An estimated 20% to 40% of adults experience insomnia in any given year, according to the American Academy of Sleep Medicine. People over 50, and many women of any age, are most likely to suffer from problems including having trouble falling asleep, waking too early or waking at night and not getting back to sleep. Even people who usually sleep soundly can become sleep deprived while traveling or when their careers require them to work overnight. Melatonin is a hormone produced at night by the pineal gland, near the base of the brain, and it is believed to promote sleep. Some studies have shown that melatonin may not only reduce sleep latency but also improve sleep architecture. Dijk and Cajochen29 observed that a 5 mg dose not only reduced sleep latency but also increased REM sleep and the amount of spindles. Kunz et al also found higher percentages of REM sleep with 3 mg doses of melatonin administered from 22 to 23 hours for 4 weeks. Waldhouser et al observed that melatonin reduced sleep latency and nocturnal awakenings and heightened sleep efficiency. It also shortened sleep stage 1 and lengthened sleep stage . Scientists at Harvard Medical School tested melatonin in 36 volunteers subjected to a continually changing sleep schedule in a windowless laboratory for nearly a month. The study, published in this month's edition of the journal Sleep, found that melatonin was significantly better than a placebo in aiding sleep efficiency, or the percentage of time in bed spent asleep. Study bolsters melatonin sleep claims BOSTON, Massachusetts (CNN) -- A new study is lending credence to the popular claim that the hormonal supplement melatonin can help regulate sleep patterns. Scientists at Oregon Health Sciences University tested the supplement on a small group of blind people. The blind often suffer from sleep disorders because they cannot perceive the daily cycles of light and dark that regulate the body's biological clock. The researchers found that nearly all of the subjects developed normal sleep patterns after taking melatonin. When given a placebo, their sleep remained erratic. The results were reported in this week's New England Journal of Medicine. Study participant Clifton Zang was among those who benefited from the melatonin. "I was having a hard time staying awake during class time," he said. "I'd get up in the middle of the night and then I'd study." When he took melatonin at around 8 p.m., though, Zang found he was able to get a good night's sleep. "I got about six and a half hours of sleep and I felt good," he said. "I'm wide awake and ready to go." The study authors say melatonin could also help people who aren't blind regulate their sleep. More than 20 million Americans already use it for that purpose, hoping to treat insomnia or jet lag, or lessen the effects of shift work. Experts say the best time of day to take melatonin and how much to take depends on the specific sleep disorder. Taking too much at the wrong time could worsen sleep problems instead of helping them. In the study, patients started out on high doses, then switched to a low maintenance dose once their body clocks had adjusted. Doctors have long known that melatonin is involved in regulating the body clock. It is a naturally occurring hormone whose levels rise at night and fall during the day. This new research, she said, shows "the true potential of melatonin" and how important timing is to treatment. "Our 24-hour society, with its chaotic time cures and lack of natural light, may yet reap substantial benefits, " she said. Melatonin -- It's Like Night and Day National Sleep Foundation Offers New Information About Hormone That Affects Sleep. WASHINGTON, DC, July 12, 2004 -- 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. 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. 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. For melatonin to be helpful, the correct dosage, method of delivery (e.g. oral or topical), and time of day it is taken must be appropriate to the sleep problem. While melatonin may be beneficial under some circumstances, more research must be done to study both positive and negative effects. Before making a decision to take this supplement, these important points should be considered: Melatonin can increase blood pressure and affect fertility in animals. Correct dosage, method, and time of day must be appropriate to the sleep problem for melatonin to be helpful, however, researchers are only beginning to understand this information.