Age-related sleep changes bring alterations in growth hormone and cortisol secretion, according to a report in the last weekÃƒÂs issue of The Journal of the American Medical Association. Consistent alterations of sleeping patterns accompany aging, but whether these changes contribute to decreases in growth hormone secretion and elevations in evening cortisol levels has been unknown.
Researchers from the University of Chicago, in Illinois, examined the association of age-related sleep changes and changes in growth hormone secretion and cortisol levels in 149 healthy men between the ages of 16 and 83 years. Total nightly sleep time decreased by a mean of 27 minutes per decade from midlife until the eight decade. Between early adulthood (16 to 25 years) and midlife (36 to 50 years), the percentage of slow-wave sleep fell from 18.9% to 3.4%, while the percentage of light non-rapid eye movement (REM) sleep rose from 51.2% to 67.3%. The percentage of time spent in REM sleep did not change significantly until midlife, after which it fell from 60.5% (age 51 to 60 years) to 50.6% (older than 70 years).
While time spent in slow-wave sleep was falling, growth hormone secretion was declining by nearly 75%, a change that proved independent of weight changes. In contrast, the increase in evening cortisol levels did not begin until the fifth decade, coincident with the decreases in REM sleep and increases in time spent awake. The distinct changes in sleep quality that characterize the transitions from early adulthood to midlife, on the one hand, and from midlife to old age, on the other hand, are each associated with specific alterations in hormonal systems that are essential for regulation of the bodyÃƒÂs metabolism. The scientists conclude that strategies to prevent or limit decrements of sleep quality in midlife and late life may therefore represent an indirect form of hormonal therapy with possible beneficial health consequences. These findings may not apply to women. The effects of aging on sleep regulation differ substantially between men and women.
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