Heterogeneity in the association between fine particulate matter and asthma among children

Abstract

TPS 683: Short-term health effects of air pollutants 2, Exhibition Hall, Ground floor, August 28, 2019, 3:00 PM - 4:30 PM Background/Aim: While the depth of published literature on the short-term association between fine particulate matter (PM2.5) and respiratory health is substantial, questions remain regarding the protection of sensitive sub-populations. Previously, we used a two-stage approach to generate United States (U.S.) nationally relevant effect estimates of the associations between PM2.5 and respiratory emergency department (ED) visits. We found an overall significant, positive association between PM2.5 and asthma ED visits among children <19 years but also observed between-county heterogeneity (τ2). Methods: From the previous analysis, we selected the county-specific βs for the association between PM2.5 and asthma ED visits among children. We then used a Bayesian hierarchical regression model to pool the county-specific βs with various county-level covariates measuring geographic region, poverty, minority populations, and health care access. Lastly, we calculated and visualized new rate ratios (RR) with 95% credible intervals (CI) for a 10 µg/m3 increase in PM2.5 and estimates of τ2. Results: Only models including region resulted in an appreciable decrease in τ2. We observed a consistent spatial pattern with RR highest in the Northeast and Midwest, slightly elevated in West, and consistent with the null in the South. Additionally, percent of population uninsured resulted in a slight decrease in τ2. We observed that counties with higher percent uninsured had lower RR than counties with lower percent uninsured. Conclusions: We were able to reduce τ2 by including region, and to some extent, percent uninsured in our model. While region reduced the between-county heterogeneity to nearly zero, it does not offer a specific explanation for the heterogeneity. Other factors that also vary spatially in a similar manner may contribute to the spatial pattern of the risk heterogeneity. Further analysis is needed to understand the reasons for the regional variation in the short-term association between PM2.5 and asthma ED visits among children.