Association Between Systemic Immune Inflammation Level and Poor Prognosis Across Different Glucose Metabolism Status in Coronary Artery Disease Patients

Background: Blood glucose levels significantly affect the clinical prognosis of patients with coronary artery disease (CAD), and systemic immune inflammation is a common risk factor for both CAD and diabetes. However, the relationship between immune inflammation levels and poor prognosis in patients with CAD with different glucose metabolic statuses remains unclear. Methods: Between January 2007 and December 2020, we recruited 84,645 patients with CAD. The systemic immune inflammation index (SII) was used to comprehensively reflect the immune and inflammatory levels of patients and was calculated using the following formula: neutrophils x platelets/lymphocytes. The patients were classified into nine groups according to their glucose metabolism status (diabetes mellitus [DM], pre-diabetes mellitus [pre-DM], and normal glucose regulation [NGR]). Cox regression models and competing risk Fine and Gray models were used to investigate the association between SII and clinical outcomes. Results: During the follow-up period, 12,578 patients died, including 5857 cardiovascular-related and 1251 cancer-related deaths. The risk of all-cause and cause-specific mortality increased with increasing SII tertiles in CAD patients with NGR, pre-DM, and DM. When considering glucose metabolism status, the multivariate cox regression revealed that CAD patients with DM and SII-H levels had the highest risk of all-cause mortality (1.69 [1.56-1.83]), cardiovascular mortality (2.29 [2.02-2.59]), and cancer mortality (1.29 [1.01-1.66]). Moreover, incorporating the SII into traditional risk factor models significantly improved the C-index for predicting all-cause and cardiovascular mortality. Conclusion: Systemic immune inflammation levels on admission were correlated with a higher risk of all-cause and cause-specific mortality in patients with CAD, particularly in those with DM.