Michael Mosley: how to have a better night's sleep

But in the past few years my sleep has become more erratic and broken. I find it easy to go to sleep, but often wake at 3am and fret. I know I’m not alone. According to a 2013 study by the Sleep Council the average Briton gets six and a half hours’ sleep at night, and most of us, rightly, don’t feel that is enough.

To find out what’s going on I’ve been drilling down into the science. It has been an absolute eye-opener...

What happens during sleep?

When you go to bed and close your eyes you should begin to drift off within 20 minutes or so. Passing rapidly through sleep stages 1, 2 and 3, you reach stage 4, deep sleep. Then comes REM (Rapid Eye Movement) sleep, when your eyes begin to flicker and you experience your most vivid dreams. After REM you begin to wake up a bit, before going back down into deep sleep. This cycle is repeated every 90 minutes or so throughout the night.

Making memories

During deep sleep our brains work hard, moving memories from short-term into long-term storage, allowing us more short-term memory space for the next day. If you don’t get adequate deep sleep then these memories may be lost.

You might think: “I’ll cut back during the week then make up for it at the weekend.” Unfortunately it doesn’t work like that, because memories need to be consolidated within 24 hours of being formed.

Since deep sleep is so important for consolidating memories, it’s a good idea if you are revising or taking an exam this summer to make sure you’re getting enough sleep. In one study, people who failed to do so did 40 per cent worse than their contemporaries.

Flush out the toxins

Another important thing that seems to happen in deep sleep is that toxins get washed out of the brain. What’s been found, at least in mice, is that the space between brain cells can increase during sleep, allowing the brain to flush out toxins that build up during the waking hours.

A build-up of toxins, caused by lack of sleep, may in turn make you more vulnerable to diseases like Alzheimer’s. Scientists have recently shown that the sticky amyloid plaques that are associated with Alzheimer’s disease develop more rapidly in the brains of mice if you deprive them of sleep.

Stay calm — and sleep on

When you are in REM sleep, stress-related chemicals in the brain, like noradrenaline, are switched off. It’s the only time, day or night, that this happens. It allows us to remain calm while our brains reprocess all the experiences of the day, helping us come to terms with particularly emotional events.

We get more REM sleep in the last half of the night. Which means that if you are woken unexpectedly, your brain may not have dealt with all your emotions – which could leave you stressed and anxious.

Are you getting enough?

Most of us should be getting seven to eight hours, with teenagers needing more like nine. But the truth is our sleep needs vary hugely. If you want to see if you are sleep-deprived I recommend trying the Sleep Onset Latency Test. You lie down in a quiet, darkened room in the early afternoon and set an alarm to go off in 15 minutes. If you drift off and are wakened by the alarm then you are probably sleep-deprived.

You may find it surprising that falling asleep rapidly is a bad sign, but in lab studies where people are severely sleep-deprived, researchers find that they often fall asleep in less than a minute when given the chance.

Lack of sleep can make you ill...

So what happens if we don’t get enough sleep? Well, you will probably experience problems with memories and mood. But shortage of sleep has even more profound effects than that. It can, for example, make you more vulnerable to infections. A recent study with identical twins found that when one twin was sleep-deprived it depressed their immune system and increased the number of inflammatory markers in their blood.

... and fat

Lack of sleep can also make you fatter and more prone to diseases like Type 2 diabetes. As part of the film we recruited a group of volunteers who agreed to take part in a sleep deprivation experiment, under the guidance of Dr Eleanor Scott of Leeds University.

We asked them to cut their sleep for two nights in a row. Throughout the experiment we measured their blood sugar levels and asked them to monitor how hungry they felt.

We found that not only did their blood sugar levels soar, but they had a desperate craving for sugary treats.

“I wanted lots of biscuits,” one of them told me, “and I didn’t just have one. I’d go for ten. I wrote it down in my diary: ten custard creams.”

Why, I asked Dr Scott, does lack of sleep do this? “We know that a lack of sleep alters the levels of different hormones that are involved in how we perceive appetite and hunger,” she said. “So we get more of the hormones that cause us to feel hungry, and less of the ones that cause us to feel full. We also know that if you don’t sleep well, that affects the stress hormone cortisol, and that may be another factor.”

Secrets of a good night’s sleep

Throughout The Truth about SleepI explored, along with some willing volunteers, a number of different ways to get a good night’s sleep. These ranged from the fairly obvious (stress reduction through mindfulness) to the more surprising (eating two kiwi fruit before bedtime).

I found that drinking alcohol helps me go to sleep, but also severely disrupts the quality of my sleep later on. Sleeping pills are also not a long-term answer.

Eat fibre

Oddly enough I found that eating more fibre was one of the most effective ways to increase the quality of my sleep, particularly my deep sleep. I tested this out after reading a recent study, which found that those who ate foods rich in fibre went to sleep more quickly and were less likely to wake in the night than those who ate foods packed with sugar and saturated fat.

Turn off your phone

I’ve incorporated what I learnt about sleep from making this documentary and can honestly say I’m now sleeping better than I have for years. Among other things, I’m now more careful to avoid social media at least an hour before going to bed, I’ve cut back on alcohol, I do more mindfulness practice and, if I wake up in the middle of the night, I don’t lie there fretting but get up and read a dull book for an hour or so before going back to bed (something I’d also recommend you do if you find it hard getting to sleep).

I’m now more convinced than ever of the dangers of getting too little sleep. So if you are getting less than seven hours’ sleep a night and can increase that, even just a little, it’s really worth making the effort.

The Truth about Sleep is on Thursday at 9pm on BBC1