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 mu m ( 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 mu g/m(3)) and estimated particle number concentrations ( RR 1.026 [ 95% CI 1.005 to 1.048] per 10 000 particles/cm(3)). Effects of similar strength were observed for carbon monoxide ( RR 1.014 [ 95% CI 1.001 to 1.026] per 200 mu g/m(3) [ 0.172 ppm]), nitrogen dioxide ( RR 1.032 [ 95% CI 1.013 to 1.051] per 8 mu g/m(3) [ 4.16 ppb]), and ozone ( RR 1.026 [ 95% CI 1.001 to 1.051] per 15 mu g/m(3) [ 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.