Weighted health status in the Medicare population: development of the Weighted Health Index for the Medicare Current Beneficiary Survey (WHIMCBS).

We present an approach to constructing an aggregate index of health at the population level with data from Medicare beneficiaries using the 1991 (N = 12,667), 1995 (N = 15,590), and 1997 (N=17,058) Medicare Current Beneficiary Survey (MCBS). Similar to other work with survey data, we develop a weighted health status index from which one can calculate a point in time health status score for any beneficiary. Scores range from 1.0, representing "excellent health and no activity limitation", to 0.0, representing deceased. Sequences of numerically weighted health states experienced over time can be summed to calculate years of healthy life for beneficiaries. We test both the stability of the scoring system when developed on independent samples, as well as the sensitivity of years of healthy life calculations to changes in scoring assumptions. Findings suggest that, in addition to mortality, morbidity appears to play a significant role in the years of healthy life accrued by Medicare beneficiaries since entry into the Medicare program. Further, the index scoring system is highly stable when derived on independent samples. Finally, calculations of years of healthy life are robust to changes in scoring assumptions. The weighted health index for Medicare current beneficiaries (WHIMCBS) is a stable overall index of health and may be a useful ongoing indicator of health within the Medicare population.