Short-Term Disability Fluctuations in Late Life

Abstract

Objectives: Late-life disability is highly dynamic but within-person short-term fluctuations have not been assessed previously. We analyze how substantial such late-life disability fluctuations are and whether they are associated with time-to-death, long-term disability trajectories, frailty, and sociodemographics.

Methods: Monthly survey data (Precipitating Events Project Study) on activities of daily living/instrumental activities of daily living (ADL/IADL) disability (0-9) in the last years of life from 642 deceased respondents providing 56,308 observations were analyzed with a two-step approach. Observation-level residuals extracted from a Poisson mixed regression model (first step), which depict vertical short-term fluctuations from individual long-term trajectories, were analyzed with a linear mixed regression model (second step).

Results: Short-term disability fluctuations amounted to about one ADL/IADL limitation, increased in the last 4 years of life, and were closely associated with disability increases. Associations with frailty or sociodemographics characteristics were absent except for living alone.

Discussion: Short-term disability fluctuations in late life were substantial, were linked to mortality-related processes, and represent a concomitant feature of disability increases in late life.

Keywords: Disability; Health disparities; Intraindividual variability; Longitudinal methods; Short-term fluctuations.