Similar findings were observed for the protective effect of APOE ɛ2 (AD: β = − 0.54, SE = 0.1, P = 3.7 × 10–08; CO; β = − 0.26, SE = 0.03, P = 2.1 × 10–16), with cases showing significantly higher effect size than controls (p = 0.007; Additional file 1: Table S16). The gene discussed is APOE; the disease is Alzheimer disease.