A Miller School of Medicine-led study found that Black individuals who are exposed to highly segregated neighborhoods in young adulthood exhibit declined cognitive skills in mid-life.

The study titled “Association of Racial Residential Segregation Throughout Young Adulthood and Cognitive Performance in Middle-aged Participants in the CARDIA Study” was published online in the Journal of the American Medical Association (JAMA) Neurology on May 2020 and is one of few that offer information on the association of racial residential segregation and cognitive function.

“Our findings support the notion that long-term exposure to residential segregation during young adulthood is associated with worse processing speed as early as midlife,” said Michelle R. Caunca, Ph.D., trainee in the Medical Scientist Training Program (M.D./Ph.D. Program) at the Miller School of Medicine. “This outcome may explain black-white disparities in dementia risk at an older age.”

Researchers analyzed data from 1,568 black participants in the Coronary Artery Risk Development in Young Adults (CARDIA) study. At baseline, participants had a mean age of 25 and 59.9 percent consisted of women.  

In the CARDIA study, which focuses on the development and determinants of cardiovascular disease, 5,115 black and white participants aged 18 to 30 years were recruited from four different centers. The centers included the University of Alabama at Birmingham, University of Minnesota, Northwestern University, and Kaiser Permanente.

Among the surviving CARDIA cohort, 71.8 percent attended were assessed in the 25th year of the study in 2012, when their cognition was measured, and 81.9 percent of those completed the cognitive assessments.

Residential segregation for the JAMA Neurology study was measured using a high/low clustering statistic known as Getis-Ord G. This statistic describes the percent of Blacks in a participant’s census tract compared to the surrounding larger metropolitan area.

The mean cumulative exposure to segregation was calculated across six follow-up visits from baseline to year 25 of the CARDIA study, then categorized into high, medium, and low segregation. Cognitive function was assessed in year 25 of the study using three different tests representing distinct domains of cognition.

Results showed that in the cohort study, exposure to residential segregation throughout young adulthood was associated with worse processing speed among black participants as early as midlife.

This work is in collaboration with several other researchers, including Adina Zeki Al Hazzouri, Ph.D., an assistant professor of epidemiology in the Mailman School of Public Health at Columbia University, who was formerly at the Miller School of Medicine’s Department of Public Health Sciences.

Earlier studies by Dr. Zeki Al Hazzouri and colleagues supported growing evidence that maintaining cognitive function is a lifelong process and that some of the most important risk factors may begin earlier in life.

“Studies examining racial residential segregation in the context of cognitive function are limited and thus our findings contribute to important yet sparse literature,” said Dr. Zeki Al Hazzouri. “More importantly, our research indicates that policies that address segregation and the uneven distribution of resources may be beneficial for reducing inequities in cognitive performance.”

Written by Amanda Torres

Published on June 9, 2020