Effect of uric acid levels on mortality in Japanese peritoneal dialysis patients.

Background: Unlike the situation in the general population, most studies of patients receiving hemodialysis have reported lower uric acid (UA) as associated with higher mortality. However, the relationship between UA level and mortality remains unclear among patients receiving peritoneal dialysis (PD).

Methods: We collected baseline data for 4742 prevalent PD patients (age, 63 ± 14 years; male, 61.5%; diabetes, 29.1%; median dialysis duration, 28 months) from a nationwide dialysis registry in Japan at the end of 2012. One-year all-cause and cardiovascular (CV) mortality and mortality caused by infectious disease were assessed using Cox regression analysis and competing-risks regression analysis, respectively. We used multiple imputation to deal with missing covariate data.

Results: Within 1 year, 379 patients (8.0%) died, including 129 patients (2.7%) from CV causes and 95 patients (2.0%) from infectious disease. In multivariate analysis, serum UA, treated as a continuous variable, was not associated with any outcome. Conversely, both lower (<297 µmol/L) and higher (≥476 µmol/L) UA levels were independently associated with higher all-cause mortality compared to the reference group (416 to <446 µmol/L) in analyses where serum UA was treated as a categorical variable. Body mass index (BMI) affected the association between serum UA and all-cause mortality (interaction = 0.049).

Conclusions: A U-shaped relationship appears to exist between UA levels and all-cause mortality among Japanese PD patients. Additionally, lower BMI significantly enhanced the effect of UA levels on mortality.