Association of hyperphosphatemia with an increased risk of sudden death in patients on hemodialysis: Ten-year outcomes of the Q-Cohort Study

Background and aims: Sudden death is one of the most common causes of death among patients on hemodialysis. Although hyperphosphatemia is a well-known risk factor for cardiovascular and all-cause deaths, the studies focusing on the relationship between serum phosphate levels and the risk of sudden death are limited. This study aimed to clarify the relationship between serum phosphate levels and the risk of sudden death in patients on hemodialysis. Methods: This is a multicenter, longitudinal, and observational study. A total of 3505 patients, registered in the Q-Cohort Study, who underwent maintenance hemodialysis, and were followed up for 10 years, were included. Patients were divided into quartiles on the basis of baseline serum phosphate levels: Q1 (n = 886), <4.2 mg/dL; Q2 (n = 837), 4.2–4.8 mg/dL; Q3 (n = 908), 4.9–5.6 mg/dL; and Q4 (n = 874), ≥5.7 mg/dL. Associations between baseline serum phosphate levels and sudden death were analyzed using the Cox proportional hazards model and the Fine–Gray regression model. Results: During the follow-up period, 227 patients died from sudden death. The risk for sudden death was significantly higher in the highest quartile (Q4) than in the lowest quartile (Q1) as the reference group (multivariable-adjusted hazard ratios and 95% confidence intervals: Q1, 1.00; Q2, 1.15 [0.77–1.70], Q3, 1.31 [0.89–1.93], and Q4, 1.72 [1.14–2.59]; hazard ratio for every 1-mg/dL increase in the serum phosphate level, 1.23 [1.09–1.39]; p < 0.001). Conclusions: Hyperphosphatemia is independently associated with an elevated risk of sudden death in patients on hemodialysis.