Association of the Systemic Inflammation Response Index with the One-Year All-Cause Mortality in Elderly Patients with Acute Coronary Syndrome: A Retrospective Cohort Study

Purpose: This study aimed to investigate the association between the systemic inflammation response index (SIRI) and one-year all-cause mortality, as well as major adverse cardiovascular and cerebrovascular events (MACCE), in elderly patients with acute coronary syndrome (ACS). Patients and Methods: This retrospective cohort study enrolled 963 elderly patients diagnosed with ACS at the Affiliated Hospital of Guangdong Medical University between January 2022 and December 2023, comprising those with unstable angina, non-ST elevation myocardial infarction, and ST elevation myocardial infarction. The cohort encompassed patients who underwent percutaneous coronary intervention as well as those managed conservatively, with a one-year follow-up. The primary endpoint was one-year all-cause mortality. Cox proportional hazards models were used to evaluate the association of SIRI, treated as both a continuous variable and as a categorical variable stratified by median value, with all-cause mortality and MACCE. Results: Among 963 elderly ACS patients (median age 73; 69.5% male), 132 (13.7%) died within one year. The median SIRI value was 2.89 × 10 9 /L. In continuous analyses, higher SIRI was associated with greater all-cause mortality (adjusted hazard ratio [HR] 1.031 per unit; 95% confidence interval [CI] 1.018– 1.045; P < 0.001). Compared with the low-SIRI group, the high-SIRI group had higher mortality (adjusted HR 1.543; 95% CI 1.060– 2.246; P < 0.05). High SIRI was also associated with MACCE (adjusted HR 1.037 per unit; 95% CI 1.025– 1.050; P < 0.001). Conclusion: Elevated admission SIRI is independently associated with a higher risk of one-year all-cause mortality and MACCE among elderly ACS patients.