Ambient Air Pollution Is Associated With Increased Risk of Hospital Cardiac Readmissions of Myocardial Infarction Survivors in Five European Cities

BACKGROUND: Ambient air pollution has been associated with increases in acute morbidity and mortality. The objective of this study was to evaluate the short-term effects of urban air pollution on cardiac hospital readmissions in survivors of myocardial infarction, a potentially susceptible subpopulation. METHODS AND RESULTS: In this European multicenter cohort study, 22,006 survivors of a first myocardial infarction were recruited in Augsburg, Germany; Barcelona, Spain; Helsinki, Finland; Rome, Italy; and Stockholm, Sweden, from 1992 to 2000. Hospital readmissions were recorded in 1992 to 2001. Ambient nitrogen dioxide, carbon monoxide, ozone, and mass of particles <10 microm (PM10) were measured. Particle number concentrations were estimated as a proxy for ultrafine particles. Short-term effects of air pollution on hospital readmissions for myocardial infarction, angina pectoris, and cardiac causes (myocardial infarction, angina pectoris, dysrhythmia, or heart failure) were studied in city-specific Poisson regression analyses with subsequent pooling. During follow-up, 6655 cardiac readmissions were observed. Cardiac readmissions increased in association with same-day concentrations of PM10 (rate ratio RR 1.021, 95% CI 1.004 to 1.039) per 10 microg/m3) and estimated particle number concentrations (RR 1.026 95% CI 1.005 to 1.048 per 10,000 particles/cm3). Effects of similar strength were observed for carbon monoxide (RR 1.014 95% CI 1.001 to 1.026 per 200 microg/m3 0.172 ppm), nitrogen dioxide (RR 1.032 95% CI 1.013 to 1.051 per 8 microg/m3 4.16 ppb), and ozone (RR 1.026 95% CI 1.001 to 1.051 per 15 microg/m3 7.5 ppb). Pooled effect estimates for angina pectoris and myocardial infarction readmissions were comparable. CONCLUSIONS: The results suggest that ambient air pollution is associated with increased risk of hospital cardiac readmissions of myocardial infarction survivors in 5 European cities.