摘要Background Identifying simple and effective prognostic markers is crucial for risk stratification in critically ill patients with coronary artery disease(CAD)and diabetes mellitus(DM).The anion gap(AG),a marker of acid-base homeostasis,has been associated with mortality in various diseases,but its specific role in this high-risk popu-lation remains unclear.Methods This retrospective cohort study included 4,343 patients from the MIMIC-Ⅳ da-tabase.The exposure variable was the anion gap(AG),which was modeled in three ways:as a continuous variable,as a categorical variable(Low,Middle,and High groups),and as a dichotomous variable using a cutoff of 14.5.The primary outcome was in-hospital mortality.Multivariable logistic regression models were used to adjust for poten-tial confounders,including demographics,comorbidities,vital signs,and laboratory parameters.The linearity of the association was assessed using restricted cubic splines(RCS),and the predictive performance of AG was evaluated using receiver operating characteristic(ROC)curves.Results The overall in-hospital mortality rate was 12.6％.A strong,dose-response relationship was observed between AG levels and mortality.After full adjustment,compared to the low AG tertile,the high AG tertile was significantly associated with increased mortality risk(OR:1.92,95％CI:1.43-2.58,P<0.0001).AG as a continuous variable remained an independent predictor(OR per unit increase:1.11,95％CI:1.08-1.14,P<0.0001).RCS analysis confirmed a linear association(P for nonlinearity=0.880).In ROC analysis,AG demonstrated superior predictive ability[area under the curve(AUC),AUC=0.6957)]for in-hos-pital mortality compared to sodium(AUC=0.5338),potassium(AUC=0.5),and chloride(AUC=0.6141).Conclu-sions In this cohort of ICU patients with CAD and DM from the MIMIC-Ⅳ database,an elevated anion gap was independently and linearly associated with a higher risk of in-hospital mortality.AG outperformed other common electrolytes in mortality prediction,highlighting its potential as a valuable and readily available risk stratification tool in this population.[S Chin J Cardiol 2026;27(1):12-23]