Take a nap

BALTIMORE — A cup of joe or a short nap can fend off normal afternoon sleepiness, but sleeping longer in the morning won’t keep a person who’s already gotten a full night’s sleep alert, a new study shows.

Researchers from the Sleep Research Center at Loughborough University in England tested 20 healthy young adults for daytime sleepiness. All of the volunteers got about 7.4 hours of sleep per night, and none of them complained of feeling sleepy. But when researchers put them in a quiet room and asked them to close their eyes — something the volunteers were asked to do several times in the afternoon and evening — all fell asleep within five to 10 minutes in the afternoon, indicating sleepiness. It took longer for the people to fall asleep when tested at other times, indicating that while they were drowsy in the afternoon, the people weren’t generally fatigued.

Previous studies by other groups have shown that extending nighttime sleep by 90 minutes for two weeks could help combat afternoon sleepiness, but the Loughborough team wanted to know whether naps or caffeine might also help, said Clare Anderson, lead author of the study presented Monday in Baltimore at the annual meeting of the Associated Professional Sleep Societies.

The researchers compared sleeping in for 90 minutes each morning to taking a 20-minute nap at 2:30 p.m. or taking 150 milligrams of caffeine (equivalent to about two cups of coffee) at 2:00 p.m. Each participant tried each of the three methods of combating afternoon slumps for one week. Although all of the volunteers normally drank caffeinated beverages, during the experiment they received decaffeinated drinks and took caffeine pills when tested for the effect of the afternoon caffeine kick.

When the volunteers did nothing, they fell asleep within nine minutes on average when tested at 3:30 in the afternoon. Sleeping late kept people awake only a minute longer on average than did doing nothing. Caffeine worked better, keeping people awake for about 12 minutes longer on average.

But nothing beat a nap. After a 20-minute nap, people nearly doubled the amount of time it took to fall asleep when tested later in the afternoon, indicating that they were no longer sleepy. None of the measures impaired people’s ability to fall asleep at night.

The study shows that several measures can fend off the afternoon slump, said Dennis Nicholson, a spokesman for the American Academy of Sleep Medicine and medical director of the Sleep Disorders Center at Pomona Valley Hospital in California. But “from a practical standpoint, it’s not feasible to have those naps,” he said.

Anderson said that while napping is the clear winner in combating afternoon drowsiness, caffeine is probably a more socially acceptable alternative.

“Napping is seen as some kind of laziness,” she said, “or something associated with old people.”