Current levels vs. longitudinal changes: A 7-year study on physical function, brain structure and cognition in older adults

BACKGROUND: Declines in physical function, brain structure, and cognition are common effects of aging in later life. Here we investigate whether changes in physical function and gray matter volumes over a seven-year span predict cognitive performance in older adults. METHODS: We analyzed five assessments of physical function and MRI-derived gray matter volumes in 219 older adults (mean age 73.7, SD = 2.5). We applied Bayesian linear regression models and model averaging to examine their associations with cognitive performance. We deemed associations meaningful if the inclusion Bayes factor (BFinclusion) was 3 or higher. RESULTS: Long-term memory performance was associated with current grip strength with moderate evidence (BFinclusion = 3.52). Additionally, there was moderate evidence for a relationship between hippocampal decline over time and both cognitive processing speed (BFinclusion = 4.87), and executive functions (BFinclusion = 5.34), although these associations became anecdotal when removing extreme values. Remaining physical function measures and brain volumes yielded only anecdotal evidence for or against predicting cognitive function. CONCLUSIONS: These findings provide moderate evidence that indices of current physical function and longitudinal measures of brain structure are predictive of cognitive abilities in older adults. This indicates a need for monitoring brain structure over time to characterize its relationship with cognitive function. Additionally, a global measure of physical function, such as grip strength, may serve as an indicator of a person's long-term memory, even when measured at only a single time point. These tentative findings motivate replication attempts in larger samples.