M. A. Quigley, C. Hockley, C. Carson, Y. Kelly, M. Renfrew, A. Sacker
J Epidemiol Community Health 2009;63(Suppl2):8
Objective To assess the relationship between breastfeeding and child cognitive development, and whether this relationship varies according to prematurity.
Design Population-based cohort (Sweeps 1 and 3 of the UK Millennium Cohort Study).
Participants 11 801 white singleton children born in 2000–2002.
Comparison Groups Children were grouped according to their breastfeeding status (ever vs never; and duration of any and exclusive breastfeeding). Results were stratified according to gestational age at birth: 37–42 weeks (term); 33–36 weeks (moderately preterm); and 28–32 weeks (very preterm).
Main Outcome Measures British Ability Scales (BAS) tests were administered when the children were aged 5 years. Age-adjusted ability scores and t-scores for the BAS Naming Vocabulary, Pattern Construction and Picture Similarities scales were used.
Results 11 007 children (93%) were born at term, 684 (6%) were born moderately preterm, and 110 (1%) were born very preterm. The mean BAS naming vocabulary score decreased with prematurity (110.3 in those born at term, 109.8 in those born moderately preterm, 107.9 in those born very preterm). The proportion of children ever breastfed varied according to prematurity (68% in those born at term, 62% in those born moderately preterm, 76% in those born very preterm), as did the proportion of children breastfed for at least 3 months (37% in those born at term, 27% in those born moderately preterm, 32% in those born very preterm). After adjusting for confounders (including the baby’s sex and birthweight; the mother’s age, education, social class, smoking and alcohol in pregnancy, and whether this was her first child), ever breastfeeding was associated with a higher mean BAS naming vocabulary score in children born at term (adjusted difference in mean between ever breastfed and never breastfed 1.3, 95% CI 0.6 to 2.1, p<0.001). The effect was stronger in children born moderately preterm (2.3, 95% CI 0 to 4.6, p = 0.05) or very preterm (4.6, 95% CI −1.0 to 10.1, p = 0.11). Among those children who were ever breastfed, there was a small increase in mean BAS naming vocabulary score associated with each additional month of breastfeeding. A similar effect of breastfeeding was observed when using BAS pattern construction and picture similarities scales, and BAS standardised t-scores. Further analysis will explore whether these effects are mediated through parenting and childcare factors.
Conclusions These results, based on one of the largest observational studies of the effect of breastfeeding and child development, suggest that breastfeeding is associated with improved cognitive development, particularly in those born preterm.