Dietary Potassium Intake and Mortality in Long-term Hemodialysis Patients

Abstract

Background Hyperkalemia has been associated with higher mortality in long-term hemodialysis (HD) patients. There are little data concerning the relationship between dietary potassium intake and outcome. Study design Mortality-predictability of dietary potassium intake from reported food items, estimated from the Block Food Frequency Questionnaire (FFQ) at the start of the cohort, were examined in a 5-year (2001–06) cohort of 224 HD patients in Southern California using Cox proportional hazards regression. Setting and Participants 224 long-term hemodialysis patients from 8 DaVita dialysis clinics. Predictors Dietary potassium intake ranking using Block FFQ Outcomes 5-year survival Results HD patients with higher potassium intakes had greater dietary energy, protein and phosphorus intakes and higher predialysis serum potassium and phosphorus. Greater dietary potassium intake was associated with significantly increased death hazard ratios (HR) in the unadjusted models and after incremental adjustments for case-mix, nutritional factors (including 3-month averaged predialysis serum creatinine, potassium and phosphorus, body mass index, normalized protein nitrogen appearance, and energy, protein and phosphorus intake) and inflammatory markers. The HR (95% confidence intervals) of death across the 3 higher quartiles of dietary potassium intake in the fully adjusted model (compared to the lowest quartile) were 1.4 (0.6–3.0), 2.2 (0.9–5.4) and 2.4 (1.1–7.5), respectively (p for trend: 0.03). Restricted cubic spline analyses confirmed the incremental mortality-predictability of higher potassium intake. Limitations FFQs may underestimate individual potassium intake and should be used to rank dietary intake across population. Conclusions Higher dietary potassium intake is associated with increased death risk in long-term HD patients, even after adjustments for serum potassium and dietary protein, energy and phosphorus intake and nutritional and inflammatory markers. The potential role of dietary potassium in the high mortality rate of HD patients warrants clinical trials.

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