Using group-based latent class transition models to analyze chronic disability data from the National Long-Term Care Survey 1984-2004.

Latent class transition models track how individuals move among latent classes through time, traditionally assuming a complete set of observations for each individual. In this paper, we develop group-based latent class transition models that allow for staggered entry and exit, common in surveys with rolling enrollment designs. Such models are conceptually similar to, but structurally distinct from, pattern mixture models of the missing data literature. We employ group-based latent class transition modeling to conduct an in-depth data analysis of recent trends in chronic disability among the U.S. elderly population. Using activities of daily living data from the National Long-Term Care Survey (NLTCS), 1982-2004, we estimate model parameters using the expectation-maximization algorithm, implemented in SAS PROC IML. Our findings indicate that declines in chronic disability prevalence, observed in the 1980s and 1990s, did not continue in the early 2000s as previous NLTCS cross-sectional analyses have indicated.

Issues in survey measurement of chronic disability: An example of the National Long Term Care Survey.

The National Long Term Care Survey, a longitudinal study that consisted of the screen and detailed interviews, provides a unique opportunity to illustrate issues in survey measurement of chronic disability. The original intent of the survey was to use the shorter measure of disability status in the screen interview to maximize the yield of disabled cases and then examine those cases with the longer measure in the detailed interview, identifying possible "false positive" disability cases from the screen. In this paper, we show empirically that the intended relationship between the screen and detailed NLTCS disability measures doesn't hold uniformly - the detailed measure provides significantly higher ADL disability estimates than the screen measure, contrary to the expectation. We examine whether discrepancies between the two disability measures are associated with certain features of the survey design and respondent-level characteristics, discuss implications of our findings for prevalence estimation, and provide recommendations for disability survey design.