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I'm always hearing about the importance of getting plenty of sleep. What does this mean exactly? How many hours of sleep are enough for good health?
- Jennifer / Minnesota
Mayo Clinic general health specialist Kenneth Berge, M.D., and colleagues answer select questions from readers.
Answer
The amount of sleep you need depends on many factors, especially your age. Infants typically sleep at least 16 hours a day. Most preschoolers need at least 11 hours of sleep a night, and most school-age children need at least 10 hours of sleep a night. By the teenage years, nine hours of sleep a night is usually adequate. For most adults, seven to eight hours a night seems about right.

Although some people feel rested on as few as five hours of sleep a night, recent studies call this notion into question. Researchers have found that people who sleep so little over many nights don't perform as well on complex mental tasks as do people who get closer to seven hours of sleep a night. Additionally, researchers have found that adults who get much more or less than seven hours of sleep a night have a higher mortality rate than do adults who sleep about seven hours a night.

As you get older, your sleeping patterns may change. Older adults tend to sleep more lightly and awaken more frequently during the night than do younger adults — but there's no evidence that older adults need less sleep than do younger adults.

At any age, getting enough sleep boosts your immune system. Sleep also helps your nervous system work properly. Likewise, too little sleep can leave you drowsy and unable to concentrate. Lack of sleep also impairs memory and physical performance.

So how many hours of sleep are enough for you? It's probably best to aim for about seven to eight hours of quality sleep a night. If you feel drowsy during the day — even during boring activities — you're probably not getting enough sleep. Also, remember that quality of sleep is just as important as quantity. If your sleep is frequently interrupted or cut short, you're not getting quality sleep.

If you experience frequent daytime sleepiness, even after increasing the amount of quality sleep you get, talk to your doctor. He or she may be able to identify any underlying causes — and help you get a better night's sleep.

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