Data from 1,548 African-American participants in the CARDIA study (NCT00005130) show that living in areas with higher levels of segregation between blacks and whites correlated with lower performance on cognitive tests at midlife (age 50±4). The data was reported in JAMA Neurology.
Those with the highest or mid-level of segregation had worse Digit Symbol Substitution Test (DSST) z scores (high segregation, β = −0.37 [95% CI, −0.61 to −0.13]; for medium segregation, β=−0.25 [95% CI, −0.51-0.00]) relative to those with low levels of segregation. Cognitive testing was done at year 25 of the study and included the Stroop color test (reverse coded), Rey Auditory Verbal Learning Test, and the DSST, which is a subtest of the Wechsler Adult Intelligence Scale (WAIS).
Mean cumulative exposure to segregation was calculated across 6 follow-up visits from baseline to year 25 of the study, then categorized into high, medium, and low segregation. Segregation was measured using the Getis-Ord Gi* statistic.
“Our findings support the notion that long-term exposure to residential segregation during 25 years of young adulthood is associated with worse processing speed as early as midlife,” said Adina Zeki Al Hazzouri, PhD, assistant professor of epidemiology, Mailman School of Public Health, Columbia University. “This outcome may explain black-white disparities in dementia risk at older age. Studies examining racial residential segregation in the context of cognitive function are limited, and thus our findings contribute to an important yet sparse literature. 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.”