What happens when you don’t get enough sleep?

Sleep is not optional. Getting only six hours a night is a form of slow euthanasia

Elon Musk, the chief executive of Tesla and SpaceX, hasn't been having a great few weeks. There was the bizarre – and totally unfounded – tweet calling one of the Thai cave rescuers a "paedo". His public threat to set up an agency to monitor journalists. Then there were his ill-advised, late-night forays onto Twitter, in which he managed to raise questions about the future trajectory of Tesla and spark an SEC investigation.

It all culminated in an interview, in which he said he works 120 hours every week, and hasn't taken a full week off since he had malaria in 2001.

The problem, more than a few observers have suggested, is that Elon Musk is exhausted.

In the conference room at the Tesla headquarters in California, where his board recently met to deal with the fallout from one of his late-night Twitter sessions, his sleeping bag was still lying on the floor. His travails prompted Arianna Huffington – the creator of Huffington Post and founder of Thrive Global – to write him an open letter, suggesting he get more rest. He replied on Twitter: "Ford & Tesla are the only 2 American car companies to avoid bankruptcy. I just got home from the factory. You think this is an option. It is not."


He's not alone in behaving as though sleep is optional – at best, a luxury only those without big, important jobs can afford; at worst a self-indulgent waste of time. Apple co-founder Steve Wozniak once bragged how staying awake for four days allowed him to hallucinate the idea of "putting colour into computers". Donald Trump claims to get only three to four hours a night. Rob Wiesenthal, the chief executive of Blade, an "Uber for helicopters", said he sleeps for two periods of two hours. "If you're shut down or disengaged outside the hours of nine to five . . . you're just not going to be competitive."

Humblebragging about their chronic sleep deprivation has become a badge of honour for some overachievers. And, in some respects, it’s easy to understand why. Until recently, we didn’t even really understand why we sleep. It was one of the unsolved mysteries of neuroscience.

It's all too easy to conclude that sleep is for wimps

On the face of it, evolution should have made sleep obsolete millennia ago: it renders us useless, passive and vulnerable for one-third of our lives, not engaged in any of the other vital functions that make us human – eating, reproducing, socialising, running billion dollar companies. It’s all too easy to conclude that sleep is for wimps.

And yet, there is a mounting body of evidence to suggest that doing exactly what Wiesenthal derides, and shutting down for stretches of time outside the hours of nine and five, would make us all more, not less, competitive, smarter, healthier, happier, and more likely to stick around for the long haul.

Beyond the bravado of the four-hours-a-night brigade, growing numbers of us are, in fact, anxious about sleep. The self-help sections of bookshops are heaving with titles on sleep. There are documentaries about sleep. Podcasts about it. Gravity blankets that promise to aid sleep by decreasing the stress hormone, cortisol. Gel mattress toppers that promise to keep you cool.

The nature of modern life means sleep is being attacked on several fronts: our exposure to electric light and LED light, which puts a brake on our production of melatonin; caffeine; alcohol, which suppresses vital REM sleep, and prevents us laying down memories; the pull of work, and the emergence of always-on technology; lifestyle factors like longer commute times; and the phenomenon of "sleep procrastination" – or staying up much later than you should to binge on Netflix.

As a result, two-thirds of us now don't get enough sleep – defined by the World Health Organisation as eight hours. Matthew Walker, the author of the global bestselling Why We Sleep: The New Science of Sleep and Dreams, and a professor of neuroscience and psychology at UC Berkeley, suggests we all need to give ourselves sufficient "sleep opportunity time" – which he defines as eight or nine hours in bed.

Sleeping less than six or seven hours a night demolishes your immune system, more than doubling your risk of cancer

If you get up at 7am and feel you could fall back asleep at 10am, need caffeine to get through the morning, and don’t wake up before your alarm clock, you’re probably sleep deprived, he suggests. “Routinely sleeping less than six or seven hours a night demolishes your immune system, more than doubling your risk of cancer.”

"Tiredness kills" is the stark message on the signs erected this summer along the M7 motorway. Drowsy driving is the cause of one in five accidents in Ireland, and 4,000 road deaths every year in Europe, according to the Road Safety Authority (RSA).

The tragic death of a young mother, Olivia Dunne, and the injuries inflicted on her 15-week-old baby daughter, Eabha, in 2014 showed how catastrophic the consequences of tiredness can be.

Driver Anthony Handley, in his 60s, had four hours' sleep the night before the accident, "which was not unusual for him". He had no alcohol or drugs in his system, was not distracted at the time of the incident, and was not speeding. And yet, shortly after midday, he apparently lapsed without warning into a "microsleep". His SUV veered off the road, swerved onto the footpath near Balbriggan, killing the 31-year-old mother, who was out wheeling her buggy. Baby Eabha suffered horrific injuries, but has since made a good recovery.

Handley, who had no memory of the crash, was jailed for two years in 2016, “to send out the clear message to the community that fatigue must be a phenomenon in the minds of all drivers”. That sentence was found to be unduly harsh and was reduced on appeal, and he was released last year.


In his book, Walker writes that even a two-second “microsleep” behind the wheel – defined as a lapse in concentration, during which the eyelids fully or partially close, and your brain becomes blind to the outside world – is enough to cause death. Microsleeps are usually suffered by individuals who are chronically sleep restricted – getting less than seven hours a night – and sufferers are mostly unaware of them.

The risk of a fatal lapse in concentration behind the wheel is just one more immediate effect of sleep deprivation. Less well-known are the hidden costs to our memories, judgment, decision-making, creativity and long-term health. The truth is that, far from a passive state, sleep is essential for many functions: consolidating memories; learning; making logical choices and solving problems; recalibrating our emotional circuitry; fostering creativity; repairing physical damage; clearing out toxins; preventing infection; regulating our appetite; helping our microbiome to flourish; lowering our blood pressure.

“Sleep is infinitely more complex, profoundly more interesting, and alarmingly more health-relevant” than we previously understood, says Walker. “There does not seem to be one major organ within the body, or process within the brain, that isn’t optimally enhanced by sleep and detrimentally impaired when we don’t get enough.”

So what does happen when we don’t get enough sleep?

After just one night of poor sleep, your immune system is already under siege, with a 70 per cent reduction in your stores of your natural killer cells, or lymphocyte white blood cells. Your concentration suffers – in one landmark University of Pennsylvania study, a night of no sleep resulted in a 400 per cent increase in microsleeps. More alarmingly, participants who were logging a nightly six hours’ sleep were just as performance-impaired 10 days into the study, as those who had been awake for 24 hours. Both groups had a 400 per cent increase in microsleeps.

The shorter you sleeps, the shorter your lifespan

Over the longer term, chronic sleep deprivation is linked to abnormally high blood sugar levels, diabetes, cardiovascular strokes, cancer, depression, anxiety and obesity. It is one of the key lifestyle factors that determines if you’ll get Alzheimer’s. Margaret Thatcher’s habit of getting only five hours a night set the tone for a generation of politicians: less often written about are her later years, dogged by dementia and mini-strokes. “The shorter you sleep,” Walker warns, “the shorter your lifespan.”

The biological functions of sleep are complex and myriad. When we reach the fourth, deepest stage of sleep, for example, our bodies release a growth hormone in which bruises and cuts are healed, infections are fought, and cellular damage is repaired. In children and teenagers, new cells are released which enable the body to grow. During the fifth period of sleep, REM sleep, a fatty substance called myelin, which is essential for proper neural functioning, is generated in the brain. As Alex Soojung-Kim Pang puts it in his book, Rest: Why You Get More Done When You Work Less, myelin "in the brains of children and infants helps explain how they do smart things; the incomplete myelination of the prefrontal cortex in the brains of teens helps explain why they do stupid things."

Sleep doesn’t just help our brains function: it is important for physical performance too. In one study, members of Stanford’s men’s basketball team increased their nightly sleep by an average of 110 minutes. The extra rest correlated with a 9 per cent boost in both their free-throw and three-point accuracy and a 0.7-second improvement in sprint times.

So what should we do if we’re not able to sleep?

Sleeping pills are not the answer. Neither is sedation with alcohol, which might make you drowsy, but will result in a fragmented and restless night, characterised by a lack of REM sleep. Practices drawing on cognitive behavioural therapy have been shown to be helpful – turning your room into a cool, dark cave; avoiding technology for at least 60 minutes before you sleep; limiting caffeine during the day. But most of all, advises Walker, if you do only one thing, make it this: go to bed at the same time each night, and get up at the same time every day, eight hours later.

His book argues that if people, organisations and governments truly understood the cost of sleep loss, they would have no choice but to take action. It is the “most glaring omission in the contemporary health conversation”. Frighteningly, most of us have no idea how sleep deprived we are. We have become acclimatised to constant, low-level exhaustion.

“Millions of individuals unwittingly spend years of their levels in a sub-optimal state of psychological and physiological functioning, never maximising their potential of mind or body.”