In Learning, Short Nap Is
as Good as Night's Sleep
Excerpt By Alison McCook, Reuters Health

Research has shown that people need a good night's sleep in order to perform better on a number of tests that measure different skills. Now new findings suggest that, in the case of a visual test, a short nap does the job just as well as hours of nighttime z's.

U.S. investigators found that people who took a 60- to 90-minute nap after practicing a task that tests visual perception skills improved their performance just as much as if they had gotten a full night's sleep.

And people who got both a nap and a full night's sleep showed similar improvements in test performance to what would appear after two full nights of sleep, the study's lead author told Reuters Health.

"People who had a nap and a full night of sleep actually looked like they had two nights of sleep," said Dr. Sara Mednick of the Salk Institute in La Jolla, California.

She noted that the test used in the study measures how well people can use their eyes to pick out certain objects from their surroundings, a skill that applies to many areas of life.

However, these results describe only improvements on a specific test of visual skills, and Mednick cautioned that they do not suggest that sleeping for only 90 minutes is generally as good as a full night's rest.

"I don't think you can replace a night of sleep with a nap," she said.

During the study, published in the advance online issue of Nature Neuroscience, Mednick and her team asked around 70 people to complete a basic visual test in which they had to spot a specific image on a screen filled with other images.

Tests occurred at 9 a.m. and 7 p.m. on the same day.

Some of the study participants were allowed to take a nap in the mid-afternoon, lasting either 60 or 90 minutes.

In an interview, Mednick explained that research has shown that any "improvement" in the test -- meaning, spotting the target image faster than in previous rounds -- occurred only after test takers had a good night's sleep.

In contrast, asking people to repeat the test many times on the same day, without giving them a break to sleep, tends to worsen their performance, Mednick said.

In this study, however, Mednick and her team found that people who took a nap that included both deep, slow-wave sleep and the lighter, dream-filled sleep stage known as REM showed improvements on their afternoon test that were similar to what would typically have been seen after a night's rest.

"That improvement was equal to the amount of improvement you would show if you'd had six hours of sleep," Mednick said.

"So the nap was actually as good as a night of sleep to show learning, in this specific task," she added.

And taking a nap and having a good night's sleep improved test performance even further, equivalent to what was seen from non-nappers after two nights' rest, Mednick said.

She noted that the time of day a person takes a nap is probably important. The naps that led to test improvements were those that featured both slow-wave and REM sleep, Mednick said, and naps that take place in the morning or evening -- as opposed to the afternoon -- typically contain either one or the other sleep stages.

SOURCE: Nature Neuroscience 2003;doi:10.1038/nn1078.

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