November 25, 2008

Enjoy your Thanksgiving Nap: It’s Healthy!

Just in time for Thanksgiving, some new medical advice many people will be happy to hear: Take a nice, long, turkey induced nap.

Interrupting sleep badly interrupts memory-making, convincing new research implies. However, taking a nap can increase a sophisticated form of memory that aids in seeing the big picture and become more artistic.

"Not only do we need to remember to sleep, but most certainly we sleep to remember," said Dr. William Fishbein, a cognitive neuroscientist at the City University of New York.

High-quality sleep is a thing of the past in our current world. Surveys indicate that very few adults achieve the suggested seven to eight hours every night.

Very little sleep is risky, because sleep deficiency can cause not just car accidents, but all kinds of other things. Eventually, a constant lack of sleep can wear down the body that leaves us defenseless to heart disease, diabetes and other maladies.

Nevertheless, even more ordinary than insomnia is disjointed sleep: the simple awakening that comes with aging or the sleep apnea that bothers millions, who stop breathing for 30 seconds or frequently in the night.

Certainly, scientists more and more are centering less on sleep length and more on the superiority of sleep, by investigating how sleep aids the brain develop memories so they endure. Most essential is "slow-wave sleep," a phase of very deep sleep that precedes the better-known REM sleep, or dreaming time.

Fishbein assumed a more active function for the slow-wave sleep that can appear even in a power nap. Inspired, he and graduate student Hiuyan Lau created an easy test: recording relational memory, where the brain combines individually learned facts in fresh ways.

Fishbein and Lau taught 20 English-speaking college students several simple Chinese words. Then half the students took a brief nap, being watched to ensure they didn't transition from slow-wave sleep into the REM stage.

Once they awoke, they were given a multiple-choice test of Chinese words they hadn't been taught. The students who took a nap did much better at the exam. They were also better at the non-nappers at determining new words.

"The nap group has essentially teased out what's going on," Fishbein conceded.

These students were allowed to take 90-minute nap, unrealistic for most adults. However, even a short 12-minute nap can increase some kinds of memory, adds Dr. Robert Stickgold of Harvard Medical School.

On the other hand, Wisconsin researchers temporarily interrupted nighttime slow-wave sleep by playing a beep, loud enough to agitate sleep but not to wake them up, and discovered that those people did not recall any tasks they'd learned the day before.

It just goes to show that fragmented sleep can repress the beginning of new brain cells being created in the hippocampus, where memory-making starts, enough to stop knowledge weeks after sleep returns to normal, adds Dr. Dennis McGinty of the University of California, Los Angeles.

"A short sleeper may have a very efficient deep sleep even if they sleep only four hours," notes Dr. Chiara Cirellia of the University of Wisconsin, Madison.

All in all, the findings do propose realistic suggestions: get tested for a sleep disorder is you have trouble sleeping. Stay away from what Harvard's Stickgold calls "sleep bulimia," late evenings followed by sleep-in weekends. Most of all: never feel guilty for taking a nap.


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