Modification by Multiple Social Stressors in Air Pollution-CVD Associations

Abstract

BACKGROUND AND AIM: A growing literature explores variation in pollution susceptibility by chronic psychosocial stressors (e.g., poverty, violence). It is less explored, however, whether the confluence of multiple stressors – clustered in minority and lower-income urban communities via segregation processes – may compound susceptibility, or confound observed modification by any one stressor. METHODS: We examined modification by multiple community stressors on relationships between spatio-temporal pollutant exposures and risk of cardiovascular (CVD) event in New York City, using conditional logistic regression in case-crossover, with time-stratified referent sampling. We used exhaustive data on all inpatient (admitted) CVD events presenting at NYC emergency departments from 2005-2011 (n = 837,523), fine-scale spatial maps for PM2.5, NO2, SO2, and O3 from NYC Community Air Survey, and daily EPA pollution and NOAA weather data. A range of stressor indicators were drawn from Census and administrative databases, examined against focus group and survey data to confirm relevance to residents’ stress experience. Due to concern about stressors clustering by race and ethnicity (i.e., non-random assignment into tracts), we adjusted year-round models (NO2 and PM2.5) for modification by tract composition. RESULTS:Testing stressors individually, we found significant associations between NO2 and CVD risk only in communities in the highest quintile of violent crime, felony assault, poverty, or socioeconomic deprivation (SDI); associations in all other quintiles crossed the null, as did associations for all other pollutants. In models including separate interaction terms for violent crime and SDI, NO2 was associated with significant increases in CVD risk in all quintiles. Associations for NO2 modestly increased across quintiles of increasing violence, but not SDI. CONCLUSIONS:Observed patterns of modification differed substantially when including multiple stressors modifiers, increasing observed NO2-CVD associations overall. These results suggest a need to capture community stress experience more holistically, to reduce confounding across stressors which may dampen observed pollutant-health associations and modification. KEYWORDS: air pollution, mixtures, psychosocial stressors, segregation, case-crossover, cardiovascular disease (CVD)