A new study suggests that people who sleep 8 hours or more a night, or less than 4 hours, have a slightly higher risk of dying in a given time period than those who get 6 and 7 hours of shut-eye.
However, the researchers note that they can't be sure why some of the study subjects had longer or shorter sleep periods, and there's no evidence that sleep patterns-or changing them-can truly influence mortality risk.
Some sleep experts, including those at the National Sleep Foundation (NSF), agree.
Although the study reports data that is of interest, limitations in the study methodology restrict the conclusions that can be reached, particularly about the amount of sleep needed to sustain an individual's health, safety and well-being.
In the study researchers examined the findings of a previously conducted study that included, among other things, data on the sleep habits of 1.1 million people men and women between the ages of 30 and 102.
The study subjects, friends and family members of American Cancer Society volunteers, were interviewed in 1982 about diet, exercise, sleep and health problems and then followed up 6 years later.
Participants who reported sleeping 8 or more hours or less than 4 or 5 hours a night experienced a slightly higher chance of dying-at least a 15% increase in risk -- within that time compared with those who slept 7 hours a night.
Interestingly, only one in
a thousand slept at the lower end of the time scale.
Furthermore, the researchers report that insomnia was not associated with excess mortality, although the use of a prescription sleeping pill was also associated with a slightly increased risk of dying during the six-year period.
The study does seem to indicate that fewer than 8 hours of shuteye a night are not necessarily detrimental to health.
The study was not designed to answer why sleeping longer may be deleterious or whether people could extend their life spans by sleeping less. It is possible that people who sleep longer tend to suffer from sleep apnea, a condition in which impaired breathing puts stress on the heart and brain. The need for sleep is akin to the need for food, in that getting less than people want may be better for them.
While agreeing that the risk of dying from reduced sleep is low, he added, "It's hard to know if we shouldn't be worried about five hours of sleep -- if you are talking about being able to drive a truck a thousand miles the next day, being able to concentrate, make important decisions, that's a whole other story."
The average American sleeps 7 hours on weekdays, according to the 2001 Sleep in America Poll (conducted by the National Sleep Foundation). The new study shows that it is quite safe to sleep five, six, or seven hours a night, and people who sleep less than eight hours do not need to worry.
The study's findings may lead the public to be less concerned about insomnia -- a sometimes serious condition marked by an inability to sleep. Even mild sleep deprivation is associated with increased daytime sleepiness, which may lead to adverse outcomes, such as accidents.
Insomnia is associated with impaired quality of life, functional impairment, physical symptoms, and coronary heart disease. Sleep is not bad for you and insomnia is not good.
Sleeplessness produces health consequences that were not measured in the study. The amount of sleep you get impacts how alert you are, your risk for accidents, how you perform at work and school. There's much more to life than how long you live.
The National Sleep Foundation emphasizes that substantial research serves as the basis for the recommendation that adults obtain an average of seven to nine hours of sleep each night.
The group notes that individuals will require different amounts of sleep and that if someone sleeps 8.5 hours a night and feels alert and energetic, it would be incorrect to reduce sleep time based on the study.
Archives of General Psychiatry February 15, 2002;59:131-136
One needs to be careful in evaluating these studies as 99 percent of the funding to support this type of research is from pharmaceutical companies. While it does not appear that this study was funded by the drug companies, the editorialist in the journal are clearly paid by the drug companies that make sleeping pills.
Earlier research from the University of Chicago is quite clear that sleeping less than 6.5 hours will cause disruption in insulin receptor sensitivity which will increase one's risk for diabetes, obesity, and heart disease.
While sleeping more than 8 hours may not be necessary, clearly sleeping much less than 7 hours is likely to be highly detrimental for most people.
I am currently in the process of reviewing several books on chronobiology and hope to summarize some of the findings in the near future on this very important topic.
However, everyone agrees that insomnia is not a good thing. If this is a problem for you, please be sure to check out the first link for my sleeping guidelines.