White matter hyperintensities mediate a greater proportion of age‐related lower cognitive scores in non‐Hispanic White participants compared to non‐Hispanic Black and Hispanic participants: HABS‐HD

INTRODUCTION White matter hyperintensities (WMH) are robust markers of vascular brain injury and predictors of poorer cognition, but their contributions may differ across racial and ethnic groups. METHODS We analyzed 3585 participants from the Health and Aging Brain Study–Health Disparities cohort (1264 non‐Hispanic White [NHW], 1003 non‐Hispanic Black [NHB], 1318 Hispanic). Baseline demographics, vascular risk factors, apolipoprotein E ε4, magnetic resonance imaging–derived WMH, and domain‐specific cognitive z scores were assessed. We used moderated mediation models to evaluate whether WMH mediated the age–cognition relationship by race/ethnicity. RESULTS Greater WMH volume was associated with poorer memory, executive function, processing speed, and language (all p < 0.01). Mediation by WMH varied across groups: WMH explained ≈ 30% of the age–cognition association in NHWs, 20% to 28% in NHBs, and 12% to 19% in Hispanics. DISCUSSION WMHs consistently mediated age‐related lower cognition, but group differences highlight the contribution of cardiometabolic, neuropathological, and social determinants beyond WMHs in NHB and Hispanic populations.