Effects of Promoting Long-term, Exclusive Breastfeeding on Adolescent Adiposity, Blood Pressure, and Growth Trajectories: A Secondary Analysis of a Randomized Clinical Trial

Importance Evidence that breastfeeding reduces child obesity risk and lowers blood pressure (BP) is based on potentially confounded observational studies.Objective To investigate the effects of a breastfeeding promotion intervention on adiposity and BP at age 16 years, and on longitudinal growth trajectories from birth.Design Cluster-randomized Promotion of Breastfeeding Intervention Trial.Setting Belarusian maternity hospitals and affiliated polyclinics (the clusters), allocated in 1996-1997 into intervention (n=16) or control arms (n=15).Participants 17,046 breastfeeding mother-infant pairs, of whom 13,557 (79.5%) children were followed-up at 16 years. Intervention Breastfeeding promotion, modeled on the Baby-Friendly Hospital Initiative.Main Outcome Measures Body mass index (BMI); fat and fat-free mass indices (FMI and FFMI) and percent body fat from bioimpedance; waist circumference; overweight and obesity; height; BP; and longitudinal growth trajectories. The primary analysis was modified intention-to-treat (without imputation for losses to follow-up), accounting for within-clinic clustering.Results The intervention substantially increased breastfeeding duration and exclusivity compared with the control arm (exclusively breastfed: 45% vs 6% at 3 months, respectively). Mean differences at 16 years between intervention and control groups were: 0.21 kg/m2 (95%CI:0.06, 0.36) for BMI; 0.21 kg/m2 (-0.03, 0.44) for FMI; 0.00 kg/m2 (-0.21, 0.22) for FFMI; 0.71% (-0.32, 1.74) for percent body fat; -0.73 cm (-2.48, 1.02) for waist circumference; 0.05 cm (-0.85, 0.94) for height; -0.54 mmHg (-2.40, 1.31) for systolic BP; and 0.71 mmHg (-0.68, 2.10) for diastolic BP. The odds ratio for overweight/obesity (BMI≥85th vs <85th percentile) was 1.14 (1.02, 1.28) and for obesity (BMI≥95th vs <95th percentile) was 1.09 (0.92, 1.29). The intervention resulted in a more rapid rate of gain in post-infancy height (1 to 2.8 years), weight (2.8 to 14.5 years), and BMI (2.8 to 8.5 years) compared to the control arm. The intervention had little effect on BMI z-score changes after 8.5 years.Conclusions A randomized intervention that increased the duration and exclusivity of breastfeeding did not lower adolescent obesity risk or BP. On the contrary, the prevalence of overweight/obesity was higher in the intervention arm. All mothers initiated breastfeeding, so findings may not apply to comparisons of the effects of breastfeeding versus formula-feeding. Trial Registration isrctn.org: ISRCTN37687716; and clinicaltrials.gov: NCT01561612Keywords: Breastfeeding, adiposity, stature, blood pressure, growth, childhood