Grantee Research Project Results

PM2.5 and Mortality in 207 US Cities:Modification by Temperature and City Characteristics

Citation:

Kioumourtzoglou, M.-A., Schwartz, J., James, P., Dominici, F., and Zanobetti, A. (2016). PM2.5 and Mortality in 207 US Cities:Modification by Temperature and City Characteristics. Epidemiology 27, 221-227.

Abstract:

Background The reported estimated effects between long-term PM2.5 exposures and mortality vary spatially. We assessed whether community-level variables, including socioeconomic status (SES) indicators and temperature, modify this association. Methods We used data from >35 million Medicare enrollees from 207 U.S. cities (2000–2010). For each city, we calculated annual PM2.5 averages, measured at ambient central monitoring sites. We used a variation of a causal modeling approach and fitted city-specific Cox models, which we then pooled using a random effects meta-regression. In this second stage, we assessed whether temperature and city-level variables, including smoking and obesity rates, poverty, education and greenness, modify the long-term PM2.5–mortality association. Results We found an association between long-term PM2.5 and survival (HR = 1.2; 95%CI: 1.1–1.3 per 10 µg/m3 increase in the annual PM2.5 average concentrations). We observed elevated estimates in the Southeastern, South and Northwestern U.S. (HR = 1.9; 95%CI: 1.7–2.2, 1.4; 95%CI: 1.2–1.7 and 1.4; 95%CI: 1.1–1.9 respectively). We observed a higher association between long-term PM2.5 exposure and mortality in warmer cities. Furthermore, we observed increasing estimates with increasing obesity rates, %residents and families in poverty, %black residents and %population without a high school degree, and lower effects with increasing median household income and %white residents. Conclusions To our knowledge, this is the first study to assess modification by temperature and community-level characteristics on the long-term PM2.5–survival association. Our findings suggest that living in cities with high temperatures and low SES is associated with higher effect estimates.