APOE and Alzheimer disease: Furthermore, in the largest AD case-control series (n = 5,161) analyzed for the interaction between PSEN1 p.E318G and APOE ε4 allele to date, we found that the presence of p.E318G and APOE ε4 doubles the risk for AD (OR = 10.3, 95% CI = 4.1–25.5) compared to the risk with the presence of APOE ε4 alone (OR = 4.1, 95% CI = 3.5–4.8).