In general, physical activity may guard against cognitive decline, decrease the chance of developing AD, and slow dementia onset.14,15,16 Increased physical activity is also associated with higher hippocampal and total brain volumes17 and weakened neuroimaging biomarkers associated with age.18 Increased physical activity mitigates cognitive decline owing to β-amyloid burden and gray matter volume deficit, measured through magnetic resonance imaging.13 However, it is not known whether physical activity mitigates cognitive decline in people with higher tau concentrations. This evidence concerns the gene MAPT and Alzheimer disease.