Variation in Asthma Clinical Trial Results by Environmental and Socioeconomic Exposures

Abstract

PDS 64: Health impact assessment and environmental justice, Johan Friso Foyer, Floor 1, August 26, 2019, 1:30 PM - 3:00 PM Randomized clinical trials (RCTs) are generally considered the gold standard in medical research; by randomizing participants to treatment and control arms, they maximize internal validity and reduce between-group biases. RCTs, however, do not routinely examine variation by environmental and social exposures, which may impact clinical outcomes, treatment response, and generalizability. To assess whether variation in socioeconomic positon (SEP) and environmental exposures modify treatment response, we have developed and applied Geographic Information Systems (GIS)-based methods to three RCTs performed by the NIH AsthmaNet network, which is recruiting and implementing RCTs using the same protocols across 17 U.S. cities. In preliminary analyses, we have found that: (1) compared to race-specific U.S. averages, blacks recruited into AsthmaNet disproportionately live in impoverished census tracts; recruited whites disproportionately live in wealthier tracts. (2) At baseline, traffic density and SEP predicted variation in lung function, in the hypothesized directions. (3) In one trial, we found that near-residence roadway density explained greater variation in asthma symptoms than did corticosteroid use, and that children in higher-poverty areas had significantly shorter times to first corticosteroid use. We are now refining analyses of effect modification by near-residence roadway traffic and noise exposures, neighborhood violent crime, and health care access. Using spatial analysis and GIS to understand the lived context of RCT participants – better accounting for socioeconomic and environmental factors – may improve the interpretability and applicability of RCT results, by more clearly identifying subpopulations for whom a given intervention may be most effective.