Every work day, at about 3pm in executive lavatories across the United States, a strange phenomenon has been taking place. Toilet cubicles have become engaged and the sound of deep, steady snoring is resonating from behind the closed doors.

Snores have also been heard, at around the same time, from cars in employee car parks, from office stationery cupboards and from factory store rooms. And, at one workplace, there is an employee who is to be found at his desk every afternoon, head back, with his eyes tightly shut, holding a bottle of eye drops.

It’s not that he has a problem with his eyes; it’s just that he is keen to avoid the stigma of being caught napping. In a country built on a nose-to-the-grindstone labour doctrine, catnapping in the afternoon sits about as comfortably with workplace ethics as using a toilet roll holder for a pillow.

But new scientific research is slowly changing all that — and in recent months increasing numbers of switched-on American workers have been finding enterprising places where they can slip in a few extra winks.

According to the research, taking a power nap between 60 and 90 minutes long is as good as a full night’s sleep for restoring visual alertness. It increases a person’s productivity and concentration and also improves mood and the ability to learn new things. It can even leave a person refreshed enough to squeeze a second day’s work out of the same day.

“A nap will optimise your performance,” says Dr Sara Mednick, a psychologist at the Salk Institute in La Jolla, California, who conducted the research in between power naps on a couch in her office. “We have proved that we should all get over the stigma of an afternoon nap being lazy. If you take a nap, you can work later and so you have more of your day available to you.” To prove the benefits of the power nap, two groups of people were tested for basic visual tasks and perceptual skills on a computer at 9am.

Half did not nap during the day, while the other half were fitted with electrodes and sent to nap for 60 to 90 minutes in the afternoon. All then took another test at 7pm and were sent home to have at least seven hours’ sleep before being tested again the next day at 9am.

“What we found is that performance levels decreased at 7pm in those who didn’t nap,” Dr Mednick says. “But they recovered again the next day after a full night’s sleep.” Meanwhile, the nappers fell into two categories, those who achieved REM (rapid eye movement) sleep during their nap — which is the deeper kind of slumber of the two types of sleep that make up the architecture of a full night’s rest — and those who didn’t.

The performance levels from those who didn’t get REM sleep didn’t decrease at the end of the day but they didn’t show any increase either.

“Basically, at 7pm they were at the same performance level that they were at at 9am,” Dr Mednick says. “But those who did have REM in their nap actually showed a significant improvement in their performance at 7pm.

“What was even more significant was that after a night’s sleep, there was further improvement at the 9am test the next day. Their performance was equal to people who had two full nights of sleep between test sessions.”

The key to a worthwhile nap, Dr Mednick insists, is timing. “We are finding that it is necessary for the nap to have both REM and slow-wave sleep, the two components of a full night’s sleep, in order to show improved performance.

“And the handy thing about having a nap at about 2pm is that you get a good distribution of both REM and slow-wave sleep. We have found that if you nap too early in the morning you get too much REM sleep, if you nap too late in the afternoon you have too much slow-wave sleep.

“There is something very specific about the timing of the nap. It should be at about 2pm or 3pm. It’s the time when most humans and animals experience what is called a post-prandial dip or low ebb. It’s a dip in cogno-processing and physiological responses, when a lot of us actually do feel sleepy.”

The length of nap-time is also crucial — too long and some people wake up feeling groggy and slow; too short and there is no benefit. “It’s something that each individual has to figure out,” Dr Mednick says. “And it’s something worth experimenting with. We tested on 60 to 90 minutes but, for some people, 20 minutes is the perfect kind of nap.”

Unfortunately nap-time will never replace a full night’s sleep. All the research so far has shown that napping doesn’t interfere with nighttime sleep but it should never replace it.

“The National Sleep Foundation, which has conducted many sleep surveys, has found that people in the 21st century are sleeping less and working more,” Dr Mednick says.

“If we want to improve performance and productivity, we need people to be sleeping more. Maybe the way ahead is for them to be napping more.” And maybe the time when employers offer their staff somewhere more comfortable to snooze than the lavatories is not so far off.

NAPPING FACTS

The wife of Melvin Switzer, who won a British snoring competition in 1992 with a 92-decibel snore, has gone deaf in one ear

THE PERFECT 40 WINKS

For maximum benefit, a nap should be taken about 2pm or 3pm.