Prognostic value of systemic immune-inflammation index in older patients with acute coronary syndrome

Objectives Contemporary studies assessing the importance of the systemic immune-inflammation index (SII) in older patients presenting with acute coronary syndrome (ACS) are scarce. This study investigated the impact and prognostic value of the SII regarding long-term mortality in older patients with ACS. Methods The study included 401 older patients aged 75 years and above admitted with ACS between May 2015 and December 2022. Predictors of mortality were determined using multivariate Cox regression analysis. Survival curves were generated using the Kaplan–Meier method. Results The patients’ median age was 81 (77–85) years, and 197 (49.1%) were male. The median follow-up was 23 months (Q1–Q3 : 4–43, maximum: 102). All short- and long-term deaths, including in-hospital deaths, were significantly high in patients with high SII ( P = 0.001). Inflammatory variables, including C-reactive protein, SII, the neutrophil-to-lymphocyte ratio, monocyte-to-lymphocyte ratio, and platelet-to-lymphocyte ratio, were positively correlated with the SYNTAX score (for SII; R = 0.492, P = 0.001). Multivariate Cox regression analysis revealed that age [hazard ratio (HR): 1.082, 95% confidence interval (CI): 1.051–1.114, P = 0.001], estimated glomerular filtration rate (HR: 0.988, 95% CI: 0.982–0.994, P = 0.001), SII (HR: 1.004, 95% CI: 1.001–1.006, P = 0.001), and left ventricular ejection fraction (HR: 0.959, 95% CI: 0.947–0.97, P = 0.001) were independent predictors of mortality in older patients with ACS. Kaplan–Meier analysis also showed that patients with high SII had a significantly higher mortality rate ( P = 0.001). Conclusion A high SII is an independent predictor of long-term mortality in older patients with ACS.