Alterations of body composition patterns in pre-dialysis chronic kidney disease patients

Purpose Body mass index (BMI) might be an inaccurate estimate of detailed body composition because it does not differentiate muscle from fat mass. We sought to understand the effect of kidney function decline on alterations of body composition patterns among pre-dialysis CKD patients. Methods Body composition was measured by multi-frequency bioelectrical impedance analysis (BIA). Low muscle mass was defined as appendicular muscle mass (kg) adjusted to the square of height in meters < 7.0 and 5.7 kg/m(2)in men and women, respectively. The designation of obesity by percent body fat was >= 25% in men and >= 30% in women. Alternative definition of obesity by BMI was >= 25 kg/m(2). Visceral fat area cut point was > 100 cm(2)as indication of abdominal obesity. Results Mean age of participants was 61.3 +/- 13.8 years (n = 103). The average glomerular filtration rate (GFR) was 34.0 +/- 24.2 mL/min/1.73 m(2). By BIA, the prevalence of low muscle mass was 16.5% and was comparable between both sexes. Obesity by percent body fat was identified in 71.8% of patients and 38.2% had abdominal obesity. Using BMI criteria, the prevalence of obesity was less common (55.3%) and associated with under-identification of obesity by 27.0%. Low muscle mass and obesity by percent body fat were more prevalent in the more advanced stages of CKD. By multivariable regression analysis, a 10 mL/min/1.73 m(2)decline in GFR was associated with a 0.59 kg reduction of total body muscle mass (p = 0.01), but not fat mass or BMI, after adjusting for confounders. Conclusion Low muscle mass was prevalent among pre-dialysis CKD patients. BMI commonly classified obese CKD individuals by percent body fat criteria as non-obese. The reduction of muscle mass was associated with GFR decline.