Let’s debunk a few myths. You can't make up for lost sleep by sleeping more next time, or by sleeping-in on weekends. And a too-long afternoon nap, too late in the afternoon, will disrupt your night’s sleep.
But a nap however, the so-called ‘power nap’, can be gold. Naps can restore alertness, improve mood, enhance performance, and reduce mistakes and accidents. (National Sleep Foundation.) Indeed, one study of 23,681 Greek men over six years found that the participants who napped three times per week had a 37% lower risk of dying from heart disease. (National Library of Medicine.)
“You can get incredible benefits from 15 to 20 minutes of napping. You reset the system and get a burst of alertness and increased motor performance. That's what most people really need to stave off sleepiness and get an energy boost.” (Sara C. Mednick, PhD, sleep expert.)
BUT note, a nap longer than 20 minutes can leave you with what’s called ‘sleep inertia’ (grogginess and disorientation upon waking), and can also interfere with your nighttime sleep. This is why it's best to nap between 2-4pm, no later.
Longer naps have pro’s and con’s.
Studies have shown that longer naps, while causing sleep inertia in the short term, can have longer lasting benefits during the day. A study at NASA on sleepy military pilots and astronauts found that a 40-minute nap improved performance by 34% and alertness 100%.
And elite sportspeople use napping strategically to aid performance, stamina and learn new techniques.
If you do sleep longer than 20 minutes, allow 1/2 to 1 hour to recover from the sleep inertia and become fully alert. (ie: Don’t wake and immediately operate heavy machinery, take a test, or try to win a race.)
Just like sleeping at night, it’s important to take into account your external environment’s influence over sleep when napping. Light and temperature both affect sleep onset, so aim for napping in a darker, quieter and cooler room, with the comforting weight of a blanket or similar over you.