Air pollution before and during the COVID-19 pandemic: changes in risk of acute myocardial infarction

Background and Aims Ambient PM2.5 exposure is a known risk factor for acute myocardial infarction (AMI). Myocardial infarction with non-obstructive coronary arteries (MINOCA) represents a distinct subtype of AMI from myocardial infarction with obstructive coronary disease (MI-CAD). Public health measures during the COVID-19 pandemic may have altered exposure patterns, offering a natural experiment. This study investigated changes in the association between short-term exposure to PM2.5 and AMI subtypes following the COVID-19 pandemic. Methods Using data from the nationwide JROAD-DPC database, this study analysed 270 091 first-admission AMI patients, including 23 037 MINOCA, between April 2012 and March 2022. 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 7 April 2020, as the threshold. Sensitivity analyses used alternative pandemic onset dates. Results Each 10-μg/m³ increase in lag-2 PM2.5 was significantly associated with an increased risk of AMI. 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 (pre-pandemic OR 1.303, 95% confidence interval [CI] 1.005–1.688; post-pandemic OR 1.230, 95% CI: .973–1.555; P for interaction = 0.017). Sensitivity analyses confirmed these findings. Conclusions Short-term exposure to PM2.5 is associated with increased risk of AMI. 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, particularly in specific AMI subtypes.