Too Little, Too Much Sleep Harms Health; Exercise May Shorten Sleep Duration

June 8, 2009— -- Getting too little sleep -- or too much -- may lead to a higher risk for obesity, diabetes and premature death, according to a number of studies released at this year's meeting of the Associated Professional Sleep Societies in Seattle today.

Taken together, the studies add weight to existing evidence that those who regularly get fewer than five hours of sleep or more than nine hours of sleep may be putting themselves at risk of a host of health ills.

"It's probably the most powerful medicine we have, and the truth is not enough of us take it," ABC News Medical Contributor Dr. Marie Savard said on "Good Morning America," adding that the health risks of not getting enough sleep range "from diabetes to obesity, and up to increasing the risk of premature death."

Specifically, one study found that those who slept five hours or fewer per night were 24 percent more likely to develop diabetes, while those who slept nine or more hours per night were 48 percent more likely to develop diabetes than those sleeping more typical hours.

A second study found that both black and white Americans had a greater chance of obesity when they slept five hours or fewer per night. And a third study in men found those regularly sleeping less than six hours had a greater risk for premature death.

The underlying reasons for these trends remain a mystery, Savard said, although she said that medical conditions such as sleep apnea may play a role.

To Get Longer Sleep, Skip the Workout?

A potentially more controversial piece of research out of Walter Reed Army Medical Center in Washington, D.C., found that exercise may lower the total amount of time that people sleep.

This finding flies in the face of doctors' recommendations to exercise as a way to sleep better at night. And Savard noted that the small size of the study -- which looked at 14 subjects over 23 days -- must also be taken into account.

Get Your Sleep Questions Answered at the ABCNews.com OnCall+ Wellness Center

Still, researchers found that total sleep time increased by an average of 42 minutes per night after days of low physical activity. In contrast, people slept less after days when they got a lot of exercise.

Exercise May Be Tied to Shorter Sleep but Don't Skip Workouts

"This is a small study, so I would warn you not to give up your exercise," Savard said. "What is the takeaway? I don't think we know in the end."

But she noted that the finding could be tied to the idea that those who try to pack their day with activities and tasks may not leave enough time for sleep. She also noted that those who are diligent about exercise may have more stress in general, which could also impact their ability to sleep.

"The message may be to us that we do too much," she said. "Maybe we try to fit in too many activities throughout the day."

The ABC News Medical Unit contributed to this report. Get answers to more of your questions on sleep, such as the things you can do to get a better night's sleep, how alcohol affects sleep, and sleep apnea, at the OnCall+ Wellness Center.