The Interactive\nand Joint Associations of Ambient\nPM<sub>2.5</sub> and Temperature on the Onset of Acute Coronary Syndrome:\nFindings from The Chinese Cardiovascular Association (CCA) Database-Chest\nPain Center Registry

Environmental factors are important exposures that trigger\nacute\ncoronary syndrome (ACS) onset. However, the interactive and joint\nassociations of multiple exposures on ACS onset remain unknown. A\ntime-stratified case-crossover study was conducted including 1,292,219\nACS patients who were selected from 1,895 districts/counties across\nChina during 2015–2020. The ACS conditions included ST-segment-elevation\nmyocardial infarction (STEMI), non-ST-segment-elevation myocardial\ninfarction (NSTEMI), and unstable angina (UA). Conditional logistic\nregression models were applied to estimate the interactive and joint\nassociations of particulate matter with an aerodynamic diameter ≤2.5\nμm (PM<sub>2.5</sub>) and temperature (TM) with the ACS onset.\nThe ACS onset risks increased by 0.38% for each 10 μg/m<sup>3</sup> increment in PM<sub>2.5</sub> concentration, and an inverse\nU-shaped curve of TM and risk of ACS onset was observed. The associations\nof PM<sub>2.5</sub> with the ACS onset were greater on colder days.\nThe jointly attributable fractions (AF) of PM<sub>2.5</sub> and nonoptimal\nTM was 9.93% in all ACS patients, 10.31% in females, 12.91% in patients\naged ≥65 years, 17.54% in NSTEMI patients, and 12.43% in Southern\nChina. This study suggested that joint short-term exposures to ambient\nPM<sub>2.5</sub> and moderate cold TM may substantially increase the\nonset of ACS. Furthermore, there are synergistic interactions among\nhigher PM<sub>2.5</sub> and lower TM peaks on the ACS onset.