NEW YORK (Reuters Health) - Low levels of the naturally-occurring hormone melatonin, which is thought to help regulate sleep, have been blamed for the interrupted sleep and early awakenings that plague many older people. Now, Harvard researchers have challenged this notion, presenting an alternate view that questions the value of melatonin supplements for older individuals.

The scientists don't agree that there is necessarily an age-related decline in melatonin levels. Furthermore, they believe that the sleep problems typical of older people occur because of the timing of sleep versus the timing of melatonin production. Both are governed by circadian rhythms, or the body's "inner clock," and the relationship between them appears to change with age.

In a previous study, Dr. Jeanne Duffy, who is a neuroscientist, and associates at Harvard Medical School in Boston found that healthy older individuals produced about the same amount of melatonin as young adult men. "Despite this, even these very healthy older individuals have lower sleep efficiency than ... the typical young adult," Duffy told Reuters Health.

The new study involved a subset of the previous study participants: 15 older men and women, average age about 68, and 33 young men, average age 23. The results showed, Duffy explained, that "older subjects habitually go to bed earlier with respect to melatonin secretion onset than do young adults. Older subjects also wake earlier with respect to melatonin secretion offset.

"So older subjects have the end of their usual sleep episode at a biological time when there is relatively higher melatonin levels, and despite this they still have more awakenings in the latter part of the night," Duffy said. "Our results imply that melatonin supplements will not improve the typical sleep problems of older subjects, which occur in the early morning hours."

Three studies of supplemental melatonin have shown that it improves the sleep of elderly insomniacs, according to Duffy's team. However, in these studies an inexpensive method was used to evaluate sleep quality. In a study where patients were hooked up to electrodes and spent the night in a sleep laboratory, melatonin administration did not improve sleep.

It might be possible to develop "chronobiological treatments" for sleep disruption in the elderly, the scientists suggest in their report in the February issue of the American Journal of Physiology--Endocrinology and Metabolism.

"Such treatments would include manipulating the relationship between the timing of the biological clock and the timing of the sleep-wake cycle, so as to time the usual sleep episode to occur at the biological time when it is easiest to maintain sleep," Duffy said. "This could potentially be achieved by controlling exposure to light and darkness, and we are carrying out additional studies to explore this.

"Sleep is an important biological need, and lack of adequate sleep on an ongoing basis has many consequences," she added. "While many older people have more difficulty achieving a good night's sleep, we think that they still need as much sleep as they did when they were younger adults. Studies like the one we did, funded by the National Institute on Aging, will hopefully allow us to learn how to improve the sleep of older people."

SOURCE: American Journal of Physiology--Endocrinology and Metabolism 2002;282:E297-E303.

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