APOE and Alzheimer disease: In linear regression models adjusted for age, sex, and years of education with memory scores as dependent variable and an interaction between Ng levels and APOE ε4 carrier status as an independent variable, we found that the association between Ng levels and memory scores did not statistically differ between AD APOE ε4 carriers and APOE ε4 non-carriers (β=-0.32, p = .358) (Fig. 4).