Genetically, APOE4 (~13% frequency in the general population) serves as the single greatest risk factor for late-onset familial and sporadic AD (Farrer et al., 1997; Reiman et al., 2020; Tanzi, 2012; Zlokovic, 2013), which together account for 65%–70% of AD cases (Farrer et al., 1997). Here, APOE is linked to Alzheimer disease.