Individual differences and 11-year longitudinal changes in older adults’ prospective memory: A comparison with episodic memory, working memory, processing speed, and verbal knowledge

Abstract

Prospective Memory (PM; remembering intended actions after a delay) represents a core ability contributing to everyday functioning and independence in older adulthood. Despite its high relevance for successful aging, the understanding of individual differences in level and within-person change of PM in older adulthood is currently limited. Using longitudinal data from initially 364 older adults (between 65 and 80 years of age at wave 1; 46 % female) across four waves of the Zurich Longitudinal Study on Cognitive Aging, we examined (a) individual differences and (b) longitudinal change in PM performance over up to 11 years, (c) compared differences and change in PM with other central variables of cognitive functioning (episodic memory, working memory, processing speed, verbal knowledge), and (d) explored the effect of key sociodemographic variables (education, income, sex, health) on PM. Linear mixed modeling with Bayesian estimation indicated substantial individual differences in cognitive performance, with by far the highest variability in PM. Longitudinal age-related decreases were largest for working memory and cognitive speed, relatively small for PM, while verbal knowledge remained stable. Individual differences in age-related changes in performance were only observed for processing speed and verbal knowledge, but not for PM. This pattern remained after considering various cognitive and sociodemographic covariates. This is the first longitudinal study of PM that allows an in-depth examination of individual differences in both level and change in PM with comparison to other key cognitive abilities across older adulthood. The findings highlight the complex interplay between cognitive abilities, individual differences, and development across older adulthood, with implications for understanding cognitive aging.