Longitudinal Effects of Aging on Prospective Memory

Older adults demonstrate worse prospective memory (PM) performance compared to younger individuals, which may interfere with everyday activities such as remembering to take medications on time and turning off the stove after cooking. However, the longitudinal trajectories of time-based and event-based PM in older age are not known. Participants included 329 community-dwelling older adults (50 to 90 years old) who completed a baseline evaluation and up to three follow-up visits, approximately 2.2 years apart. Participants completed the time-based and event-based PM tasks of the Memory for Intentions Test (MIsT), a naturalistic 24-hr PM task, and the Prospective and Retrospective Memory Questionnaire (PRMQ). Participants were also administered the Repeatable Battery for the Assessment of Neuropsychological Status (RBANS) and clinical measures of executive functions. Generalized linear mixed models were used to analyze longitudinal changes in each PM variable, controlling for baseline age. Participants demonstrated significant declines in event-based but not time-based laboratory PM over time. Changes in event-based PM performance were associated with changes on measures of retrospective memory, attention, and semantic fluency, while changes in time-based PM performance were associated with changes in executive functions and semantic fluency. No significant changes were observed in naturalistic PM performance, and PM symptoms were found to decline over time. These results indicate that older adults may be particularly susceptible to age-related declines in more automatic, event-based PM tasks compared to time-based PM tasks.