Your Hormones
When you were young, your mother may have told you that you
need to get enough sleep to grow strong and tall. She may have
been right! Deep sleep triggers more release of growth hormone,
which fuels growth in children and boosts muscle mass and the
repair of cells and tissues in children and adults. Sleep’s effect on
the release of sex hormones also encourages puberty and fertility.
Your Guide to Healthy Sleep
15
What Does Sleep Do for You?
Consequently, women who work at night and tend to lack sleep are,
therefore, more likely to have trouble conceiving or to miscarry.
Your mother also probably was right if she told you that getting
a good night’s sleep on a regular basis would help keep you from
getting sick and help you get better if you do get sick. During sleep,
your body creates more cytokines—cellular hormones that help the
immune system fight various infections. Lack of sleep can reduce
the ability to fight off common infections. Research also reveals
that a lack of sleep can reduce the body’s response to the flu vaccine.
For example, sleep-deprived volunteers given the flu vaccine
produced less than half as many flu antibodies as those who were
well rested and given the same vaccine.
Although lack of exercise and other factors are important contributors,
the current epidemic of diabetes and obesity appears to be
related, at least in part, to chronically getting inadequate sleep.
Evidence is growing that sleep is a powerful regulator of appetite,
energy use, and weight control. During sleep, the body’s production
of the appetite suppressor leptin increases, and the appetite stimulant
grehlin decreases. Studies find that the less people sleep, the
more likely they are to be overweight or obese and prefer eating
foods that are higher in calories and carbohydrates. People who
report an average total sleep time of 5 hours a night, for example,
are much more likely to become obese compared to people who
sleep 7–8 hours a night.
A number of hormones released during sleep also control the body’s
use of energy. A distinct rise and fall of blood sugar levels during
sleep appears to be linked to sleep stage. Not getting enough sleep
overall or enough of each stage of sleep disrupts this pattern. One
study found that, when healthy young men slept only 4 hours a
night for 6 nights in a row, their insulin and blood sugar levels mimicked
those seen in people who were developing diabetes. Another
study found that women who slept less than 7 hours a night were
more likely to develop diabetes over time than those who slept
between 7 and 8 hours a night.
Some people appear to need only
about 7 hours to avoid problem sleepiness whereas others need
9 or more hours of sleep. Sleep needs also change throughout the
lifecycle. Newborns sleep between 16 and 18 hours a day, and
children in preschool sleep between 10 and 12 hours a day. Schoolaged
children and adolescents need at least 9 hours of sleep a night.
The hormonal influences of puberty tend to shift adolescents’
biological clocks. As a result, teenagers are more likely to go to bed
later than younger children and adults, and they tend to want to
sleep later in the morning. This sleep–wake rhythm is contrary to
the early-morning start times of many high schools and helps
explain why most teenagers get an average of only 7–7.5 hours of
sleep a night.
As people get older, the pattern of sleep also changes—especially
the amount of time spent in the deep sleep stages. Children spend
more time than adults in these sleep stages. This explains why
children can sleep through loud noises and why they might not
wake up when they are moved from the car to their beds. During
adolescence, a big drop occurs in the amount of time spent in deep
sleep, which is replaced by lighter, stage 2 sleep. Between young
adulthood and midlife, the percentage of deep sleep falls again—
from less than 20 percent to less than 5 percent, one study suggests—
and is replaced with lighter sleep (stages 1 and 2). From midlife
through late life, people’s sleep has more interruptions by wakefulness
during the night. This disruption causes older persons to lose more
and more of stages 1 and 2 non-REM sleep as well as REM sleep.
Many older people complain of difficulty falling asleep, early morning
awakenings, frequent and long awakenings during the night,
daytime sleepiness, and a lack of refreshing sleep. Many sleep
problems, however, are not a natural aspect of sleep in the elderly.
Because older people are more likely to have many illnesses that can
disrupt sleep, their sleep complaints often may be due, in part, to
illnesses or the medications used to treat them. In fact, one study
found that the prevalence of sleep problems is very low in healthy
older adults. Other causes of some of older adults’ sleep complaints
are sleep apnea, restless legs syndrome, and other sleep disorders
that become more common with age. Also, older people are
more likely to have their sleep disrupted by the need to urinate
during the night.
Some evidence shows that the biological clock shifts in older people,
so they are more apt to go to sleep earlier at night and wake up
earlier in the morning. No
evidence indicates that
older people can get by
with less sleep than
younger people.
One study found that a daytime nap after a lack of sleep at night
did not fully restore levels of blood sugar to the pattern seen with
adequate nighttime sleep. If a nap lasts longer than 1 hour, you may
have a hard time waking up fully.
Try to get outside in natural
sunlight for at least 30 minutes each day. If possible, wake
up with the sun or use very bright lights in the morning.
A number of factors can make a person susceptible to sleep apnea.
These factors include:
Throat muscles and tongue that relax more than normal while
asleep
Enlarged tonsils and adenoids
Being overweight—the excess fat tissue around your neck
makes it harder to keep the throat area open
Head and neck shape that creates a somewhat smaller airway
size in the mouth and throat area
Congestion, due to allergies, that can also narrow the airway
Family history of sleep apnea
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