Association between hemoglobin-to-red cell distribution width ratio and critically ill patients with atrial fibrillation: A retrospective cohort study.

ObjectiveTo investigate the association between the hemoglobin-to-red cell distribution width ratio (HRR) and in-hospital and 30-day mortality among critically ill patients with atrial fibrillation (AF).MethodsWe conducted a retrospective cohort study of AF patients from the MIMIC-III and IV databases. Patients were divided into HRR quartiles. The primary outcomes were in-hospital and 30-day mortality. Kaplan-Meier survival curves, dose-response analysis, and multivariable regression models assessed HRR-mortality associations, with subgroup and sensitivity analyses for robustness.ResultsAmong 21,625 patients (median age 75.0 years, 59.8% male), in-hospital and 30-day mortality rates were 14.8% and 24.5%. Mortality was inversely related to HRR, with Q1 showing higher risk than Q4 (in-hospital: 20.0% vs. 12.7%). Dose-response analysis revealed linear HRR-mortality relationships. In adjusted models, each 0.1-unit HRR increase reduced risk by 37% for in-hospital mortality (OR: 0.63, 95% CI: 0.60-0.66) and 31% for 30-day mortality (HR: 0.69, 95% CI: 0.67-0.71). Compared with Q1, Q4 was associated with 79% lower adjusted odds of in-hospital mortality and a 71% lower adjusted hazard of 30-day mortality. Subgroup analyses confirmed consistent protective associations, with modification by age and myocardial infarction.ConclusionsHigher HRR was independently associated with lower in-hospital and 30-day mortality in critically ill patients with atrial fibrillation. Higher HRR associates with improved survival, supporting its potential role as a complementary marker for risk assessment and prognostic evaluation.