[to top of second column]
Cognitive and motor skills tests every few waking hours measured the volunteers' ability to stay alert and attentive, with results compared to similar volunteers getting a normal amount of sleep.
The well-rested can catch up from the occasional all-nighter fairly easily. But as the study wore on and the volunteers became more sleep-deprived, the rejuvenation they felt each time they awoke increasingly proved a facade, Cohen reported Wednesday in the journal Science Translational Medicine.
They functioned OK during their first few waking hours, especially that first week. But then their reaction times steadily worsened with each hour they stayed awake, with a big drop in performance between the first and second weeks of sleep deprivation, he found.
That daytime decline was subtle, and the people's circadian rhythms provided a bit of rescue. Know how most people get a bit tired in the afternoon? Even these sleep-deprived volunteers got an energy boost then, as their circadian rhythms kicked in.
But when they stayed up past bedtime yet again, their performance suddenly plummeted just as their circadian rhythm reached its natural lowest point, Cohen's team found. The drop was so sharp that he concluded these people were increasingly vulnerable to accidents and errors.
"When exposed to the next all-nighter, they really fall apart much faster than they previously would," said Cohen, also a neurologist at Beth Israel Deaconess Medical Center.
Stay tuned: Scientists don't yet know how quickly you recover from chronic sleep loss once you resume a good bedtime, Cohen said.
Copyright 2010 The Associated Press. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.
< Recent articles
Back to top
News | Sports | Business | Rural Review | Teaching & Learning | Home and Family | Tourism | Obituaries
Law & Courts |
Spiritual Life |
Health & Fitness |
Calendar | Letters to the Editor