A prospective Netherlands Cooperative Study on the Adequacy of Dialysis (NECOSAD) found that obesity is strong risk factor for loss of residual kidney function after initiation of dialysis.

Dr. Christiane Drechsler, from Leiden University Medical Center, and team investigated 1271 patients starting dialysis treatment for the first time between 1997 and 2006 to find the effect of body mass index (BMI) on decline in kidney function and risk of anuria.

The patients grouped according to BMI determined at 3 months baseline after the start of dialysis were BMI less than 20 kg/m (underweight); BMI 20 to 25 (normal weight); BMI 25 to 30 (overweight); or BMI 30 or greater (obese).

The patients mean age was 59 years, mean BMI was 24.8, and mean glomerular filtration rate (mGFR) was 4.7 mL/min.

Dr. Drechsler and colleagues reported that overweight or obesity significantly increased the decline in kidney function during the 18 months after the initiation of dialysis therapy but underweight did not affect the kidney function.

Specifically, reference normal weight patients had a mean decrease in mGFR of 1.2 mL/min/year. Patients who were obese lost 1.2 mL/min more mGFR per year, reflecting a 100% greater loss of residual kidney function per year compared with patients with normal weight, the investigators point out.

Overweight patients lost 0.4 mL/min more mGFR per year, whereas underweight patients lost 0.6 mL/min less mGFR per year when compared to normal weight patients.

Among all BMI groups, the adjusted relative risk of anuria was similar. During the study period, a total of 297 patients developed anuria.

Future interventional studies are required to show whether obese dialysis patients might benefit from a healthy weight reduction, Dr. Drechsler and colleagues conclude.