How Much Sleep Do We Need?
The amount of sleep each person needs depends on many factors, including
age. Infants generally require about 16 hours a day, while teenagers
need about 9 hours on average. For most adults, 7 to 8 hours a night
appears to be 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. 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.
People tend to sleep more lightly and for shorter time spans as they get
older, although they generally need about the same amount of sleep as
they needed in early adulthood. About half of all people over 65 have
frequent sleeping problems, such as insomnia, and deep sleep stages in
many elderly people often become very short or stop completely. This
change may be a normal part of aging, or it may result from medical
problems that are common in elderly people and from the medications and
other treatments for those problems.
Experts say that if you feel drowsy during the day, even during boring
activities, you haven't had enough sleep. If you routinely fall asleep
within 5 minutes of lying down, you probably have severe sleep
deprivation, possibly even a sleep disorder. Microsleeps,
or very brief episodes of sleep in an otherwise awake person, are
another mark of sleep deprivation. In many cases, people are not aware
that they are experiencing microsleeps. The widespread practice of
"burning the candle at both ends" in western industrialized societies
has created so much sleep deprivation that what is really abnormal
sleepiness is now almost the norm.
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 100,000 motor vehicle accidents
and 1500 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 have trouble keeping your eyes focused, if you can't stop yawning,
or if you can't remember driving the last few miles, you are probably
too drowsy to drive safely.
Source: US NIH,
National Institute of Neurological Disorders and Stroke
Disclaimer: All NINDS health-related material is provided for information purposes
only and does not necessarily represent endorsement by or an official
position of the National Institute of Neurological Disorders and Stroke
or any other Federal agency. Advice on the treatment or care of an
individual patient should be obtained through consultation with a
physician who has examined that patient or is familiar with that
patient's medical history.
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