It’s surprising how we spend our lives. Reach your 78th birthday and according to some back-of-the-envelope calculations, you will have spent nine of those years watching television, four years driving a car, 92 days on the toilet, and 48 days having sex.
But when it comes to time-consuming activities, there’s one that sits head and shoulders above them all. Live to 78, and you may have spent around 25 years asleep. In an effort to claw back some of that time it’s reasonable to ask: how long can we stay awake – and what are the consequences of going without sleep?
Any healthy individual planning to find out through personal experimentation will find it tough going. "The drive to sleep is so strong it will supersede the drive to eat," says Erin Hanlon, an assistant professor at the University of Chicago's Sleep, Metabolism and Health Centre. "Your brain will just go to sleep, despite all of your conscious efforts to keep it at bay."
Why sleep at all?
Exactly why the urge to sleep is so strong remains a mystery. "The exact function of sleep is still to be elucidated," says Hanlon. She adds, however, that there is something about sleep that seems to “reset” systems in our bodies. What’s more, studies have shown that routine, adequate sleep promotes healing, immune function, proper metabolism, and much more – which is maybe why it feels good to arise refreshed after a serious snooze.
On the flip side, insufficient slumber has been linked to greater risks of diabetes, heart issues, obesity, depression and other maladies. To avoid those latter outcomes, we are wracked with uncomfortable sensations when we burn the midnight oil: we lack energy, feel groggy, and find that our heavy eyelids press on aching eyes. As we continue to fight off sleep, our ability to concentrate and form short-term memories slackens.
If we ignore all these side effects and stay up for days on end, our minds become unhinged. We get moody, paranoid, and see things that aren’t really there. "People start to hallucinate and go a bit crazy," says Atul Malhotra, the Director of Sleep Medicine at the University of California, San Diego. (Long-haul truckers have an evocative term for this hallucinatory phenomenon: "seeing the black dog". When a shadowy apparition appears on the roadway, so the advice goes, it's time to pull the lorry over.)
Many studies have documented the body's parallel decline during sleep deprivation. Stress hormones such as adrenaline and cortisol increase in the blood, in turn elevating blood pressure. Meanwhile, heart rhythms get out of whack and the immune system falters, says Malhotra. Sleep-deprived people accordingly feel anxious and are likelier to come down with an illness.
Still, all the havoc wreaked by a bout of insomnia or a few all-nighters does not seem permanent, disappearing after solid shuteye. "If there's any damage, it's reversible," says Jerome Siegel, a professor at the Centre for Sleep Research at the University of California, Los Angeles.
When the curtain never falls
But what if sleep never can come? A rare genetic disease called Fatal Familial Insomnia provides one of the starkest pictures of the consequences of extreme sleeplessness.
但如果永远不睡觉会怎么样？有一种名为致死性家族性失眠症(Fatal Familial Insomnia)的遗传疾病，让我们得以了解这种极端情况下最严酷的后果。
Only about 40 families worldwide have FFI in their gene pools. A single defective gene causes proteins in the nervous system to misfold into "prions" that lose their normal functionality. "Prions are funny-shaped proteins that screw these people up," says Malhotra. The prions clump in neural tissue, killing it and forming Swiss cheese-like holes in the brain (which is exactly what happens in the best-known human prion disorder, Creutzfeldt-Jakob disease). One area that is particularly badly affected in people with FFI is the thalamus, a deep brain region that controls sleep. Hence the debilitating insomnia.
An afflicted individual suddenly goes days on end without rest and develops weird symptoms such as pinpoint pupils and drenching sweats. After a few weeks, the FFI victim slips into a sort of pre-sleep twilight. He or she appears to be sleepwalking and exhibits those jerky, involuntary muscle movements we sometimes have when falling asleep. Weight loss and dementia follow, and eventually, death.
Still, sleeplessness per se is not thought to be the lethal agent, because FFI leads to widespread brain damage. "I don't think it is sleep loss that kills these individuals," says Siegel. Similarly, the oft-used torture tactic of depriving human prisoners of sleep is not known to have summarily caused anyone to die (although they will still suffer horribly).
Along these lines, animal sleep deprivation experiments provide more evidence that a lack of sleep in its own right might not be deadly, but what prompts it may well be.
Studies by Allan Rechtschaffen at the University of Chicago in the 1980s involved placing rats on discs above a tray of water. Whenever the rat tried dozing off, as revealed by changes in measured brain waves, the disc would rotate and a wall would shove the rat towards the water, startling it back awake.
All rats died after about a month of this treatment, though for unclear reasons. Most likely, it was the stress of being awoken – on average a "thousand times a day" says Siegel – that did the rats in, wearing down their bodily systems. Among other symptoms, the rats exhibited body temperature dysregulation and lost weight despite an increased appetite.
"That’s the problem in interpreting sleep studies in humans and animals: You can't thoroughly deprive a person or an animal of sleep without their cooperation and not impose a fair amount of stress," says Siegel. If death occurs, "the question is, 'is it the stress or the sleep loss?' It's not an easy distinction."
Wake up! Wake up!
All of this may well put most people off exploring the limits of our capacity to go without sleep, but the question remains: how long can we stay awake? The most widely cited record for voluntarily staving off sleep belongs to Randy Gardner, at the time a 17-year-old high school student in San Diego, California. For a science fair project in 1964, Gardner did not hit the hay for 264 hours straight, or just over 11 days, according to scientists who monitored him towards the end of his vigil. Numerous other, less credible accounts abound, including one of a British woman in 1977 who won a competition to continuously rock in a rocking chair (presumably by a landslide) by doing so for 18 days.
Overall, the jury is out on just how long a human could ever stay awake, but perhaps that's a good thing. Acknowledging the injury people might cause to themselves through intentional sleep deprivation, the Guinness Book of Records stopped keeping track of this particular superlative last decade.