Aging and late-life termina decline in perceptual speed: A comparison of alternative modeling approaches

Individual changes in perceptual speed were modeled as a conditional function of age and time-to-death. Alternative time-structured models were evaluated in a Swedish population-based, age-homogeneous sample (Gothenburg H70; N = 764) of individuals assessed at ages 70, 75, 79, 85, 88, 90, 92, 95, 97, and 99. Modeling time as proximity to death accounted better for the heterogeneity of individual changes than an age-based time structure. Time-to-death was a significant predictor of individual differences in rates of change in the age-based model but age did not significantly predict individual differences in rates of change in the model structured by proximity to death. In both the age-based and death-based time-structured models, accelerated changes prior to time of death were observed and provide support for the terminal-decline hypothesis. Identification of health-related factors and other sources of causal heterogeneity of aging-related change can make productive use of alternative time specifications that emphasize congruency between within-person change processes and aggregate population change.