If you’re feeling especially tired today — and it’s Monday — it may be because you didn’t get your normal recharge of sleep this past weekend.
So says a new study published in the journal Sleep by David Dinges and his colleagues.
Researchers came to this conclusion after analyzing the results of a sleep deprivation study on 159 healthy, middle-aged adults.
A group of 142 participants were sleep-deprived by allowing them only four hours of sleep for 5 consecutive nights. But before the sleep deprivation, these subjects were first given two nights of 10-hour sleep periods, to ensure all participants started at similar sleep levels.
They were then allowed randomized doses of recovery sleep ranging from zero hours to 10 hours for per night.
The other 17 participants in the study spent 10 hours in bed on all nights.
To measure the effects of these sleep manipulations, researchers administered 30-minute computer-based assessments that measured things like attention span and reaction time every 2 hours while the subjects were awake.
Those whose sleep had been restricted were found to have a shortened attention span, impaired alertness and reduced reaction time. But their cognitive functioning returned to normal range after just one full night of sleep.
The study also showed, not surprisingly, that people who had no sleep during the experiment performed significantly worse than normal.
“You don’t realize now just how far off normal you are or how much more alert you could be if you’ve gotten more sleep,” says Dr. David F. Dinges, one of the study authors and Chief of the Division of Sleep and Chronobiology at the University of Pennsylvania School of Medicine.
Dinges also says people who chronically receive less sleep than their body needs — typically 7 to 8 hours a night — need regular recovery periods of sleep because most people cannot handle sleeping only a few hours a night. But ideally, most people should try and get a good night’s sleep every night and not rely on recovery sleep on the weekends alone.
“Getting recovery sleep is important and that may take more than a day, ” says Dinges.
The upshot? Weekends allow most of us to “recover” some of the cognitive functioning we lose during the week due to abbreviated or shortened sleep schedules. Even just one night of significant sleep — e.g., 10 hours — can be enough to put us back on track for the upcoming week.
So if you’re feeling especially lethargic or tired today, the answer may be as simple as not getting enough sleep on the weekends.
Banks, S., Van Dongen, H.P.A., Maislin, G., & Dinges, D.F. (2010). Neurobehavioral Dynamics Following Chronic Sleep Restriction: Dose-Response Effects of One Night for Recovery. Sleep, 33, 1013-1026.