Abstract P120: Racial Differences in Midlife Brain Health and the Role of Cardiometabolic Risk

Abstract

Introduction: Blacks are at a higher risk for adverse brain-related outcomes, including stroke and dementia. Due to associations of vascular risk factors with brain health, differences in brain health may result from a greater burden of vascular risk factors in blacks, especially in midlife. However, the role of vascular risk factors in midlife racial disparities in brain health have been underexplored. We thus examined racial differences in midlife brain health and tested whether vascular and metabolic risk factors partly explain cross-sectional racial differences. Hypothesis: A composite cardiometabolic risk (CMR) score statistically mediates cross-sectional relationships between race and brain health measures. Methods: 747 adults (20.6% black) aged 30–54, underwent MRI to assess cerebral blood flow (CBF) and morphology. Components of composite CMR were: body mass index, waist circumference, high-density lipoproteins, triglycerides, glucose, insulin, SBP, and DBP. Mediation was tested using the PROCESS v2.14 macro. All models were adjusted for age, sex, income, education, and intracranial volume. Results: Blacks exhibited lower gray matter volume, smaller hippocampi, less cortical surface area, and a thinner cerebral cortex than whites (all p’s<0.05). We observed no significant differences in CBF by race. CMR partially mediated the association of race with gray matter volume (6.94% mediation) and cortical surface area (9.33% mediation). Independent of CMR, there was a direct effect of race on hippocampal volume, cortical surface area, and cortical thickness. The effect was equivalent to: 6.9, 9.59, 13.06, and 9.98 years of aging, respectively. Conclusions: Race differences in some indicators of brain health are evident in midlife. Cardiovascular and metabolic risk factors may partly explain some of these differences. These results have implications for understanding vascular contributions to disparities in brain health prior to the onset of stroke and other clinical outcomes.