Short-term exposure to ambient air pollution increased in-hospital non-ST-elevation myocardial infarction mortality risk, but not ST-elevation myocardial infarction: case-crossover based evidence from Beijing, China

Abstract

Background: Previous studies have shown that air pollution affects the incidence of ST-segment elevation myocardial infarction (STEMI) and non-ST-segment elevation myocardial infarction (NSTEMI) differently. However, limited studies have examined the impact of air pollution on the mortality of these acute myocardial infarction (AMI) subtypes.

Methods: Using AMI hospitalization data from Beijing (2013-2019), we applied a time-stratified case-crossover design with conditional Poisson regression models to evaluate associations between short-term exposure to six pollutants (PM_2.5, PM₁₀, SO₂, NO₂, CO, and O₃) and daily in-hospital mortality for overall AMI, STEMI, and NSTEMI. Subgroup analyses based on demographics, comorbidities, and coronary artery disease (CAD) history were conducted to identify vulnerable populations. Additionally, a retrospective case-control analysis with multivariable logistic regression involved all AMI admission cases, was conducted to explore whether the association between air pollution exposure and in-hospital AMI mortality is independent of other mortality risk factors.

Results: During the study period, there were 149,632 AMI admissions, with 10,983 in-hospital deaths (4,361 STEMI and 4,299 NSTEMI). Elevated levels of PM_2.5, PM₁₀, SO₂, NO₂, and CO on admission day were significantly associated with increased in-hospital mortality for overall AMI and NSTEMI, but not for STEMI. The effect of pollutants on NSTEMI mortality was greater in patients with old myocardial infarction (OMI) or percutaneous coronary intervention/coronary artery bypass grafting (PCI/CABG) history. In case-control analysis with multivariable logistic regression, increased pollutants concentration remained significantly associated with in-hospital NSTEMI mortality after adjusting for other mortality risk factors.

Conclusion: Short-term exposure to PM_2.5, PM₁₀, SO₂, NO₂, and CO increases the risk of in-hospital AMI mortality, particularly for NSTEMI. Individuals with CAD history require more protective measures due to the vulnerability to air pollution.

Keywords: ST-elevation myocardial infarction; acute myocardial infarction; air pollution; case-crossover; in-hospital mortality; non-ST-elevation myocardial infarction.

Figure 1

Summary of daily air pollution concentrations in Beijing during 2013–2019. IQR, interquartile range; SD, standard deviation.

Figure 2

Relative risks (RRs) with 95% CIs of in-hospital mortality for overall AMI, STEMI, and NSTEMI per interquartile range (IQR) increase in air pollutant concentration in single pollutant model. *indicates p <0.05. The IQR of daily concentrations of PM_2.5, PM₁₀, SO₂, NO₂, CO, and O₃ were 63.33 μg/m³, 74.23 μg/m³, 10.30 μg/m³, 26.91 μg/m³, 0.67 mg/m³ and 58.32 μg/m³, respectively.

Figure 3

Relative risks (RRs) with 95% CIs of in-hospital mortality for overall AMI, STEMI, and NSTEMI per interquartile range (IQR) increase in air pollutant concentration: subgroup analyses. CKD, chronic kidney disease; OMI, old myocardial infarction; PCI/CABG, percutaneous coronary intervention or coronary artery bypass grafting. *indicates p <0.05. Brackets and asterisk (*) indicate statistical significance of Z tests for between-group comparisons (P_z <0.05). The IQR of daily concentrations of PM_2.5, PM₁₀, SO₂, NO₂, CO, and O₃ were 63.33 μg/m³, 74.23 μg/m³, 10.30 μg/m³, 26.91 μg/m³, 0.67 mg/m³ and 58.32 μg/m³, respectively.

Figure 4

Odds ratios (ORs) with 95% CIs of in-hospital mortality among overall AMI, STEMI, and NSTEMI per interquartile range (IQR) increase in air pollutant concentration in multivariable logistic regression in case–control analysis. * indicates p <0.05. The IQR of daily concentrations of PM_2.5, PM₁₀, SO₂, NO₂, CO, and O₃ were 63.33μg/m3, 74.23μg/m3, 10.30μg/m3, 26.91μg/m3, 0.67mg/m3 and 58.32μg/m3, respectively.