How Much Sleep Do You Really Need?

“It’s popular to brag that you aren’t getting enough sleep,” Dinges says. “People will say, ‘I only need four hours of sleep a night,’ but in large scale sleep studies, we find that these people are incredibly rare; they represent less than one percent of the population.”

So how come it still seems like everyone and his mother is getting less than the recommended seven to eight hours, without batting an eyelash? We tend to overestimate our ability to go without sleep, while underestimating the amount of sleep we’re actually getting, says Dinges. Those 20 minutes you dozed off in the back of a taxi? That counts. So does an hour nap you took mid-flight. In the end, it’s the total amount of sleep you get in any 24 hour period that matters, not simply the sleep you average during the course of a night. “If you can get five hours of sleep at night plus a one hour nap, that's six hours of sleep, period” says Dinges.  In addition, he believes, most people don't advertise the fact that they catch up on sleep during their days off.

Still, despite these sneaky, overlooked catnaps, Dinges predicts that over 50 percent of the U.S. adult population is chronically sleep deprived. If you include the millions of people who have sleep disorders, he estimates that number jumps to 65 percent.

It's always going to be a balancing act.

As rational individuals, we are constantly tasked with making choices that leads to the most beneficial outcomes.

And sometimes, even when we know the medical and mental price, that elusive “most beneficial result” requires a sacrifice in the form of sleep.

In a recent study, Mark Showalter and Eric Eide, economists at Brigham Young University, challenged the conventional medical wisdom that success requires more, not less, sleep.

Related: Debunking 5 Common Myths About Sleep

While the medical recommendation for adolescents (10-17) is 8.5 to 9.25 hours a night, Showalter and Eide found that 16- to 18-year-olds perform better academically (based on data from a representative sample of 1,724 primary and secondary school students' standardized test scores) when they shaved about two hours off that recommended time.

Both authors emphasize that their definition of ‘optimal’ differs from a medical definition of the word. While most sleep researchers examine its effects on physical and mental health, Eide and Showalter's study looked at its effect on academic performance. "We're not looking at the effects of sleep on other health outcomes. We're simply describing the highest performing kids tend to sleep less than 9.25 hours that the medical literature had established as the guideline," says Eide.

"If you are sleeping you are not doing something else like studying or spending time with friends," Showalter explains. "There is an opportunity cost with sleeping that really hadn't been addressed in the medical literature."

While replicating a version of their study for adults is close to impossible – unlike teenagers, we're (thankfully) no longer subjected to mandatory standardized tests – Eide speculates that this same relationship is true for adults as well.

"If you were to look at earnings of adults as an outcome and you observed that people with high earnings tended to sleep less than people with lower earnings, that wouldn't be too surprising," he says.

Laura Entis is a staff writer at
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