How were changes in neighborhood racial segregation linked to blood pressure?

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Earlier cross-sectional evidence linked racial residential segregation to hypertension prevalence among non-Hispanic Black people, but how changes in exposure related to blood pressure changes remained unclear. The study examined associations between changes in neighborhood-level racial residential segregation and changes in systolic and diastolic blood pressure over 25 years.

This observational study used longitudinal data from 2,280 Black participants in the Coronary Artery Risk Development in Young Adults (CARDIA) study, a prospective investigation of adults aged 18 to 30. Baseline examinations took place at field centers in four US locations from March 25, 1985, to June 7, 1986, followed by re-examinations over the next 25 years. The outcomes were within-person changes in systolic and diastolic blood pressure across six examinations over 25 years.

Researchers assessed racial residential segregation using the Getis-Ord Gi* statistic, which measures the standard-deviation difference between a neighborhood's racial composition, expressed as the percentage of Black residents, and that of the surrounding area. Segregation was classified as high (Gi* >1.96), medium (Gi* 0–1.96), or low (Gi* <0). Fixed-effects linear regression modeled the association between within-person changes in segregation exposure and blood pressure while tightly controlling for time-invariant confounders. Data were analyzed from August 4, 2016, to February 9, 2017.

At baseline, 974 of the 2,280 participants (42.7%) were men and 1,306 (57.3%) were women. Of the 2,280, 1,861 (81.6%) lived in high-segregation neighborhoods, 278 (12.2%) in medium-segregation neighborhoods, and 141 (6.2%) in low-segregation neighborhoods.

For each 1-standard-deviation increase in segregation score, systolic blood pressure increased by a mean of 0.16 mm Hg (95% CI, 0.06–0.26), after adjustment for interactions of time with age, sex, and field center. Among the 1,861 participants (81.6%) living in high-segregation neighborhoods at baseline, reduced segregation exposure was associated with reduced systolic blood pressure. Compared with high segregation, the mean systolic blood pressure difference was −1.33 mm Hg (95% CI, −2.26 to −0.40) for medium segregation and −1.19 mm Hg (95% CI, −2.08 to −0.31) for low segregation, after adjustment for time and its interactions with baseline age, sex, and field center. Changes in segregation were not associated with changes in diastolic blood pressure.

The researchers concluded that decreases in exposure to racial residential segregation were associated with reductions in systolic blood pressure. They said the study adds to a small but growing body of evidence that policies reducing segregation may have meaningful health benefits.