Association between systemic inflammation response index and atrial fibrillation in chronic obstructive pulmonary disease: a multicenter cross-sectional study

Background Systemic inflammation plays a critical role in the pathogenesis of both chronic obstructive pulmonary disease (COPD) and atrial fibrillation (AF). As an emerging biomarker reflecting systemic inflammatory status, the association between the systemic inflammation response index (SIRI) and the risk of AF in patients with COPD remains unclear. Therefore, this study aimed to investigate the association between SIRI levels and the risk of AF in patients with COPD. Methods In this multicenter cross-sectional study, we enrolled 1,133 hospitalized COPD patients from May 2021 to May 2024 at the First Affiliated Hospital of Wenzhou Medical University and Quzhou People's Hospital. Patients were categorized into four groups based on SIRI quartiles. We used multivariate logistic regression, restricted cubic spline (RCS) analysis, and receiver operating characteristic (ROC) curves to evaluate the association between SIRI and AF risk. Subgroup, interaction, and sensitivity analyses were conducted to assess robustness and effect modification. Results Among the study population, 225 patients (19.85%) had AF. After full adjustment, this cross-sectional analysis demonstrates that each 1-unit increase in SIRI was associated with a 4.6% higher AF risk (OR = 1.046, 95% CI: 1.018–1.075, p = 0.002). Patients in the highest SIRI quartile had a 116.2% increased risk compared to those in the lowest quartile (OR = 2.162, 95% CI: 1.325–3.527, p = 0.002). RCS analysis revealed a significant linear dose–response relationship between SIRI and AF risk. ROC analysis showed that combining SIRI with conventional risk factors improved predictive accuracy for AF (AUC = 0.818, 95% CI: 0.787–0.848, p < 0.001). A significant interaction was observed among smokers (interaction p = 0.006), and results remained robust in sensitivity analyses. Conclusion Elevated SIRI levels are independently associated with an increased risk of AF in patients with COPD, especially among smokers. As a simple and readily accessible biomarker of low-grade systemic inflammation, SIRI may serve as an effective tool for assessing the risk of atrial fibrillation in patients with COPD.