Temporal Patterns of Change in Physical and Cognitive Performance

Background This study examined the relation between declines in physical and cognitive performance in older people. Method A population-based cohort of 7483 adults (average age 72 years) were interviewed. Physical performance was assessed with three standardized tests and a combination of four cognitive tests was used to assess cognitive function. Rate of change in physical and cognitive performance was determined for each interval between interviews. In mixed effects linear regression models adjusted for age, sex, race and study time, and change in each factor was used to predict change in the other factor. We examined time associations by using change in the predictor measured one, two or three intervals before the outcome change. Results Decline in cognitive function was most strongly predicted by physical decline in the same 3-year interval. The decline in cognitive function was weaker in the one-time interval after the decline in physical function and was not significant in later intervals. When a decline in cognitive function was used to predict a decline in physical function, the results were similar. The strongest association occurred in the same time interval so that declines in cognitive and physical performance tend to occur together. Conclusion Decline in cognition and physical function seem to occur together in a short timeframe. It is important to investigate the reasons for these changes that are short-term to guide the development of interventions.