Short-term effects of air pollution on coronary events. Importance of seasonal variations

Background Air pollution contributes to an enhanced cardiovascular morbidity burden including the trigger of acute coronary syndromes. The aim of this study, is to investigate the effects of a short-term exposure to air pollutants, as assessed by Nitrogen dioxide (NO 2 ), Particulate Matter (PM) 2.5 and 10 concentrations, on coronary event onsets in Strasbourg, France. Materials and method An observational, retrospective, epidemiological study was conducted in Strasbourg between 2012 and 2014. The cases comprised coronary events in inhabitants of Strasbourg as identified by the MONICA Project. The data on daily air pollution provided a measurement of the 24-hour average concentration of NO 2 , PM 10 and PM 2.5. Results A total of 1265 coronary events were recorded within 1096 days (on average 1.154/day). The NO 2 concentration was higher than 30 μg/m 3 for 677 days (61.8%). Higher daily coronary events rates were evidenced when NO 2 concentrations were measured above 30 μg/m 3 1.208 [95% CI 1.128–1.289 vs. 1.067 (95% CI 0.961–1,172) P  = 0.009]. No impact of PM on daily coronary events could be demonstrated. A marked seasonality of NO 2 , PM 2.5 and PM 10 concentrations characterized by an increase during winter, and a decrease during the summer could be established. The seasonality of coronary events was evidenced simultaneously. After adjustments were made to account, for the time and the month, no independent impact of NO 2 , PM 2.5, or PM 10 on daily coronary events could be demonstrated. Conclusions Higher daily coronary events were recorded when NO 2 concentrations peaked above > 30 ug/m 3 . An important seasonality of air pollution, which was concurrent with a coronary event burden could be demonstrated. After the time adjustment, no independent impact of the air pollution on coronary events could be determined. The specific impact of cold weather conditions, of a concurrent respiratory infection, or of the decrease in the number of hours of sunshine deserves further investigation.