Long-term impact of air pollution on heart failure readmission in unstable angina patients

Cardiovascular disease remains the leading cause of death worldwide, with air pollution's impact on cardiovascular health being closely monitored. However, the specific effects of air pollution on the risk of hospital readmission for heart failure (HF) in patients with unstable angina (UA) have not been fully explored. We conducted a retrospective study involving 12,857 consecutive patients diagnosed with acute coronary syndrome (ACS) between January 2015 and March 2023. After rigorous screening, we included 8,737 patients with UA in the analysis. Furthermore, we used a Cox proportional hazards regression model to examine the relationship between air quality indicators and hospital readmission for HF in patients with UA. Additionally, a decision tree model identified air quality indicators levels that had the most significant impact on readmission for HF risk. After adjusting for confounding factors, we found that elevated levels of PM10 [hazard ratio (HR) = 1.003, 95% confidence interval (CI): 1.000-1.005, p = 0.04453] and CO (HR = 1.013, 95% CI: 1.005-1.021, p = 0.00216) were associated with an increased risk of hospital readmission for HF in UA patients. Specifically, patients exposed to PM10 levels above 112.5 µ g/m³ had a 1.61-fold higher risk of readmission for HF in UA patients. (HR = 1.609, 95% CI: 1.190-2.176, p = 0.00201), and those exposed to CO levels above 37.5 mg/m³ had a 2.70-fold higher risk of readmission for HF in UA patients. (HR = 2.681, 95% CI: 1.731-4.152, p < 0.00001). Higher concentrations of PM10 and CO significantly increased the risk of HF (HF) readmission in patients with UA after discharge, particularly when PM10 levels exceeded 112.5 ug/m³ and CO levels surpassed 37.5 ug/m³. Besides, female patients with UA, with fewer underlying diseases, were more susceptible to the adverse effects of PM10 and CO.