It's happened to all of us: Our night selves screw over our morning selves. You stayed up too late having fun or working hard, and the next day you can barely stay awake. All you can think about is a glorious 20-minute rest to embolden you for the rest of your day. But will all those extra ZZZ's really help you concentrate better, or be more creative?
The short answer is yes. But you have to be careful how you do it. Sleep varies a lot between individuals. How much you need per night, the best stage of sleep from which you should wake—all of that can vary depending on your genetics, your age, and your personality, says Rebecca Spencer, an associate professor of psychological and brain sciences at the University of Massachusetts, Amherst. Culture can play a role, too; in Spain, for example, the siesta culture means more sleep during the day but less at night.
But in America, there's a trend that supersedes these individual differences: Americans are more sleep-deprived than ever. More than a third of us aren't getting enough sleep, according to a 2016 report from the Centers for Disease Control and Prevention. Over time, too little sleep has been associated with an increased risk of a number of chronic health conditions, like obesity, diabetes, heart disease, mood disorders like depression and anxiety, and alcoholism.
"Most of us spend a lot of time exercising, watching what we eat, and seeing our doctors, but we forget there's a whole eight hours per night that affect what we do during the day," says Rajkumar Dasgupta, an assistant professor of clinical medicine at the Keck School of Medicine at the University of Southern California.
Sleep deprivation also has a noticeable effect on cognition—our brains simply don't function as well when we haven't slept enough. "When you're sleep deprived, only bad things happen to your mood, concentration, health, and immune system. It's not good to be sleep deprived," Dasgupta says.
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Napping can reverse some of the negative effects of sleep deprivation (that is, if you're a normal sleeper with regular sleep and wake schedules—let's leave out people with sleep disorders like narcolepsy). "All aspects of cognitive functioning are also affected by sleep deprivation. So when you nap, it improves those performance levels," says Melissa Mallis, the president and chief scientist of M3 Alertness Management, a consulting company that helps organizations combat fatigue among employees.
After a nap, studies have shown, people tend to be more alert, more creative (that is, if they get into REM sleep, which typically takes longer than the 20 minutes of a power nap), learn better, and retain memories better.
The thing is, it has to be the right kind of nap. Our natural body rhythm, called the circadian rhythm, dips around 3 PM, which makes that a great time to nap. Ideally, it should only last about 20 to 30 minutes. Longer than that, and you risk getting into some of the deeper stages of sleep from which it's harder to wake and might leave you feeling groggy for an hour or so once the nap has ended. Scientists call this sleep inertia. Napping too long also puts you at risk of throwing off your nighttime sleep, which could leave you feeling even more sleep deprived the next day.
That's important to keep in mind if you work at a place where employers encourage napping, such as Google or Uber, or go to a college with designated nap spaces. "Overall I think the nap trend is good—there's more appreciation for sleep and valuing it," Spencer says. "But I think you need to do it smartly and not abuse naps."
If you're getting a full seven to eight hours of sleep every night and you still feel sleepy during the day, you may want to talk to your doctor as you might have a condition such as sleep apnea that is decreasing the quality of your nightly rest.
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