Contrary to popular perception, people who sleep too long are just as likely to face serious health consequences as people who sleep too little. That’s the rather startling conclusion of a study conducted in 2002 by Daniel Kripke, a researcher at the Scripps Clinic Sleep Center in La Jolla, California. Kripke’s analysis was based on an examination of the average amount of nightly sleep reported by more than 1 million Americans who had participated in a research project on cancer prevention. A comparison of death rates among the participants in that study showed that individuals who averaged between 6.5 hours and 7.5 hours of sleep a night tended to live longer than those who slept less than 6.5 hours or more than 8 hours daily.
The results, which have since been corroborated by other researchers, challenge the long-held notion that the more sleep one gets, the better the health benefits. In fact, according to Kripke, what his study showed was that individuals who sleep 8.5 hours or longer a night are actually more at risk than those who sleep a mere five hours a night. In general, long sleep appears to begin at 8 hours, while short sleep means getting less than 6.5 hours of sleep a night.
Overall, many illnesses, including depression, obesity and heart disease can result from a lack of sleep or an over-abundance of it, according to Kripke. However, it is hard to say exactly how much sleep is ideal for preventing specific types of illnesses, he noted. For instance, while diabetes was lowest among those who averaged 7 hours of sleep a night, some other illnesses had their lowest points among 9-hour sleepers. It is also hard to extrapolate from the data whether short sleepers can extend their longevity by sleeping longer, or if a long sleeper can benefit by sleeping less, according to Kripke.
As mixed as some of the results are, it is nevertheless important for people to know that short sleep is not necessarily as bad as many might have assumed. According to Kripke, there continues to be a widely held belief that sleeping 8 or more hours daily is vital to good health and longevity. This misperception is based on unproven hearsay and has caused many individuals to remain in bed longer than they want to or need to. Very often, individuals who think they need to sleep longer have trouble falling asleep and end up with insomnia and frequent waking up at nights. Studies in the U.S, Britain and other parts of Europe have shown that such individuals can actually benefit from restricting their time in bed. According to Kripke, for many individuals shorter sleep can be more effective at treating insomnia than sleeping pills.