Lack of sleep has been blamed for everything from poor driving to memory problems. Now, researchers think they’ve started to pinpoint why: week-long sleep studies of people resting for 10 hours a night vs. six hours showed significant changes in gene activity.

When sleep was restricted to under six hours a night, researchers noted that 444 genes showed suppressed activity, and 267 genes showed more activity. Those genes control everything from the body’s immune system to its reaction to stress.

NEWS: New Bio-Bulbs Could Help You Sleep

“The surprise for us was that a relatively modest difference in sleep duration leads to these kinds of changes,” study author Professor Derk-Jan Dijk, director of the Surrey Sleep Research Centre at Surrey University, told The Guardian. “It’s an indication that sleep disruption or sleep restriction is doing more than just making you tired.”

The team’s study, published in the Proceedings of the National Academy of Sciences, analyzed the sleep patterns of 26 healthy men and women who spent two separate weeks in a lab where they were allowed to spend 10 hours in bed one week, and six the other week. During the longer nights, the participants averaged 8.5 hours of sleep. They averaged 5 hours, 42 minutes during the shorter nights.

BLOG: Alarm Clock Shocks You Awake

Genes that govern the body’s wake-sleep cycles were dramatically affected, meaning that some sleep loss could provoke ongoing sleep issues.

One expert not involved in the study urged caution, however.

“We must be careful not to generalize such findings to, say, habitual six-hour sleepers who are happy with their sleep,” Jim Horne, professor of psychophysiology at Loughborough University’s Sleep Research Center, told The Guardian.

Besides, sleep can adapt to some change, and should also be judged on its quality, not simply on its total amount.”

Photo: iStockPhoto