SAN DIEGO, Feb 14, 2002 (United Press International via COMTEX) -- Research released Thursday on more than 1 million adults shows people who get 6 1/2 to 7 1/2 hours of sleep a night have a lower death rate than those sleeping more than eight or less than six hours.
Daniel F. Kripke, of the University of California at San Diego's Department of Psychiatry, told United Press International: "The study does not prove that somebody will live longer if they set the alarm earlier, nor do we advise people to restrict sleep. What we emphasize is that somebody who is a short sleeper has nothing to worry about."
"Personally, I feel fatigued if I don't get eight hours sleep, and so that is what I choose to do," Kripke said.
Experts who reviewed the study also urged caution in interpreting the findings.
The study, based on a survey done by the American Cancer Society in the 1980s, showed participants who reported sleeping eight hours or more or six hours or less died more frequently -- with an increased risk of about 15 percent.
The research showed, however, "reports of 'insomnia' were not associated with excess mortality hazard." People who used sleeping pills were much more likely to die, many from suicide by using the pills.
The authors concluded: "Patients can be reassured that short sleep and insomnia seem associated with little risk. ... Slight risks associated with eight hours sleep (or more) and sleeping pill use need further study."
The authors said no causal relationship has been proven between the length of sleep and risk of death. The results appear this week in the Archives of General Psychiatry, a journal of the American Medical Association.
David N. Neubauer, associate director of the Johns Hopkins Sleep Disorders Center and a member of the psychiatry department at Johns Hopkins in Baltimore, said: "The wrong conclusion to draw from all of this is that this study shows that we should cut back on our sleep to try to achieve a healthier and longer life, because there really isn't evidence for that. In fact, there is increasing evidence in the opposite direction."
Neubauer said the survey doesn't say anything about causation. "This is really not measuring health. This is measuring death. There's a huge gap between measuring health and measuring death. There's a huge gap between being healthy and being dead," he said.
The study also does not address quality of life or safety, Neubauer stressed. "We believe that sleep deprivation is a huge problem and that our whole society suffers tremendously because of widespread sleep deprivation," he noted.
Endocrine and immune system changes can occur with sleep deprivation. "We recommend the amount of sleep that people will achieve on their own without an alarm clock, and for most people that's about eight hours," he said.
Phyllis C. Zee, director of the Sleep Disorders Center at Northwestern Memorial Hospital in Chicago, said the results were interesting but further research is needed.
"I don't think that in this study a causal relationship has been established between sleep duration and longevity, and therefore, based on the findings in this study, one can not and should not conclude that sleeping less than eight hours a day is good for you, or for that matter, sleeping 6 1/2 hours a day is enough or safe."
Kripke said the study "does not prove that long sleep in itself is unsafe. It does prove that something associated with long sleep, maybe not sleep duration itself, is less safe."
Zee told United Press International the population surveyed was not representative of the general population and the data may not applicable to the population as a whole. Survey participants were friends and relatives of volunteers working for the American Cancer Society and were not selected at random by any scientific approach.
Zee noted although the study attempted to control for chronic health disorders, medical disorders may have contributed to the longer sleep duration that was found.
Mark Rosekind, who heads up Alertness Solutions, a scientific consulting firm dealing with safety and alertness problems, based in Cupertino, Calif. called the study "a provocative finding" and said attention must be paid to the results because of the large sample size and the efforts to control for interfering variables.
"I would be extremely cautious given that this is a data set from 1982," he said. "I would be concerned about telling people that 6 1/2 hours is safe and healthy."
Decreases in performance show up rapidly in many people who get only 6 1/2 hours of sleep, said Rosekind, who worked for seven years as director the fatigue countermeasures program at the NASA Ames Research Center.
(Written by Joe Grossman in Santa Cruz, Calif.)
Copyright 2002 by United Press International.