Health: Sleep All Day!

Do melatonin supplements really help people sleep? Millions of jet-lagged and sleep-deprived Americans--citing countless self-help articles--insist they do. But the scientific evidence has been slim. There's no question that the hormone helps the brain tell a.m. from p.m.--regulating sleep cycles and circadian timing--when it is produced naturally by the body at night. What was lacking was clear evidence that taking melatonin in supplement form had the same sleep-inducing effect.

That's why there's so much interest in a study in the current issue of the journal Sleep. Researchers at Brigham and Women's Hospital and Harvard Medical School set out to test melatonin's effects and found that the supplements can indeed be a potent sleep aid--but only during daylight hours.

The study was small, with just 36 volunteers, but rigorous and well designed. Researchers housed each participant in a soundproof room with dim lighting, no windows and no hint of real time. For most of the four-week study, the volunteers were kept on strict 20-hour cycles of sleep and wakefulness. The "forced desynchrony" was intended to throw the body's 24-hour clock out of whack, according to the study's lead author, James Wyatt, while mimicking the off-hour sleep-wake cycle that shift workers and jet-lagged travelers often struggle with. Every "night" of the study, the subjects were given either melatonin or a placebo 30 min. before bedtime.

People who took melatonin supplements, researchers found, slept significantly longer than the placebo group, but only in periods of sleep that occurred during the volunteers' biological day--that is, when their bodies were not producing natural melatonin. During the sleep cycles that happened to fall at night in real time, when melatonin is already being released by the brain, taking an extra dose of the hormone worked no better than taking a placebo. "It seems that what melatonin is doing," says Wyatt, "is knocking out the wake-promoting drive, which normally happens during the day, from your circadian clock."

On average, melatonin users had a daytime sleep efficiency of at least 83%--meaning they slept 83% of the time they spent in bed--compared with 77% in the placebo group. That translates to an extra half an hour of shut-eye--relatively comparable to what one gets with a prescription sleep aid like Ambien or Lunesta.

But that doesn't mean the pills are interchangeable. Melatonin works on a completely different neurological system than the prescription drugs and, as the study suggests, won't help you at night or if you experience insomnia because of something other than jet lag or a graveyard shift.

On the other hand, says Wyatt, people don't seem to build up a tolerance to melatonin, and even small amounts, like the 0.3-mg dose used in the study, are effective. Studies show also that melatonin is safe for adults, at least in the short term, with few side effects. "But the first thing I recommend before starting anything," says Wyatt, "is to have a chat with your primary-care doctor."