People Who Sleep Less Live Longer, U.S. Study Finds
Researchers from the University of California at San Diego found in a study of adults aged 30 to 102 that people who slept eight hours a night were 12 percent more likely to die within the study's six-year period compared to those sleeping seven hours. The increased risk rose to 15 percent for participants reporting more than eight hours or less than 4-1/2.
"People who sleep five, six or seven hours have nothing to worry about. There is no evidence that people need eight hours of sleep ... the only basis for that is it's what grandma used to say," Reuters quoted Dr. Daniel Kripke, a UCSD professor of psychiatry and the study's lead author, as saying in an interview.
He said the study shows that longer sleep is a risk factor for cancer as well as heart disease and stroke, but more research is needed to determine whether sleeping longer should be added to the growing list of one-time pleasures -- like smoking and alcohol -- now deemed hazardous to your health.
Other researchers also cautioned against strict interpretation of the findings. "Many studies show that if people don't get adequate sleep they are very sleepy during the day. Their ability to perform tasks is impaired, the risk of accident is higher and people are crabby," said James Walsh, a sleep scientist and president of the National Sleep Foundation. He also said the San Diego study was not a true random sampling of the population and more studies are needed.
Kripke, an eight-hour-a-night sleeper, said the average American gets 6-1/2 hours of shut-eye, which is just fine. "Neither in terms of health or survival is there any evidence that eight hours of sleep is better than six or seven. Nor is there any evidence that longer sleepers are rich or have more fun," he added.
Walsh said the weight of evidence still suggests that the average adult needs 7-1/2 to 8-1/2 hours of sleep to be wide awake, energetic and alert during the day.
---- Insomnia Does Not Increase Death Risk ----
The study found little, if any, connection between death rates and insomnia, which it said patients commonly complain of even when their sleep duration is within normal ranges.
Kripke said people who take sleeping pills were shown to have a slightly higher death rate than others, but because the data was collected in the 1980s, the results are not necessarily reflective of newer types of sleeping pills.
The research, which addressed sleep issues as part of a broader cancer prevention study done with the American Cancer Society, is published in Friday's issue of the **** Archives of General Psychiatry****.
An accompanying commentary by Dr. Daniel Buysse and Dr. Marry Ganguli of Western Psychiatric Institute and Clinic in Pittsburgh also cautioned that sleep deprivation can raise accident rates.
The best survival rates were found for people who slumbered seven hours a night -- about 32 percent of women in the study and 34 percent of the men fell into this category. People with as little as five hours of sleep lived longer than participants with eight hours or more per night.
The study was not designed to say how much longer a person who gets between five and seven hours of sleep will live when compared to people who average eight or more hours.
Heart disease was the most common cause of death, followed by stroke and cancer.
The study was designed to account for dozens of variables, such as age, health problems and education, that would affect life span. The mean age was 57 for women and 58 for men.
Although the research was conducted from 1982 to 1988, the results have not been available until recently because of technological constraints and the length of time required to analyze the vast amount and variety of data.
The Sleep Foundation's Walsh said the study does not prove that people who get seven hours of sleep have longer lives -- it shows only a statistical relationship.
"One shouldn't conclude that there aren't any negatives to either insomnia or short sleep," he added. "Mortality is not the only health-related factor. If quality of life is dramatically worse, I think most people would choose longer sleep as opposed to living in a fog of sleepiness."
Kripke likened the habit of lingering in bed to overeating. "Everyone knows that eating too much is bad for you. If you eat a little bit less than you desire, you will live longer," he said. "It is also true that if we look across the mammalian kingdom, the short sleepers live longer."
He said some sleep loss actually acts as an antidepressant.