Lack of sleep alters hormones, metabolism
2006-09-30 20:21:58FOR RELEASE: 21 OCTOBER 1999 AT 20:00 ET US
University of Chicago Medical Center
http://www.medcenter.uchicago.edu/
Lack of sleep alters hormones, metabolism
Chronic sleep loss can reduce the capacity of even young adults to perform
basic metabolic functions such as processing and storing carbohydrates or
regulating hormone secretion, report researchers from the University of
Chicago Medical Center in the October 23 issue of The Lancet. Cutting back
from the
standard eight down to four hours of sleep each night produced striking
changes in glucose tolerance and endocrine function -- changes that resembled
the
effects of advanced age or the early stages of diabetes -- after less than one
week.
Although many studies have examined the short-term effects of acute, total
sleep deprivation on the brain, this is the first to investigate the impact of
chronic, partial sleep loss on the body by evaluating the metabolism and
hormone secretion of subjects subjected to sleep restriction and after sleep
recovery.
"We found that the metabolic and endocrine changes resulting from a
significant sleep debt mimic many of the hallmarks of aging," said Eve Van
Cauter, Ph.D., professor of medicine at the University of Chicago and
director of the study.
"We suspect that chronic sleep loss may not only hasten the onset but could
also increase the severity of age-related ailments such as diabetes,
hypertension, obesity and memory loss."
Cutting back on sleep is an extremely common response to the time pressures of
modern industrial societies. The average night's sleep decreased from about
nine hours in 1910 to about 7.5 hours in 1975, a trend that continues.
Millions of shift workers average less than five hours per work day. Previous
studies,
however, have measured only the cognitive consequences of sleep loss.
Van Cauter and colleagues Karine Spiegel and Rachel Leproult chose to focus
instead on the physiologic effects of sleep loss, how sleep deprivation
altered basic bodily functions such regulating blood-sugar levels, storing
away energy
from food and the production of various hormones.
They followed 11 healthy young men for 16 consecutive nights. The first three
nights the subjects were allowed to sleep for eight hours, from 11 p.m. to 7
a.m. The next six nights they slept four hours, from 1 a.m. to 5 a.m. The
following seven nights they spent 12 hours in bed, from 9 a.m. to 9 p.m. All
subjects received identical diets.
The researchers constantly assessed each volunteer's wakefulness and heart
rate. They performed sleep studies on the last two eight-hour nights, the last
two four-hour nights, and the first and last two 12-hour nights. They
performed glucose tolerance tests on the fifth day of sleep deprivation and
the fifth
day of sleep recovery and monitored glucose and hormone levels every 30
minutes on
the sixth day of deprivation and of recovery.
They found profound alterations of glucose metabolism, in some situations
resembling patients with type-2 diabetes, during sleep deprivation. When
tested during the height of their sleep debt, subjects took 40 percent longer
than
normal to regulate their blood sugar levels following a high-carbohydrate
meal. Their ability to secrete insulin and to respond to insulin both
decreased by
about 30 percent. A similar decrease in acute insulin response is an early
marker of diabetes.
The differences were particularly marked when tested in the mornings. "Under
sleep debt conditions, our young lean subjects would have responded to a
morning glucose tolerance test in a manner consistent with current diagnostic
criteria for impaired glucose tolerance," note the authors. Impaired glucose
tolerance is an early symptom of diabetes.
Sleep deprivation also altered the production and action of other hormones,
dampening the secretion of thyroid stimulating hormone and increasing blood
levels of cortisol, especially during the afternoon and evening. Elevated
evening cortisol levels are typical of much older subjects and are thought to
be related to age-related health problems such as insulin resistance and
memory impairment.
All of these abnormalities quickly returned to baseline during the recovery
period, when subjects spent 12 hours in bed. In fact, as the subjects spent
more than eight hours a night in bed, their laboratory values moved beyond the
"normal" or baseline standards, suggesting that even eight hours of sleep does
not produce the fully rested state. Young adults may function best after more
than eight hours of rest each night.
"While the primary function of sleep may very well be cerebral restoration,"
note the authors, "our findings indicate that sleep loss also has consequences
for peripheral function that, if maintained chronically, could have long term
adverse health effects."
Funding for this study was supplied by the Research Network on Mind-Body
Interactions of the MacArthur Foundation (Chicago), the U.S. Air Force Office
of Scientific Research and the National Institutes of Health.
________
FOR RELEASE: 21 OCTOBER 1999 AT 19:00 ET US
Center for the Advancement of Health
Sleep debt affects metabolic functions
Chronic sleep loss can have a detrimental effect on metabolic functions, new
research shows.
"The state of sleep debt has a harmful impact on carbohydrate metabolism and
endocrine function," write Karine Spiegel, PhD, and colleagues in the October
23, 1999 issue of The Lancet, a leading British medical journal. These effects
are commonly seen as part of the normal aging process, and persistent sleep
debt may, therefore, increase the severity of age-related chronic disorders.
During this century, the average number of hours that people spend asleep per
night in more-developed countries has decreased from nine hours to 7.5 hours.
The change has been made to accommodate increased demands of work, with
around-the-clock production, shift work, etc, as well as more leisure
activities. The consensus is that sleep is beneficial for the brain but not
for the rest of the body. There have been reports that the number of hours
asleep
each night can be voluntarily decreased without affecting daytime sleepiness,
mood, or cognitive function.
The scientists at the Department of Medicine, University of Chicago,
investigated whether sleep debt can alter metabolic and hormonal functions.
Eleven young men were enrolled into the study, and their carbohydrate
metabolism and hormonal functions were studied. For the first three nights,
the men were in bed for eight hours (fully rested condition). For six nights
they
were in bed for four hours per night (sleep-debt condition), and for the last
seven nights they were in bed for 12 hours per night. The investigators took
measurements during the day of glucose tolerance, cortisol concentrations (a
hormone that helps to regulate blood sugar concentrations), heart rate,
sleepiness, and the profiles of hormones of the hypothalamus, and the
pituitary and adrenal glands.
At the end of the sleep-debt conditions, glucose concentrations in the blood
were higher than in the fully rested conditions, and concentrations of
thyrotropin, which regulates the release of thyroid hormones, were lower.
Cortisol concentrations in the evening were increased after sleep debt, as was
the activity of the sympathetic nervous system, which controls many of the
body's "involuntary" functions.
The research was supported by a grant from the Research Network on Mind-Body
Interactions of the MacArthur Foundation, by a grant from the U.S. Air Force
Office of Scientific Research, and by grants from the National Institutes of
Health.
Posted by the Center for the Advancement of Health < http://www.cfah.org