Here’s a warning for those who get very little sleep during the week but figure they can make it up by sleeping late on Saturday: It just doesn’t work that way.
A new study at the University of Pennsylvania School of Medicine shows that those who accumulate a sleep debt over long periods of time may need multiple nights of extra sleep to get back to the “plus” side. The study involved 159 healthy adults with an average age of 30, which is the largest number of subjects to be involved in a single laboratory-based experiment on sleep restriction. Their findings are published in the August issue of the journal Sleep.
Participants in the study were only allowed to sleep from 4 a.m. to 8 a.m. for five consecutive nights. Then they were randomly assigned to one of six doses of recovery sleep ranging from zero to 10 hours in bed for one night. Seventeen of the participants made up a control group that spent 10 hours in bed on all nights. In the morning, researchers tested the participants on tasks designed to assess so-called neurobehavioral functions including alertness, reaction times and other indicators of mental impairment.
The scientists found that the participants neurobehavioral functions improved after the recovery night, but lapses of attention, sleepiness (as reported by subjects), reaction times and fatigue scores all remained higher than initial levels.