STOCKHOLM—Obesity is a strong risk factor for the decline in residual renal function (RRF) after patients start dialysis, researchers in The Netherlands say.
The finding is important because prior studies have shown that preservation of residual renal function in dialysis patients is associated with better survival, noted lead investigator Christiane Drechsler, MD, of Leiden University Medical Center in Leiden.
It is unclear, however, whether obese dialysis patients would benefit from attempts to normalize their weight, given that some data suggest that high BMI is associated with improved survival, she observed. She reported preliminary findings here at the 2008 congress of the European Renal Association-European Dialysis and Transplant Association.
Dr. Drechsler and her colleagues studied 1,271 dialysis patients with RRF. Baseline glomerular filtration rate (GFR) was highest (5.8 mL/min) among the 122 obese patients. It was 5.1 mL/min among the 417 overweight patients, 4.6 mL/min among the 620 normal-weight patients, and 3.5 mL/min among the 112 underweight patients. Within 18 months after patients started dialysis, patients with normal weight had a mean GFR decline of 1.2 mL/min per year.
Compared with these patients, the adjusted loss of GFR was 0.5 mL/min per year higher for overweight patients and 1.2 mL/min per year higher for obese patients. For underweight patients, GFR decline was 0.6 mL/min per year lower than in normal-weight patients.
Additionally, underweight was in crude analyses associated with a 50% increased risk of anuria, compared to patients with normal weight. However, this was mainly due to the difference in baseline diuresis.
Dr. Drechsler’s group defined underweight as a BMI (kg/m2) less than 20, normal weight as a BMI of 20 or higher but less than 25, overweight as a BMI of 25 or higher but less than 30, and obesity as a BMI of 30 or higher.