The red cell distribution width to albumin ratio (RAR) for predicting prognosis in spontaneous intracerebral hemorrhage: a retrospective cohort study using the MIMIC-IV database

Red blood cell distribution width to albumin ratio (RAR) has emerged as an emerging marker for assessing inflammatory and nutritional status. This study aims to investigate the association between RAR and clinical outcomes in patients with spontaneous intracerebral hemorrhage (sICH). Data on sICH patients were obtained from the Medical Information Mart for Intensive Care IV (MIMIC-IV) database for this retrospective cohort study. The primary exposure was the RAR. The primary outcome was 90-day all-cause mortality, and secondary outcomes included 30-day and 365-day all-cause mortality. The optimal RAR cutoff value for predicting 90-day mortality was determined via receiver operating characteristic (ROC) analysis by maximizing Youden’s index. Based on this cutoff, patients were stratified into a high-RAR group and a low-RAR group. Subsequently, propensity score matching (PSM) was employed to control for confounding factors. Cox regression models, Kaplan-Meier survival analysis, restricted cubic spline (RCS) analysis, and subgroup analyses were used to assess the associations between RAR and all-cause mortality. Among 817 patients with sICH (55.08% male), the optimal RAR cut-off value for predicting 90-day mortality was 3.90. Based on this threshold, patients were stratified into a high-RAR group (> 3.90, n = 380) and a low-RAR group (≤ 3.90,n = 437). Cox regression analysis revealed that a high RAR was independently associated with an increased risk of all-cause mortality, with hazard ratios (HR) of 1.78 (95% CI 1.25–2.50, P < 0.001) at 30 days, 1.84 (95% CI 1.36–2.50, P< 0.001) at 90 days, and 1.65 (95% CI 1.25–2.18, P < 0.001) at 365 days. To address potential baseline confounding, PSM was performed using 1:1 nearest-neighbor matching with a caliper width of 0.05, resulting in a balanced cohort of 195 patients in each group. Post-matching Cox regression analysis consistently showed that patients in the high-RAR group had a significantly increased risk of all-cause mortality at 30 days, 90 days, and 365 days. Both before and after PSM, Kaplan-Meier survival curves demonstrated significantly lower survival rates at 30 days, 90 days, and 365 days in the high-RAR group compared to the low-RAR group (log-rank test, all P < 0.05). RCS analysis revealed a significant dose-response relationship between RAR and prognosis in sICH patients (P < 0.05), with no evidence of significant nonlinearity (P > 0.05). The forest plot constructed from subgroup analysis showed that the association between RAR and all-cause mortality at 90 days and 365 days remained robust across all subgroups, with no statistically significant interactions (P > 0.05). Within the subgroups of patients aged > 65 years or those with comorbid hypertension, individuals with high RAR exhibited a significantly higher risk of 30-day all-cause mortality compared to those with low RAR. Elevated RAR levels at admission are independently associated with an increased risk of all-cause mortality at 30 days, 90 days, and 365 days in sICH patients, indicating that RAR may serve as a simple and reliable biomarker for prognostic assessment.