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

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.

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 (BF_inclusion) was 3 or higher.

Long-term memory performance was associated with current grip strength with moderate evidence (BF_inclusion = 3.52). Additionally, there was moderate evidence for a relationship between hippocampal decline over time and both cognitive processing speed (BF_inclusion = 4.87), and executive functions (BF_inclusion = 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.

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.