Mixed trends in population health among older adults.

R are just beginning to find some evidence of improving health in the older population (see the report in this issue by Spiers, Jagger, and Clarke, 1996; also see Crimmins and Ingegneri, 1993; Manton, Corder, and Stallard, 1993; Manton, Stallard, and Corder, 1995; Waidmann, Bound, and Schoenbaum, 1995). While the evidence is not unequivocal in indicating improving health, it is the first evidence of a trend in this direction. Two decades ago, when mortality began to decline rapidly among the old, the assumption was that health also must be improving; and that as soon as health was adequately measured, improving health would be documented. Early in this quest for evidence of improving health, health was viewed as a unidimensional concept with a variety of operational definitions; use of any of the operational definitions was expected to yield similar trend results. Over the years, it became clear that initial expectations were too simplistic because we came to understand that health is a multidimensional concept with complex interrelationships among its dimensions (Liang, 1986; Verbrugge and Jette, 1994); that the measurement of each dimension is more complicated than we originally thought; and that the relationship between mortality change, its causes, and population health is more complex than we had heretofore understood (Bonneux et al., 1994; Crimmins, Hayward, and Saito, 1994). Our improved understanding has led us to better interpret past empirical findings and to understand that future trends in health cannot be simplistically predicted. The multiple dimensions of health are conceptually quite different. Health problems include having diseases, conditions, impairments, functional losses, and disabilities. Selfperceived health status is an overall personal assessment based on all these facets of health (Liang, 1986; Verbrugge and Jette, 1994). Because the dimensions of health may be affected by different processes, there is no reason that all dimensions should change in the same way at the same time, nor that self-perceived health status should change in the same way that any one dimension does. The seemingly contradictory change observed in the Melton Mowbray population — improvement in ADL functioning and deterioration in self-perceived health status — is logically possible (Spiers, Jagger, and Clarke, 1996). Persons can improve in their ability to perform such basic functions as transferring, toileting, dressing, and getting about the home without raising their self-assessment of health to "good. " In fact, Verbrugge (1989) has noted a similar paradox in trends in health indicators for the United States from 1972-1981. During this time, reported disability and disease presence increased, yet there was no change in self-perceived health. Over the years we have come to understand that trends in each of our operational definitions of "health" are affected not only by changes in "health" but also by trends in factors other than "health" which are external to the individual. Much research on the older population uses ability to perform ADL and I ADL functions as indicators of "health. " These indicators are conceptually indicators of disability as they represent ability to provide personal care and independent living or expected social roles for the old. Certainly, we expect trends in these indicators of disability to be affected by trends in "health" problems such as the presence of diseases or conditions. For instance, reduction in the amount of congestive heart failure or stroke should reduce the difficulty some people have in getting around the house. Decreases in dementia would enable more people to perform the tasks necessary to live independently. Changes in the prevalence of these diseases should affect ADL or IADL performance; however, changes in the environment in which these activities are performed can also cause change in these indicators of disability (Verbrugge and Jette, 1994). Changes in homes, such as the number of stairs or the placement of bathrooms, may make it easier or more difficult to get around; changes in clothes (e.g., the reduction in buttons or zippers) and shoes (e.g., slip-ons or Velcro fasteners versus tie shoes) can make dressing easier or harder; changes in the availability of prepared food and cooking technology (e.g., frozen meals and microwave ovens) can make providing meals for oneself easier. Often, the indicators of ADL or IADL inability are based on the use of assistance from another person. Many people who probably could do tasks alone accept help if it is readily available. Thus, changes in living arrangements which lead to change in the availability of household members may lead to changes in the level of reported ADL and IADL inability. None of these would be changes in "health" as some would think of it, but they would be changes in disability levels. It is not clear how closely related such changes would be to one's self-perception of health.