Good night's sleep doesn't have to be long

Research finds people who sleep more than eight hours a night have shorter life spans than those who sleep six to seven hours.

By Victoria Stagg Elliott, amednews staff. March 11, 2002.

Daniel F. Kripke, MD, a San Diego-based psychiatrist, has patients coming to him all the time, concerned that they do not sleep the oft-cited standard of eight hours a night.

He asks them how they feel during the day. If they report that they feel well-rested and function well, he attempts to convince them that they don't need sleeping pills or the other therapies they have read about or seen advertised on television.

How much sleep is enough?
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Now, Dr. Kripke has even more evidence that the amount of sleep those patients are getting is enough.

According to a study he authored in the February Archives of General Psychiatry, people who reported sleeping six to seven hours a night had the greatest survival rate over a six-year period. Those who slept more than eight or less than six hours a night had the greatest risk of death. Those who took sleeping pills also had shorter life spans.

Dr. Kripke, a professor of psychiatry with the University of California, San Diego, says his study is not meant to make long sleepers worry, but to reassure shorter sleepers that they shouldn't necessarily be concerned.

"If a patient feels rested with five, six or seven hours of sleep, then they don't need to worry that they need eight hours, and they certainly don't need to take sleeping pills," he said. "It's really a message of reassurance."

A study found that people who took sleeping pills had shorter life spans.

The study was cheered by consumer advocates concerned about the links between manufacturers of sleeping pills and sleep studies. Dr. Kripke's study was funded by the American Cancer Society and the National Institutes of Health.

"If the NIH would fund more studies untainted by industry influence, we are likely to find out that other 'disorders' are not valid either," said Vera Hassner Sharav, president of the Alliance for Human Research Protection.

Validity of research questioned

But many sleep experts found the research highly suspect because of the methodology and conclusions that are not necessarily relevant to their patients' concerns.

The study used a questionnaire from the American Cancer Society to 1.1 million participants in the group's Cancer Prevention Study. However, the original study was not designed to scrutinize sleep issues. Assessment of sleep amount was self-reported, and insomnia was not defined.

"An open-ended question without defining the term is unlikely to get a consistent answer," said Robert D. Ballard, MD, director of the sleep disorders program at National Jewish Medical and Research Center, Denver. "Also, people are often inaccurate in retrospectively assessing their sleep."

The study also drew conclusions based on mortality, but physicians who treat sleep disorders say their patients are not worried about death but about poor quality of life related to sleep deprivation -- depression, memory problems, relationship difficulties, and increased accident risk.

"The duration of sleep doesn't matter," said Deelip Chatterjee, MD, director of the neuro sleep laboratory at Barnert Hospital in Paterson, N.J. "It's the sleep symptoms that matter."

Co-morbidities that could be aggravated by short sleeping were also factored out of the study.

"Nobody believes that if you don't get a magical amount of sleep that you die because of sleep loss," Dr. Ballard said. "People think it would contribute to morbidity and even mortality via its effect on other conditions like hypertension, heart disease and cancer. They factored all that out of their comparison."

And while a link may be drawn between amount of sleep and mortality, it's not clear what those links mean. Is sleeping a long or short time a sign of illness or the cause? Will deliberately changing a person's sleep patterns positively affect their life expectancy?

"We don't know if setting the alarm clock earlier would cause any change," Dr. Kripke said. "Personally, I sleep about 81/2 hours, and I'm not about to change."

ADDITIONAL INFORMATION:

How much sleep is enough?

Study objective: To determine mortality risks associated with varying amounts of sleep.
Participants: More than 1 million men and women, ages 30-102, who participated in the American Cancer Society's Cancer Prevention Study II.
Method: Participants completed health questionnaires including questions about sleep duration, problems with insomnia and sleeping pill use. Survival or date of death was determined for 98% of participants. More than 30 possible co-morbidities were factored out.
Findings: Those who slept less than six hours a night or more than eight had higher mortality rates than those who slept seven. Those who slept more than 8.5 hours had a 15% increased risk of death. Men who slept less than 4.5 hours and women who slept less than 3.5 hours also had a 15% increased risk of death. Sleeping pill use was also associated with increased mortality.

Source: Archives of General Psychiatry, February

Weblink

Abstract, "Mortality Associated With Sleep Duration and Insomnia," Archives of General Psychiatry, February (vol. 59, issue 2) (http://archpsyc.ama-assn.org/issues/current/abs/yoa20380.html)

National Sleep Foundation statement on the study (http://www.sleepfoundation.org/pressarchives/nsfstatement.html)