Anti-aging experts ask: Will human lifespan reach 120?

Next, to a remarkable degree we are each responsible for the quality of our old age.

For example, at the annual meeting of the Society for Neuroscience in November 1996, scientists were told of new experiments using genetically engineered viruses that may one day combat Alzheimer's, Parkinson's and the effects of brain damage from strokes.

Other researchers reported that estrogen may relieve symptoms of Alzheimer's in post-menopausal women.

"We will be able to prevent, even reverse, aging within two decades," asserts Dr. Michael Fossel in his book "Reversing Human Aging" (William Morrow & Co.).

Cancer will become merely a bad memory, he writes, and "Alzheimer's and heart disease, for example, will become trivial and rare."

"Aging is not inevitable. The war on aging has begun."

That's the official slogan of the American Academy of Anti-Aging Medicine, founded in 1993 by a group of physicians and scientists dedicated to slowing and eventually halting the aging process, say Dr. Ronald Klatz, president of the academy, and Dr. Robert Goldman, president of the National Academy of Sports Medicine, in their book "Stopping the Clock: Dramatic Breakthroughs in Anti-Aging and Rejuvenation Techniques" (Keats Publishing).

The MacArthur Foundation Network on Successful Aging, an interuniversity, interdisciplinary consortium of researchers, was established in 1985 to discover and study the factors that enable people to age successfully.

Directed by Dr. John W. Rowe, president of New York's Mount Sinai Medical Center and School of Medicine, the network has challenged stereotypes of old age and identified factors that we can control.

The factors shown to be the major predictors of high functioning in old age are: (1) education, (2) exercise and (3) a sense of efficacy: in other words, a sense that one is able to influence what happens to oneself on a daily basis.

"One exciting aspect of our findings to date is that the factors we've found to be predictors of successful aging are all things we can control or modify," says Rowe.

"Now that we've identified these factors, it's our responsibility as scientists to design intervention studies in older individuals and populations. It's time to change people's lives, not just study them."

For example, if you are a sedentary 45-year-old, is it too late to start bicycling in the mornings, study Spanish in the evenings and increase your chances of aging successfully? Rowe says this is just the kind of intervention study needed next to apply the network's new knowledge.

Possibly the most powerful anti-aging weapon we have is the mind, say Klatz and Goldman.

"Numerous studies have shown that your health is greatly affected by how you react to stressful events in life -- setbacks or deadlines, conflicts and losses," they write.

"By the same token, changing your reactions, learning to meditate or other relaxation techniques and generally committing to a positive, open attitude toward life can help make you younger, expanding your abilities to maintain a vigorous and energetic lifestyle."

We need not repeat here the widely published reports that lower-fat, higher-fiber diets in conjunction with exercise are healthier for anyone at any age compared to a high-fat, low-fiber, sedentary lifestyle.

Perhaps less often discussed is the anti-aging potential of several hormones.

"At the present time, this is the most interesting aspect of aging because we can do something about it. The hormones that keep us young are now readily replaceable," say Dr. Elmer Cranton and William Fryer in their book "Resetting the Clock" (M. Evans & Co.):

Now recognized as a major player in the repair and upkeep of the adult body, the human growth hormone "has such startling effects in older people that it alone may significantly extend longevity and vastly improve quality of life," Cranton and Fryer write.

DHEA, our chief adrenal hormone, is the most common steroid in blood. Research on it continues. Melatonin may control the body's aging clock, and we know it can help us sleep -- "acting like a clock," writes Leonard Hayflick in his book "How and Why We Age" (Ballantine).

He reports one 1993 University of Texas study revealing that "melatonin, unlike other hormones, is a powerful anti-oxidant -- more powerful than other anti-oxidants like beta-carotene and vitamins C and E," he says. Expect more melatonin studies.

The female sex hormones estrogen and progesterone, which form postmenopausal women's hormone replacement therapy, still create some controversy. But Cranton and Frye assert, "statisticians know that women who take them live longer and someday all women may know what a sacrifice they are making if they avoid them."

Testosterone, the male sex hormone, "has become some men's secret weapon against aging," write Cranton and Frye.

"Will it go mainstream, as estrogen has done? We are on the verge of such a breakthrough."

According to Klatz and Goldman, "Many reputable anti-aging scientists are predicting average life spans of 120 to 150 years before 2046."

But Hayflick asserts that our life expectation would increase by about 17 years if we rid ourselves of the two leading causes of death today: cardiovascular diseases and cancer.

"I do not believe that we will soon have the ability to manipulate what appears to be the fixed human life span of 115 years," Hayflick says.

"If the past is any guide, it might be 10,000 years or more before the maximum human life span reaches even 120 years."

Still, Fossel points out that history is also made from dreams.

"Smallpox has disappeared; we are blasé as we fly across continents; computers talk to us and even begin to listen to us," he writes.

"This book is a promise and a warning," Fossel says. "It is a promise of a time when we will live longer and much healthier lives -- of 100, 200, possibly 500 years. It is also a warning of what could happen when we do."