Many of us struggle to get a good night's sleep and that may have become heightened over the past few weeks as the world battles a pandemic. British doctor and TV presenter Michael Mosley has taken part in numerous sleep experiments and tested many sleep remedies. In this extract from his new book, Fast Asleep, he looks at the science behind what it takes to drift into dreamland.

8pm: your wind-down routine

Stop eating

Ideally, you will have finished your last meal of the day at least three hours before you go to bed. That is what I was recently advised by Dr Satchin Panda, a professor at the Salk Institute in the US and a world expert in chronobiology and circadian clock research. He is the scientist behind a form of intermittent fasting called time restricted eating (TRE), which is practised by numerous celebrities, such as Hugh Jackman and Miranda Kerr, as well as some of the major techies in Silicon Valley. The head of Twitter, Jack Dorsey, does it, as does Geoffrey Woo, the CEO of HVMN, a "human enhancement" company.

Intermittent fasting is practised by numerous celebrities including Miranda Kerr. Photo / Mark Sherborne
Intermittent fasting is practised by numerous celebrities including Miranda Kerr. Photo / Mark Sherborne

The idea behind TRE is that limiting the window within which you eat will help you lose weight, improve your cholesterol and blood sugar levels, make you sharper and help you sleep better.

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In one form of TRE, 16:8, you might stop eating at 8pm and not eat again until midday the next day. It is called 16:8 because you go 16 hours without eating and eat all your meals within an eight-hour window.

Dr Panda told me that he thinks most people will find 14:10 easier to stick to, and that is what he aims for himself. He has an evening meal with his family around 6pm and then doesn't eat again until 8am the next morning.

Why does he think it is so important to stop eating several hours before bed? Well, it is mainly to do with your core body temperature. Your body temperature naturally starts to fall as bedtime approaches, driven by your circadian clock. This fall also helps

trigger sleep. The trouble with late-night eating is it raises body temperature. When a late-night snack hits your stomach, your gut has to spring into action to break down and absorb the food you've just eaten.

This increase in gut activity means your core body temperature will remain high, just when you want it to go down.

One of the other major benefits of TRE is that it gives the lining of your gut, which takes a fearful bashing during the day, more time to repair itself. It's a bit like trying to repair a motorway; you can't do it while cars are driving up and down in the day, so you have to wait till night-time to close it down.

If you don't give your gut time to repair, you may develop a condition called leaky gut syndrome, which occurs when bacteria that are living in your guts escape through the damaged stomach lining into your bloodstream, causing inflammation, bloating and pain.

Hugh Jackman also practises time-restricted eating. Photo / File
Hugh Jackman also practises time-restricted eating. Photo / File

Dr Panda told me that once you get used to his regime you no longer get late-night munchies. In fact, you will find, after a couple of weeks, that if you do have a late-night snack it will leave you feeling uncomfortably bloated.

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Alcohol: a mixed blessing

A couple of years ago, Israeli scientists recruited 224 teetotal diabetics and randomly allocated them to drinking a medium-sized glass (150ml) of either red wine, white wine or mineral water with their evening meal, every evening, for two years. The wine and water were provided free of charge and the empty bottles collected afterwards to make sure they really were drinking regularly.

So what happened? Well, red-wine drinkers will be delighted to hear it was the group drinking red wine who came out on top. Not only were there significant improvements in their cholesterol and blood sugar levels, but they also reported better-quality sleep.

In another more recent study, this time carried out by an American team, researchers found that exposing mice to small amounts of alcohol, equivalent to a human drinking a glass of wine, made their glymphatic systems (the channels in your brain that open up in deep sleep) more efficient at washing out the brain and removing waste.

What makes this study particularly intriguing is that the woman behind it, Dr Maiken Nedergaard, is also the scientist who first revealed the existence of the glymphatic system in 2012. As she points out, "Studies have shown that while heavy drinking for many years leads to an increased risk of cognitive decline, low-to-moderate alcohol intake is associated with a lower risk of dementia. This study may help explain why."

I personally find that one glass of red wine with dinner has little effect on my sleep but a couple of glasses makes it measurably worse. If you drink every night and suffer from insomnia, do try giving up drinking for a week and see what happens.

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I recently met a woman at a party who said she used to drink half a bottle of wine every night and thought it was helping her sleep. But when she gave up drinking for a week (because she was taking antibiotics), she quickly noticed how much better she felt.

"After years of waking up almost every night and fretting, now I almost always sleep through the night and I feel fantastic. I have so much energy. I still drink on special occasions but giving up routine drinking has changed my life."

9.30pm: find something soothing to do

Dim the lights

By 9.30pm, your pineal gland should be busy pumping out the hormone melatonin, which in turn will be orchestrating the rest of your brain, getting it lined up for a night of sleep. Melatonin levels typically start to rise about 9pm and peak in the early hours of the morning.

Really bright light switches off the production of melatonin, particularly light in the blue frequency. That's why mobile phone manufacturers now sell products that reduce the amount of blue light they emit at night. But, as I've said before, this is a bit of a con.

The problem with mobile phones and tablets is not so much the light they produce but the fact that they stimulate the brain just when you need to slow down.

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Ideally, you should switch off the bright lights in your house and go for more subdued lighting. Tim Peake, the British astronaut who spent six months on the International Space Station, told me they have recently altered the lighting on the space station so it gradually changes, over the course of a "day", from light that is more in the blue frequency first thing, to light that is more in the red frequency as the "day" progresses, mimicking the light changes that happen back on Earth.

The Hadza, hunter-gatherers who live in Tanzania, shun artificial lighting and have no word for "insomnia". They gather around the campfire at night, to share stories and experiences, before heading to bed a few hours after the sun has set.

Have a warm bath

Studies have shown that having a warm bath or shower an hour before bedtime can help you fall asleep and stay asleep.

