|
An internal clock
may determine how much sleep you really need, according to
new research.
This internal clock,
or circadian rhythm, programs your body to have a biological
day and a biological night. During the biological night there
are changes in hormone levels, body temperature and the tendency
to sleep. More specifically, melatonin is secreted, cortisol
concentration in the blood increases, core body temperature
is lowered and sleepiness increases.
In the study, which
compared 10 long sleepers (more than nine hours a night) with
14 short sleepers (less than six hours a night), long sleepers
had a longer biological night than short sleepers. Findings
were based on measures such as hormone levels, body temperature
and sleepiness and indicate that internal circadian signals
vary among different people.
These differences
may explain why some people sleep more than others, and the
fact that people have varying lengths of biological nights
may explain why it can be difficult to change sleep habits
willfully.
The causes of these
differences remain unknown, however researchers say that genetics
and behavior are possible explanations.
Chronic sleep loss
has been found to have negative effects on carbohydrate metabolism,
automomic balance and evening cortisol concentrations. These
effects can contribute to age-related problems such as diabetes,
hypertension and memory loss.
Researchers concluded
that sleep needs vary from person to person, and that society
could benefit from finding ways to accommodate individual
sleep needs.
Journal
of Clinical Endocrinology and Metabolism January 2003;88:24-30
| 