Serum phosphate and mortality in incident dialysis patients in Australia and New Zealand

Aim Hyperphosphataemia is associated with increased adverse outcomes, including mortality. Re‐examining this association using up‐to‐date data reflecting current and real‐world practices, across different global regions and in both haemodialysis and peritoneal dialysis patients, is important. Methods We describe the association between serum phosphate and all‐cause and cardiovascular mortality in incident dialysis patients between 2008 and 2018 using the Australia and New Zealand Dialysis and Transplant (ANZDATA) Registry. Time‐dependent Cox proportionate hazards models were used. Models were adjusted for available covariates and fitted for the overall cohort, and also each dialysis modality. Results 31 989 patients were followed over 97 122 person‐years at risk (mean age at first dialysis 61 years, 38% female, 67% haemodialysis). We observed a U‐shaped association between serum phosphate and all‐cause mortality. In the fully adjusted model, categories of serum phosphate above and below 1.25–1.99 mmol/L were associated with progressively higher risk, reaching a hazard ratio of 2.13 (95% CI 1.93–2.36, p