Additional analyses supported the robustness of these associations. Because Neuroticism and Conscientiousness are moderately correlated, we tested whether these were independent effects. When we repeated the analyses with all five factors entered in the regression model simultaneously, scoring in the top quartile of neuroticism (HR = 2.53; 95%CI = 1.23–5.23) or the bottom quartile of conscientiousness (HR = 2.63; 95%CI =1.10–6.26) was still associated with increased risk of AD. We further tested whether the combination of high neuroticism and low conscientiousness increased vulnerability to AD beyond the main effects, but we found no significant interaction. The results remained essentially the same when we excluded individuals younger than age 50 at baseline or those who developed AD within 2 years of the baseline personality assessment (p’s < 0.05 for both neuroticism and conscientiousness). In the full sample, we also tested whether the association of the five major factors with incident AD was different for men and women, but we found no significant interactions.
