A novel finding from our meta-analysis was that agreeable people have a reduced risk of AD. We interpret this finding with caution, since none of the individual studies show a significant association, and therefore replication in additional samples is particularly warranted. Still, it is worth considering that agreeableness measures interpersonal tendencies, and an inclination to be altruistic and cooperative might facilitate the formation of interpersonal connections and the stability of social networks.42 Extraversion, however, the other major personality dimension that shapes interpersonal tendencies, was not associated with risk of AD. Another possibility is that individuals who score low on Agreeableness tend to be aggressive, competitive, and antagonistic, which increase risk of cardiovascular disease.43, 44 Thus, the greater cardiovascular burden carried by antagonistic individuals may contribute to their risk of AD.
