Effect of breastfeeding duration on lung function is modified by maternal history of asthma and atopy

Despite its known beneficial effects, there have been conflicting reports on whether breastfeeding confers protection from asthma in late childhood.

In the Isle of Wight birth cohort (n=1456), breastfeeding practices and duration were prospectively assessed at birth and at the 1 and 2 year visits. Breastfeeding duration was categorized as “not breastfed” (n=196); “<2 months” (243); “2 and <4 months” (142) and “>=4 months” (374). Lung function was assessed at age 10 (n=1033): forced vital capacity (FVC); forced expiratory volume in 1 second (FEV1); FEV1/FVC ratio; and peak expiratory flow (PEF). Maternal history of asthma and allergy were assessed at birth. Birthweight, sex, and current height and weight were adjusted for.

FVC was increased by 53.0 +/- 20.1ml (p=0.008); FEV1 by 37.5 +/- 19.0ml (p=0.049); and PEF by 160.3 +/- 62.9ml (p=0.01) in those who were breastfed for at least 4 months compared to those who were not. Stratification showed that this effect was modified by maternal history of asthma and atopy. Compared to those who were not breastfed, children of non-atopic non-asthmatic mothers who were breastfed for at least 4 months showed a significantly increased FVC (60.0 +/- 23.3ml; p=0.01) and PEF (164.6 +/- 75.9ml; p=0.03). This positive effect on lung function was not found in children with atopic non-asthmatic and atopic asthmatic mothers.

Breastfeeding for at least 4 months enhances lung growth in children. Maternal history of asthma and atopy abolishes this effect. Future studies need to elucidate the mechanisms that drive these findings.