Dialysis Association of Body Mass Index With Decline in Residual Kidney Function After Initiation of Dialysis Christiane Drechsler, MD, 1 Renée de Mutsert, MSc, 1 Diana C. Grootendorst, PhD, 1 Elisabeth W. Boeschoten, MD, PhD, 2 Raymond T. Krediet, MD, PhD, 3 Saskia le Cessie, PhD, 4 Christoph Wanner, MD, 5 and Friedo W. Dekker, PhD, 1 for the NECOSAD Study Group Background: Obesity is a risk factor for loss of kidney function in the general population, but it is unknown whether it proceeds to affect residual kidney function when patients require dialysis. Our aim was to study the effects of body mass index (BMI) on decline in kidney function and risk to develop anuria after initiation of dialysis therapy. Study Design: Prospective cohort study. Setting & Participants: 1,271 incident dialysis patients from 38 centers in The Netherlands participating in the Netherlands Cooperative Study on the Adequacy of Dialysis (NECOSAD) between 1997 and 2006. Predictor: BMI assessed at 3 months after the initiation of dialysis therapy (baseline) and categorized into 4 groups: less than 20, 20 or greater to 25, 25 or greater to 30, and 30 or greater kg/m 2 . Outcomes & Measurements: The decrease in measured glomerular filtration rate (mGFR) was determined by means of linear mixed models and adjusted for age, sex, primary kidney disease, dialysis modality, smoking, cardiovascular disease, and normalized protein nitrogen appearance and additionally for proteinuria, blood pressure, and baseline mGFR. Cox regression analysis was used to calculate hazard ratios for the development of anuria. Results: Patients had a mean age of 59  15 years, BMI of 24.8  4.1 kg/m 2 , and mGFR of 4.7  3.3 mL/min. During 18 months of follow-up, the decrease in mGFR in patients with normal weight was 1.2 mL/min/y (95% confidence interval [CI], 0.7 to 1.6). Compared with those values, adjusted losses of mGFR were 0.4 mL/min/y (95% CI, 0.02 to 0.8) greater for overweight and 1.2 mL/min/y (95% CI, 0.5 to 1.8) greater for obese patients. In contrast, the decrease in underweight patients was 0.6 mL/min/y (-0.1 to 1.3) less. Anuria occurred in 297 patients; the risk was similar among BMI groups after adjustment for confounders and baseline diuresis. Limitations: Patients with missing BMI or mGFR values at baseline were excluded. Conclusion: Obesity is a strong risk factor for the decline in kidney function after initiation of dialysis therapy. Whether obese dialysis patients might benefit from a healthy weight reduction needs to be studied further. Am J Kidney Dis 53:1014-1023. © 2009 by the National Kidney Foundation, Inc. INDEX WORDS: Obesity; body mass index; kidney function; glomerular filtration rate; dialysis; cohort study. R esidual kidney function is beneficial for dialysis patients. Greater residual kidney function is associated with lower mortality risk and better quality of life. 1-6 Therefore, its preser- vation is important among the strategies to re- duce mortality and improve the quality of life of long-term dialysis patients. Obesity is a risk factor for the decline in kidney function in the general population. Sev- eral studies have found excess weight to be associated with a greater risk of developing chronic kidney disease 7-12 and end-stage renal disease (ESRD). 13,14 The underlying pathophysi- ological mechanisms may be the development of glomerular hyperfiltration and glomerulo- megaly, 15-17 and structural changes in the kidney are also referred to as obesity-related glomeru- lopathy. 18 These consequences of the negative From the 1 Department of Clinical Epidemiology, Lei- den University Medical Center, Leiden; 2 Hans Mak Insti- tute, Naarden; 3 Department of Nephrology, Amsterdam Medical Center, Amsterdam; 4 Department of Medical Statistics, Leiden University Medical Center, Leiden, The Netherlands; and 5 Divison of Nephrology, University of Würzburg, Würzburg, Germany. Received July 16, 2008. Accepted in revised form Novem- ber 11, 2008. Originally published online as doi: 10.1053/j.ajkd.2008.11.027 on February 17, 2009. A list of the NECOSAD study investigators appears at the end of this article. Address correspondence to Christiane Drechsler, MD, Leiden University Medical Center, Department of Clinical Epidemiology, PO Box 9600, 2300 RC Leiden, The Nether- lands. E-mail: c.drechsler@lumc.nl © 2009 by the National Kidney Foundation, Inc. 0272-6386/09/5306-0015$36.00/0 doi:10.1053/j.ajkd.2008.11.027 American Journal of Kidney Diseases, Vol 53, No 6 (June), 2009: pp 1014-1023 1014