Résumé
Neuroticism is a major risk factor for neurodegenerative disorders, such as Alzheimer's disease and related dementias. This study investigates whether neuroticism is associated with white matter hyperintensities and whether this measure of brain integrity is a mediator between neuroticism and cognitive function. Middle-aged and older adults from the UK Biobank (N = 40,602; aged 45–82 years, M = 63.97, SD = 7.66) provided information on demographic and health covariates, completed measures of neuroticism and cognition, and underwent magnetic resonance imaging from which the volume of white matter hyperintensities was derived. Regression analyses that included age and sex as covariates found that participants who scored higher on neuroticism had more white matter hyperintensities (β = 0.024, 95% CI 0.015 to 0.032; p < .001), an association that was consistent across peri-ventricular and deep brain regions. The association was reduced by about 40% when accounting for vascular risk factors (smoking, obesity, diabetes, high blood pressure, heart attack, angina, and stroke). The association was not moderated by age, sex, college education, deprivation index, or APOE e4 genotype, and remained unchanged in sensitivity analyses that excluded individuals with dementia or those younger than 65. The mediation analysis revealed that white matter hyperintensities partly mediated the association between neuroticism and cognitive function. These findings identify white matter integrity as a potential neurobiological pathway that accounts for a small proportion of the association between neuroticism and cognitive health.