Hemoglobin-to-red blood cell distribution width ratio and in-hospital mortality in patients with non-traumatic subarachnoid hemorrhage: a retrospective cohort study

Non-traumatic subarachnoid hemorrhage (SAH) carries a high in-hospital mortality rate, and reliable biomarkers for early risk stratification are lacking. This study investigated the association between the hemoglobin-to-red blood cell distribution width ratio (HRR) and in-hospital mortality in patients with non-traumatic SAH. A total of 1,161 patients were identified from the Medical Information Mart for Intensive Care IV (MIMIC-IV) database. Multivariable logistic regression, subgroup analyses, and sensitivity analyses were performed to assess the association between HRR and in-hospital mortality. An exploratory analysis of hospital-acquired pneumonia (HAP) was further conducted using competing risk models. Lower HRR was significantly associated with increased in-hospital mortality. In the fully adjusted model, each 0.10 increase in HRR was associated with reduced mortality risk (OR = 0.873, P = 0.005). This association remained consistent across subgroup and sensitivity analyses. Incorporating HRR into the clinical model improved risk discrimination and reclassification. In the exploratory HAP analysis, although conventional regression indicated an inverse association, competing risk analysis showed that HRR was not independently associated with HAP, whereas its association with in-hospital mortality remained significant. HRR is independently associated with in-hospital mortality in patients with non-traumatic SAH and may serve as a readily available biomarker for early risk stratification.