What a New MRI Study Reveals About Brain Aging and Racial Disparities

Emerging research, based on established magnetic resonance imaging (MRI) markers of cognitive health, suggests the possibility of accelerated brain aging in middle-age Black adults.

Drawing data from two racially and ethnically diverse cohort studies with mean ages of 55 and 75, researchers reviewed brain MRI scans to assess cortical thickness and white matter hyperintensity (WMH) in midlife and late life Black, Latinx and White study participants.¹ The study authors noted that cortical thickness is a standard biomarker in neurodegeneration cascade models for Alzheimer disease, and WMH, a marker of small vessel cerebrovascular disease, may be associated with stroke risk, cognitive decline, and Alzheimer disease.

In their recently published study of 1,467 participants, researchers noted a stronger age association with WMH for late-life Latinx participants and a marginally higher increase in WMH volume for late-life White participants. However, a strong association of age with WMH in Black participants was similar between midlife and late life. The study authors noted a similar pattern when assessing age association with cortical thickness, which was greater in late life for White and Latinx individuals but remained relatively unchanged between midlife and late life in Black individuals.¹

“Among Latinx and White participants, there was an inflection in age slopes between midlife to late life while there was no difference or inflection in age slopes between midlife and late life Black participants, suggesting accelerated brain aging in middle-age Black individuals,” wrote Adam M. Brickman, Ph.D., a professor of neuropsychology in the Department of Neurology at Columbia University, and colleagues.

Citing a previously established “weathering hypothesis,” the study authors suggested that the differences in brain aging may be attributed to a cumulative effect of chronic or recurring stressors related to socioeconomic and environmental adversities in “historically excluded populations.”²

“We postulate that race and ethnicity disparities in brain aging are due to lifetime cumulative exposure to structural and social forces that elevate subsequent exposure to risk factors for brain pathology,” noted Brickman and colleagues.

The study authors also noted self-reporting of the study participants on health conditions related to cardiovascular disease. While stroke and heart disease history were similar across groups in both of the original cohort studies, self-reported diabetes and hypertension were more prevalent in Black participants in the younger cohort study while Latinx participants had a higher rate of diabetes in the older cohort study. The researchers added that a history of hypertension was more common among Black and Latinx individuals than White individuals in the older patient cohort.

In regard to study limitations, the authors pointed to the cross-sectional study design. They suggested that a longitudinal study design would help reduce potential bias and provide more clarity on causality. Brickman and colleagues also acknowledged a low percentage of White individuals (6.4 percent) in the younger original cohort study may have inhibited statistical power of the study.¹

References

1. Turney IC, Lao PJ, Renteria MA, et al. Brain aging among racially and ethnically diverse middle-aged and older adults. JAMA Neurol. 2022 Nov 14. doi: 10.1001/jamaneurol.2022.3919. Online ahead of print.

2. Geronimus AT. The weathering hypothesis and the health of African-American women and infants: evidence and speculations. Ethn Dis. 1992;2(3):207-21.