Short-term fluctuations in elderly people's sensorimotor functioning predict text and spatial memory performance: The MacArthur successful aging studies

Background: While age-related increases of between-person variability in a variety of cognitive measures are commonly reported in cross-sectional stud ies, the nature of short-term intraindividual fluctuation in elderly people 's performance is relatively unexplored. Objective: The goal of the present study is to examine short-term fluctuations in elderly people's sensorimot or functioning and their relations to individual differences in verbal and spatial memory. Methods: Fluctuations in old adults' (mean = 75.71 years, S D = 6.93 years) sensorimotor performance were investigated by biweekly meas urements spanning approximately 7 months. Sensorimotor performance was meas ured by three walking tasks, including the du ration a nd the nu m ber of s teps ta ken to wa Ik a 360-degree circle and to walk in feet both at normal and fast pace. Performances of verbal and spatial memory were assessed by weekly measurements of digit memory span, memory for short text and spatial recognition. Results: The magnitude of intraindividual fluctuation in most sensorimotor and memory tasks examined was at least half as great as the l evel of individual differences across persons. In addition, intraindividual fluctuation in sensorimotor performance is a relatively stable individual attribute, which correlates positively with age and negatively with the lev els of sensorimotor, text and spatial memory performance. Although a substa ntial amount of individual differences in intraindividual fluctuation was s hared with mean performance level, variance component and hierarchical regr ession analyses showed that intraindividual fluctuation in walking steps ad ded significant independent contribution over and above that given by level of performance in predicting text and spatial memory. Conclusion: Taking t hese results together, we suggest that intraindividual fluctuations in elde rly people's performance should not be ignored or simply treated as measure ment error; rather, they are potentially important empirical variables for understanding sensory and cognitive aging and the nature of intraindividual response variations in general. Copyright (C) 2001 S. Karger AG, Basel.