These associations might be explained, in part, by the links between personality and health-related behaviors, lifestyle factors, and clinical conditions. Low conscientiousness and high neuroticism are associated with cigarette smoking,7 physical inactivity,28 and obesity,9 which in turn are risk factors for dementia.2 Neuroticism is a strong vulnerability factor for major depression,6 which is also associated with AD.2, 29, 30 Personality traits are related to coping skills, and chronic stress over the lifespan might contribute to the inability to cope with the neurodegenerative process underlying AD. Direct physiological pathways are another plausible mechanism, given that low conscientiousness and high neuroticism are related to inflammatory markers such as IL6, CRP, and WBC counts.8, 31 Neuroticism is also related to level of brain derived neurotrophic factors (BDNF),32 which is thought to play an important role in neurodegenerative disorders. Another possibility is shared genetic liability. For example, in a large founder population33 but not in other samples,34 variants in the DYRK1A gene were associated with conscientiousness. The gene DYRK1A maps in the Down syndrome critical region on chromosome 21, its activity is up-regulated by
