When stratified by APOE ε4 carrier status, the association between the rs242557 SNP and AD risk was observed to be stronger in the individuals with APOE ε4-positive genotype (with no heterogeneity, I2 = 0, OR = 1.24, 95% CI = 1.08, 1.43, P = 0.003) than without stratification (OR = 1.03, 95% CI = 1.00, 1.06, P = 0.078) under the allelic model. Here, APOE is linked to Alzheimer disease.