The lesser you sleep, the shorter your life: the new sleep science. Leading neuroscientist Matthew Walker explains why sleep deprivation is increasing our risk of cancer, heart attack and Alzheimer’s – and what you can do about it.

Matthew Walker dreads the question “What do you do?” At parties, it signals the end of his evening. His new acquaintance will inevitably cling to him like ivy. On an aeroplane, while everyone is sleeping, he usually ends up running hours-long sessions for other passengers and crew. “I’ve begun to lie,” he says. “Seriously. I just tell people I’m a dolphin trainer. It’s better for everyone.”

Walker is a sleep scientist. To be specific, he is the Director of the Center for Human Sleep Science at the University of California, Berkeley.  This research institute’s goal, possibly unachievable, is to understand sleep’s impact on us, from birth to death, in sickness and in health.

Why are we so sleep-deprived? What has changed in the last 75 years? In 1942, less than 8% of the population was trying to survive on six hours or less sleep. In 2017, almost one in two people are trying to do the same. The reasons are seemingly obvious. “First, we electrified the night,” Walker says. “Light is a profound degrader of our sleep. Second, there is the issue of work: not only the porous borders between when you start and finish, but longer commuter times too. No one wants to give up time with their family or entertainment, so they give up sleep instead. And anxiety plays a part. We’re a lonelier, more depressed society. Alcohol and caffeine are more widely available. All these are the enemies of sleep.”

It has a powerful effect on the immune system, which is why, when we have the flu, our first instinct is to go to bed. Reduce sleep for even a single night, and resilience reduces drastically. If you are tired, you are more likely to catch a cold. The well-rested also respond better to the flu vaccine. Walker said studies show that lesser sleep can also affect our cancer-fighting immune cells. Many epidemiological studies report that working at night and any disruption to circadian rhythm increases the odds of developing various cancers.

So what can an individual do? First, they should avoid pulling “all-nighters”, at their desks or on the dance floor. After being awake for 19 hours, you’re as cognitively impaired as someone who is drunk. Second, you should start thinking about it as part of a routine, like going to the gym (with the key differences being that it’s free and, if you’re like me, you find it more enjoyable).

“People use alarms to wake up,” Walker says. “So why don’t we have a bedtime alarm to tell us we’ve got half an hour, that we should start cycling down?” We should start thinking of midnight more in terms of its original meaning: as the middle of the night. Schools should consider later starts for students; such delays correlate with improved IQs. Companies should consider rewarding rest. Productivity rises, and motivation, creativity and even levels of honesty improves. Tracking devices can be used to measure sleep, and some far-sighted companies in the US already give employees time off if they clock enough of it. People, by the way, should avoid sleeping pills. Among other things, they can have a deleterious effect on memory.

What questions does Walker still most want to answer? For a while, he is quiet. “It’s so difficult,” he says, with a sigh. “There are so many. I would still like to know where we go, psychologically and physiologically, when we dream. Dreaming is the second state of human consciousness, and we have only scratched the surface so far. But I would also like to find out when sleep emerged. I like to posit a ridiculous theory, which is: perhaps sleep did not evolve. Perhaps it was the thing from which wakefulness emerged.” He laughs. “If I could have some kind of medical Tardis and go back in time to look at that, well, I would sleep better at night.”