Physiologic Clues of Aging

Research on the physiology of aging is puzzling out the characteristics of normal aging -- aging in the absence of disease. Studies are also looking at behavioral factors, such as diet and exercise, and at what happens in key organ systems as people age.

We don't know very much about the man who lived to 120 years of age, but we can assume that he escaped the diseases that kill many people in their 70s and 80s. In fact, escape from disease is the most common reason that all of us can now expect to live longer than our grandparents.

Chronic diseases and disability were once thought inseparable from old age. This view is changing rapidly as one disease after another joins the ranks of those that can be prevented or at least controlled, often through changes in lifestyle.

We now know, for example, that most people can avoid lung disease by not smoking. And heart disease and stroke rates have fallen at the same time that Americans have lowered their fat consumption, begun to exercise more, and quit smoking.

If chronic disease is not intrinsic to the aging process, as many gerontologists now believe, then what is? What are the universal or "normal" aging processes?

Normal Aging

Many of the answers to this question are coming from the Baltimore Longitudinal Study of Aging (BLSA). In this long-term study, begun in 1958, researchers are studying the aging process in more than 1,000 people from age 20 to age 90 and beyond.

They have found that variations in human development increase as people age and that organ systems within a single individual can change at different rates. This suggests that genetic, lifestyle, and disease processes all affect the rate of aging and that several distinct processes are involved.

More information on normal aging comes from NIA's Biomarkers of Aging project. Begun in 1987, this 10-year effort is singling out key biological signs that characterize the aging process. The project is based on the idea that biomarkers are a better measure of an organism's aging status than chronological age itself. Once the biomarkers have been identified, it will be easier to study normal aging, diseases, and anti-aging interventions.

Researchers investigating the physiology of aging have focused on two organ systems in particular that seem to serve as pacemakers of declining functions. One of these, the endocrine system, is discussed on pages 19-21. The other is the immune system.

See also Aging and The Immune System