Too Much Work Proves Tiring Despite Good Sleep
Posted on Saturday, August 10 @ 00:00:00 EDT by dhf

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BALTIMORE -- Workers with a heavier cognitive workload experience fatigue and sleepiness regardless of how much rest they actually get, researchers reported here.

Control subjects who have a moderate workload and normal sleep rated their fatigue level about 20 on a visual analog scale (VAS), while similarly healthy individuals with a heavier workload averaged about 30 points higher in fatigue scores (P<0.05), reported Namni Goel, PhD, from the University of Pennsylvania in Philadelphia, and colleagues, at the annual meeting of the Associated Professional Sleep Societies.

"What we found was a workload effect whether one was sleep restricted or not," Goel told MedPage Today. "If the subject had a high workload, they had greater fatigue and sleepiness even if they were sleeping 8 hours a day." She noted that a fatigue effect, as expected, was seen in all individuals who were sleep deprived.

Sleep loss is known to degrade cognitive function, but it's uncertain if waking cognitive activity produces negative effects on fatigue and sleepless independent of sleep loss, the authors stated.

For this study, 63 healthy individuals (average age of 33 and 29 females) with no sleep pathology completed a 10-day controlled lab experience with randomization to one of four conditions:

  • Moderate cognitive workload and sleep restriction
  • High cognitive workload and sleep restriction
  • Moderate cognitive workload and no sleep restriction
  • High cognitive workload and no sleep restriction

Participants had three workload test sessions per day of either 120 minutes (high workload) or 60 minutes (moderate workload). Those without a sleep restriction were allowed 8 hours of rest for five nights. Those with a sleep restriction were allowed 4 hours a night over five nights.

On the self-rated VAS, when the scores of those with a greater cognitive workload were averaged, there was a large and significant difference, Goel said. She also said that on the 9-point sleepiness scale, those who had a higher cognitive workload showed a 2-point difference in being sleepier that was significant (P<0.05).

While workload did significantly increase subjective fatigue and sleepiness, it did not impact behavioral attention, physiological alertness, or executive functioning (P>0.005 for all), the authors reported.

Finally, sleep restriction produced significant cumulative increases in behavioral attention lapses, and decreases in behavioral attention response speed (P<0.05 for both).

"The results of this study provide the first experimental evidence that the amount of cognitive workload produces negative effects on subjective aspects of neurobehavioral performance independent of sleep loss," the group wrote. "Cognitive workload is an important factor worthy of consideration in a broad range of laboratory and applied settings in which demanding workloads are common."

"This is a very interesting finding," said Matthew Thimgan, PhD, from the Missouri University of Science and Technology in Rolla. "The more taxing the work, the more impact it is likely to have on how a person feels, how tired they are, and how much rest they are going to need."

"The results here are similar to what has been seen in studies on vacations, that workers who have time off tend to be more productive," he told MedPage Today.

"You can't just say 'Keep working more and you will get more accomplished.' It is not linear," he added.

This study was supported by the National Space Biomedical Research Institute.

The authors and Thimgan reported no conflicts of interest.

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