APOE and Alzheimer disease: As expected, the APOE genotype and allele frequency distributions of the AD samples differed significantly from those of the control group (χ2 = 87.146, df = 5, P = 2.671 × 10−17 and χ2 = 92.374, df = 2, P = 8.735 × 10−21, respectively; Table 2).