The association between systemic immune-inflammation index and mortality of elderly chronic bronchitis patients complicated by acute myocardial infarction

Objectives To explore the relationship between the systemic immune-inflammation index (SII) and in-hospital mortality in elderly individuals diagnosed with chronic bronchitis (CB) complicated by acute myocardial infarction (AMI). Methods This retrospective observational study included 252 elderly patients diagnosed with CB complicated by AMI, who were consecutively enrolled based on standardized diagnostic criteria. Patients were categorized into a survival group ( n = 204) and a mortality group ( n = 48) according to in-hospital outcomes. Demographic, clinical, and laboratory parameters collected at admission were extracted from electronic medical records for analysis, and the SII was calculated for all subjects. Group differences were analyzed using the Mann–Whitney U test, t -test, or chi-square test, selected in accordance with the distributional characteristics of the data. Parameters exhibiting significant intergroup variation underwent univariate logistic regression analysis, and variables with notable associations were subsequently introduced into a multivariate regression model. Finally, ROC curve analysis was conducted to determine the prognostic value of the SII in predicting the risk of in-hospital mortality. Results Overall patient characteristics showed that non-survivors had markedly higher inflammatory markers and altered lipid profiles compared with survivors. Analysis using univariate logistic regression revealed strong associations of Hb, TC, LDL-C, CRP, and SII with the likelihood of mortality. Multivariate logistic regression identified LDL-C (OR = 29.174, P < 0.001), CRP (OR = 1.135, P < 0.001), and SII (OR = 1.001, P < 0.001) as independent predictors of in-hospital mortality. ROC analysis demonstrated that SII had strong discriminative ability (AUC = 0.864), and the combination of SII, CRP, and LDL-C yielded the highest predictive performance (AUC = 0.935). Conclusion Among elderly individuals suffering from CB in combination with AMI, a higher SII emerged as an independent determinant of in-hospital mortality.