Ambient PM2.5 and acute incidence of myocardial infarction in China: a case-crossover study and health impact assessment

Background and purpose: Evidence investigating the association between ambient fine particulate matter (PM2.5) and acute incidence of myocardial infarction in developing countries is limited. This study aims to investigate linear and nonlinear patterns for the association between PM2.5 and acute incidence of myocardial infarction based on multicounty registry dataset and evaluate the reduction of premature myocardial infarction incidence under different pollution control objectives in China. Methods: Thirty-six thousand six hundred and seventy-nine registered myocardial infarction incidence cases from 15 Chinese counties from January 1, 2013, to December 31, 2017, were obtained. We adopted a time-stratified case-crossover design with conditional logistic regression models. Results: With a 10 μg/m3 increase in PM2.5 exposure, there was an increase of 0.98% (95% CI: 0.40%–1.57%) in acute incidence risk of myocardial infarction. The corresponding values for males and individuals aged over 74 years were 1.58% (95% CI: 0.82%–2.35%) and 1.19% (95% CI: 0.35%–2.05%) respectively, indicating higher risks than other groups. The nonlinear concentration–response curve indicated a steeper slope under daily exposure below 50 μg/m3 and the marginal avoided premature morbidity became larger under the current air quality standard. Conclusions: The robust findings from this study may suggest the necessity for a continuous reduction of PM2.5 exposure concentration from the perspectives of public health.