Overweight patients on hemodialysis have a survival advantage, a new study confirms.


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GLASGOW—A European study confirms that overweight and obese patients have a survival advantage on hemodialysis when compared with normal-weight patients, researchers reported. Furthermore, a weight loss of 3% over the first year of dialysis was associated with a higher mortality rate compared with patients whose weight remained stable or who gained weight.


“We know a high BMI in the general population is associated with an increased risk of cardiovascular disease and all-cause mortality, but in maintenance hemodialysis patients, baseline obesity paradoxically appears to be associated with improved survival,” lead investigator Charles Chazot, MD, of NephroCare in Tassin, France, told delegates here at the 43rd Congress of the European Renal Association-European Dialysis and Transplant Association.


Investigators analyzed data from approximately 6,000 end-stage renal failure patients treated in 85 dialysis centers in Portugal, France, and Italy. All patients had less than one month of previous renal replacement therapy and their BMI was classified according to World Health Organization criteria. At baseline, 46% of the cohort had a normal BMI (20-24.9 kg/m2) whereas 14% were underweight (BMI less than 20 kg/m2). Twenty-eight percent were overweight (BMI 25-29.9 kg/m2) and 11% were obese (BMI 30-39.9 kg/m2). Only 0.7% of the cohort was morbidly obese (BMI greater than 40 kg/m2), making interpretation of findings in this small subgroup difficult, Dr. Chazot noted. The prevalence of diabetes and coronary artery disease was significantly higher in overweight and obese patients compared with those in the underweight or normal BMI range.


Despite higher comorbidity rates in the overweight and obese groups, their risk of death was about 30% lower than that of underweight and normal-weight patients, and this survival advantage persisted after accounting for age, diabetes and other comorbidities.


The “reverse” relationship between BMI and survival in hemodialysis patients was first reported by French investigatorsin 1982, Dr. Chazot noted. Twenty-five years later—and in a population that is now significantly older with many more comorbidities than earlier dialysis populations—“this relationship is still present,” he said, “and this confirms the reverse epidemiology [concept] previously reported in U.S. hemodialysis patients.”


Kamyar Kalantar-Zadeh, MD, MPH, and his colleagues earlier this year reported in the American Journal of Clinical Nutrition (2006;83:202-210) that the risk of death was four times higher among maintenance hemodialysis patients with a body fat content of less than 12% compared with those who had a body fat content of 24%-36%. In the same study, the risk of death was also twice as high among patients who lost 1% of their body fat or less over a six month-interval compared to patients who gained at least 1% over the same time interval.