This nationwide study, published in the European Heart Journal, used the JROAD-DPC database to analyze 270,091 first-admission AMI patients between April 2012 and March 2022, including 23,037 cases classified as myocardial infarction with non-obstructive coronary arteries (MINOCA). The analysis specifically evaluated whether the association between short-term PM2.5 exposure and AMI subtypes differed before and after the onset of COVID-19-related public health measures.

A time-stratified case-crossover design with conditional logistic regression estimated the odds ratio (OR) for each 10-μg/m³ increase in PM2.5 exposure at a 2-day lag. The study period was divided into pre-pandemic and post-pandemic phases using April 7, 2020, as the threshold. Sensitivity analyses applied alternative pandemic onset dates.

Each 10-μg/m³ increase in lag-2 PM2.5 was significantly associated with increased AMI risk. ORs for overall AMI and myocardial infarction with obstructive coronary artery disease (MI-CAD) remained largely unchanged across periods. Attenuation of PM2.5-related risk was observed for MINOCA (pre-pandemic OR 1.303, 95% CI 1.005–1.688; post-pandemic OR 1.230, 95% CI 0.973–1.555; P for interaction=0.017). Sensitivity analyses yielded consistent findings.

As a case-crossover observational analysis, associations were identified, and causality cannot be established. Findings suggest differential patterns across AMI subtypes following the pandemic period.