Doing Life in Slow Motion

Insufficient sleep at different times slow you down even if you do not notice

(RxWiki News) So you think you function just fine on five or six hours of sleep each night? Chances are, you just don't realize you're moving slightly slower.

A recent study, though small, with only a dozen people, found that missing sleep while shifting sleep times has a more profound impact on the way people operate than they might expect.

"Get at least 7 to 9 hours of sleep each night."

The study, led by Marc Pomplun, of the Department of Computer Science at the University of Massachusetts Boston, involved 12 participants whose sleep was manipulated over a month.

During the first week, all the participants were given 10 to 12 hours a night to sleep, to be sure they had more than sufficient rest.

The following three weeks, however, they were only scheduled for 5.6 hours of sleep each night, and their bed time shifted according to a 28-hour cycle, which somewhat mimics chronic jet lag on a person's sleep cycles.

Participants completed visual search tasks on the computer, which the researchers timed and rated in terms of accuracy.

"Our team decided to look at how sleep might affect complex visual search tasks because they are common in safety-sensitive activities, such as air-traffic control, baggage screening, and monitoring power plant operations," said senior author Jeanne F. Duffy, PhD, MBA, an associate neuroscientist at Brigham and Women's Hospital.

"These types of jobs involve processes that require repeated, quick memory encoding and retrieval of visual information, in combination with decision making about the information," she said.

The researchers found that the longer the participants were awake, the more slowly they found what they were looking for on the computer tests.

As the study wore on, the participants identified relevant information for the computer search tests more slowly: their times were worse in the second and third weeks of the special sleep schedule than on the first week of the special schedule.

Yet the participants themselves did not appear to notice that they had slowed down more in the second and third weeks. Their self-ratings of their sleepiness were only slightly worse in the second and third weeks than in the first week of the special study schedule.

The participants also performed the tasks more slowly during the hours between midnight and 6 AM - even though the participants were isolated from any indications of the time of day during the study.

The accuracy of the participants' tests, however, did not seem to suffer after they had been awake for a while or depending on the time of day.

"This research provides valuable information for workers, and their employers, who perform these types of visual search tasks during the night shift because they will do it much more slowly than when they are working during the day," said Dr. Duffy. "The longer someone is awake, the more the ability to perform a task, in this case a visual search, is hindered, and this impact of being awake is even stronger at night."

The study was published July 26 in the Journal of Vision. The research was funded by a grant from the National Institutes of Health.

In addition, some of the authors were individually funded by the Fund to Sustain Research Excellence and fellowships from the La Roche and Novartis Foundations, Jazz Pharmaceuticals, and the Natural Sciences and Engineering Research Council of Canada. The authors declared no conflicts of interest.

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Review Date: 
August 9, 2012