Dietary Potassium Intake and Mortality in Long-term Hemodialysis Patients

Noori, Nazanin; Kalantar-Zadeh, Kamyar; Kovesdy, Csaba P.; Murali, Sameer B.; Bross, Rachelle; Nissenson, Allen R.; Kopple, Joel D.

doi:10.1053/j.ajkd.2010.03.022

« Previous Next »American Journal of Kidney Diseases
Volume 56, Issue 2 , Pages 338-347, August 2010

Dietary Potassium Intake and Mortality in Long-term Hemodialysis Patients

Nazanin Noori, MD, PhD
- Harold Simmons Center for Chronic Disease Research and Epidemiology, Los Angeles Biomedical Research Institute at Harbor-UCLA Medical Center, Torrance, CA
- Division of Nephrology and Hypertension, Los Angeles Biomedical Research Institute at Harbor-UCLA Medical Center, Torrance, CA
Kamyar Kalantar-Zadeh, MD, MPH, PhD
- Harold Simmons Center for Chronic Disease Research and Epidemiology, Los Angeles Biomedical Research Institute at Harbor-UCLA Medical Center, Torrance, CA
- Division of Nephrology and Hypertension, Los Angeles Biomedical Research Institute at Harbor-UCLA Medical Center, Torrance, CA
- David Geffen School of Medicine at UCLA and UCLA School of Public Health, Los Angeles, CA
- Address correspondence to Kamyar Kalantar-Zadeh, MD, MPH, PhD, Harold Simmons Center for Chronic Disease Research and Epidemiology, Los Angeles Biomedical Research Institute at Harbor-UCLA Medical Center, 1124 West Carson St, C1-Annex, Torrance, CA 90502
Csaba P. Kovesdy, MD
- Salem Veterans Affairs Medical Center, Salem, VA
Sameer B. Murali, MD
- Harold Simmons Center for Chronic Disease Research and Epidemiology, Los Angeles Biomedical Research Institute at Harbor-UCLA Medical Center, Torrance, CA
Rachelle Bross, RD, PhD
- Division of Nephrology and Hypertension, Los Angeles Biomedical Research Institute at Harbor-UCLA Medical Center, Torrance, CA
Allen R. Nissenson, MD
- David Geffen School of Medicine at UCLA and UCLA School of Public Health, Los Angeles, CA
- DaVita Inc, Lakewood, CO
Joel D. Kopple, MD
- Harold Simmons Center for Chronic Disease Research and Epidemiology, Los Angeles Biomedical Research Institute at Harbor-UCLA Medical Center, Torrance, CA
- Division of Nephrology and Hypertension, Los Angeles Biomedical Research Institute at Harbor-UCLA Medical Center, Torrance, CA
- David Geffen School of Medicine at UCLA and UCLA School of Public Health, Los Angeles, CA

Received 11 November 2009; accepted 3 March 2010. published online 28 June 2010.

Background

Hyperkalemia has been associated with higher mortality in long-term hemodialysis (HD) patients. There are few data concerning the relationship between dietary potassium intake and outcome.

Study Design

The mortality predictability of dietary potassium intake from reported food items estimated using the Block Food Frequency Questionnaire (FFQ) at the start of the cohort was examined in a 5-year (2001-2006) cohort of 224 HD patients in Southern California using Cox proportional hazards regression.

Setting & Participants

224 long-term HD patients from 8 DaVita dialysis clinics.

Predictors

Dietary potassium intake ranking using the Block FFQ.

Outcomes

5-year survival.

Results

HD patients with higher potassium intake had greater dietary energy, protein, and phosphorus intakes and higher predialysis serum potassium and phosphorus levels. Greater dietary potassium intake was associated with significantly increased death HRs in unadjusted models and after incremental adjustments for case-mix, nutritional factors (including 3-month averaged predialysis serum creatinine, potassium, and phosphorus levels; body mass index; normalized protein nitrogen appearance; and energy, protein, and phosphorus intake) and inflammatory marker levels. HRs for death across the 3 higher quartiles of dietary potassium intake in the fully adjusted model (compared with the lowest quartile) were 1.4 (95% CI, 0.6-3.0), 2.2 (95% CI, 0.9-5.4), and 2.4 (95% CI, 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 the population.

Conclusions

Higher dietary potassium intake is associated with increased death risk in long-term HD patients, even after adjustments for serum potassium level; dietary protein; energy, and phosphorus intake; and nutritional and inflammatory marker levels. The potential role of dietary potassium in the high mortality rate of HD patients warrants clinical trials.

Index Words: Dietary potassium, food frequency questionnaire, mortality, hemodialysis