Prognostic Value of the Albumin-to-Alkaline Phosphatase Ratio for All-Cause Mortality in Older Patients Initiating Hemodialysis: A Multicenter Cohort Study

Background Serum albumin and alkaline phosphatase (ALP) are established biomarkers of adverse outcomes. The albumin-to-alkaline phosphatase ratio (AAPR) has demonstrated prognostic value in various chronic diseases, but its relevance to mortality in older end-stage kidney disease (ESKD) patients remains unclear. Methods We analyzed ESKD patients aged ≥ 70 years who initiated hemodialysis at 16 university hospitals in South Korea. Patients were stratified into AAPR tertiles (low ≤ 0.224; moderate 0.225–0.440; high > 0.440), and associations with all-cause mortality were assessed using Kaplan–Meier survival and Cox proportional hazards models adjusted for demographic, clinical, and laboratory factors. Results The study included 1,990 patients with a mean age of 77.4 ± 5.3 years, of whom 55.7% were male. During a median follow-up of 5.9 years, 1,197 patients (60.1%) died. Mortality was highest in the lowest AAPR tertile (66.6%) and lowest in the highest tertile (53.3%; P  = 0.012). In fully adjusted Cox proportional hazards models, patients in the lowest AAPR tertile had a significantly higher risk of all-cause mortality compared with those in the highest tertile (HR 1.28, 95% CI 1.08–1.51, P  = 0.004). Furthermore, lower AAPR levels as a continuous variable were independently associated with increased mortality risk (HR 1.08, 95% CI 1.02–1.13; P  = 0.008), with a non-linear association observed in restricted spline analysis. Subgroup analyses demonstrated a consistent prognostic trend of AAPR across all clinical subgroups, without significant interaction effects. Conclusion Lower AAPR independently predicts higher all-cause mortality in older ESKD patients initiating hemodialysis.