Why We Fall Apart

With the reliability theory's view of aging, researchers now have, generally at least, a why and a how of aging. We age because our makeup includes irreplaceable but redundant parts, many of which are defective, and we age as each of those parts inevitably stops working. Having such a theory can help focus biomedical research on interventions that can slow or control aging.

One of the greatest of such interventions would be a way to avoid the developmental damage responsible for the high initial damage load that marks our lives. Even such a simple thing as an adequate supply of vitamins (folic acid, in particular) and other micronutrients for expectant mothers prevents extensive DNA damage and many inborn defects. For example, pregnant mice fed antioxidants, which decrease damage to DNA and other cellular structures, produce longer-lived offspring. This line of research could lead to the prevention of age-related diseases before birth, analogous to improving the manufacturing process of a computer chip.

We could also do better at preventing damage to tissues and organs. The elimination of widespread chronic infections and hidden inflammation helps to delay the onset of arthritis, atherosclerosis, diabetes, Alzheimer's disease, and some types of cancer. And while we're at it, we should learn to repair our bodies better when we're wounded or weakened by disease.

Living organisms already have numerous mechanisms of repair--for example, cells killed by everything from scratches to sunburn are continuously replaced by new ones, which are formed by stem cells, cells that can multiply to form many types of tissue. Scientists have been studying what's called the hormesis effect, the observation that a little bit of poison activates an organism's self-repair mechanisms, having the side effect of protecting it against other hazards than the poison itself. If we could learn to control such a protective effect, we might be able to slow or prevent the loss of cells and systems that leads to aging.

Finally, we could learn to replace our damaged organs, substituting the young and healthy for the old and failing. Many researchers now believe that one day the human life span could be greatly extended by replenishing aging organs with stem cells. We are just now starting down this road. Such regenerative medicine and tissue engineering may sound like science fiction, but a growing number of scientists are taking the first steps to grow tissues and organs to replace failed ones. Laboratories around the world are making progress in building replacement lung, kidney, liver, and heart tissue.

Reliability theory suggests that there might be no single underlying aging process. Instead, aging may be largely an emergent property of redundant systems. Such systems can have a network of destruction pathways, each associated with particular manifestations of aging, whether menopause or Alzheimer's disease. Metaphorically speaking, our life span is a time bomb with many fuses burning at different speeds. Cutting off only one fuse may be inadequate--we need to take care of them all.