Ratio of red blood cell distribution width to albumin level and mortality outcomes in population with chronic kidney disease

Background Chronic kidney disease (CKD) is one of the major public health issues worldwide. The red blood cell distribution width to albumin ratio (RAR) has emerged as a reliable and accessible marker to reflect inflammation and nutrition, suggesting underlying associations with prognosis in CKD population. Methods Using data from the National Health and Nutrition Examination Survey 1999 to 2018 and the National Death Index, 3965 patients with CKD were enrolled in this study. Weighted Cox proportional hazards regression models were employed to investigate the associations of RAR with all-cause mortality, cardiovascular disease (CVD) mortality, and cancer mortality. Restricted cubic spline (RCS) analysis was used to detect non-linear relationships and threshold effects. Stratified analysis was conducted to evaluate interactions of potential variables. Results Across the entire follow-up period, a total of 1163 fatal events occurred. Weighted Cox analysis revealed RAR was independently associated with all-cause mortality (HR, 1.81, 95%CI, 1.60 - 2.06, P < 0.001), CVD mortality (HR, 1.89, 95%CI, 1.59 - 2.26, P < 0.001), and cancer mortality (HR, 1,76, 95%CI, 1.46 - 2.11, P < 0.001). RCS analysis demonstrated non-linear relationships for all-cause mortality (P for non-linear < 0.001) and CVD mortality (P for non-linear < 0.001), while a linear relationship was observed for cancer mortality (P for non-linear = 0.113). Subgroup analysis identified age, gender, urine albumin-to-creatinine ratio and poverty income ratio as potential interactive factors. Conclusion These findings suggested that RAR had robust associations with both all-cause and cause-specific mortality in CKD patients. Future clinical trials are required to elucidate the underlying processes.