Physical Activity, Alzheimer's Disease and Cognition Relative to APOE Genotype

In this study, the investigators follow up on their past research exploring the effects of physical activity on cognitive performance and underlying mechanisms. In particular, the investigators are interested in the potentially different effects that might be realized as a function of a person's genetic risk for Alzheimer's disease. In this study, the investigators extend past work by proposing a randomized clinical trial to: (a) test the causal link between physical activity and cognitive performance in middle-aged adults (40-65 years) with a family history, and (b) determine if the effect is moderated by apolipoprotein epsilon-4 (APOE4) carrier status. The investigators will collect neuroimaging measures of cerebral structure, white matter integrity, and resting state connectivity; assess putative biological markers; and (using moderated mediation analyses) increase understanding of underlying mechanisms and of the extent to which effects are moderated by APOE4 carrier status. To test hypotheses, the investigators will randomly assign 240 cognitively normal, middle-aged adults to a 1-year virtual physical activity program or a usual care control. Those in the intervention will participate in a year-long physical activity program including aerobic exercise performed on your own and resistance exercises led in virtual exercise sessions with an instructor 1 hour/day for 3 days/week for 1 year. Those in the usual care control condition will be asked to maintain their normal lifestyle for one year and then will be given a short-term fitness center membership (contingent upon completion of testing sessions). The investigators will assess cognitive performance at pre-, mid-, and post-test, and obtain MRI scans and blood samples at pre-, mid- and post-test. The investigators will examine the effects of physical activity on cognitive performance and on neurological and biological mechanisms and will explore the moderating role of APOE4.