How much sleep do you 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 nine hours on average. For
most adults, seven to eight hours a night appears to be the
best amount of sleep, although some people may need as few as five
hours or as many as 10 hours of sleep each day. Women in the first
three 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 five 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.
National Institutes of
Health
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