Association between neonatal serum bilirubin and childhood obesity in preterm infants.

Background: Serum bilirubin levels are inversely associated with obesity in adults. We are interested in whether neonatal jaundice is associated with childhood obesity in preterm infants.

Methods: Data were obtained from the US Collaborative Perinatal Project. Neonatal bilirubin levels were used as exposure factors for obesity at age 7 years. Logistic regression models were used to control for potential confounders and calculate odds ratios (ORs). A generalized estimating equation (GEE) model was used to correct for intracluster correlation coefficient. SAS was used for all statistical analyses.

Results: In the study subjects, 865 of 5019 preterm infants were obese at age 7 years. While neonatal total serum bilirubin (TSB) rose 1 mg/dl, body mass index (BMI) increased 0.03 kg/m (95% confidence interval (CI) 0.02, 0.04). Compared with infants with TSB <3 mg/dl, the ORs (95% CIs) for obesity in infants with 3 mg/dl≤ TSB <6 mg/dl, 6 mg/dl≤ TSB <9 mg/dl, 9 mg/dl≤ TSB <12 mg/dl and TSB ≥12 mg/dl were, respectively, 1.18 (0.87, 1.59), 1.25 (0.93, 1.67), 1.52 (1.11, 2.09), and 1.67 (1.22, 2.07). By using subtypes of bilirubin as exposure factors and the GEE model to correct for intracluster correlation coefficient, similar trends of associations were observed.

Conclusion: Neonatal bilirubin levels have positive trends of associations with childhood obesity in preterm infants.