You want to fight fat and aging? Sleep on it
By: Steve Fish Man
The Miami Herold, June 6, 2001
Fabiola Rivas, a 25-year-old graduate student, recently bought an
especially piercing alarm clock. ``It tells me I have to get up now,'' she
says. That's 5 a.m. Once awake, she throws on some clothes and stumbles
out of her apartment. By 6 a.m., she's beginning her workout, a 2
1/2-kilometer swim.
Rivas is what scientists call a short sleeper. Yet at 25, Rivas is in
excellent condition and by most measures the picture of health. So what's
the big deal?
After all, as a country, we're not too far from Rivas' schedule. The
National Sleep Foundation has reported that we sleep an average of less
than seven hours a night weekdays. At the turn of the last century,
Americans slept a dreamy nine hours a night. These days, the notion of
substituting productivity for rest is ingrained in the American way of
life.
We're engaged in what amounts to a national sleep-deprivation experiment.
And for a sleep researcher like Dr. Eve Van Cauter, a University of
Chicago professor, Rivas' desire to keep in shape is a perfect opportunity
to tweeze out its results.
She has recruited Rivas, and 50 others, for the largest study of its kind.
After six days of six- to seven-hour nights -- no naps permitted -- Rivas
comes into the University of Chicago lab for blood tests designed to
reveal how well her sleep-deprived hormones are functioning. The
preliminary results, not yet published in a scientific journal, are
frightening.
``Her metabolism just isn't as effective,'' reports one of the researchers
in the study. What Van Cauter is poised to announce is that short sleepers
such as Rivas may be on the road to hypertension, weight gain, diabetes,
even premature aging.
``We are not made for sleep debt,'' says Van Cauter.
Van Cauter feels she has made a break-through discovery. If she's right,
then a good night's sleep of at least eight hours may be as fundamental to
lasting health as nutrition and exercise.
Hormones are the body's regulatory system. They contribute to how well the
body processes food into energy -- or, conversely, stores it as fat. They
signal the body to grow and to repair itself. They help fight stress.
Diabetes, weight gain, even aging seem to be regulated by the hormonal
system.
But for all their importance, hormone levels were thought to be the same
no matter what time of day a blood sample was taken. Then scientists found
that hormone levels spiked at precise times. Sleep seemed to trigger the
release of certain hormones.
Consider growth hormone, which helps the body process its primary fuel,
glucose. In kids, growth hormone actually triggers growth. After puberty,
it functions as a kind of youth-maintenance hormone. It helps keep tissue
in good condition, skin taut, bones solid.
Without growth hormone, glucose tends to be stored as fat. By
investigating what sleep does to the hormones, Van Cauter realized, you
could explore the consequences of sleep, or sleep loss, on health.
``Growth hormone levels have been known for years to be tightly linked to
deep sleep,'' said Dr. Alejandro Chediak, chief of the Sleep Disorders
Center at Mount Sinai Medical Center in Miami Beach. Most secretion of
these hormones happens during deep sleep.
``Imposed sleep deprivation or diseases are associated with reductions in
growth hormone levels and may in indirect ways affect aging,'' Chediak
said.
In the past, scientists studied the impact of sleep loss on brain function
only -- on memory, concentration, alertness -- as if sleep was designed
exclusively for the brain. For many years, a primary argument in sleep
circles was over how much sleep the brain really needed. Not more than
four or five hours, one British researcher argued.
However, when Dr. David F. Dinges, at the University of Pennsylvania
School of Medicine, allowed people to sleep only six hours a night for two
weeks, one quarter were unable to keep from dozing the next day.
One 1999 study, co-authored by Dinges, drew this conclusion: On some
reaction-time tests, people who didn't get a good night's sleep performed
as badly as or worse than those who were legally drunk.
REACTIONS ASKEW
``The brain sputters when it's deprived of sleep,'' says Dinges. ``People
have trouble paying attention. They don't react as quickly. They don't
remember . . . things that they've just seen or heard.''
Sleep is critical in development of the brain, Chediak said. Sleep loss in
children can lead to growth defects, behavioral problems and difficulties
in school.
"It's clear there are a variety of effects of sleep that go beyond
restorative properties,'' Chediak said. ``Sleep helps us maintain a
healthy immunological system and fight infection.''
Everyone knows that ``when you're sleep deprived and you're run-down,
you're more likely to develop a cold,'' Chediak said. Sick people with a
fever tend to sleep a lot to compensate, and during that sleep they
secrete substances that boost their ability to fight infection.
It was not until the late 1980s that Van Cauter began to examine how sleep
loss affects hormone levels. ``One small thing occurs even with a single
night of sleep deprivation,'' says Van Cauter. ``The next day the level of
the stress hormone cortisol is higher in the evening.''
Van Cauter then did an experiment in which, for six days, she let subjects
at the University of Chicago -- all healthy men, aged 18 to 27 -- sleep
only four hours a night.
Results showed that four hours of sleep a night for only six nights
clobbered the body's hormone production. Every hormone Van Cauter looked
at was disturbed. After six days, the subjects seemed prediabetic, on
their way to weight gain. Moreover, they had the hormonal profile of a
much older person.
AGING, DIABETES
Does ongoing sleep deprivation -- even of a few hours a night -- cause a
person to age more quickly? Could sleeplessness be a factor in the
national obesity epidemic? In diabetes? Those seemed to be the
implications.
When her first results were published in a landmark paper in the British
medical journal The Lancet in 1999, they made a splash.
``What's groundbreaking is that she's found potentially dangerous effects
of lack of sleep on healthy people,'' says Dr. Michael Twery, acting
director of the National Center on Sleep Disorders Research.
Last summer, another Van Cauter paper published in the Journal of the
American Medical Association suggested that with reduced sleep quality,
growth-hormone production falls -- especially in men, but also in women.
With less growth hormone, the body tends to store more fat. Growth hormone
helps turn it into fuel. If you eat and exercise the same but sleep less,
you'll produce less growth hormone, and that may mean that you're more
likely to put on weight.
Exercise is a positive, but giving up sleep to get it may not be.
If loss of sleep can cause health problems, it's fair to wonder if adding
sleep could cure them. ``Sleep is the medicine for sleep loss,'' Stanford
University's Dr. William Demerit, an elder statesman of sleep study, says.
Chediak, at Mount Sinai, agrees that ``it's always best to do what your
body demands.''
``There are lots of other things that sleep does for us that we just don't
understand yet,'' Chediak said. ``This is a small piece of the puzzle.''
Herald medical writer Christine Morris contributed to this report.
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