APOE and Alzheimer disease: Within two longitudinal cohorts of middle-aged and older adults (40-89 years old), we analyzed serial ASL perfusion measures in AD-vulnerable regions to determine 1) the association between cerebral perfusion trajectories and age; 2) the modifying effect of APOE ε4 status and sex on the relationship between cerebral perfusion trajectories and age; 3) the role of cardiometabolic measurements in the foregoing associations.