A neurologist says a small dose of caffeine is the secret to naps. Brice Faraut, who researches the effects of restricted sleep at the Hôtel-Dieu Hospital in Paris, knows all the tricks in the book to combat sleep deprivation. In his new book, Saved by the Siesta, he reveals why a cup of coffee can go hand in hand with a nap. Napping, he says, is "becoming more culturally acceptable" and research shows naps are "a very effective and versatile remedy for sleep deprivation".
"There is scientific evidence that the practice can not only cure extreme fatigue, but also combat drowsiness, pain, immunological fragility, stress, hypertension, obesity, and cardiovascular disease," he said. Brice says that drinking coffee immediately before a nap for 20 to 30 minutes will help you deal with that groggy feeling when you wake up, reports The Times. "Caffeine takes about 20 minutes to kick in and stimulate the brain, which means you'll stay asleep, but after a 20 to 30 minute nap, caffeine will help you wake up more alert for the next four to six hours," says Brice.
Brice's odd approach to boosting energy in the middle of the day has been studied, with promising results. For example, a Japanese study of 10 adults showed that those who took a 15-minute caffeinated nap performed better on computer tasks than those who took a nap followed by washing their face or exposed to bright light.
Coffee and sleep don't usually go hand in hand - if there's one general piece of advice for sleep-deprived people, it's usually to avoid caffeine. While it can help keep you energized for work that needs to be done right away, it can also damage your sleep patterns by keeping you up late into the night.
It takes the body about four to six hours to break down half the effects of caffeine, called the "half-life," according to the Sleep Foundation. That is, if you drink coffee in the afternoon, it can keep you awake when you want to go to bed at 10 pm. Even if you don't feel the effects of coffee anymore, its effect on the brain – to block adenosine, a chemical that promotes sleep – can leave you dizzy. Brice agrees and suggests countering this problem by not napping too late. A 20-minute nap after 5 p.m. can backfire because it “can make it harder to fall asleep at night”, he says.
As a rule of thumb, he recommends an interval of at least six hours between naps and nighttime naps.
Brice also recommends sticking to the sweet spot of naps for 20 to 30 minutes. Anything more can make you feel worse. "The restorative nature of a nap is determined by the stage of sleep you're in when you do it," he says. "Within five or ten minutes of naps you are mostly in light slow-wave sleep, whereas deep slow-wave sleep, the most restorative type, occurs after about 20 minutes." Being forced to wake up by an alarm during a deep sleep can leave you feeling confused and uncomfortable.
"A ten-minute strong nap is usually enough to offset the effects of an hour's sleep deprivation at night and is the perfect preparation for an afternoon meeting," says Brice. "The advantage is that it won't cause post-sleep dizziness, although it also doesn't last long enough to produce restorative slow-wave sleep."