Increase in BMI over time is associated with fluid overload and signs of wasting in incident peritoneal dialysis patients

Objectives: Peritoneal dialysis (PD) patients may suffer changes in nutritional status after starting PD. Several markers can be used to evaluate these modifications, such as body mass index (BMI), serum albumin, and serum creatinine. Fluid overload should be considered because it can overestimate or underestimate nutritional status. The objective of this study was to evaluate the BMI changes over time in incident PD patients and identify interactions among BMI, signs of fluid overload, serum albumin, and serum creatinine.

Design: The study included a cohort of 1,997 incident PD patients of the BRAZPD recruited from 2004 to 2007. Sociodemographic data and BMI classification were obtained at baseline. The evolutions of BMI and body weight were assessed over a period of 29 months. Changes in the evolution were analyzed when a patient presented with albumin < 3.8 g/dL, creatinine < 7.0 mg/dL, or the presence of edema. Data analysis was performed using linear mixed-effects regression models as the main statistical procedure.

Results: BMI increased over time (29 months) by an average of 0.05 kg/m(2) per month, and body weight increased by 0.11 kg/month for a total increase of 3.08 kg. BMI decreased by 0.12 kg/m(2) in the presence of albumin < 3.8 g/dL and by 0.38 kg/m(2) in the presence of creatinine < 7.0 mg/dL. BMI increased by 0.61 kg/m(2) in the presence of edema. BMI increased in the presence of edema and albumin < 3.8 mg/dL or edema and creatinine < 7.0 mg/dL.

Conclusions: There is a mean increase in the BMI of incident PD patients over time, and these changes may be, at least partly, due to fluid overload, leading to distortions of body weight. When the patients presented with lower serum albumin or creatinine levels, the BMI values were reduced, suggesting that a reduction in lean mass and an increase in fat mass may be occurring in these patients.