Claim For Sleep Drug Is Contested

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November 11, 1999

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HARVARD GAZETTE ARCHIVES

By William J. Cromie
Gazette Staff

Older people are being barraged by claims in newspapers, in magazines, and on television advising them that levels of the hormone melatonin in their bodies are decreasing every day. As natural levels of the hormone decrease, goes the pitch, they should be replaced by nonprescription supplements.

Why? One major reason is that melatonin seems to be a natural sleep inducer, so reduced levels, the reasoning goes, can lead to sleeping problems.

That's not so, says Charles Czeisler, a professor of medicine at the Harvard Medical School. He and his colleagues just completed a study that compares nighttime levels of melatonin in younger men with those in healthy men and women ranging in age from 65 to 81 years.

"We deduce from our findings that, as healthy people age, their melatonin concentrations do not decline," Czeisler says. "If older people have trouble sleeping, it's not because their melatonin levels are declining."

Health stores sell melatonin in 3-, 5-, and 10-milligram tablets, which can raise levels of the hormone hundreds of times higher than normal. You can even buy brands claiming to be melatonnin that may not contain any of the drug. No Food and Drug Administration testing is required to guarantee either the potency or safety of this nonprescription drug.

"No large-scale scientific study has ever been done to determine its safety or efficacy," notes Czeisler, who is also director of circadian and sleep disorders medicine at Brigham and Women’s Hospital.

The hormone is produced by the pineal gland, a tiny, cone-shaped organ deep in the brain. The amount secreted depends on light levels and is lowest in daylight, highest at night. (Even switching on the bathroom light at night lowers melatonin levels.)

The popular idea that the amount produced starts to decrease as early as age 40 gave rise to the notion that the pineal gland serves as a clock to measure aging. "Our study shows that this is simply not true," says Jamie Zeitzer, a postdoctoral fellow in Czeisler’s laboratory.

Zeitzer, Czeisler, and their colleagues compared melatonin levels of 34 healthy men and women, 65 to 81 years old, with those of 101 healthy younger men, ages 18 to 30. Younger women were not included because the menstrual cycle can change levels of the hormone irrespective of light.

The experimenters verified that all of these people were not users of aspirin, ibuprofen, and/or other drugs that suppress melatonin production. None took any medications or had sleep problems. They drank no alcohol or caffeine and did not smoke during the three days and nights they spent isolated in a laboratory. All maintained their normal sleep schedules, and the researchers took regular blood samples to quantify their melatonin production.

"Our results clearly demonstrate that most healthy older people have nighttime melatonin concentrations in their blood comparable with those of young adults," Czeisler says. "This does not mean that melatonin will not help some older people as it does some young people whose sleeping problems may be tied to insensitivity to the hormone. If taking melatonin supplements should prove to be efficacious, however, a physician's assessment of each person’s natural melatonin system should be undertaken before supplements are recommended, regardless of age."

So what should oldsters do if they can’t fall asleep and lack of melatonin is not the cause? Czeisler advises regularity. "Go to bed the same time every night," he says. "Sleep in a cool, dark, quiet room. Some people who can’t sleep turn on the television or radio, but that adds to the difficulty. Shun caffeine in any form after lunch; that includes coffee, tea, cola, and chocolate. If none of that works, consult a sleep-disorder specialist."