But don't press the snooze bar too many times, because oversleeping might bring the same result.

Those are the surprising findings of a new study that suggests too little or too much sleep could lead to the blood sugar disease, at least in older people.

"This is one additional piece of information bolstering the common recommendation for sleeping seven to eight hours a night," said study co-author Dr. Daniel Gottlieb, an associate professor of medicine at Boston University.

Gottlieb and his colleagues examined statistics on the health of 1,486 participants in a 1995-1998 study that studied the cardiovascular effects of sleep disorders that affect breathing. The participants were aged 53-93.

The goal of the researchers was to see if they could find a link between sleep levels and impaired ability to process glucose, a hallmark of diabetes. They report their findings in this week's issue of the Archives of Internal Medicine.

Compared with those who slept seven to eight hours, those who slept fewer than five hours were 2.5 times more likely to have diabetes. The diabetes rate was slightly lower -- 1.7 times -- for those who slept six hours.

The diabetes rates were also higher -- by 1.7 times -- for those who slept more than nine hours.

Since the researchers adjusted the statistics to remove any influence of gender, age, race or body type, Gottlieb said it seemed likely that there was a direct cause-and-effect connection between sleep and diabetes.

After all, previous studies showed that people forced to sleep for only four hours a night began to develop problems processing glucose, he noted.

The link between diabetes and longer sleep times "is a lot harder to explain," Gottlieb said. "We don't know very much about what might be the cause. It's my belief that people who are sleeping nine hours or more a night are usually doing so because they have some underlying disorder."

According to previous studies, Americans have been sleeping less over the past several decades. The median sleep time for American adults aged 40-79 was eight hours per night in 1959; it dropped to seven hours in 2002, with more than one in three sleeping fewer than seven hours.

Dr. Jennifer G. Robinson, a professor of medicine and epidemiology at the University of Iowa, said the findings make sense because disruptions in sleep rhythms put high levels of stress on the body.

"We certainly are understanding, really within the last decade, about the complexities of sleep and the prevalence of sleep disorders," she said. "It's quite high, and there's certainly a lot of potential for adverse health impacts."

As for the link between sleep and diabetes, she added that depression could play a role because affected people sleep too much or too little. "We know that depression is related to inflammation, diabetes and heart disease," she said.

The good news? "Because of all the research, we're finding that there are things we can do to help people sleep better," Robinson said.

(China Daily/Agencies April 28, 2005)