BACKGROUND: We examine whether broad factors and specific facets of personality are associated with increased risk of incident Alzheimer's disease (AD) in a long-run longitudinal study and a meta-analysis of published studies. METHODS: Participants (n = 1671) were monitored for up to 22 years from a baseline personality assessment. The meta-analysis pooled results from up to five prospective studies (n = 5054). RESULTS: Individuals with scores in the top quartile of neuroticism (hazard ratio = 3.1; 95% confidence interval = 1.6-6.0) or the lowest quartile of conscientiousness (hazard ratio = 3.3; 95% confidence interval = 1.4-7.4) had a threefold increased risk of incident AD. Among the components of these traits, self-discipline and depression had the strongest associations with incident AD. The meta-analysis confirmed the associations of neuroticism (P = 2 × 10(-9)) and conscientiousness (P = 2 × 10(-6)), along with weaker effects for openness and agreeableness (P < .05). CONCLUSIONS: The current study and meta-analysis indicate that personality traits are associated with increased risk of AD, with effect sizes similar to those of well-established clinical and lifestyle risk factors.