Long-term benefits of breastfeeding on brain and body development among 9–10-year-olds: modulated by socioeconomic environment

Importance It is yet unknown if breastfeeding (bf) benefits, to brain and body development of children, persist into peri-adolescence and vary by socioeconomic environments (SEEs). Objective We aim to investigate SEE-independent and SEE-modulated relationships between bf duration and child brain structure and adiposity markers during peri-adolescence. Design, setting and participants This was a cross-sectional study of children aged 9–10 enrolled in the multi-center Adolescent Brain and Cognitive Development (ABCD) Study®. Exposure(s) Bf duration was self-reported. Neighborhood-level SEE was assessed using area deprivation index (ADI). Main Outcome(s) T1-weighted magnetic resonance imaging was used to assess global brain measures: volumes of white, cortical, and subcortical gray matter (GM), cortical thickness, and surface area (SA). Adiposity markers included age- and sex-specific body mass index (BMI z- scores), waist circumference, and waist-to-height ratio (WHtR). Mixed effects models examined associations of bf duration with brain structure and adiposity markers controlling for sociodemographic, pre- and post-natal covariates. Stratified analysis was performed by tertiles of ADI. Results The sample consisted of 7,511 children (51.7% males; 18.8% no bf, 35.3% 1-6 months, 24.9% 7-12 months, 21.0% >12 months). Child’s total SA (β (95% CI) = 0.053 (0.033, 0.074); FDR corrected P <0.001), cortical (β (95% CI) = 0.021 (0.010, 0.032); FDR corrected P <0.001) and subcortical GM volume (β (95% CI) = 0.016 (0.003, 0.030); FDR corrected P <0.001) increased monotonically with bf duration, after controlling for covariates. Child’s BMI z -scores (β (95% CI) = -0.040 (−0.063, -0.016); FDR corrected P =0.001), waist circumference (β (95% CI) = -0.037 (−0.060, -0.014), FDR corrected P =0.002) and WHtR (β (95% CI) = -0.040 (−0.064, -0.018), FDR corrected P =0.001) decreased monotonically with increased bf duration, after controlling for covariates. Bf duration was inversely associated with adiposity in children from high- and medium-ADI neighborhoods. Bf duration was positively associated with SA across ADI tertiles. Conclusions and Relevance Our results imply that long-term benefits of bf on body and brain development in offspring increase as bf duration increases, particularly in children from low SEEs. Policies and social support aimed to incremental increases in bf duration among women from low SEEs would confer long-term benefits for offspring. Key Points Question Do benefits of breastfeeding(bf), on children’s brain and body development, persist long-term and are these benefits uniform across socioeconomic environments (SEEs)? Findings Longer bf duration is associated with lower adiposity, greater cortical and subcortical gray matter volume, and cortical surface area in 9–10-year-old children. Children from lower SEEs showed stronger negative relationships between bf duration and adiposity. Children across all SEEs demonstrated positive relationships between bf duration and surface area. Meaning Our results imply that long-term benefits to child brain and body development increase with bf duration; and children from lower SEEs benefited more from longer bf duration.