Books).

Download a sampler of Fast Asleep, free, here.