Ambient Air Pollution and Out-of-Hospital Cardiac Arrest in Beijing, China.

Air pollutants are associated with cardiovascular death; however, there is limited evidence of the effects of different pollutants on out-of-hospital cardiac arrests (OHCAs) in Beijing, China. We aimed to investigate the associations of OHCAs with the air pollutants PM2.5-10 (coarse particulate matter), PM2.5 (particles ≤2.5 μm in aerodynamic diameter), nitrogen dioxide (NO₂), sulfur dioxide (SO₂), carbon monoxide (CO), and ozone (O₃) between 2013 and 2015 using a time-stratified case-crossover study design. We obtained health data from the nationwide emergency medical service database; 4720 OHCA cases of cardiac origin were identified. After adjusting for relative humidity and temperature, the highest odds ratios of OHCA for a 10 μg/m³ increase in PM2.5 were observed at Lag Day 1 (1.07; 95% confidence interval (CI): 1.04-1.10), with strong associations with advanced age (aged ≥70 years) (1.09; 95% CI: 1.05-1.13) and stroke history (1.11; 95% CI: 1.06-1.16). PM2.5-10 and NO₂ also showed significant associations with OHCAs, whereas SO₂, CO, and O₃ had no effects. After simultaneously adjusting for NO₂ and SO₂ in a multi-pollutant model, PM2.5 remained significant. The effects of PM2.5 in the single-pollutant models for cases with hypertension, respiratory disorders, diabetes mellitus, and heart disease were higher than those for cases without these complications; however, the differences were not statistically significant. The results support that elevated PM2.5 exposure contributes to triggering OHCA, especially in those who are advanced in age and have a history of stroke.