Personality traits and blood-based biomarkers of neurodegeneration and astrogliosis.

The personality traits neuroticism and conscientiousness are associated with the risk of clinical dementia and other neurodegenerative diseases. Less is known about the association between personality and biological markers of the underlying brain pathology. This study examined the relationship between Five-Factor Model personality traits and blood-based biomarkers of neuroaxonal injury (Neurofilament Light, NfL) and astrogliosis (Glial Fibrillary Acidic Protein, GFAP). Participants (N = 4076; mean age 67; 59.9% female; 19.3% cognitively impaired) were from the Health and Retirement Study. Personality traits were assessed using the Midlife Development Inventory. Simoa immunoassays were used to measure NfL and GFAP from plasma extracted from venous blood. In regression analyses with age and sex as covariates, higher neuroticism was associated with higher NfL; extraversion, openness, agreeableness, and conscientiousness were associated with lower NfL. In fully adjusted models that accounted for demographic, behavioral, and health-related factors, conscientiousness remained a predictor of lower NfL (β=-0.039, p < .001). Personality traits were generally unrelated to GFAP, although conscientiousness had a marginal inverse association in the basic model but not in the fully adjusted model (β=-0.023, p = .061). These associations were not moderated by cognitive status, timing of the personality assessment (concurrent or at ≥2 years before biomarkers), age, sex, or APOE ε4 status. In conclusion, conscientiousness and other personality traits are associated with neuroaxonal integrity in older adults. Future longitudinal research is required to determine whether personality is a risk factor or whether these associations reflect the biological impact of neurodegeneration on personality.