Association of red blood cell distribution width to albumin ratio with all-cause and cardiovascular mortality among adults with MASLD

Metabolic dysfunction-associated steatotic liver disease (MASLD) is a growing global health burden. Identifying robust prognostic biomarkers is crucial for early risk stratification. The red blood cell distribution width to albumin ratio (RAR) has emerged as a potential biomarker reflecting inflammation and nutritional status. This study aimed to evaluate the association between RAR and both all-cause and cardiovascular mortality among adults with MASLD. Data from the National Health and Nutrition Examination Survey 1999–2018 were analyzed. MASLD was defined using the United States Fatty Liver Index (USFLI ≥ 30), combined with cardiometabolic criteria. Participants were categorized into RAR quartiles. Weighted Cox proportional hazards models, Fine-Gray competing risk models, and restricted cubic splines were employed to the association between RAR and mortality. Stratified and sensitivity analyses were conducted to test robustness. Among 6,287 MASLD patients (mean age 51.39 years, 42.69% female), there were 1,161 all-cause deaths and 324 cardiovascular deaths over a median follow-up of 9.2 years. In the fully adjusted Model 3, individuals in the highest RAR quartile had a higher risk of all-cause mortality (hazard ratio [HR] = 2.41, 95% confidence interval [CI] = 1.87–3.10, P < 0.001) and cardiovascular mortality (HR = 3.39, 95% CI = 2.17–5.31, P < 0.001) compared to those in the lowest quartile. Each unit increase in RAR was associated with a 93% increase in all-cause mortality (HR = 1.93, 95% CI = 1.62–2.30, P < 0.001) and a 130% increase in cardiovascular mortality (HR = 2.30, 95% CI = 1.83–2.90, P < 0.001). No significant nonlinear associations were found. A significant age interaction was observed in all-cause mortality ( P for interaction < 0.05), with stronger associations seen among younger individuals. Sensitivity analyses confirmed the robustness of these findings. Higher RAR levels were significantly associated with increased all-cause and cardiovascular mortality in adults with MASLD. RAR holds potential as a risk stratification tool for MASLD adults in clinical practice.