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Brief Naps More Recuperative for Sleep Deprived.

LAS VEGAS -- For people who are sleep deprived, a 10-minute nap is more effective than a 30-minute nap in producing an immediate and sustained recovery in alertness, mood, and performance.

The finding suggests that a brief nap may be the most efficient way to recover from the adverse effects of sleep deprivation, Dr. Leon Lack said at a joint meeting of the American Academy of Sleep Medicine and the Sleep Research Society.

He and his associates compared brief naps with longer naps following acute nocturnal sleep restriction. They enrolled 12 college students with a mean age of 20 years and no history of sleep complaints or daytime napping. Subjects got 5 hours of sleep on each evening prior to laboratory sessions in which they participated in each of three napping conditions: no nap, a to-minute nap, and a 30-minute nap, presented in a counterbalanced order, said Dr. Lack of the department of psychology at Flinders University in Adelaide, Australia.

Investigators administered the Stanford Sleepiness Scale, the Profile of Mood States, and cognitive performance tasks (symboldigit substitution and letter cancellation) three times during each session: before the nap, 5 minutes after the nap, and 35 minutes after the nap. They assessed objective alertness by sleep-onset latency measured before the nap and 1 hour after the nap.

The 10-minute nap yielded significant increases in subjective alertness and cognitive performance at 5 minutes and 35 minutes after napping. Vigor also was improved 35 minutes after napping, Dr. Lack reported.

In contrast, the 30-minute nap produced immediate declines in subjective alertness, mood, and performance that were comparable to the no-nap condition. This was followed by trends of recovery on all measures, with letter cancellation performance showing significant improvement by 35 minutes after the 30-minute nap.

This indicates a relatively brief detrimental effect of sleep inertia following the 30-minute nap. At no point up to an hour following the naps did the benefits of the 30-minute nap exceed those of the 10-minute nap, he said.

In a related study, Thomas Stauble and his associates in the laboratory of human chronobiology at Cornell University in New York found that nighttime sleep is not impaired when adults take daytime naps. The finding may have implications for older patients, especially those in nursing homes who are encouraged to nap during the day.

Mr. Stauble and his associates enrolled five subjects aged 55 or younger and four aged 66 or older. Two successive nights of ad libitum sleep were immediately followed by 72 hours in the sleep lab.

Subjects were assigned to a "nap day" (more than 30 minutes of sleep between 9 a.m. and 6 p.m.) during one day, and a "wake day" (less than 30 minutes of sleep between 9 a.m. and 6 p.m.) during another day Six subjects had a nap day followed by a wake day; the sequence was reversed for the other three subjects. The nighttime sleep episodes immediately following these daytime periods were analyzed; these episodes were more than 4 hours in length and started between 8 p.m. and 3 a.m.

Sleep duration, sleep efficiency, and slowwave sleep levels were similar during the nighttime sleep periods following a daytime nap and during the sleep periods following a day without napping, he reported.

In subjects 66 years and older, napping appeared to influence sleep composition. Investigators observed reductions in REM sleep levels in nighttime sleep episodes that were preceded by daytime naps.

Mr. Stauble said that he and his associates have launched a study to examine the effects of nap composition and circadian placement on nocturnal sleep measures.
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Publication:Family Practice News
Article Type:Brief Article
Geographic Code:1USA
Date:Sep 15, 2000
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