In most modern societies, adults will often sacrifice sleep during the week to make time for other demands then sleep longer on the weekend to recover from that lost sleep. Recent research has shown that even a few days of lost sleep can have adverse effects, including  an increase in daytime sleepiness, poor daytime performance, an increase of inflammation in the body, and impaired blood sugar regulation. The last two effects could be at least partially responsible for why less sleep negatively affects health in other ways and can shorten lifespan. Many people believe they can make up for lost sleep lost  by sleeping more on the weekend, but it’s not clear if this recovery sleep can adequately reverse these adverse effects of sleep loss.

To help find an answer to this question, a team of researchers led by Alexandros N. Vgontzas of the Penn State University College of Medicine, placed 30 volunteers on a sleep schedule that mimicked a sleep restricted work week followed by a weekend with extra recovery sleep. The researchers assessed the volunteers’ health and performance using a variety of different tests at various times during this sleep schedule.

Researchers discovered that the volunteers’ sleepiness increased significantly after their sleep was restricted, but returned to baseline after getting recovery sleep. Levels of the molecule in blood that serves as a marker for the amount of inflammation present in the body increased significantly during sleep restriction, but returned to normal after recovery sleep as well. Also, levels of a hormone that serves as a marker of stress didn’t change during sleep restriction, but significantly lowered after recovery sleep.

The volunteers’ measures on a performance test that assessed their ability to pay attention deteriorated significantly after sleep restriction, but did not improve after recovery sleep. This result suggests that recovery sleep over only a single weekend may not be able to reverse all the effects of sleep lost during the work week.

“Two nights of extended recovery sleep may not be sufficient to overcome behavioral alertness deficits resulting from mild sleep restriction,” the authors of the study write. “This may have important implications for people with safety-critical professions, such as health-care workers, as well as transportation system employees.”

“The long-term effects of a repeated sleep restriction and sleep recovery weekly cycle in humans remains unknown,” they also write.

This study is titled “The Effects of Recovery Sleep After One Workweek of Mild Sleep Restriction on Interleukin-6 and Cortisol Secretion and Daytime Sleepiness and Performance”  and appears in the American Journal of Physiology-Endocrinology and Metabolism which is published by the American Physiological Society.