Association of a Modifi ed Physiologic Index With Mortality and Incident Disability: The Health, Aging, and Body Composition Study

THE relationship between aging and disease is complex. One theory is that aging is independent of disease pathogenesis. This is based on the relatively consistent observation that a decline in function with age is seen between and within species with widely different physiology and pathology ( 1). This separation may be artifi cial, though, and belie our poor understanding of the aging – disease dichot-omy ( 2). A second theory argues that aging and disease pathogenesis are inextricable and, in the extreme, are in fact the same process expressed in different terms ( 2). This theory may be less tenable because over time organisms exhibit facets of aging which do not appear like disease and which occur without concomitant disease pathogenesis ( 1). A third, more moderate theory contends that aging is partly divisible from disease pathogenesis, that the two hav