Adults who sleep eight hours or more may have shorter life spans than those who sleep less, says a new research. But experts say the study is flawed.
Based on a nationwide survey of 1.1 million adults, the study by Daniel Kripke of the University of California and others found that those who slept eight hours a night were 12 percent more likely to die within six years than those who got 6 1/2 to 7 1/2 hours, reported the online edition of USA Today.
The increased risk was more than 15 percent for those who reported getting more than 8 1/2 hours sleep, the study published in February's Archives of General Psychiatry found.
The participants were from ages 30 to 102. "Additional studies are needed to determine if setting your alarm clock earlier will actually improve your health," Kripke said.
Sleep experts, however, pointed out flaws in the research.
"Participants were not randomly selected, the study relied on their recollections and did not ask if they took naps, and it did not look at the quality of their sleep or whether they felt drowsy all day," they said.