Associations Between Weight Loss, Kidney Function Decline, and Risk of ESRD in the Chronic Kidney Disease in Children (CKiD) Cohort Study

Background: Anorexia and malnutrition are associated with poor outcomes in children with chronic kidney disease (CKD). Study Design: Observational cohort study. Setting & Participants: We assessed changes in body mass index (BMI) as kidney function declines and its association with risk for end-stage renal disease (ESRD) among 854 participants followed between 2005 to 2013 in the CKD in Children (CKiD) Study. Predictors: Repeated measurements of estimated glomerular filtration rate (eGFR) by serum creatinine concentration in our trajectory analysis using mixed models; change in BMI z score (per year) after eGFR decreased to < 35 mL/min/1.73 m(2) in logistic regression models. Outcomes: Repeated measurements of BMI z score (as a reflection of weight status) in our trajectory analysis; ESRD in logistic regression models. Results: During amean longitudinal follow-up of 3.4 years, BMI z scores remained stable until eGFR decreased to < 35 mL/min/1.73 m(2). When eGFR decreased to < 35 mL/min/1.73 m(2), a mean decline in BMI z score of 0.13 (95% CI, 0.09-0.17) was noted with each 10-mL/min/1.73 m(2) further decline in eGFR. This was statistically significantly different from the weight trajectory when eGFR was >= 35 mL/min/1.73 m(2) (P < 0.001). Among children and adolescents with significant weight loss (defined as decline in BMI z score >0.2 per year) after eGFR decreased to < 35 mL/min/1.73 m(2), the odds of ESRD was 3.28 (95% CI, 1.53-7.05) times greater compared with participants with stable BMI z scores (BMI z score change per year of 0-0.1). Limitations: Observational nature of our study, lack of longitudinal assessments of inflammatory markers. Conclusions: In children and adolescents with CKD, weight loss mostly occurs when eGFR decreases to < 35 mL/min/1.73 m(2), and this weight loss was associated with higher risk for ESRD. Further studies are needed to define the reasons for the association between weight loss and more rapid progression to ESRD in children and adolescents.