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

Abstract

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, setting, and participants: Cluster-randomized Promotion of Breastfeeding Intervention Trial. Belarusian maternity hospitals and affiliated polyclinics (the clusters) were allocated into intervention (n = 16) or control arms (n = 15) in 1996 and 1997. The trial participants were 17 046 breastfeeding mother-infant pairs; of these, 13 557 children (79.5%) were followed up at 16 years of age between September 2012 and July 2015.

Interventions: Breastfeeding promotion, modeled on the Baby-Friendly Hospital Initiative.

Main outcomes and measures: Body mass index (BMI, calculated as weight in kilograms divided by height in meters squared); fat and fat-free mass indices and percentage of 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: We examined 13 557 children at a median age of 16.2 years (48.5% were girls). 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 (95% CI, 0.06-0.36) for BMI; 0.21 kg/m2 (95% CI, -0.03 to 0.44) for fat mass index; 0.00 kg/m2 (95% CI, -0.21 to 0.22) for fat-free mass index; 0.71% (95% CI, -0.32 to 1.74) for percentage body fat; -0.73 cm (-2.48 to 1.02) for waist circumference; 0.05 cm (95% CI, -0.85 to 0.94) for height; -0.54 mm Hg (95% CI, -2.40 to 1.31) for systolic BP; and 0.71 mm Hg (95% CI, -0.68 to 2.10) for diastolic BP. The odds ratio for overweight/obesity (BMI ≥85th percentile vs <85th percentile) was 1.14 (95% CI, 1.02-1.28) and the odds ratio for obesity (BMI ≥95th percentile vs <95th percentile) was 1.09 (95% CI, 0.92-1.29). The intervention resulted in a more rapid rate of gain in postinfancy height (1 to 2.8 years), weight (2.8 to 14.5 years), and BMI (2.8 to 8.5 years) compared with the control arm. The intervention had little effect on BMI z score changes after 8.5 years.

Conclusions and relevance: A randomized intervention that increased the duration and exclusivity of breastfeeding was not associated with lowered 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 vs formula feeding.

Trial registration: isrctn.org: ISRCTN37687716; and clinicaltrials.gov: NCT01561612.

Conflict of interest statement

Conflict of Interest Disclosures: None

Figures

Figure 1. Flow diagram of progress of clusters and individuals through PROBIT recruitment and follow-up phases I, II, III and IV

aDuring PROBIT III, 6 deaths were reported in the intervention arm. Data checking during PROBIT IV found one of these children had been incorrectly reported as deceased and data were amended. bOf the 13557 seen at PROBIT IV, 12072 were seen at both PROBIT II & III, 274 were not seen at either PROBIT II & III, 449 were seen at PROBIT II but not seen at III, and 762 were seen at PROBIT III but not seen at II. Of the 3489 children randomized but not followed up at 16 years, 267 attended the excluded site, 116 died since randomization, 2674 were lost to follow- up, and 432 were unable or unwilling to come for their clinic visit.

Figure 2. Predicted difference in mean weight, height and BMI z-score (with 95% confidence intervals) in the intervention arm compared to control arm

Predicted size in the intervention compared to the control at age 1, 6.5, 11.5 and 16.2 years