['We tested the hypothesis that neuroticism moderates the association between APOE (apolipoprotein E) genotype and two major outcomes, cognitive function and Alzheimer disease. We also explored whether other personality dimensions (extraversion, openness to experience, agreeableness, and conscientiousness) moderate the associations of APOE with these outcomes.', 'Primary analyses of existing randomized clinical trial data.', 'Six-hundred two older adults (mean age of 78 years at baseline).', "APOE genotype, the NEO-Five Factor Inventory, the Alzheimer's Disease Assessment Scale-Cognitive: measured every 6 months for 6.5 years) and relevant covariates.", 'Fully adjusted multivariate analyses showed that the association between the presence of APOE [Latin Small Letter Open E]-4 allele(s) and both outcomes was evident among individuals with high levels of neuroticism and extraversion but not among persons with low levels of these traits.'] Do personality factors moderate the associations between apolipoprotein genotype and cognitive function as well as late onset Alzheimer disease?