Although you may put off going to sleep in order to squeeze more activities
into your day, eventually your need for sleep becomes overwhelming. This need
appears to be due, in part, to two substances your body produces. One
substance, called adenosine, builds up in your blood while you’re awake. Then,
while you sleep, your body breaks down the adenosine. Levels of this substance
in your body may help trigger sleep when needed. A buildup of adenosine and
many other complex factors might
explain why, after several nights of less than optimal amounts of sleep, you build up a sleep debt. This may cause you to sleep longer than normal or at unplanned times during the day.
explain why, after several nights of less than optimal amounts of sleep, you build up a sleep debt. This may cause you to sleep longer than normal or at unplanned times during the day.
Because of your body’s internal processes, you can’t adapt to
getting less sleep than your body needs. Eventually, a lack of sleep catches up
with you. The other substance that helps make you sleep is a hormone called melatonin.
This hormone makes you naturally feel sleepy at night. It is part of your
internal “biological clock,” which controls when you feel sleepy and your sleep
patterns. Your biological clock is a small bundle of cells in your brain that
works throughout the day and night. Internal and external environmental cues,
such as light signals received through your eyes, control these cells. Your
biological clock triggers your body to produce melatonin, which helps prepare
your brain and body for sleep. As melatonin is released, you’ll feel
increasingly drowsy. Because of your biological clock, you naturally feel the
most tired between midnight and 7 a.m.
You also may feel mildly sleepy in the afternoon between 1 p.m.
and 4 p.m. when another increase in melatonin occurs in your body. Your
biological clock makes you the most alert during daylight hours and the least
alert during the early morning hours. Consequently, most people do their best
work during the day. Our 24/7 society, however, demands that some people work
at night. Nearly one-quarter of all workers work shifts that are not during the
daytime, and more than two-thirds of these workers have problem sleepiness
and/or diffiulty sleeping. Because their work chedulesare at odds with powerful
sleep-regulating cues like sunlight, night shift workers often fid themselves
drowsy at work, and they have diffiulty falling or staying asleep during the
daylight hours when their work schedules require them to sleep.
The fatigue experienced by night shift workers can be dangerous. Major
industrial accidents—such as the Three Mile Island and Chernobyl nuclear power
plant accidents and the Exxon Valdez oil spill—have been caused, in part, by mistakes
made by overly tired workers on the night shift or an extended shift. Night
shift workers also are at greater risk of being in car crashes when they drive
home from work during the early morning hours, because the biological clock is
not sending out an alerting signal. One study found that one-fith of night
shift workers had a car crash or a near miss in the preceding year because of
sleepiness on the drive home from work.
Night shift workers are also more likely to have physical
problems, such as heart disease, digestive troubles, and infertility, as well
as emotional problems. All of these problems may be related, at least in part,
to the workers’ chronic sleepiness, possibly because their biological clocks
are not in tune with their work schedules. See “Working the Night Shift” on
page 9 for some helpful tips if you work a night shift. Other factors also can
inflence your need for sleep, including your immune system’s production of
hormones called cytokines.
Cytokines are made to help the immune system fiht certain
infections or chronic inflmmation and may prompt you to sleep more than usual.
The extra sleep may help you conserve the resources needed
to fiht the infection. Recent studies confim that being well rested improves the body’s responses to infection. People are creatures of habit, and one of the hardest habits to break is the natural wake and
sleep cycle. Together, a number of physiological factors help you sleep and wake up at the same times each day
to fiht the infection. Recent studies confim that being well rested improves the body’s responses to infection. People are creatures of habit, and one of the hardest habits to break is the natural wake and
sleep cycle. Together, a number of physiological factors help you sleep and wake up at the same times each day
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