Interactive effects of diurnal temperature range and air pollution on myocardial infarction incidence: an individual-level case-crossover study

Climate change and air pollution have garnered increasing attention in recent years due to their potential to contribute to various diseases, including myocardial infarction (MI). However, no previous studies have explored the interactive effects of diurnal temperature range (DTR) and air pollution on MI. This study employed an individual-level time-stratified case-crossover design to investigate 391,901 MI patients in central China between 2017 and 2020. Daily estimated air pollutant concentrations for each patient were extracted from gridded datasets based on their residential addresses on both case and control days. Conditional logistic regression models were used to examine the lagged effects and exposure-response relationships between short-term exposure to air pollutants, DTR, and MI. Additionally, the relative excess odds due to interaction (REOI), proportion attributable to interaction, and synergy index were applied to quantify the interaction effects. Subgroup analyses were further conducted by gender and age (≥ 65 years old and < 65 years old) to identify vulnerable populations. Exposure to all six air pollutants (PM2.5, PM10, SO2, NO2, CO, O3) was significantly associated with an elevated risk of MI. The risks of PM2.5, PM10, SO2, and CO became more pronounced after exceeding specific threshold concentrations. For O3 exposure, MI risk was reduced when concentrations were below the critical threshold but increased when this threshold was exceeded. High DTR was independently associated with an increased MI risk. Significant antagonistic interactions between air pollutant exposure and high DTR were observed across multiple lag periods. This study reveals that the adverse effects of air pollutants on MI are attenuated under high DTR conditions, highlighting the complex interplay between DTR and air pollution in the pathogenesis of MI.