(610) Environmental exposures and disparities in infant mortality: a positive deviance analysis

Objective: To identify factors that buffer adverse associations between county-level vulnerability and infant mortality disparities.

Study Design: We conducted a positive deviance analysis of United States vital statistics data from 2017 to 2019, evaluating variation in county Black-white infant mortality difference (BW-IMD) per 1000 live births with Environmental Justice Index (EJI), a CDC index of social vulnerability, health vulnerability, and environmental burden. Using linear regression, we modeled the association between county BW-IMD and EJI. Among counties with above median EJI scores, we identified positive deviant counties (PDC) as those with observed BW-IMD >1.96 standard deviations below predicted. We used Wilcoxon tests to compare median EJI component measures between PDC and typical counties (TC), with p values < 0.001 considered to be statistically significant.

Results: BW-IMD data was available for 2922 US counties, with a median BW-IMD of 6 per 1000 (range 2.6 to 11.6).  Higher EJI scores were associated with higher BW-IMD (p< .0001). Among 1794 counties with EJI >50% (Figure), 24 (1.3%) were PDC. Compared with TC, PDC had higher proportions of residents who were not non-Hispanic white, spoke English “less than well,” rented their homes, and had household income < $75,000. PDC had fewer residents without internet access, who were 65 or older, had a disability, or lived in a mobile home. Chronic conditions were also less prevalent, including cancer, high blood pressure, and poor mental health. Overall environmental burden percentile was higher in PDC, with higher percentile scores for air pollution and proximity to transportation infrastructure, but better scores for built environment, including walkability and proximity to green space.

Conclusion:

Positive deviance analysis identified protective factors for BW-IMD in high EJI counties, including non-White and non-English speaking communities, internet access, population health, walkability, and green space. Policies to strengthen community, wellbeing, and infrastructure have the potential to impact perinatal health disparities.