Ambient air pollution and emergency department visits and hospitalisation for cardiac arrest: a population-based case-crossover study

Background: The association between ambient air pollution and cardiac arrhythmia has been explored in numerous studies; however, the small subgroup of cardiac arrest has not been closely studied thus far. The aim of the present study was to assess the association between traffic-related ambient air pollution and emergency hospital visits for cardiac arrest. Methods A bidirectional time-stratified case-crossover design was used. The setting was the Reykjavik capital area and the study population were the inhabitants 18 years and older identified by zip codes. Cases were those who had made emergency visits to Landspitali University Hospital during the period 2006 to 2017 and who were given the primary discharge diagnosis of cardiac arrest according to The International Classification of Diseases 10th edition (ICD-10), code I46. The pollutants were NO 2 , PM 10 , PM 2.5 , and SO 2 with adjustment for H 2 S, temperature and relative humidity. Results The 24-h mean NO 2 was 20.7 µg/m 3 , mean PM 10 was 20.5 µg/m 3 , mean PM 2.5 was 12.5 µg/m 3 , and mean SO 2 was 2.5 µg/m 3 . PM 10 level was positively associated with the number of emergency hospital visits (n = 453) for cardiac arrest. Each 10 µg/m 3 increase in PM 10 was associated with increased risk of cardiac arrest (ICD-10: I46), odds ratio (OR) 1.093 (95%CI 1.033–1.162) on lag 2, and OR 1.118 (95%CI 1.031–1.212) on lag 0–2. Significant associations were shown between exposure to PM 10 on lag 2 and on lag 0–2 and increased risk of cardiac arrest in the age, gender, and season strata. Females and those 71 years and older were at higher risk for cardiac arrest, OR 1.193 (95%CI 1.059–1.344), and OR 1.186 (95%CI 1.066–1.320) on lag 2, per 10 µg/m 3 increase in PM 10 , respectively. Significant associations were sporadically found for NO 2 and SO 2 and emergency hospital visits for cardiac arrest, but these associations were weaker and did not show a discernable pattern. Conclusions A new endpoint was used for the first time in this study: cardiac arrest (ICD-10 code I46). Short-term increase in PM 10 concentrations was associated with cardiac arrest. The effect seemed higher among the elderly and females. Future ecological studies of this type and their related discussions should perhaps concentrate more on precisely defined endpoints.