Impact of meteorological parameters and air pollution on emergency department visits for cardiovascular diseases in the city of Zagreb, Croatia

The aim of this study was to investigate whether nitrogen dioxide (NO2), ozone (O-3), and certain meteorological conditions had an impact on cardiovascular disease (CVD)-related emergency department (ED) visits in the metropolitan area of Zagreb. This retrospective, ecological study included 20,228 patients with a cardiovascular disease as their primary diagnosis who were examined in the EDs of two Croatian University Hospitals, Sisters of Charity and Holy Spirit, in the study period July 2008-June 2010. The median of daily CVD-related ED visits during the study period was 28 and was the highest during winter. A significant negative correlation was found between CVD-related emergency visits and air temperature measured no more than three days prior to the visit, and the highest negative correlation coefficient was measured two days earlier (R=-0.266, p=0.001). The number of CVD-related emergency visits significantly correlated with the average NO2 concentration on the same day (R=0.191, p<0.001). The results of multiple stepwise regression analysis showed that the number of CVD-related emergency visits depended on air temperature, and NO2 and O-3 concentrations. The higher the air temperatures, the lower the number of daily CVD-related emergency visits (p<0.001). An increase in NO2 concentrations (p=0.005) and a decrease in O-3 concentrations of two days earlier (p=0.006) led to an increase in CVD-related ED visits. In conclusion, the decrease in O-3 concentrations and the increase in NO2, even if below the legally binding thresholds, could be associated with an increase in CVD-related emergency visits and a similar effect was observed with lower temperature measured no more than three days prior to the visit.