The Red Cell Distribution Width-to-Albumin Ratio Predicts 1-Year Mortality in Patients with Chronic Obstructive Pulmonary Disease: Evidence From MIMIC-IV and NHANES.

Purpose: The red blood cell distribution width-to-albumin ratio (RAR) is an emerging biomarker that reflects systemic inflammation and nutritional status. However, its prognostic value in patients with chronic obstructive pulmonary disease (COPD) remains unclear. This study aimed to evaluate the predictive value of RAR for 1-year all-cause mortality in patients with COPD and to explore its clinical relevance. Patients and methods: We conducted a retrospective analysis using two independent cohorts: hospitalized COPD patients from the MIMIC-IV database (2008-2019, n = 2649) and community-dwelling individuals with COPD from the NHANES database (2003-2018, n = 2415). RAR levels were stratified into quartiles (Q1-Q4). Multivariable logistic regression models were used to examine the association between RAR and 1-year all-cause mortality. Generalized additive models (GAMs) assessed nonlinear relationships. Receiver operating characteristic (ROC) analysis evaluated the predictive performance of RAR compared with other markers such as NLR, PLR, and RDW. Results: Higher RAR levels were independently associated with an increased risk of 1-year all-cause mortality in patients with COPD. In the MIMIC-IV cohort, the highest quartile (Q4) had an OR of 7.90 (95% CI: 6.05-10.32; P < 0.001) compared to Q1. In the NHANES cohort, the OR for Q4 was 11.16 (95% CI: 4.42-28.18; P < 0.001). ROC analysis revealed that RAR achieved a higher area under the curve (AUC) (0.801 in MIMIC-IV and 0.787 in NHANES) than other markers, indicating superior discriminatory ability. Conclusion: RAR serves as an independent predictor of 1-year all-cause mortality in patients with COPD. By integrating indicators of systemic inflammation and nutritional status, RAR provides a reliable tool for clinical risk stratification.