Infants require about 16 hours a day
Teenagers need about 9 hours on average
Most adults need 7 to 8 hours a night for the best amount of sleep, although some people may need as few as 5 hours or as many as 10 hours of sleep each day
Women in the first 3 months of pregnancy often need several more hours of sleep than usual

However, experts say that if you feel drowsy during the day, even during boring activities, you haven't had enough sleep.

Sleep Deprivation Debits

The amount of sleep a person needs also increases if he or she has been deprived of sleep in previous days. Getting too little sleep creates a "sleep debt," which is much like being overdrawn at a bank. Eventually, your body will demand that the debt be repaid. We don't seem to adapt to getting less sleep than we need, while we may get used to a sleep-depriving schedule, our judgment, reaction time, and other functions are still impaired.

Consequences of Too Little Sleep

Too little sleep may cause:

Memory problems
Depression
A weakening of your immune system, increasing your chance of becoming sick
Increase in perception of pain

The Dangers of Sleep Deprivation

Many studies make it clear that sleep deprivation is dangerous. Sleep-deprived people who are tested by using a driving simulator or by performing a hand-eye coordination task perform as badly as or worse than those who are intoxicated.

Sleep deprivation also magnifies alcohol's effects on the body, so a fatigued person who drinks will become much more impaired than someone who is well rested.

Driver fatigue is responsible for an estimated 56,000 motor vehicle accidents and 1,500 deaths each year, according to the National Highway Traffic Safety Administration. Since drowsiness is the brain's last step before falling asleep, driving while drowsy can -- and often does -- lead to disaster. Caffeine and other stimulants cannot overcome the effects of severe sleep deprivation.

The National Sleep Foundation says that if you: