THE MAGIC EIGHT

Neuroscience professor Matthew Walker, author of the international bestseller ‘ Why We Sleep’, explains why better slumber could improve your life and the steps you can take to achieve it

Why is sleep so important? It’s a big question, one that took me an entire book to answer. Firstly, it’s essential to realise that every major physiological system in the body and every operation of the mind is wonderfully enhanced when you get enough sleep, and demonstrably impaired when you don’t. It’s not an optional lifestyle luxury, it’s a non- negotiable, biological necessity and the single most effective thing that we can do to reset our brain and body. The decimation of good sleep throughout industrialised nations is having a catastrophic impact, and this silent, sleep -loss epidemic is fast becoming one of the greatest health challenges of the current century. In fact, every disease we fear in the developed world has significant and often causal links to insufficient sleep.

We should be sleeping around eight hours a night. How do we know that? Quarantine a group of people who say they only need six or seven hours by cutting them off from family, friends, phones, clocks and daylight, tell them to rest as their bodies wish and, once they’ve cleared their ‘sleep debt’, they will average eight to nine hours. When that figure drops below seven hours, objective brain and body impairments can be measured, and the number of people who can survive well on six hours sleep or less without showing any detrimental effect, rounded up to a whole number and expressed as a percentage of the population, is zero, which is quite a definitive statistic.

Several things have distanced us from our natural sleep rhythms, and the first is light. As a modern society, we’re deprived of darkness; we wake up, go to school or work and come home again accompanied by electric light. Even on a cloudy day, the strength of natural light is greater than the brightest office, but we exist in a dull consistency, without introducing our bodies to the rise and fall that regulates us and signals when we should be awake or asleep. Darkness releases melatonin, a hormone that encourages the onset of sleep, yet in the evening we bathe ourselves in electric light – often at computer screens, whose blue LED light suppresses that melatonin, so our brains don’t realise it’s time for bed. The result is that we feel drowsy during the day and alert at night, regularly hovering between wakefulness and sleep.

Work hours, commutes and entertainment consumption have all increased over the past century, while our allotted night’s sleep gets squeezed in a vice-like grip. A 1942 survey by poll organisation Gallup found that the average adult slept around 7.9 hours per night. Now, data shows that the average American adult sleeps six hours 31 minutes, with British people clocking up six hours 49 minutes, and the Japanese a mere six hours 20 minutes. Millions of years of evolution dictated the need for eight hours, yet in less than 80 years we’ve compressed that by 20-25 per cent. Sleep is as essential as food, water and oxygen – imagine a change that constrained the amount of oxygen we breathe by that same percentage.

Stigma also comes into play, and in the 21st century, sleep has an image problem. We’ve labelled getting sufficient shut-eye as being lazy or slothful, and some wear their sleep deprivation like a badge of honour. Also keeping us awake are anxiety and stress, which are the principle causes of insomnia. This revved-up, fight-or-flight state of mind makes it difficult, if not impossible, to fall asleep.

So, what can we do to encourage a good night’s sleep? My number one piece of advice is this: go to bed and wake up at the same time every day, no matter what – on weekdays and at the weekend. Even if you’ve had a bad night’s rest previously, you need to reset the following evening. Next, avoid caffeine and alcohol. A single cup of tea or coffee robs you of around 20 per cent of REM sleep, which helps clear your body of the toxic proteins known to be associated with Alzheimer’s, and is critical for emotional first aid, providing the brain with a form of overnight therapy that makes you feel better able to cope with any difficult experiences. In context, a human would need to age ten to 15 years to reduce their REM sleep by the same amount. Drinking alcohol at night is also known to negatively affect your REM sleep – it may be a sedative, but sedation is not sleep.

In the hour before bed, try to stay away from all digital screens (including smartphones) and turn off half of the lights in your house; you’ll be surprised at how drowsy you become. Heat is also a contributing factor when it comes to poor rest, as bodies need to drop their core temperature by about one degree Celsius, which is why it’s easier to fall asleep quickly in a cold room. 16-18 degrees Celsius is ideal – open the window if it’s safe to do so. If you still can’t sleep, don’t stay in bed restless for too long. Why? Because your brain quickly learns to associate your bed with being awake. Many people tell me that they nod off easily on the sofa, then get into bed and can’t sleep. If sleeplessness lasts for more than 20 minutes, get up and go somewhere different. Don’t eat, don’t check your emails, but try reading in dim light. Only head back to bed when you’re tired, in order to reprogramme the bedsleep link. ‘ Why We Sleep’, on sale now (£9.99, Penguin)