Researchers reported in the Journal of the American Medical Association that sleep patterns are shortened and growth hormone levels are reduced in men starting as young as 25. Contrary to popular belief, this suggests that men start going through a hormonal change of life called somatopause well before mid-life. This in turn sets in motion the weight gains and flabbiness that aging brings on in later decades.

By age 45, most men have almost entirely lost the ability to generate significant amounts of deep sleep, which is the period when growth hormone secretion mainly takes place, said researchers at the University of Chicago. "These changes in sleep quality provide an early biological marker of aging in men,'' said Eve Van Cauter, a professor of medicine and director of the study.

On top of that, there is further deterioration of sleep that begins in the 50s with men getting less sleep overall and experiencing more and longer awakenings during the night.

Van Cauter said the research findings indicate that growth hormone replacement therapy, which has mainly been tested on elderly men and women, might better be targeted at individuals in early middle age based on logic alone. "We begin estrogen replacement as soon as women enter menopause, not 20 years later. If men go through 'somatopause' a loss of growth hormone between 25 and 45, why should we wait another 20 years to initiate treatment?''

Although total sleep remained constant as young men moved into mid-life, the proportion of slow wave or deep sleep decreased from nearly 20 percent of a normal night's sleep among those under 25 to less than 5 percent for those over 35. Growth hormone secretion also declined by about 75 percent during that decade. After age 50, a night's sleep declines by about a half-hour every decade. And REM (rapid eye movement), or dream, sleep declines to about half the levels experienced by young adults. This loss of dream time appears to be associated with increased levels of the stress-related hormone cortisol.

Anti-Aging Perspective:

This study continues to demonstrate the importance of getting a good night's rest and how it affects our hormonal system.

Preliminary studies hint that boosting deep sleep can also increase hormone secretion. Sleep deprived individuals age faster. It's that simple.

Cortisol, a "fight or flight'' hormone that heightens attention and alertness, normally peaks in the morning and declines into the afternoon and evening. But those with decreased REM sleep will have levels of the hormone remain relatively high well into the night. This could make sleep more fitful and promote awakenings, the researchers said. It also could case memory deficit, insulin resistance and even a decline of the immune system seen in old age. These are all the effects of cortisol, the one hormone that increases with age and that which is considered "bad" for aging.