BACKGROUND: Alzheimer's disease (AD) risk-reduction strategies (e.g., increasing physical activity, improving mobility) have garnered increasing attention in the literature. However, the effect of such modifiable factors on the preclinical trajectories of brain and cognitive health may be moderated by non-modifiable biomarkers associated with AD.

OBJECTIVE: In a longitudinal sample of non-demented older adults, we examine the independent predictors everyday physical activity (EPA) and mobility on executive function (EF) performance and change. Next, we test whether these predictions are modified by interactions between age and AD genetic risk.

METHODS: This accelerated longitudinal design included adults (n = 532, M age = 70.4, age range 53-95) from the Victoria Longitudinal Study. We tested the independent effects of EPA and Mobility (i.e., gait, balance), moderation by Apolipoprotein E (i.e., APOEɛ4+, ɛ4-) and age (young-old, middle-old, old-old), and interactions between APOE and age on performance and 9-year change in an EF latent variable.

RESULTS: First, higher levels of both EPA and Mobility were associated with better EF performance and less decline. Second, the interaction between age and APOE showed that low EPA and older age was associated with poorer EF performance and steeper EF decline for APOEɛ4 + carriers, and low mobility was associated with poorer EF performance and steeper EF decline for APOEɛ4 + carriers than the non-risk carriers.

CONCLUSION: In non-demented older adults, age moderated the effects of both EPA and Mobility on EF performance and change. However, this moderation occurs differentially across APOE4 status.