Impact of COVID-19 pandemic on the association between short-term exposure to PM2.5 and risk of acute myocardial infarction

Background Acute myocardial infarction (AMI) is a major cause of morbidity and mortality, and myocardial infarction with nonobstructive coronary arteries (MINOCA) represents a heterogeneous subgroup. Ambient PM2.5 exposure has been associated with cardiovascular events, and COVID-19 public health measures may have altered exposure patterns and related risks. Purpose The aim of this study was to investigate the association between short-term exposure to PM2.5 and AMI subtypes and changes in these relationships following the onset of the pandemic. Methods Using nationwide data from the JROAD-DPC database, we analyzed 270,091 first-admission AMI patients including 23,037 MINOCA from April 2012 to March 2022. A time-stratified case-crossover design with conditional logistic regression was applied to estimate 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 based on April 7, 2020, with sensitivity analyses conducted using alternative threshold dates. Results Across all seasons, each 10-µg/m³ increase in PM2.5 was significantly associated with an increased risk of AMI, with the highest absolute risk observed in spring. Although the ORs for overall AMI and MI-CAD remained largely unchanged between periods, a significant attenuation of the PM2.5-related risk for MINOCA was observed post-pandemic (pre-pandemic OR: 1.035, 95% CI: 1.007-1.064; post-pandemic OR: 0.990, 95% CI: 0.925-1.061; P for interaction=0.010). Sensitivity analyses confirmed these findings. Conclusions Short-term exposure to PM2.5 was associated with increased AMI risk, particularly during spring. The observed reduction in MINOCA risk following the COVID-19 pandemic suggested that public health interventions aimed at reducing air pollution exposure may reduce cardiovascular risks.