Association of body size with health status in patients beginning dialysis.

BACKGROUND Greater weight-for-height has been associated with prolonged survival in patients with end-stage renal disease (ESRD) but not in the general population. The association between body size and health status has not been carefully evaluated. OBJECTIVES We compared the self-reported health status of 2467 participants in the Dialysis Morbidity and Mortality Study Wave 2 by using body mass index (BMI; in kg/m2) to approximate body size and composition. DESIGN BMI was categorized into 4 groups (<19, 19 to <25, 25 to <30, and > or = 30) corresponding to World Health Organization criteria for underweight, normal-weight, overweight, and obese status. We adjusted for demographic, clinical, and laboratory factors that may have confounded the association between body size and health status. RESULTS Scores on the physical component summary and the physical functioning scale were significantly lower for obese subjects than for those with normal weight or moderately high BMI after adjustment for demographic factors, comorbidity, and laboratory markers of nutritional status. Mental component summary and symptom scores were unrelated to BMI. The underweight group scored lower on many Medical Outcomes Study 36-Item Short Form scales than did the normal-weight group. CONCLUSIONS Whereas higher BMI has consistently been associated with enhanced dialysis-related survival, health status-particularly physical function-may be impaired by obesity. Additional longitudinal studies of body weight and composition are needed for a better understanding of the complex effects of obesity and undernutrition in persons with ESRD and advanced chronic kidney disease.