Effect of breast feeding in infancy on blood pressure in later life: systematic review and meta-analysis

Abstract

Objective: To determine whether breast feeding in infancy compared with bottle feeding formula milk is associated with lower mean blood pressure at different ages.

Design: Systematic review.

Data sources: Embase, Medline, and Web of Science databases.

Study selection: Studies showing the effects of feeding in infancy on blood pressure at different ages.

Data extraction: Pooled mean differences in blood pressure between breast fed infants and those bottle fed formula milk, based on random effects models.

Data synthesis: The pooled mean difference in systolic blood pressure was -1.10 mm Hg (95% confidence interval -1.79 to -0.42 mm Hg) but with significant heterogeneity between estimates (P < 0.001). The difference was largest in studies of < 300 participants (-2.05 mm Hg, -3.30 to -0.80 mm Hg), intermediate in studies of 300-1000 participants (1.13 mm Hg, -2.53 to 0.27 mm Hg), and smallest in studies of > 1000 participants (-0.16 mm Hg, -0.60 to 0.28 mm Hg). An Egger test but not Begg test was statistically significant for publication bias. The difference was unaltered by adjustment for current size and was independent of age at measurement of blood pressure and year of birth. Diastolic blood pressure was not significantly related to type of feeding in infancy.

Conclusions: Selective publication of small studies with positive findings may have exaggerated claims that breast feeding in infancy reduces systolic blood pressure in later life. The results of larger studies suggest that feeding in infancy has at most a modest effect on blood pressure, which is of limited clinical or public health importance.

Fig 1

Mean differences in systolic blood pressure (95% confidence intervals) between breastfed and bottle fed participants. Box area proportional to inverse of variance, with horizontal lines showing 95% confidence intervals. y axis in ascending order of mean age (years) at which blood pressure was measured. Dashed vertical line and diamond (95% confidence interval) is pooled estimate based on a random effects model

Fig 2

Begg's funnel plot (pseudo 95% confidence limits) showing mean difference in systolic blood pressure by standard error of mean difference

Fig 3

Mean differences in diastolic blood pressure (95% confidence intervals) between breastfed and bottle fed participants. Box area proportional to inverse of variance, with horizontal lines showing 95% confidence intervals. y axis in ascending order of mean age (years) at which blood pressure was measured. Dashed vertical line and diamond (95% confidence interval) is pooled estimate based on a random effects model