Reductions in acute myocardial infarction burden linked to short-term PM<sub>2.5</sub> exposure: Evidence from the Chinese CCA Registry

<sec>Background<p>PM<sub>2.5</sub> (fine particulate matter with aerodynamic diameter ≤ 2.5μm) concentrations have substantially declined in the past decade across China, but temporal changes of morbidity burden of acute myocardial infarction (AMI) attributable to short-term exposures to PM<sub>2.5</sub> and its various chemical constituents, including black carbon (BC), organic matter (OM), ammonium (<inline-formula><tex-math id="M1">$ {\mathrm{NH}}_{\mathrm{4}}^{\mathrm{+}} $</tex-math></inline-formula>), nitrate (<inline-formula><tex-math id="M2">$ {\mathrm{NO}}_{\mathrm{3}}^{\mathrm{-}} $</tex-math></inline-formula>) and sulfate (<inline-formula><tex-math id="M3">$ {\mathrm{SO}}_{\mathrm{4}}^{\mathrm{2}\mathrm{-}} $</tex-math></inline-formula>) in China remain unknown. </p></sec><sec>Methods<p>A time-stratified case-crossover design was applied in 785,052 AMI cases across China during 2017-2020. We utilized conditional logistic regression models to estimate the excess risks (ERs) and attributable fractions (AFs) from AMI onset attributable to short-term exposures (lag01 day) to PM<sub>2.5</sub> and constituents, and used linear regression models to estimate temporal changes of AFs of AMI morbidity. </p></sec><sec>Results<p>The annual average reductions in concentrations of PM<sub>2.5</sub> mass, BC, OM, <inline-formula><tex-math id="M4">$ {\mathrm{NH}}_{\mathrm{4}}^{\mathrm{+}} $</tex-math></inline-formula>, <inline-formula><tex-math id="M5">$ {\mathrm{NO}}_{\mathrm{3}}^{\mathrm{-}} $</tex-math></inline-formula> and <inline-formula><tex-math id="M6">$ {\mathrm{SO}}_{\mathrm{4}}^{\mathrm{2}\mathrm{-}} $</tex-math></inline-formula> during 2017-2020 were respectively 3.05μg/m<sup>3</sup>/year, 0.15μg/m<sup>3</sup>/year, 0.70μg/m<sup>3</sup>/year, 0.31μg/m<sup>3</sup>/year, 0.44μg/m<sup>3</sup>/year, and 0.51μg/m<sup>3</sup>/year. Correspondingly, the annual average reductions in AFs were recorded as -0.53% (95%CI: -0.92%, -0.15%), -0.29% (95%CI: -0.43%, -0.15%), -0.45% (95%CI: -0.78%, -0.12%), -0.33% (95%CI: -0.51%, -0.16%), -0.36% (95%CI: -0.59%, -0.13%), and -0.48% (95%CI: -0.86%, -0.10%), respectively. The temporal reduction of PM<sub>2.5</sub>-attributed and chemical constituents-attributed AFs were greater in females, people aged ≥65 years, non-ST-segment-elevation myocardial infarction (NSTEMI) cases, and people resided in Southern China. </p></sec><sec>Conclusions<p>As the concentration of PM<sub>2.5</sub> mass and chemical constituents decreased over the years, the decline was observed in the morbidity burden of AMI attributable to PM<sub>2.5</sub> and its constituents across China from 2017 to 2020.</p></sec>