Any purely physical theory of aging cannot help but be incomplete. Consider arthritis, one of the most common symptoms of age. In medical school we were taught that common arthritis (or osteo-arthritis) is a degenerative disorder. This means that its cause is simple wear and tear.
After a lifetime of hard use, the cushioning cartilage in large weight-bearing joints deteriorates, which explains why the knee and hip joints, which carry the burden of supporting the body, tend to be favored sites for arthritis.
The synovium, the smooth lining that cushions the bones where they meet, also becomes inflamed or deteriorated, leading to the pain, swelling, and burning of arthritis. Sometimes the synovial fluid dries up, and the bones grind against each other, creating pits or bone spurs. This kind of degeneration has plagued mankind since the Stone Age.
As the cause of arthritis, wear and tear appeals to common sense, but it fails to explain several things. Some people never become arthritic, even though they subject their joints to extreme stress. Other people develop arthritis after a lifetime of sedentary desk work, not to mention that certain favorite spots for the disease, such as the fingers, are not called upon to bear weight at all.
Newer theories of arthritis look to hormones, genetics, autoimmune breakdown, diet, and other factors; in the end, no clear cause is known.
However, emotional factors have been strongly linked to another major type of arthritis, rheumatoid arthritis. This disorder seems to favor women who have a marked tendency to repress emotion, who adopt passivity and depression as a mode of coping with stress rather than getting angry or confronting serious emotional issues.
The disease can get worse under stress, and, for inexplicable reasons, it can also disappear, perhaps in obedience to a deeper current of change.
Adapted from Ageless Body, Timeless Mind, by Deepak Chopra (Three Rivers Press, 1998).