Women's Health - February 2005

Little Sleep Benefit From Melatonin, Study Shows

A US government review of more than 50 studies on the effect of melatonin on sleep has found little evidence that the supplement helps people drift off.

While melatonin does aid sleep in a certain group of people whose biological clocks are out of kilter, researchers found it does not promote sleep among the most common users of the supplement - those suffering from jet lag or weary shift workers.

"A lot of people take melatonin for jet lag and shift work, but we found no good evidence to justify the use of melatonin in this context," says study author Dr. Terry Klassen, director of the Evidence-Based Practice Center at the University of Alberta in Edmonton, Canada.

Insomnia a Major Problem for Americans

According to the National Institutes of Health, approximately 40 million Americans suffer from chronic, long-term sleep disorders each year, and an additional 20 million experience occasional sleeping problems. Insomnia tends to increase with age and affects about 40 percent of women and 30 percent of men.

The most common sleep disorders are insomnia, sleep apnea, restless leg syndrome (particularly among elderly people), and narcolepsy, a condition in which people suddenly fall asleep for short periods of time even if they are well-rested.

Melatonin is a hormone found in the brain that helps the body's sleeping and waking schedule. Typically, melatonin levels rise in the evening, causing sleepiness, and are lower in the morning to induce waking.

The study, which was funded by the National Institutes of Health's National Center for Complementary and Alternative Medicine, was published online by the Agency for Healthcare Research and Quality (AHRQ).

The report is the most comprehensive look at the science behind the claims that melatonin is a beneficial sleep aid, Dr. Klassen says.

"There has been a lot of emphasis on individual studies rather than the overall picture, but when you put it all together, it tells a more compelling story," he explains.

The researchers found the quality of the studies varied, with those that looked at the effects of melatonin on normal sleepers generally of lower quality than those studies that looked at people with sleep problems.

Further, Dr. Klassen notes, all the studies tended to be small and of short duration, with an average length of a few months, so that the long-term effects of melatonin could not be assessed.

Debate Over Melatonin Benefit Continues

The authors also noted that in the studies assessing the benefits of melatonin for normal sleepers, "there was considerable evidence of possible publication bias in the selection of the studies analyzed," they write. "We found a greater number of studies reporting positive results compared to negative results."

The one area where melatonin did seem to work was with a group of people with a condition called "delayed sleep phase syndrome," which means that otherwise healthy people have a biological quirk that prevents a normal sleep cycle. For these people, Dr. Klassen says, taking melatonin appeared to improve their sleep.

"Melatonin helped to reset their biological clock," he says, so that on average it reduced the time it took them to fall asleep by about a half-hour.

Dr. Klassen says that although many people swear that melatonin works for them when they are suffering from jet lag, the science simply does not back up these claims.

"It could be a placebo [inactive substance] effect, or the fact that sleep disorders vary, and that someone would get better anyway," he says.

"When people go into stores, if a bottle of melatonin has the word 'sleep' on it, there is an implied medical claim that they're going to sleep better, and this report doesn't support these implied benefits," says Dr. Meir Kryger, author of A Woman's Guide to Sleep Disorders. "It's a very good study."

This is exactly why evidence-based studies are so important, Dr. Klassen says.

"This is a huge issue, and an area where we should be spending money to fund rigorous testing of these claims," he says.

Always consult your physician for more information.