The effect of this enrichment is observable in the earlier median AAO of AD cases that are homozygous, heterozygous or negative for the APOE-ε4 allele (respectively 64, 70 and 75 years) compared to a population sample (70, 74.5, 82 years, as estimated from Reiman et al. [57]). This evidence concerns the gene APOE and Alzheimer disease.