A primary goal in defining the long-term care population is developing a definition that can easily be translated into service and manpower estimates. To the extent feasible, it also should be compatible with available data and measures. Such estimates can then be translated into expenditure estimates for purposes of budgeting and health planning.
One approach, counting the number of people with chronic conditions, provides an informative but not entirely satisfactory estimate of service needs because many conditions have few, if any, consequences for health care utilization behavior (Haber 1971 and 1973).
Inventories of the number of people who report limitations in their usual activity are also an informative measure for some epidemiological purposes. But "usual activity" varies with age, occupation, work-force participation, and self-perceived role. This variation raises some questions concerning validity and reliability of the concept when used as a survey item with a retired population.
Similarly, a National Health Interview Survey item that asks whether or not an individual stays in bed most days because of a chronic condition has somewhat limited consequence for manpower-need estimates. This is so because it is not clear that human intervention would alter those individuals' conditions. In addition, they are a very small group; in 1980, only 17,000 nondependent persons, or less than one-tenth of 1% of the aged population, reported staying in bed most days due to a chronic condition (Weissert 1985).
The notion of functional disability as the criterion for inclusion in the long-term care population comes closer to the mark by focusing on an individual's ability to perform basic functions. Need for human help in daily functioning has direct implications for manpower estimates and long-term care expenditure projections. Nonetheless, even this measure is not problem free. Definitions of functional disability vary in the nature of the functional disabilities included as well as the degree of impairment. Definitions also differ by the duration of the disability, although most people accept the 1957 distinction offered by the Commission on Chronic Illness that care is long-term when it lasts more than 90 days.
For purposes of this paper, we have chosen to estimate functional dependency as it is most commonly defined by long-term care researchers. That is, dependency in activities of daily living (ADL), mobility, and instrumental activities of daily living (IADL). These measures repeatedly have been shown to be reliable and valid in helping to identify problems that require treatment or care, and they are readily available in a number of comprehensive assessment and information systems (Katz 1983), including several national surveys.
This is not to say that they are the only measures of the need for long-term care that might have been used. Other reliable measures of an elderly person's ability to perform physical functions include the Barthel Index, which includes a measure of muscle strength among other subscales; the Kenney Self-Care Evaluation, which includes additional measures of personal hygiene not measured by the Katz scale; and many others (Kane and Kane 1981). Few of these scales and measures have been widely used in national surveys, however, despite their potential to yield considerable additional detail on the elderly population's need for care.