Ambient air pollutants and risk of fatal coronary heart disease among kidney transplant recipients

Abstract

Background: There is increasing evidence that specific ambient air pollutants are associated with coronary heart disease (CHD) morbidity and mortality. Because kidney transplant recipients have prevalent traditional and nontraditional risk factors, they may constitute a sensitive subgroup. Study Design: Retrospective cohort. Setting & Participants: This study includes 32,239 nonsmoking adult kidney transplant recipients who underwent transplant in 1997-2003, identified through the US Renal Data System and living in the United States within 50 km of an air pollution monitoring station. Predictor: Long-term ambient pollutant ozone and particulate matter ≤10 μm (PM 10), assessed from monthly concentrations of ozone and PM 10 calculated from ambient monitoring data by the US Environmental Protection Agency Air Quality System and interpolated to zip code centroids according to patients' residence. Outcomes: Outcomes of interest were death from CHD and natural-cause mortality. Results: For the entire transplant cohort, average pollutant levels for ozone and PM 10 were 25.5 ± 4.4 parts per billion (ppb) and 25.3 ± 6.4 μg/m 3, respectively. Correlation between ozone and PM 10 values was low, but statistically significant (P < 0.001). There were deaths from CHD (n = 267) and natural causes (n = 2,076) during the 7-year study period. For each 10-ppb increase in ozone, the risk of fatal CHD increased by 35% (RR, 1.35; 95% CI, 1.04-1.77) in the single-pollutant model and 34% (RR, 1.34; 95% CI, 1.03-1.76) in the 2-pollutant model. No independent association was found between CHD and PM 10. No significant association was identified for PM 10 or ozone level and natural-cause mortality (RR, 1.09; 95% CI, 0.99-1.21). Limitations: Exposure assignment based on only residential location. Conclusions: For kidney transplant recipients, ambient ozone levels potentially are associated with higher risk of fatal CHD. These findings may have implications for regulations governing air pollution and the development of individual CHD risk-reduction strategies. © 2011 National Kidney Foundation, Inc.