Should you drink more coffee? Should you take melatonin? Can you train yourself to need less sleep? A physician’s guide to sleep in a stressful age.
During residency, I worked hospital shifts that could last 36 hours, without sleep, often without breaks of more than a few minutes. Even writing this now, it sounds to me like I’m bragging or laying claim to some fortitude of character. I can’t think of another type of self-injury that might be similarly lauded, except maybe binge drinking.
Technically the shifts were 30 hours, the mandatory limit imposed by the Accreditation Council for Graduate Medical Education, but we stayed longer because people kept getting sick. Being a doctor is supposed to be about putting other people’s needs before your own. Our job was to power through.
The shifts usually felt shorter than they were, because they were so hectic. There was always a new patient in the emergency room who needed to be admitted, or a staff member on the eighth floor (which was full of late-stage terminally ill people) who needed me to fill out a death certificate. Sleep deprivation manifested as bouts of anger and despair mixed in with some euphoria, along with other sensations I’ve not had before or since.
I remember once sitting with the family of a patient in critical condition, discussing an advance directive—the terms defining what the patient would want done were his heart to stop, which seemed likely to happen at any minute. Would he want to have chest compressions, electrical shocks, a breathing tube? In the middle of this, I had to look straight down at the chart in my lap, because I was laughing. This was the least funny scenario possible. I was experiencing a physical reaction unrelated to anything I knew to be happening in my mind. There is a type of seizure, called a gelastic seizure, during which the seizing person appears to be laughing—but I don’t think that was it. I think it was plain old delirium. It was mortifying, though no one seemed to notice.
No matter what happened to my body, I never felt like it was dangerous for me to keep working. I knew I was irritable and sometimes terse, and I didn’t smell the best, but I didn’t think anything I did was unsafe. Sleep experts often liken sleep-deprived people to drunk drivers: They don’t get behind the wheel thinking they’re probably going to kill someone. But as with drunkenness, one of the first things we lose in sleep deprivation is self-awareness.
In a high-school science-fair experiment in 1964, a 17-year-old stayed awake for 11 days. Since then, standards for science-fair safety have changed.
It’s this way of thinking—that you can power through, that sleep is the easiest corner to cut—that makes sleep disturbance among the most common sources of health problems in many countries. Insufficient sleep causes many chronic and acute medical conditions that have an enormous impact on quality of life, not to mention the economy. While no one knows why we sleep, it is a universal biological imperative; no animal with a brain can survive without it. Dolphins are said to sleep with only half their brain at a time, keeping partially alert for predators. Many of us spend much of our lives in a similar state.
Since my residency, I’ve become sort of obsessive about sleep—how much we really need, how to optimize it, whether there are ways to game the system. What can be said definitively about sleep and wakefulness? What I’ve found is a perpetual divide between what’s known to scientists and what most people do.
How much sleep do I actually need?
One 2014 study of more than 3,000 people in Finland found that the amount of sleep that correlated with the fewest sick days was 7.63 hours a night for women and 7.76 hours for men. So either that is the amount of sleep that keeps people well, or that’s the amount that makes them least likely to lie about being sick when they want to skip work. Or maybe people who were already sick with some chronic condition were sleeping more than that—or less—as a result of their illness.
Statistics are tough to interpret. Isolated studies are tougher. That’s why the American Academy of Sleep Medicine and the Sleep Research Society convened a body of scientists from around the world to answer this question through a review of known research. They looked at the effects of sleep on cardiovascular disease, cancer, obesity, cognitive failure, and human performance, vetting each paper based on its scientific strength.
The consensus: Most adults function best after seven to nine hours of sleep a night. Going to sleep and waking up at consistent times each day is valuable too. When we get fewer than seven hours, we’re impaired (to degrees that vary from person to person). When sleep persistently falls below six hours per 24, we are at an increased risk of health problems.
Can I train myself to need less sleep?
As an experiment for his high-school science fair in 1964, a 17-year-old San Diego boy named Randy Gardner stayed awake for 264 hours. That is 11 days. Since 1964, the standards for science-fair safety have changed.
The project attracted the attention of the Stanford sleep researcher William Dement, among others. Dement and other researchers took turns watching and assessing the young man’s consciousness. By all accounts, he took no stimulant medications. Nor did he seem to suffer any permanent deficits. Dement said that on day 10, Gardner even beat him at pinball. The boy later said of his experiment that the key to staying awake was “just talking yourself into it.”
I asked David Dinges, the chief of the division of sleep and chronobiology at the University of Pennsylvania, how many people could do anything close to that without dying. He replied that “when animals are sleep-deprived constantly, they will suffer serious biological consequences. Death is one of those consequences.”
That said, cases like Gardner’s—of people who suffered great sleep deprivation without major setbacks—are well documented. A small number of people, sometimes called “short sleepers” and commonly thought to make up perhaps 1 percent of the population, seem to thrive on only four or five hours a night. Dinges said that “we probably do have people among us—and not necessarily 1 percent; there may be many more than that—who can actually tolerate sleep loss better than others.” This proposition has been borne out in studies of participants in transoceanic sailing races, which did not afford them the luxury of long blocks of sleep. The winners tended to be the people who slept the least, often in multiple short bursts.
The concept of sleeping in short bursts has spread since those races began, in the 1960s. Today, a small global community of people practices “polyphasic sleeping,” based on the idea that by partitioning your sleep into segments, you can get away with less of it.
Though it is possible to train oneself to sleep in spurts instead of a single nightly block, Dinges says it does not seem possible to train oneself to need less sleep per 24-hour cycle. And he notes that even for the 1 percent (or so) who can survive on less sleep and function well cognitively, we still don’t know how the practice might be affecting metabolism, mood, and myriad other factors. “You may be cheerful, but not cognitively fit. Or you may be cognitively fit, but hard to be around because you’re pushy or hyperactive.”
Around the time of Gardner’s historic science project, the U.S. military got interested in sleep-deprivation research: Could soldiers be trained to function in sustained warfare with very little sleep? The original studies seemed to say yes. But when the military put soldiers in a lab to make certain they stayed awake, performance suffered. Cumulative deficits accrued with each night of suboptimal sleep. The less sleep the soldiers got, the more deficits they suffered the next day. But as with my own residency experience, they couldn’t tell that they had a deficit.
“They would insist that they were fine,” said Dinges, “but weren’t performing well at all, and the discrepancy was extreme.”
This finding has been replicated many times over the intervening decades, even as many professions continue to encourage and applaud sleep deprivation. In one study published in the journal Sleep, researchers kept people just slightly sleep deprived—allowing them only six hours to sleep each night—and watched the subjects’ performance on cognitive tests plummet. The crucial finding was that throughout their time in the study, the sixers thought they were functioning perfectly well.
Effective sleep habits, like many things, seem to come back to self-awareness.