Melatonin, a hormone involved
in the regulation of the sleep/wake cycle, may
help night shift workers get more rest during
daylight hours, according to the findings of a
small study published in the journal Sleep. Melatonin,
which is released by the brain primarily during
the hours of sleep, is also available as an oral
supplement.
"If for reasons of being a shift worker or due
to travel across time zones you have to sleep
at a strange hour, this is precisely when taking
melatonin will help you fall asleep faster and
stay asleep longer," lead investigator Dr. James
K. Wyatt, of Rush University Medical Center in
Chicago stated.
"The findings really point out how important
our brain's 24-hour clock, also called the circadian
system, is to being able to remain awake and alert
throughout the day (and) how the circadian system
can therefore get in the way of attempts to sleep
during the day."
Other researchers have investigated whether melatonin
improves sleep when taken before daytime naps
or before normal nighttime sleep. Some studies
have reported positive findings, but most of them
had significant limitations, such as very short
study periods or a lack of female study participants,
which limited the extent to which the findings
could be generalized.
Wyatt and his colleagues at Harvard Medical School
in Boston conducted a month-long study of the
sleep-facilitating effect of melatonin. The study
included 21 men and 15 women between 18 to 30
years old, who were healthy and free of any sleep
disorders.
The subjects' normal sleep/wake patterns and
melatonin production were observed for 3 days.
They were then put on a 20-hour sleep-wake schedule,
"simulating a traveler crossing four time zones
eastward every day," study co-author Dr. Charles
A. Czeisler, now at Rush University Medical Center
in Chicago.
The study participants took 0.3 or 5 milligrams
of melatonin or a look-alike placebo pill 30 minutes
before each scheduled sleep period, which lasted
about 7 hours. This schedule was maintained for
about 3 weeks. The study was conducted in a private,
windowless suite in a research center that was
sound-isolated and had no windows or any other
cues of the time of day.
Compared with the placebo group, sleep times
were longer in the melatonin group during the
hours of the day when the body does not normally
produce the hormone.
"We believe melatonin is directly suppressing
your body's 24-hour clock and in particular suppressing
the circadian system's drive for wakefulness...in
some ways dampening that wake-up signal," Wyatt
said. However, when melatonin was taken during
the nighttime hours, when the body usually produces
its own melatonin, no additional benefit was observed.
It appears to be a chase in which "more is not
better," Wyatt said. "If you're trying to sleep
when your body wants you to, taking a pill of
melatonin will provide no additional benefit."
"Even when given melatonin, daytime sleep still
falls short of the quality and quantity of nighttime
sleep," Wyatt added. "Humans are just biologically
designed to sleep at night," he added.
SOURCE: Sleep, May 1, 2006.
