Consistent with prior research, we observed that, relative to those with no APOE-ε4 alleles, risk for cognitive impairment increased as APOE-ε4 allele count increased from one allele (IRR = 1.24, 95% CI [1.15–1.34], P<0.001) to two (IRR = 1.57, 95% CI [1.26–1.96], P<0.001) (Model 2.1). This evidence concerns the gene APOE and Cognitive impairment.