Short‐Term Ambient Air Pollution Exposure and Risk of Out‐of‐Hospital Cardiac Arrest in Sweden: A Nationwide Case‐Crossover Study

Abstract

Background Air pollution is one of the main risk factors for cardiovascular disease globally, but its association with out‐of‐hospital cardiac arrest at low air pollution levels is unclear. This nationwide study in Sweden aims to investigate if air pollution is associated with a higher risk of out‐of‐hospital cardiac arrest in an area with relatively low air pollution levels. Methods and Results This study was a nationwide time‐stratified case‐crossover study investigating the association between short‐term air pollution exposures and out‐of‐hospital cardiac arrest using data from the SRCR (Swedish Registry for Cardiopulmonary Resuscitation) between 2009 and 2019. Daily air pollution levels were estimated in 1×1‐km grids for all of Sweden using a satellite‐based machine learning model. The association between daily air pollutant levels and out‐of‐hospital cardiac arrest was quantified using conditional logistic regression adjusted for daily air temperature. Particulate matter <2.5 μm exposure was associated with a higher risk of out‐of‐hospital cardiac arrest among a total of 29 604 cases. In a multipollutant model, the association was most pronounced for intermediate daily lags, with an increased relative risk of 6.2% (95% CI, 1.0–11.8) per 10 μg/m 3 increase of particulate matter <2.5 μm 4 days before the event. A similar pattern of association was observed for particulate matter <10 μm. No clear association was observed for O 3 and NO 2 . Conclusions Short‐term exposure to air pollution was associated with higher risk of out‐of‐hospital cardiac arrest. The findings add to the evidence of an adverse effect of particulate matter on out‐of‐hospital cardiac arrest, even at very low levels below current regulatory standards.