Personality and Incident Alzheimer's Disease: Theory, Evidence, and Future Directions.

Personality, especially the dimensions of neuroticism and conscientiousness, has prospectively predicted the risk of incident Alzheimer's disease (AD). Such a relationship could be explained by personality and AD risk having a common cause such as a gene; by personality creating a predisposition for AD through health behavior or inflammation; by personality exerting a pathoplastic effect on the cognitive consequences of neuropathology; or by AD and personality change existing on a disease spectrum that begins up to decades before diagnosis. Using the 5-dimensional taxonomy of personality, the present review describes how these models might arise, the evidence for each, and how they might be distinguished from one another empirically. At present, the evidence is sparse but tends to suggest predisposition and/or pathoplastic relationships. Future studies using noninvasive assessment of neuropathology are needed to distinguish these 2 possibilities.