Racial discrimination accelerates age-related increases in serum neurofilament light chain among African American women: examination of change from midlife to older adulthood

OBJECTIVES: Neurofilament light (NfL) is a biomarker of neurodegeneration that increases with age, yet the trajectory of this increase and its susceptibility to psychosocial stressors remain unclear. Racial discrimination is a psychosocial stressor disproportionately experienced by African Americans (AAs) that may accelerate neurodegenerative processes. METHODS: This study analyzed 15 years of longitudinal data from AA women to examine the relationship between racial discrimination reported at midlife and age-related changes in serum NfL (sNfL) levels. Because it is typically a chronic stressor, we hypothesized that racial discrimination at midlife would forecast accelerated age-related increases in sNfL levels across 15 years. RESULTS: Multilevel growth models were used to estimate linear and nonlinear trajectories of sNfL as a function of age. Results showed a significant acceleration in sNfL levels after age 40, resulting in a nonlinear growth function. Moreover, racial discrimination moderated the relationship between age and sNfL, with higher levels of discrimination reported in midlife associated with a more pronounced acceleration in sNfL, particularly in late midlife (after age 55). DISCUSSION: These findings suggest that racial discrimination may contribute to the acceleration of age-related changes in sNfL, a biomarker of neurodegeneration. They further indicate that magnitude of increases in sNfL with age may be sensitive to external stressors and so highlight the potential for targeted interventions to mitigate stress-related risks for accelerated sNfL among AA women.