The frequency of ApoE ε3 in sporadic AD was lower than that in healthy controls, and the differences were statistically significant (OR 0.642, 95% CI [0.564–0.731], P < 0.001): ε2/ε3 (OR 0.668, 95% CI [0.555–0.804], P < 0.001) and ε3/ε3 (OR 0.595, 95% CI [0.510–0.694], P < 0.001). Here, APOE is linked to Alzheimer disease.