Sleep deprivation

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.

Genetics

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.

The sweet spot

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.

Beyond the numbers

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 See more In-depth