In addition to effect sizes that are similar to other major risk factors for AD, the meta-analyses indicated a high degree of consistency across studies; all strongly supported the association of neuroticism and conscientiousness with risk of AD. This lack of heterogeneity is a notable finding, given the differences in demographic characteristics of the samples, study design, and length of the follow-up. Furthermore, the greater statistical power afforded by combining multiple samples suggested a significant association for the openness factor, which was significant in only one of the primary studies,16 and for agreeableness. There was no significant association for extraversion.
