Print out this article and hand it to your boss. Tell them Harvard thinks you should take a nap. Honest.
Researchers at the Harvard School of Public Health and the University of Athens Medical School have just released findings from a large study that shows how mid-day napping reduces one's chance of coronary mortality by more than a third. So go ahead and nap—a short daily snooze might ward off a heart attack later in life.
Researchers studied 23,681 individuals living in Greece who had no history of coronary heart disease, stroke or cancer when they first volunteered. The researchers also controlled for risk factors such as diet and exercise, going beyond prior studies that have tried to explore the benefits of napping but ended up with conflicting results. More than six years later, the exemplary nappers, men and women who napped at least three times per week for an average of at least 30 minutes, had a 37 percent lower coronary mortality risk than those who took no siestas. The so-so nappers, who only snoozed occasionally, showed a reduction in mortality of about 12 percent. That sounds good, but it’s not statistically significant, say researchers. The lesson: if you're going to nap, be ambitious and do it several times a week.
The authors of the report, which appears today in The Archives of Internal Medicine, say they believe an afternoon nap in a healthy person may act as a stress-relieving process, since there is considerable evidence linking stress to incidence of death from coronary heart disease. The protective effect of napping, they've discovered, is especially strong among working men and is weak among retirees, likely a reflection of the different stress levels that those two groups have to deal with. (There were too few deaths among working women taking part in the study to draw conclusions).
Siestas are common in Mediterranean regions like southern Italy and southern Greece, as well as several Latin American countries, all of which happen to have low mortality rates from coronary disease. Several of those areas are famed for a Mediterranean diet that makes heavy use of heart-friendly foods like olive oil. "But people are careless there," says Dimitrios Trichopoulos, a professor of epidemiology at the Harvard School of Public Health and one of the napping study's authors. "They don't exercise and health care is mediocre. Yet they have lower coronary mortality rates. It couldn't just be the olive oil. That's why we started exploring the effects of the siesta."
Harvard is not alone in reporting the benefits of napping: NASA sleep researchers have found that a nap of 26 minutes can boost performance by as much as 34 percent. A 2006 study from the Stanford University School of Medicine found that napping resulted in improved mood, increased alertness and reduced lapses in performance among doctors and nurses.
The French, for their part, are already trying to incorporate the news into their labor policies: France's Health Minister, Xavier Bertrand, told reporters this month that the government—which already allows for a 35-hour work week—will be studying the effects of after-lunch naps at volunteer firms and will promote on-the-job naps if they prove useful. "Why not take a nap at work?" Bertrand told reporters. "It can't be a taboo subject."
Ah, France. But the United States is a bit trickier when it comes to taking mid-day naps. "When I used to live in Greece I took naps every day," says Harvard's Trichopoulos. "But now that I'm living in Boston as a professor, it's just not an option." Some researchers are hoping American attitudes about the merits of the afternoon siesta will change, given the medical evidence piling up in favor of the practice. There is just no good excuse for failing to nap, work or no work, explains Dr. Sara C. Mednick, a research scientist at the Salk Institute for Biological Studies in La Jolla, Calif., and author of the recent book "Take a Nap! Change Your Life." "We're learning that the benefits are not just related to alertness," she says. "Being overtired, results in a range of problems, from decreased libido to increased risk for diabetes." But how do we fit a siesta into an already-packed day? "Just make sure you get a late checkout if you're at hotel, or catch a bit of sleep in your car during lunch breaks," she advises.
Mednick's research focuses on the relationship between memory and napping. One of her recent studies found that napping had a positive effect on blood flow to the areas of the brain responsible for memory behavior. "In non-nappers the blood flow decreases over the course of the day; for nappers the flow is constant." That loss of blood flow, she points out, is the main culprit in that end-of-day dip in energy, when most office workers’ brains are not at their best.
If you are able to sneak away from your boss's line of sight, how long should you nap? Mednick says that to boost basic alertness a power nap of 20 minutes should do the job. "But slow-wave sleep, which is more restorative, especially for tissue repair and special memory, can be achieved with a 20-to-50-minute nap." If you want to complete one full sleep cycle, including REM sleep (the stage of sleep characterized by rapid eye movement), that would require a 90-minute nap. A nap of that length is good for improving visual and auditory skills, of particular importance to radiologists or other specialties that rely on a keen eye.
For last year's Stanford nap study, researchers recruited 49 doctors and nurses with nighttime shifts and allowed half the group to take a 40-minute nap in the middle of their shift. At shift's end, both groups underwent a series of tests, including a 40-minute simulated car drive, a simulated IV insertion and a NASA questionnaire that measured mood states including anger and fatigue. The nappers were better drivers, while the non-nappers continually crashed. The nappers also completed IV-insertions more quickly and scored higher for vigor.
Contrary to popular opinion, napping isn't for the lazy or depressed. Famous nappers have included Bill Clinton, Lance Armstrong, Leonardo da Vinci and Thomas Edison. The moral of the story: to be über-productive, just rest your head. You snooze, you gain.