Association between Potential Renal Acid Load and 10-Year Mortality in Patients on Hemodialysis

Background: Dietary intake has long been known to influence acid-base balance. Recently, higher dietary acid load (DAL) has been reported to be associated with increased risk of incidence and progression of chronic kidney disease. However, the association between DAL and mortality in patients on maintenance hemodialysis (MHD) has not been evaluated. In this study, we investigated the association between DAL and mortality and analyzed the kinds of food that affect DAL in Japanese patients on MHD. Methods: We retrospectively analyzed baseline laboratory data, self-administered diet history questionnaire results, and 10-year mortality rates in 44 patients (26 men, 67.9±10.4 years) on MHD who participated in a randomized, double-blind, crossover pilot trial of rice endosperm protein supplementation which was conducted in 2013. DAL was estimated from nutrition intake using potential renal acid load (PRAL). Patients were divided into tertiles according to PRAL score to explore its association with all-cause mortality. Cox proportional hazards regression with adjustment for age and sex was performed to estimate hazard ratios (HRs) and 95% confidence intervals (CIs) for all-cause mortality. In addition, multivariable logistic regression was performed to estimate odds ratios (ORs) for the kinds of food that significantly affected PRAL score. Results: During the 10-year observation period, a total of 19 patients (43%) died. Mean PRAL score was 11.0 mEq/L. A higher PRAL score was significantly associated with higher all-cause mortality. The multivariable-adjusted HR for all-cause mortality in the highest tertile compared with the lowest tertile of PRAL score was 3.88 (95% CI, 1.10-13.61). Multiple logistic regression analysis showed a significant association between higher PRAL score and lower intake of green and yellow vegetables (OR, 5.40; 95%CI, 1.37-21.26) and fruits (OR, 4.76; 95% CI, 1.30-16.76). Conclusion: Our findings suggested that high PRAL score is positively associated with all-cause mortality in patients on MHD. Low intake of fruits and vegetables would increase PRAL score and might affect the risk of mortality in Japanese patients on MHD. Further studies, including prospective ones, are needed to confirm whether DAL affects mortality in patients on MHD.