How much sleep you need depends on factors such as age and health status. You may need to experiment to find your personal sweet spot. By Mayo Clinic Staff

You've heard the standard advice: Get eight hours of sleep a night. But is that true across the board? The answer seems to be that it depends.

As you would expect, infants and toddlers need the most sleep — nine to 10 hours at night plus naps during the day. School-age children, including teens, do best with nine to 11 hours a night. Most adults require seven to eight hours of sleep each night.

While older adults need about the same amount of sleep as younger adults, older adults tend to sleep more lightly and for shorter periods than do younger adults. Older adults often compensate by spending more time in bed at night or napping during the day.

Changes in a woman's body during early pregnancy can increase the need for sleep. Yet pregnancy symptoms, including nausea and vomiting, frequent urination, back pain, leg cramps, and heartburn, may make it difficult to sleep.

People who have chronic asthma or bronchitis tend to have more problems falling asleep and staying asleep than healthy people, either because of their breathing difficulties or because of their medications. Other chronic painful or uncomfortable conditions — such as arthritis, congestive heart failure, gastric reflux and sickle cell anemia — also can make it hard to get enough sleep.

Certain commonly used prescription and over-the-counter medicines contain ingredients that can keep you awake. These ingredients include decongestants and steroids. Heart and blood pressure medications known as beta blockers can make it difficult to fall asleep and can cause more awakenings during the night.

If you're sleep deprived, the amount of sleep you need increases. And if you consistently skimp on sleep, a sleep debt builds up that affects your health and quality of life.

Many people try to make up for lost sleep during the week by sleeping more on the weekends. But if you've lost too much sleep, sleeping in on a weekend can't completely erase your sleep debt. In addition, sleeping later on the weekends can affect your biological clock, making it harder to go to sleep at the right time on Sunday nights and get up on time on Monday mornings.

Do some people just need fewer hours of sleep a night? Yes, it's estimated that somewhere between 1 and 5 percent of the population are short sleepers — people who sleep six hours or less a night without ill effects. The need for less sleep tends to run in families, as does the need for more sleep, which suggests a genetic basis for sleep duration.

Studies suggest that getting less than seven hours — or more than nine hours — of sleep a night is associated with increased risk of health problems and psychiatric disorders, especially mood disorders, and a higher mortality rate.

The most important factor in determining how much sleep you need is whether you routinely feel sleepy during the day. Do you tend to fall asleep in low stimulus situations, such as long drives, reading, watching television, talking on the phone or completing desk work? If you do, you're likely not getting enough sleep.

Take steps to increase the amount of sleep you're getting. If that doesn't help you feel more rested and alert during the day, consult your doctor. He or she can look for possible underlying causes, such as sleep apnea, that can be treated to improve your sleep quality and reduce daytime sleepiness.

Sep. 28, 2013