ABSTRACT
THE aging of the United States population, recent develop-ments in medical treatment, and improvements in health behaviors have resulted in a dramatic increase in the elderly population. Unfortunately, many elderly people experience functional disabilities that compromise their quality of life, so the added years of life can be marred by physical impairment. As a consequence, preservation of functional independence in elderly persons has become an important goal of medical research. Although it was once commonly believed that functional decline was inevitable in old age, recent studies have revealed that some elderly people seem to be protected from functional decline, and a significant proportion of impaired elderly people regain physical functioning (Beckett et al., 1996; Crimmins & Saito, 1993).
