AT A FRIEND’S BIRTHDAY DINNER in the mid-1990s, I was seated with several high-ranking government officials, who–to my surprise and possibly as a ploy to keep away from controversial topics–spent the entire meal discussing naps. For example, the napping habits of Albert Einstein, who after lunch sat with his heavy wristwatch in one hand, which he dangled over the edge of his chair. When the watch fell, the noise woke Einstein–nap over. All of my dinner partners talked about locking their office doors for short or sometimes longer postprandial snoozes.
In recent years, the nap has become better accepted–and better studied. According to a Pew Research Center Study, one-third of adults in the United States take naps, and more men report napping than women. And New York-based MetroNaps has installed “sleeping pods” for Google, Huffington Post and other organizations, according to a recent Wall Street Journal article. Northwestern football coach Pat Fitzgerald implemented a mandatory nap time on game days, and is now credited with more victories than any previous Northwestern football coach.
Naps can improve mood, alertness and performance as well as boost creativity, reduce stress and aid in weight loss. “A nap allows information to move from temporary storage to more permanent storage, from the hippocampus to the cortical areas of the brain,” explains Rebecca Spencer, neuroscientist at the University of Massachusetts, Amherst, and an advocate for reinstating naps in pre-schools. “You’ve heard the phrase, ‘You should sleep on it.’ Well, that’s what we’re talking about.” As a result, the hippocampus is cleared of recent learning to make room for more. Sleeping before learning also primes the brain to absorb more.
The National Sleep Foundation recommends a nap of 20 to 30 minutes to improve short-term alertness. A NASA study found that a 40-minute nap improved pilots’ performance by 34 percent and alertness by 100 percent. And a recent study in the journal “Sleep,” comparing the benefits of naps of different lengths and no naps, found that a 10-minute nap produced the most benefit in reduced sleepiness and improved cognitive benefit without causing post-nap grogginess or interfering with nighttime sleep.
“We use naps to compensate for sleep loss, although you can’t make up for terrible nights,” said Dr. Helene Emsellem, medical director of the Center for Sleep and Wake Disorders in Chevy Chase. “The length of a nap is very personal. For some a five-to-10-minute nap can provide improvement for the next few hours. And a nap in the 20- to 30-minute range can reset you.”
As for how different-length naps fit with sleep cycles, the Wall Street Journal article explained that 60 minutes may be better for “cognitive memory processing” because that amount of time includes “slow wave” sleep. The article described a study in which learning a task was followed by different-length naps and no nap at all; tested one week later, the 60-minute nappers performed far better on the task, while the 10-minute nappers performed as badly as those who took no nap at all. Ninety minutes is what makes up a full sleep cycle, which has been shown to bolster creativity as well as memory.
But long naps come with greater risk of grogginess–what’s called sleep inertia or “sleep drunkenness.” Emsellem described “the edge we live on: It’s the in-between zone of 45 minutes to an hour that can make you feel poorly.” And, warning that long naps too late in the day can cause “huge problems with the sleep cycle, making it hard to go to sleep and pushing you into the land of the night owl”–she suggests the best napping hours are from 2 to 4 pm.
How best to nap? Most experts advise finding a place with limited noise and light, and sleeping at least partially upright to reduce sleep inertia. They also suggest drinking a caffeinated drink before napping to smooth the transition back to a waking state and to avoid the post-nap inertia. In a multi-center study on the effectiveness of naps and/or caffeine, the combination of the two had the most beneficial effect.
Sleep deprivation can reduce cognitive functions and impair memory. When focused, someone who is severely sleep-deprived can deliver the same results as someone who is not; but when the brain starts to lose focus, the healthy sleeper can compensate and increase attention, while the sleep-deprived brain has more trouble righting itself. According to experts at Stanford University School of Medicine’s Sleep Center, “a tell-tale sign of being very sleep-deprived” is dreaming during a nap that lasts 20 minutes or less.
Naps are not for everyone. People who take longer naps and wake very groggy can have trouble if they must perform immediately, and sleep inertia can be worse and last longer in people who are very sleep-deprived. Also, some people have trouble sleeping anywhere other than a bed, or during the daytime. Research on people who do not nap shows that these individuals move more quickly into deeper sleep stages when compared with experienced nappers, who are better at keeping their nap sleep light. The latter also show greater improvements in performance after napping than non-nappers.
The nap stigma still exists: Some people believe naps indicate laziness or low standards. Dr. Emsellem noted that a “startling number” of companies with facilities for napping found that these were unused, and some have changed the nap rooms back into work rooms. “The media and public education can make napping more acceptable,” she said. “But attitudinal changes take time.”
Nappers are in good company: In addition to Einstein, nappers have included Winston Churchill, John F. Kennedy and Thomas Edison, along with Ronald Reagan and George W. Bush.