Reasons why you need to sleep

By JANE E. BRODY
Think you do just fine on five or six hours of shut-eye? Chances are, you are among the many millions who unwittingly shortchange
themselves on sleep.
Research shows that most people require seven or eight hours of sleep to function optimally.
Failing to get enough sleep night after night can compromise your health and may even shorten your life. From infancy to old age, the
effects of inadequate sleep can profoundly affect memory, learning, creativity, productivity and emotional stability, as well as
your physical health.
According to sleep specialists at the University of Pittsburgh School of Medicine and Western Psychiatric Institute and Clinic, among others,
a number of bodily systems are negatively affected by inadequate sleep: the heart, lungs and kidneys; appetite, metabolism and weight
control; immune function and disease resistance; sensitivity to pain; reaction time; mood; and brain function.
Poor sleep is also a risk factor for depression and substance abuse, especially among people with post-traumatic stress disorder, according to Anne Germain, associate professor of psychiatry at the University of Pittsburgh.
People with PTSD tend to relive their trauma when they try to sleep, which keeps their brains in a heightened state of alertness.
Dr. Germain is studying what happens in the
brains of sleeping veterans with PTSD in hopes
of developing more effective treatments for
them and for people with lesser degrees of
stress that interfere with a good night’s sleep.
The elderly are especially vulnerable. Timothy
H. Monk, who directs the Human Chronobiology
Research Program at Western Psychiatric,
heads a five-year federally funded study of
circadian rhythms, sleep strength, stress
reactivity, brain function and genetics among
the elderly. “The circadian signal isn’t as
strong as people get older,” he said.
He is finding that many are helped by standard
behavioral treatments for insomnia, like
maintaining a regular sleep schedule, avoiding
late-in-day naps and caffeine, and reducing
distractions from light, noise and pets.
It should come as no surprise that myriad bodily
systems can be harmed by chronically shortened
nights. “Sleep affects almost every tissue in
our bodies,” said Dr. Michael J. Twery, a sleep
specialist at the National Institutes of Health.
Several studies have linked insufficient sleep to
weight gain. Not only do night owls with
shortchanged sleep have more time to eat,
drink and snack, but levels of the hormone
leptin, which tells the brain enough food has
been consumed, are lower in the sleep-deprived
while levels of ghrelin, which stimulates
appetite, are higher.
In addition, metabolism slows when one’s
circadian rhythm and sleep are disrupted; if not
counteracted by increased exercise or reduced
caloric intake, this slowdown could add up to 10
extra pounds in a year.
The body’s ability to process glucose is also
adversely affected, which may ultimately result
in Type 2 diabetes. In one study, healthy young
men prevented from sleeping more than four
hours a night for six nights in a row ended up
with insulin and blood sugar levels like those of
people deemed prediabetic. The risks of
cardiovascular diseases and stroke are higher
in people who sleep less than six hours a night.
Even a single night of inadequate sleep can
cause daylong elevations in blood pressure in
people with hypertension. Inadequate sleep is
also associated with calcification of coronary
arteries and raised levels of inflammatory
factors linked to heart disease. (In terms of
cardiovascular disease, sleeping too much may
also be risky. Higher rates of heart disease
have been found among women who sleep more
than nine hours nightly.)
The risk of cancer may also be elevated in
people who fail to get enough sleep. A Japanese
study of nearly 24,000 women ages 40 to 79
found that those who slept less than six hours a
night were more likely to develop bosom cancer
than women who slept longer. The increased
risk may result from diminished secretion of the
sleep hormone melatonin. Among participants in
the Nurses Health Study, Eva S. Schernhammer
of Harvard Medical School found a link between
low melatonin levels and an increased risk of
bosom cancer.
A study of 1,240 people by researchers at Case
Western Reserve University in Cleveland found
an increased risk of potentially cancerous
colorectal polyps in those who slept fewer than
six hours nightly.
Children can also experience hormonal
disruptions from inadequate sleep. Growth
hormone is released during deep sleep; it not
only stimulates growth in children, but also
boosts muscle mass and repairs damaged cells
and tissues in both children and adults.
Dr. Vatsal G. Thakkar, a psychiatrist affiliated
with New York University, recently described
evidence associating inadequate sleep with an
erroneous diagnosis of attention deficit
hyperactivity disorder in children. In one study,
28 percent of children with sleep problems had
symptoms of the disorder, but not the disorder.
During sleep, the body produces cytokines,
cellular hormones that help fight infections.
Thus, short sleepers may be more susceptible to
everyday infections like colds and flu. In a study
of 153 healthy men and women, Sheldon Cohen
and colleagues at Carnegie Mellon University
found that those who slept less than seven
hours a night were three times as likely to
develop cold symptoms when exposed to a cold-
causing virus than were people who slept eight
or more hours.
Some of the most insidious effects of too little
sleep involve mental processes like learning,
memory, judgment and problem-solving. During
sleep, new learning and memory pathways
become encoded in the brain, and adequate
sleep is necessary for those pathways to work
optimally. People who are well rested are better
able to learn a task and more likely to remember
what they learned. The cognitive decline that
so often accompanies aging may in part result
from chronically poor sleep.
With insufficient sleep, thinking slows, it is
harder to focus and pay attention, and people
are more likely to make poor decisions and take
undue risks. As you might guess, these effects
can be disastrous when operating a motor
vehicle or dangerous machine.
In driving tests, sleep-deprived people perform
as if drunk, and no amount of caffeine or cold
air can negate the ill effects.
At your next health checkup, tell your doctor
how long and how well you sleep. Be honest:
Sleep duration and quality can be as important
to your health as your blood pressure and
cholesterol level.
This is the first of two columns on inadequate
sleep.
A version of this article appeared in print on
06/18/2013, on page D5 of the NewYork edition
with the headline: Harming Our Health With
Eyes Wide Open.
Source:
http://well.blogs.nytimes.com/2013/06/