a Lot of Sleep?
Blame It on Body Clock
NEW YORK (Reuters Health) -
If you feel like you need a lot more sleep than your peers, you
may find the results of a new study comforting. The study suggests
that the body's internal clock programs some people to sleep longer
than others, researchers report.
This internal clock, or circadian
rhythm, controls when we sleep and wake and plays a role in other
biological processes as well, such as temperature regulation and
In an interview with Reuters Health,
Dr. Daniel Aeschbach explained that the body's internal clock
creates a signal that divides the circadian cycle into two distinct
periods--a biological day and a biological night.
During the biological night, we
experience changes in hormone levels, body temperature and the
propensity to sleep, explained Aeschbach, who was at the National
Institute of Mental Health in Bethesda, Maryland, when the study
"Somehow the clock programs an
internal night during which it favors rest and sleep," said Aeschbach,
who is now at Brigham and Women's Hospital and Harvard Medical
School in Boston, Massachusetts.
Although most adults average 7.5
hours of sleep a night, some people get by on less sleep while
others seem to need more z's. Researchers suspect that there is
a physiological explanation for sleep differences, but exactly
what this might be has been uncertain.
In the study, Aeschbach and his
colleagues compared long sleepers, who usually slept more than
nine hours a night, and short sleepers, who usually got less than
six hours a night. Participants were kept awake in a sleep lab
for 40 hours so that both long and short sleepers would be living
under the same conditions.
Based on several measures, including
hormone levels, body temperature and sleepiness, long sleepers
had a longer biological night than short sleepers. "This means
that there are differences in internal circadian signals," Aeschbach
The findings are reported in the
January issue of the Journal of Clinical Endocrinology and Metabolism.
These differences, the Boston researcher
noted, could help account for variations in the amount people
sleep. The fact that the length of the biological night seems
to vary from person to person may also help explain why it is
difficult to change sleep habits willfully, he added.
What causes the differences remains
unknown, however, according to the Boston researcher. Genetics
and behavior are two possible explanations, he said.
The results of the study support
the idea that sleep needs vary from person to person, Dr. Scott
A. Rivkees of Yale University in New Haven, Connecticut, states
in an editorial that accompanies the study.
Noting that "we seem to value our
alarm clocks more than our internal clocks," Rivkees suggests
that our society needs to find a way to accommodate each person's
individual sleep requirements.
SOURCE: Journal of Clinical Endocrinology
and Metabolism 2003;88:24-30.
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