Need an excuse to take a mid-afternoon snooze? Here’s a pretty good one. (Photo: Getty Images)
Naps may be good for more than helping you stay alert and focused during the day — according to a small new study, they could also be a boon to the body’s immune system.
Researchers from the Université Paris Descartes-Sorbonne Paris Cité found that after a night of little sleep, a 30-minute nap had beneficial effects on levels of hormones associated with the immune system.
"Napping may offer a way to counter the damaging effects of sleep restriction by helping the immune and neuroendocrine systems to recover," study researcher Brice Faraut, PhD, said in a statement. “The findings support the development of practical strategies for addressing chronically sleep deprived populations, such as night and shift workers.”
For the study, published in the Journal of Clinical Endocrinology & Metabolism, researchers had 11 healthy 25-to-32-year-old men undergo two three-day sessions of sleep testing in a lab setting, where meals and lighting were all controlled by the researchers.
For each session, the study participants spent eight hours in bed one night, were only allowed two hours of sleep the second night, and then were allowed to have unlimited sleep the third night. But the sessions differed this way: For one of the sessions, the participants were not allowed to take any naps after the night of two hours’ sleep. But for the other session, the participants were able to take two 30-minute naps during the day following the night of two hours’ sleep.
Researchers gauged participants’ hormone levels through collection of urine and saliva samples, and found that when the men were limited to just two hours of sleep at night, their levels of norepinephrine were 2.5 times higher than when they got eight hours’ sleep. (Norepinephrine is a hormone that plays a role in the body’s fight-or-flight response, and can increase blood pressure and heart rate.) But when the men were allowed to take the 30-minute naps in the morning and afternoon, “these changes in norepinephrine levels were not present,” the researchers wrote in the study.
Levels of interleukin-6 — a protein that’s involved in inflammation and the body’s infection response — also seemed to be affected by the sleep deprivation. Levels of the protein decreased when the participants got two hours of sleep at night, but the levels remained normal when they got two hours’ sleep but were allowed to nap.
The new findings add to a body of research on sleep and the immune system, which seems to show a sort of bidirectional relationship between the two, says Philip Gehrman, PhD, CBSM, an assistant professor in the Department of Psychiatry at the University of Pennsylvania and member of the Penn Sleep Center, who was not involved in the new study. “Some aspects of the immune response promote better sleep, while others disrupt sleep,” Gehrman tells Yahoo Health.
For instance: When people sleep more when they’re sick, “that’s because some of the immune markers produced make us feel sleepy,” he says. “One theory is we have that system in place because it gets us to sleep more when we’re sick, and that it helps our immune system.”
But in general, it’s known that when we sleep better, our immune system tends to be stronger. And it’s certainly possible that if a person is sleep-deprived, a nap can at least help to counter some of the effects of a weakened immune system, he says.
And while it may not seem like 30 minutes of mid-day shut-eye is a lot, Gehrman notes that “you can get a lot of bang for your buck with a short nap.” In fact, he says, research shows that shorter naps — think minutes, not hours — are associated with increased alertness. “There’s something that’s happening very fast when we nap that is really not understood,” he says. “But it doesn’t surprise me that only a 30-minute nap would have such a positive benefit.”
For a nap with maximum effectiveness, Gehrman suggests keeping your snooze to under 30 minutes, and taking one in the mid-afternoon when you hit that dip in alertness. “And of course, the closer you get to bed, the more a nap is a bad idea,” he advises.
And if you’re sick? Nap away: “I kind of say when you’re sick, all bets are off — just get the sleep you need,” he says. “The sleep is just going to be better for you. Don’t worry about it being a power nap.”