Association of Brain Volumes and White Matter Injury With Race, Ethnicity, and Cardiovascular Risk Factors: The Multi-Ethnic Study of Atherosclerosis

Abstract

Background Cardiovascular risk factors are associated with cognitive decline and dementia. Magnetic resonance imaging provides sensitive measurement of brain morphology and vascular brain injury. However, associations of risk factors with brain magnetic resonance imaging findings have largely been studied in White participants. We investigated associations of race, ethnicity, and cardiovascular risk factors with brain morphology and white matter (WM) injury in a diverse population. Methods and Results In the Multi-Ethnic Study of Atherosclerosis, measures were made in 2018 to 2019 of total brain volume, gray matter and WM volume, and WM injury, including WM hyperintensity volume and WM fractional anisotropy. We assessed cross-sectional associations of race and ethnicity and of cardiovascular risk factors with magnetic resonance imaging measures. Magnetic resonance imaging data were complete in 1036 participants; 25% Black, 15% Chinese-American, 19% Hispanic, and 41% White. Mean (SD) age was 72 (8) years and 53% were women. Although WM injury was greater in Black than in White participants in a minimally adjusted model, additional adjustment for cardiovascular risk factors and socioeconomic status each attenuated this association, rendering it nonsignificant. Overall, greater average WM hyperintensity volume was associated with older age and current smoking (69% greater vs never smoking); lower fractional anisotropy was additionally associated with higher diastolic blood pressure, use of antihypertensive medication, and diabetes. Conclusions We found no statistically significant difference in measures of WM injury by race and ethnicity after adjustment for cardiovascular risk factors and socioeconomic status. In all racial and ethnic groups, older age, current smoking, hypertension, and diabetes were strongly associated with WM injury.

Keywords: brain magnetic resonance imaging; cardiovascular risk factors; race and ethnicity; white matter injury.

Figure 1. Magnetic resonance imaging‐derived total brain volume (A) and white matter hyperintensity volume (B) by age within racial or ethnic groups, with linear fit (line) and 95% CI (shaded)

Figure 2. Associations between cardiovascular risk factors and brain MRI measures in 1036 MESA participants based on multivariable* models

*Regression models include sex, race and ethnicity, MESA site, total intracranial volume (for magnetic resonance imaging volumes), and all cardiovascular risk factors in the leftmost column. †White matter hyperintensity volume presented as percent difference per indicated unit of the exposure based on the geometric mean ratio‡ Fractional anisotropy presented as Z scores; low white matter fractional anisotropy is interpreted as indicating poor white matter integrity. For fractional anisotropy, the x axis has been reversed to aid interpretation. BMI indicates body mass index; BP, blood pressure; eGFR, estimated glomerular filtration rate; HDL, high‐density lipoprotein; LDL, low‐density lipoprotein; MESA, Multi‐Ethnic Study of Atherosclerosis; and MRI, magnetic resonance imaging.