Sleep, science and how to beat social jetlag

A good night’s sleep is a serious matter, says Robert Colvile. Not just your mood but your health is at stake

Sleep is surprisingly little understood. Scientists still haven’t agreed on how it evolved, or what its purpose is. What we do know, however, is that it is vital – and that many of us aren’t getting enough.

This is partly a symptom of what I call “the great acceleration” – the speeding up of everyday life, driven largely by technology. As we work and play harder, sleep gets squeezed out. Studies show that we’re getting less and worse sleep: in one survey only 15% of Britons said they felt refreshed by it.

We’ve all read the warnings about reading iPhones in bed. But while that’s part of the problem (because of the wavelengths of light they emit), there’s something much bigger going on. What we think of as the body clock isn’t one clock at all. It’s billions of them embedded into our every cell. This is why we get jet lag: those billions of clocks, and the processes they govern (such as digestion or light-dark perception), get out of kilter with each other.

The great acceleration has nudged our bodies out of synch with the day/night cycle – and the result is what experts call social jet lag. We live at “work o’clock”, wrenching ourselves back to normal at weekends. According to Till Roenneberg, one of the world’s leading sleep researchers, “the majority of the population in the industrialised world” suffers from this “forced synchrony” and pays the price in terms of health and wellbeing – not least since those clocks also control vital processes such as detoxification or DNA repair.

The more antisocial your schedule, the greater the problems. Shift work is now classified as a probable carcinogen by the World Health Organisation, following monitoring of night workers such as nurses as well as studies in which mice were forced to flip their day/night cycle. As well as increased cancer risk, the animals developed all kinds of other problems and had shorter life spans.

Long night shifts have been held responsible for all manner of accidents, including Chernobyl (where the workers had been on duty for at least 13 hours). One of the key symptoms of sleep deprivation – just like being drunk – is that you don’t realise how badly off you are. When scientists monitored junior doctors at night, they found “micro-sleep” events happening all over their brains: they would be partly or largely asleep in the middle of conversations, and even operations.

Even those with kinder schedules suffer and social jet lag can cause us to fall into a “stimulant-sedative loop”: caffeine to wake us up in the morning, booze to calm us down in the evening. But alcohol or sleeping tablets don’t give us proper, natural sleep, meaning that we need even more stimulants to get going again.

So how can we fix this? We do need to look after night workers better – and put down the iPhone before bed. But we can also find and follow our “chronotype”. Being a lark or an owl is not just a matter of psychological preference, it’s genetically determined. Some of us tend to feel more awake and alert late on; others spring up at the crack of dawn. (The standard diagnostic “morningness-eveningness” questionnaire is widely available online; AutoMEQ has been used since 1976.)

People should probably be working hours that suit their chronotype; jobs with shifting schedules should go to those in the middle of the spectrum, who find it easier to adjust. If we built our schedules around when we were biologically programmed to feel best, we’d be more productive – and happier and healthier, too.