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Daily Dose

How long does it take to pay back your sleep debt?

Think you can skimp on an hour or two of shut-eye every night during the week and just pay it back on the weekends by sleeping in? That’s not going to cut it if you want your brain to be at full functioning capacity, finds a study published in the American Journal of Physiology — Endocrinology and Metabolism. While other studies have found that a weekly sleep debt can be erased by sleeping for, say, 12 hours on a Friday night, this recent research suggests that our brains may not fully recover even if we’re not feeling fatigued.

The researchers had 30 volunteers sleep six hours in a sleep lab for six consecutive nights and then allowed them to sleep for 10 hours a night for three nights. The extra sleep helped lower elevated levels of stress hormones from the sleep deprivation and alleviated sleepiness.

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But study participants had lower scores on cognitive tests — measuring alertness and reaction times — than they had at the beginning of the study when they were well rested.

Does this mean a sleep debt can never be paid back? Not at all, said study author Alexandros Vgontzas, director of the sleep research and treatment center at Penn State University. But it may take longer to settle up and restore the brain to full function than previously believed.

Deborah Kotz can be reached at dkotz@globe.com. Follow her on Twitter @debkotz2.
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