Sleep hogs beware. A new study suggests that individuals who sleep eight hours or more a night actually have an increased death rate compared with those who average just six or seven hours. The findings appear today in the Archives of General Psychiatry.

Daniel F. Kripke of the University of California at San Diego and his colleagues scrutinized the sleeping habits of more than 1.1 million adults aged 30 to 102, taking into consideration such variables as age, diet, exercise, previous health problems and known risk factors such as smoking. The team found that subjects who slept seven hours a night had the best survival rates. In fact, according to the report, the group sleeping eight hours a night were 12 percent more likely to die over the course of the study than were those sleeping seven hours a night. Moreover, people sleeping as little as five hours a night also lived longer than eight-hours-plus sleepers did. There does appear to be a minimum rest requirement, however, because sleeping less than four hours a night was also associated with an increased death rate.

According to Kripke, this study's subject pool is the first large enough to differentiate between seven and eight hours of sleep. But the results do not explain the reasons behind the relationship between long slumber and an increased death rate. "We don't know if long sleep periods lead to death," Kripke notes. "Additional studies are needed to determine if setting your alarm clock earlier will actually improve your health." But if you're one of the lucky ones who feel alert after six hours of snoozing, rest assured. Says Kripke, "From a health standpoint, there is no reason to sleep longer."