The frequencies of ApoE ε3 and ε2 in AD were lower than those in healthy controls, and the differences were statistically significant (ε3: OR 0.539, 95% CI [0.504–0.576], P < 0.001; ε2: OR 0.771, 95% CI [0.705–0.843], P < 0.001). Here, APOE is linked to Alzheimer disease.