Falling Asleep on the Job? Growth Hormone Changes Hit Earlier Than Expected in Men

Medically Reviewed by Charlotte E. Grayson Mathis, MD
From the WebMD Archives

Aug. 15, 2000 -- Too many sleepless nights not only make you feel old, but it may actually speed up aging by throwing your hormones out of whack -- at least if you're a male.

A new study shows that aging-related changes in sleep patterns hit men at a much earlier age than had been previously thought -- by the age of 45 -- and that they coincide with striking changes in two hormones, growth hormone and cortisol, that are linked to many processes associated with aging. By 45, the researchers found, most men have entirely lost the ability to fall into the type of sleep called deep slow-wave (SW) sleep.

Many scientists are already testing whether treatment to replace growth hormone lost with age might reverse or prevent some aspects of aging, such as obesity and poor tolerance for exercise. But because of the latest findings, the study's lead author, Eve Van Cauter, PhD, tells WebMD that perhaps this replacement therapy should start in much younger men. Van Cauter, whose study was published in TheJournal of the American Medical Association, also says drugs that improve the quality of sleep might help.

"Growth-hormone replacement therapy should be started at a much earlier age than usually envisioned, i.e. around 40-45 years of age," says Van Cauter, a professor of medicine at the University of Chicago. She suggests that the use of growth hormone in men would be similar to how estrogen replacement is given to women around menopause.

"We found that the percentage of sleep that is deep SW sleep decreases from 18.9% to 3.4% from early adulthood to midlife, and that this change is paralleled by a decrease in growth hormone secretion," Van Cauter tells WebMD.

In addition, Van Cauter and colleagues identified a second stage of aging-related sleep change, which begins at midlife and coincides with changes in the secretion of the stress-related hormone cortisol. "We also found that from midlife to late life, there is an increase in time awake and a decrease in REM [rapid-eye-movement stage] sleep," she says. "This is paralleled by a trend toward higher evening cortisol levels."

Growth hormone deficiency has been studied extensively in the elderly, and is associated with increased obesity, loss of muscle mass, and reduced capacity for exercise. Disordered sleep can reduce growth hormone secretion, and some experimental drugs that induce slow-wave sleep also increase growth hormone levels.

For the study, Van Cauter and colleagues analyzed data from 149 healthy men, aged 16-83 years, who had undergone sleep studies and for whom 24 hour measurements of cortisol and growth-hormone levels were available. The study included only men because women's sleep patterns do not deteriorate in early to mid-adulthood as men's do.

Louis J. McNabb, MD, of the Sleep Disorders Institute at St. Jude Medical Center in Fullerton, Calif., tells WebMD that Van Cauter's report raises an interesting question about the relationship between aging, sleep, and hormonal changes. But McNabb says this observation doesn't show that losing sleep causes these hormonal changes or vice versa.

"Going from the observation that these changes occur together to the conclusion that there is a causal relationship is a long leap," McNabb, who was not involved in the study, tells WebMD.

Even if there is a causal relationship, McNabb is not convinced it is clinically important. "Is the question whether men over age 55, most of whom have these sleep and growth hormone changes, can function well on a daily basis? If so, the answer is yes. The heads of most of our major corporations are over 55. Most of our presidents have been over 55. Most men do just fine regardless of the age-related drop-off in delta or slow-wave sleep."

The most intriguing possibility raised by Van Cauter's research is that restoring SW sleep might reverse the decline of growth hormone in young to middle-aged men and thus protect against some of the physical changes associated with aging.

Marc R. Blackman, MD, a renowned growth hormone researcher and author of an editorial accompanying the study, writes that "therapeutic interventions [to prevent these age-related changes] should be assessed relatively early in life. ... Clearly, more research into this promising area is indicated, as the potential benefits to the aging population are substantial." Blackman is with the department of medicine at The Johns Hopkins University School of Medicine in Baltimore.

Says Van Cauter: "There is a need to develop a new type of 'sleeping pill' that specifically increases SW sleep instead of simply facilitating sleep onset and preventing awakening, which is all the currently available [sleeping pills] do."