Association between nitrogen dioxide exposure and out-of-hospital cardiac arrest onset in China: A multicenter, time-stratified, case-crossover study

Studies on the association between nitrogen dioxide (NO2) exposure and out-of-hospital cardiac arrest (OHCA) are limited and present inconsistent results. In the context of global urbanization, a large population is exposed to high ambient NO2 pollution, highlighting the need for further clarification of NO2-related health hazards. Furthermore, previous studies mostly applied exposure data from monitoring stations, with relatively few investigations examining acute effects using high-resolution modeled data. To explore the association between NO2 and cardiac OHCA onset risk, a time-stratified case-crossover study was conducted using data from emergency medical service (EMS) systems across 23 Chinese provinces throughout 2020. Conditional logistic regression models were used to investigate the potential association between NO2 and OHCA onset. Individual-level NO2 data from both models and monitoring stations were analyzed separately to evaluate their comparability in practice. The analysis incorporated 76,263 EMS-attended cardiac OHCA onsets. The health estimates from NO2 predictions and measurements were comparable without statistically significant differences, with each 10 mu g/m3 increase associated with a 1.16% (95% confidence interval [CI]: 0.38-1.94%) and 1.03% (95% CI: 0.37-1.69%) increase in the risk of OHCA onset, respectively. This nationwide multicenter study demonstrated adverse effects of NO2 exposure on OHCA onset in a large population residing in regions with higher and variable NO2 levels. These findings contribute robust epidemiological evidence to this field and offer new evidence to support global policymaking, particularly in developing countries. Additionally, modeled NO2 predictions with high resolution and coverage can serve as effective alternatives to traditional monitoring station data in epidemiological studies.