DEAR DOCTOR K:
I’ve heard a lot about the harmful effects of insufficient sleep. But are there any dangers of sleeping too much?
Over the years we’ve learned that sleep is important for a variety of reasons. It appears to be vital for forming long-term memories. It also helps you to digest what you have learned the previous day. Sleep promotes concentration and restores energy; it helps to keep your immune system functioning well and to regulate eating patterns.
The average adult needs seven to nine hours. Does it matter whether you get more or less than the ideal amount of sleep? That’s tough to answer — in part, because the effects of sleep are difficult to separate from other factors that can affect the quality or duration of your sleep.
Studies have linked short sleep duration — five hours or less each night — with a number of health problems, including high blood pressure and diabetes. Sleep deprivation is also a major contributor to car accidents, accounting for an estimated 100,000 accidents per year in this country.
Surprisingly, there may also be health problems associated with too much sleep. Large, well-designed studies have analyzed the relationship between amount of sleep and length of life. Thousands of people have answered detailed questionnaires about their sleep habits and their health status over many years.
In these studies, the death rates for people who sleep the least — and the most — are higher than those people whose sleep time falls in the middle.
The reason isn’t clear. It’s possible that a related factor may be responsible. Specifically, people with certain diseases and conditions may both sleep longer and die sooner. In other words, it may not be the fact that they sleep longer that causes them to die sooner.
For example, people who sleep excessively might be drinking too much, and it could be the drinking that’s impairing their health. As another example, some people suffering from major depression sleep longer. Depression, in turn, is linked to heart disease and to suicide.
There are other common health problems that also cause people to sleep more and that may shorten life. These include:
- thyroid disease
- kidney or liver disease
- a sleep disorder such as obstructive sleep apnea
Some medications used to treat serious illnesses also can make a person groggy and sleepy. That’s another way that sleeping long hours might be linked to dying sooner.
In summary, I’d say that there is little evidence that simply sleeping unusually long hours — like more than nine hours a night — actually shortens your life. And there are plenty of healthy people who regularly sleep more than nine hours a night.
But if you asked your question because you’ve found yourself sleeping a lot more than you used to, check it out with your doctor. The long hours may not be hurting you, but they could be a sign of an underlying medical condition that could hurt you.