The haplotypes of the human apolipoprotein E gene (APOE) exert strong, divergent effects on aging, with the ε4 allele being the greatest genetic predictor of late onset AD incidence [6–8], whereas the ε2 allele is protective against AD risk [9, 10], and is a predictor itself of longevity, independent of AD [11, 12]. The gene discussed is APOE; the disease is Alzheimer disease.