Feeling sleepy after lunch? Your body knows what it needs. Napping doesn't just feel good in the moment -- it recharges your body and your brain in these surprising health-boosting ways:
Naps improve your heart health and longevity.
Naps can hardly be considered aerobic exercise, but they're just as good for your heart. In 2007, a study of 24,000 adults done by the Harvard School of Public Health found that nappers were 40 percent less likely to die of heart disease than non-nappers. Working men received the most benefit of all.
Daytime napping for 45 minutes has also been shown to lower blood pressure and improve the rate of cardiovascular recovery after mental stress, according to 2011 research at Allegheny College.
How to benefit: Nap every day.
The Harvard study was done in Greece, which has a long-standing "siesta culture." Regular (daily) nappers were found to be better protected than occasional nappers, who, in turn, had more protection against heart disease than non-nappers. People who make a habit of napping are also more likely to fall asleep quickly when taking a nap.
"A lot of people don't realize that you don't need a really long nap," says Karl Doghramji, director of the Jefferson Sleep Disorders Center at Jefferson University Hospital in Philadelphia. "Just putting your head down where you are helps."
Naps help you avoid gaining weight.
True, you don't burn many calories during sleep. But sleep provides other weight-control benefits. In a 2010 Japanese study of 35,000 adults, reported in the journal Sleep, those who slept five to six hours a day were twice as likely to become overweight as those who slept seven to nine hours. An earlier study from Columbia University compared sleep patterns and obesity and found that those who got five to seven hours of sleep per night were 50 percent more likely to be obese than seven-to-nine-hour sleepers. Very light sleepers -- those who snatch just two to four hours a night -- are 73 percent more likely to be obese.
Lack of sleep decreases levels of the hormone leptin (which makes you feel full) and increases levels of the hormone ghrelin (which makes you feel hungry). As you hit the post-lunch energy slump -- which is actually a natural dip in your circadian rhythm, Doghramji says -- you may have less afternoon resistance to junk food, too.
A 2012 study in the Journal of Nursing Administration found higher obesity levels among nurses who work long hours. Among the remedies suggested: an organizational climate that supports napping in the workplace.
How to benefit: Nap at the right time.
It's best to start a nap during the noon-to-1 p.m. window, when most people's energy naturally flags. (Your body clock has natural dips in its 24-hour cycle.) Also, avoid taking your naps too late in the day. After around 3 p.m., daytime sleep will start to interfere with night sleep. (Shift workers, however, benefit from napping just before their shift begins.)
Naps enhance sexual health.
Insufficient sleep can lead to a cascade of effects that squelch libido. If you're not sleeping well, you're more apt to be tense, cross, and fatigued -- not conditions associated with putting one "in the mood." In the National Sleep Foundation's 2007 Sleep in America survey, about one-third of women said they were too tired for sex. In the 2010 edition of the survey, one-fourth of respondents of both genders said the same.
Napping is one way to restore mood and energy while reducing stress, which can in turn stir sexual desire -- and in a happy circular effect, in turn improve mood, energy, and stress levels.
In a 2011 University of Chicago study, 24-year-old men who slept fewer than five hours a day had the testosterone levels of men 15 years older; the researchers noted that lower testosterone, in turn, diminishes sexual desire and performance. (Testosterone naturally falls by one to two percent a year as a man ages.)
How to benefit: Nap on the go.
Sleep (like sex) isn't limited to the bed. "A dark, noise-free room is more satiating from a sleep standpoint, but you can sleep anywhere, even sitting up at your desk," Doghramji says. If you can't sack out on the nearest sofa, try curling up on a yoga mat on the floor, or nap in your car.
More surprising ways naps improve your health
Naps boost your memory and creativity.
It's crazy to associate napping with laziness. A 2010 study at the University of California, Berkeley found that the brain loses some ability to absorb new information over the course of a normal day, but a nap can reverse this decline. Sleep -- including napping -- helps transfer memories from their temporary hold in the brain's hippocampus locations to more permanent storage in the neocortex. Other studies have linked naps to improved performance on memory tests and word-recall tests.
Naps as short as six minutes and as long as 90 minutes have been shown to provide cognitive boosts. In one study, naps of 60 to 90 minutes improved perception skills to the same degree as did eight hours of sleep.
Napping long enough to dream is especially useful for processing and storing information. A study at Boston's Center for Sleep and Cognition at Beth Israel Deaconess Medical Center found that students who trained on a maze task and then took a 90-minute nap performed better on a later maze test than those who had stayed awake. Dreams help the brain make connections you might not have noticed when conscious.
How to benefit: Nap short to refresh, nap long to rethink.
A study in the journal Sleep pointed to the 10-minute "power nap" as the optimal length for recharging cognitive performance without feeling groggy afterward. But for creative thinking and major memory consolidation, you want to cycle though all five sleep stages, which requires a 60- to 90-minute nap. (It's different for everyone, but after about 30 minutes, humans tend to transition into deep sleep, which can be hard to wake from and will leave you feeling even more tired, a transitional state known as sleep inertia.)
Naps improve alertness, keeping you safer.
Lack of sleep is associated with more accidents for drivers and shift workers. Even the nuclear accidents at Chernobyl and Three Mile Island, the Exxon Valdez oil spill in Alaska, and the explosion of the space shuttle Challenger have been partly blamed on sleep deprivation, according to the Harvard Medical School Division of Sleep Medicine.
Napping, on the other hand, can improve alertness, motor dexterity, accuracy, and judgment, studies have shown. A NASA study on sleepy military pilots and astronauts found that a 40-minute nap improved performance by 34 percent and alertness by 100 percent, according to the National Sleep Foundation. Another study, in the journal Sleep, compared naps of different lengths; the 10-minute "power nap" came up the winner for adding alertness without making you groggy afterward.
How to benefit: Try combining naps and caffeine.
Comparative studies have found that drinking caffeine immediately before a 20-minute nap raises alertness for sleepy drivers more than either caffeine or sleep alone (and more than rolling down the window and singing to the radio). That's because it takes up to half an hour for caffeine to kick in -- so after your nap, you get an extra jolt of alertness when the caffeine boost hits. Other research has found that combining a nap before shift work with caffeine consumed during the shift can reduce accidents and other impairments in performance.