Your mother always told you to get eight hours of sleep. A recent study suggests that those who sleep six to seven hours per night may live longer, however.

According to an article by University of California-San Diego professor Daniel Kripke, people who sleep just six or seven hours per night have a lower mortality rate than those who sleep the conventional eight or nine.

The study included 1.1 million men and women between the ages of 30 and 102 years of age. It was conducted by the American Cancer Society from 1982 through 1988.

The study found that those who sleep eight hours or more, and those who sleep six hours or less, were subject to a significantly increased mortality rate.

“I wouldn’t put too much emphasis on this study,” said Selden Spencer, doctor of neurology at McFarland Clinic. “Too many factors go into sleep for the individual.”

“There are a number of flaws scientifically with this study,” said Marc Shulman, staff physician for the health center.

“Longevity appears to be increased slightly, but it says nothing about the quality of life,” Shulman said. “The study also doesn’t take napping or daytime drowsiness into effect. If anything, this study gives us more questions for more research.”

Sleeping less than six hours is detrimental health and causes an accumulated sleep-lag, just as sleeping 10 or more hours is unhealthy, Shulman said.

“I don’t know why people sleep longer or shorter any more than I know why people have long or short noses,” Spencer said.

The amount of sleep an individual needs changes with age. Babies need a much larger amount of sleep than elderly people do. Studies show that teenagers and those in their 20s are more productive when they sleep eight to nine hours a night, Shulman said.

“I wouldn’t take this study and say that you should only sleep seven hours a night, especially if you’re college-aged because that’s a population that has not been looked at,” Shulman said.