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.
Magazine Cover image
Explore the January/February 2017 Issue
Check out more from this issue and find your next story to read.
View More
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.
read more in next page
