Everybody knows that they’re supposed to get 7-9 hours of sleep per night, and if you’re like the vast majority of people, this conventional wisdom applies to you. Sleep deprivation causes direct, measurable physical harm. For most people, not getting enough rest on a regular basis translates to a list of healthy problems that seems to grow longer every time sleep scientists shed light on it. However, researchers have also long observed that some people tolerate sleep loss better than others.
Do you know somebody who claims to get by just fine on as little as six hours of sleep? Firs, it’s important to note that some people go through most of their lives chronically sleep deprived without knowing it. Go without enough sleep for long enough, and eventually, you’ll forget what being truly well-rested feels like. Some people under-sleep but think they feel okay, while tests measuring their reaction times, reasoning, and more would reveal the reality. This is especially true for those who burn the midnight oil five days a week and sleep in on the weekends. Contrary to popular belief, you cannot "catch up" on sleep with an extended snooze-fest. You also can’t compensate with caffeine and energy drinks forever.
However, according to a group of researchers at the University of California, a tiny percentage of people may carry a rare gene mutation that allows them to sleep for as little as four to six hours per night and function normally. In a clinical setting, where one’s need for sleep is determined by a battery of physical and mental tests, they perform at a level that would be inaccessible to the vast majority of the population on the same amount of sleep. A number of studies since then have reached similar conclusions.
Importantly, short sleepers have not trained themselves to rely on less sleep (as more than one article floating around the internet would lead you to believe). They are the way they are because of their genetic makeup, so don’t be fooled by claims that you can just get used to sleeping less than 7 hours per night.
If you go on holiday and find that without external influences (i.e. your alarm clock and morning espresso buzz), you naturally sleep for fewer than 7 hours and feel perfectly fine, there’s a small chance you might be a natural short-sleeper. However, the research is far from conclusive, and the safest bet is to assume that you need 7-9 hours like the rest of us.