But for it to have an effect you probably have to be in the bath for at least 10 minutes and it has to be at least an hour before bedtime. Why? Well, not surprisingly, getting into a hot bath will heat you up. It will also increase the circulation of blood to your skin, hands and feet. When you get out of the bath, after a good, long soak and don your kimono, your body will continue to radiate heat. In time this will cool down your core temperature. The critical words are "in time"'. This whole cycle of heating and cooling takes about an hour. Simply dashing into the shower for a couple of minutes just before jumping into bed (which is what I tend to do most nights) isn't going to make you sleepy.

Listen to music

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According to the National Sleep Foundation, studies have shown that older adults who listen to relaxing music before bed fall asleep faster, sleep longer, wake up less during the night and rate their nights as more restful. Apparently, slow tunes with a rhythm of 60 to 80 beats per minute, which you're likely to find in classical, jazz or folk music, are the most effective sleep inducers.

10.30pm: countdown to sleep

Try keeping a 'to-do' journal

The idea is that you write down a list of the things you need to do the next day. This will, hopefully, mean you spend less time agonising about your to-do list in the middle of the night.

Does this work? Yes, there is evidence that it does. A small study of American university students found that those who spent five minutes writing about the day ahead went to sleep an average of nine minutes faster.

Nine minutes doesn't sound a lot but it is similar to the impact of taking a sleeping pill.

Keeping a journal also reduced the tendency to wake up in the night. While you've got your journal out, you might also want to write in it three good things that happened to you that day. It can be anything from a friend admiring your clothes to watching a great sunset. Expressing gratitude, also known as "counting your blessings", is a proven way to reduce stress, one of the main causes of insomnia.

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Consider taking melatonin

There are dangers to taking sleeping pills, at least in the long term. I take the occasional sleeping pill, such as zopiclone, when I travel long distance. It really helps me sleep on the plane and also combat jet lag when I land. I don't use it otherwise.

Melatonin is different. It is a hormone that is produced by the pineal gland, a pea-shaped structure in the middle of your brain. It is connected to your brain clock, the suprachiasmatic nucleus (SCN). When it gets dark, your SCN tells your pineal gland to start releasing melatonin. Rising levels of melatonin help co-ordinate the other parts of your brain that tip you into sleep. Levels peak at around 3am and then decline.

Synthetic melatonin is widely available and can be quite effective.

So who should take it and when? As we get older, our brains tend to produce less melatonin, which could be why our sleep deteriorates. That is also why melatonin works best in people over the age of 55.

In the UK, Australia and most of Europe, you can only get melatonin on prescription, whereas in the US you can pick it up at any chemist. I normally buy a few bottles when I am in the US, or order them online from a reputable American company like iherb. It is perfectly legal to buy melatonin this way, but it is illegal to sell it on.

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In the US, controlled-release melatonin is the recommended first-line treatment for older adults with insomnia. It has very few side effects (I have never noticed any); in fact, in one study there were fewer side effects in those taking melatonin than in those taking placebo pills.

An Australian government report from 2011 concluded that taking 2mg of melatonin, one to two hours before bedtime, was safe and effective for people over the age of 55. They said it was safe to consume it daily for up to 13 weeks and that, unlike sleeping pills, there was no evidence that you get rebound insomnia when you stop. Taking it every night for months on end may not be a great idea because in a study in which people took melatonin or a placebo every day for six months, the researchers found that by six months there was not much difference between the two groups.

Though it appears to be safe, the Australian government report suggested it should not be used by children, pregnant women or those with liver problems.

Although you are supposed to take it an hour or so before going to bed, I prefer taking it at 3am, when I wake up and find it hard to get back to sleep. Since melatonin has a half-life of 3–4.5 hours, this should make me dopey the next morning, but it doesn't.

I take 2mg, slow-release, but if that doesn't work you could try experimenting with higher doses (up to 5mg is safe). Unless I'm jet-lagged, I take melatonin no more than once or twice a week.

Dr Michael Mosley. Photo / Supplied
Dr Michael Mosley. Photo / Supplied

The long night of the soul

Let's assume that you follow my advice and go to bed at 11pm, after having a lovely pre-bed routine, then quickly fall asleep and wake up feeling refreshed and thinking: "I must recommend this book to other people."

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But what if you don't? What if you are still lying there, staring at the ceiling, listening to your partner snoring away, worrying about not going to sleep and besieged by negative thoughts?

Night-time breathing exercises to reduce stress and pain

Yogic breathing (pranayama) is a form of controlled breathing that has been practised for thousands of years. It is often done in conjunction with meditation or yoga. It reduces stress by activating the parasympathetic system, part of your autonomic nervous system.

Activating the parasympathetic system causes your heart to slow and your blood pressure to drop. When I am struggling to sleep, the first thing I attempt is deep breathing, also known as belly breathing. In everyday life we tend to take shallow breaths, so this may feel a bit weird to start with.

You start by taking a slow, deep inhale through the nose, allowing the air to really fill your lungs. Put a hand on your belly – you should feel it inflate. Hold it for a count of two, then breathe out slowly through your mouth. The first few times you do it, it will feel unnatural, so you need to practise during the daytime.

You will notice that as you do this, your heart rate will slow and you will start to feel more relaxed. There are lots of different breathing techniques. The one I favour is 4-2-4.

• Breathe in deeply through your nose while mentally counting to 4.

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• Hold your breath to a count of 2.

• Breathe out through your mouth to a count of 4.

• Try doing this for a couple of minutes. It should feel really relaxing.

Fast Asleep by Dr Michael Mosley.
Fast Asleep by Dr Michael Mosley.

Fast Asleep
By Dr Michael Mosley
Published by Simon & Schuster
RRP: $35