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The Effect of Altering ADL Thresholds on Active Life Expectancy Estimates for Older Persons

¹ Department of Sociology and Office of Population Research, Princeton University, Princeton, New Jersey.
² Department of Sociology and Center for Demographic Studies, Duke University, Durham, North Carolina.

Address correspondence to Scott M. Lynch, Department of Sociology, Princeton University, Princeton, NJ 08544. E-mail: slynch{at}princeton.edu

Objectives. Research on disability and active life expectancy (ALE) has often criticized the measurement of disability but has rarely empirically investigated the effect of changing measurement. The purpose of this study was to determine whether altering the number of activities of daily living (ADLs) required to consider an individual "disabled" affects population-based ALE estimates after considering parametric uncertainty and sampling error.

Methods. The authors develop a Bayesian approach to estimating multistate life tables for a three-dimensional state space, using data on community-dwelling older adults from the 1989 and 1994 National Long Term Care Survey analytic files. Empirical confidence intervals for ALE are compared across 6 models using successively higher ADL cutoffs for defining individuals as being disabled.

Results. After considering sampling and other errors in the estimation of transition probabilities, the authors found that altering the threshold for measuring disability has relatively little effect on ALE estimates, especially with higher ADL-level thresholds and at older ages.

Discussion. The implications of the results include that disability measurement, including altering the definition of being disabled and possibly expanding the state space of a model, may not affect population-based estimates of ALE.