Association between stress hyperglycemia ratio and 28-day all-cause mortality in critically ill atrial fibrillation patients: a retrospective cohort study based on the MIMIC-IV database.

Background: Atrial fibrillation (AF) is a prevalent arrhythmia linked to high mortality rates. The stress hyperglycemia ratio (SHR) serves as a novel marker for acute metabolic stress; however, its significance in critically ill patients with AF is not yet fully understood. This study seeks to investigate the correlation between SHR and 28-day all-cause mortality among critically ill patients diagnosed with AF. Methods: This study utilized the Intensive Care Medicine Information Market (MIMIC-IV v2.2) database to identify and enroll 2,050 adult patients admitted to intensive care units (ICU) with AF. The SHR was calculated using the formula: SHR = inpatient blood glucose (mg/dL) / [28.7 × glycosylated hemoglobin (HbA1c) (%) - 46.7]. Patients were then divided into four groups (Q1-Q4) based on quartile SHR values. The primary outcome was 28-day all-cause mortality. Statistical analysis employed a multivariate Cox proportional hazards regression model to evaluate associations between SHR groups and mortality risk. To explore potential nonlinear relationships between SHR and mortality, restricted cubic spline (RCS) fitting was conducted. Kaplan-Meier survival curves were plotted to visually demonstrate survival differences among groups, with intergroup comparisons performed using log-rank tests. Boruta machine learning algorithms were applied for feature selection to identify key predictors. Finally, extensive sensitivity analysis and subgroup stratification analyses (categorized by age, gender, and comorbidities) were conducted to validate the robustness and reliability of core conclusions. Results: RCS analysis revealed a U-shaped association between SHR and 28-day mortality (nonlinear P<0.001), with the lowest risk point at SHR =1.01. Compared to the Q1 group, the Q4 group (SHR ≥1.36) exhibited a significantly increased 28-day mortality risk [adjusted hazard ratio (HR) =1.89, 95% confidence interval (CI): 1.31-2.74]. Boruta algorithm identified SHR as a relatively important predictive variable, with its significance independent of confounding factors such as age and weight score. Sensitivity analyses consistently demonstrated that high SHR significantly elevated mortality risk across all subgroups (age, sex, diabetes status, etc.), with each subgroup showing HR >1 and P<0.05. Conclusions: SHR serves as an independent predictor of 28-day all-cause mortality in critically ill AF patients, and its U-shaped association highlights the critical role of metabolic stress in prognosis. Monitoring SHR may provide a clinical basis for risk stratification and individualized glucose management in AF patients.