Relationship between Fine Particulate Matter Exposure and Out-of-Hospital Cardiac Arrest of Cardiac Origin: A Nationwide Registry-Based Japanese Study

Background: Sudden cardiac arrest is a leading cause of cardiovascular death. We aimed to examine the association of short-term exposure to particulate matter of diameter ≤2·5 μm (PM2·5) with factors including incidence of out-of-hospital cardiac arrests (OHCAs) of cardiac origin, efficacy of basic life support measures, and eventual prognosis. Methods: We utilised data from the prospective, nationwide, population-based All-Japan Utstein Registry of OHCAs occurring throughout all 47 Japanese prefectures. We obtained PM2·5 concentrations and other air pollutants from atmospheric environmental database of the National Institute for Environmental Studies. A time-stratified, case-crossover design was applied to study the association of prefecture-specific estimates of PM2·5 with OHCA-related factors using a conditional logistic regression analysis. Estimations were combined with a random-effects meta-analysis for higher accuracy. Findings: The study included 103 189 bystander-witnessed OHCAs of cardiac origin that occurred from April 2011 to December 2016. A 10-μg/m3 increase in the average PM2·5 concentration on the day of OHCA over that on the day prior was associated with a 1·6 (95% CI, 0·1-3·1)% increase. PM2·5-exposure was closely associated with OHCAs presenting with asystole (2·1 [0·2-4·1]%) as compared to those with other initial cardiac rhythms. Occurrence of unfavourable prognosis such as 1-month mortality (1·5 [0·0-3·2]%) was estimated, and both chest compressions and rescue breathing were associated with higher 1-month mortality (4·6 [0·4-9·0]%) than chest-compression-only type of cardiopulmonary resuscitation (1·2 [-0·7-3·1]%) in OHCA patients with PM2·5-exposure. Interpretation: Increase in PM2·5 concentrations triggers OHCAs of cardiac origin, which commonly present with initial asystole, leading to poor outcomes. The impact of rescue breathing for cardiac origin-OHCA patients affected by short-term exposure to PM2·5, requires further study. Funding: Environment Research and Technology Development Fund (5-1751) of the Ministry of Environment, Japan, and Grants-in-Aid for Scientific Research (17K19821) of the Japan Society for Promotion of Science. Declaration of Interest: None. Ethical Approval: They conducted the study with approval from the Ethics Committee of Kawasaki Medical School (Approved Number: 3383).