Our general sleep patterns – being sleepy at night and awake during the day – are guided to a great extent by our exposure to light and darkness. A key factor in these patterns may be a natural hormone called melatonin.
Melatonin is made by the body’s pineal gland, a pea-sized gland located just above the middle of the brain. During the day, the pineal is inactive, however, as the sun goes down, darkness activates the pineal, and melatonin production begins. As melatonin levels in the blood rise, we also become less alert – and sleepy. The next morning, with daylight, melatonin decreases and alertness replaces the sleepiness.
Available as a dietary supplement, synthetic melatonin is the only hormone sold in the United States without a prescription. “Because it so easily available, many people use melatonin for their sleep problems, although they may do so without being fully aware of what it can do and when,” says Richard L. Gelula, chief executive officer of the National Sleep Foundation (NSF). “Our Web page on melatonin is one of the most frequently visited sites, so we know there is good possibility that people with sleep problems may be searching for information and self treating,” Gelula adds.
In order to provide the public with the most up to date information and research on melatonin, NSF has created a new brochure, Melatonin: The Basic Facts, explaining what the hormone is, how it works, how and when it can be effective, care that should be taken when using the hormone, and additional research that is needed.
Melatonin levels stay elevated for about 12 hours, beginning at about 9:00 p.m. until approximately 9:00 a.m. Although the time of the night and day affects melatonin levels, light and darkness can be even more important factors. In addition to sunlight, artificial indoor lighting can be bright enough to prevent its release. This may be a special problem for shift workers, particularly those who work late night/early morning rotations. First, natural body rhythms encourage night time sleepiness, but bright indoor lighting can help them stay awake. At the conclusion of their shifts, they go into the daylight, which further inhibits the release of the melatonin needed to help them sleep when they get home.
In addition to its hypnotic properties (i.e., can induce or maintain sleep), melatonin may also act as a chronobiotic (or circadian) drug, since if taken at appropriate times, it has been found to advance or delay the sleep-wake cycle. Depending on when it is taken, melatonin can re-set the circadian clock that affects alertness and sleepiness, a characteristic that can be helpful for travelers suffering from jet lag. The new NSF brochure offers useful information for using melatonin in this way.
In addition to shiftworkers and travelers, other people take melatonin to try to improve their sleep. While some studies show the hormone may help shorten the amount of time it takes to fall asleep and reduce the number of awakenings during the night, other research indicates that melatonin does not help with falling asleep or maintaining sleep or with promoting daytime alertness.