Effect of Breastfeeding on Lung Function in Childhood and Modulation by Maternal Asthma and Atopy
Authors: Mahr Todd A. 
Published: October 2008

Guilbert TW, Stern DA, Morgan WJ, Martinez FD, Wright AL. Am J Respir Crit Care Med. 2007;176(9):843–848
PURPOSE OF THE STUDY. Breastfeeding and its relationship to the development of subsequent asthma remain controversial. To clarify these complex issues, this study examined the association between lung function and infant-feeding practices.
STUDY POPULATION. A population-based cohort of healthy infants was enrolled at birth in the Children's Respiratory Study in Tucson, Arizona (n = 1246); the analysis was of 679 study participants on whom lung-function testing was performed at ages 11 and/or 16 years and provided data regarding infant-feeding practices.
METHODS. In the Children's Respiratory Study in Tucson, feeding practices were assessed prospectively on the basis of questionnaires completed at enrollment and well-child visits. Formula introduction was categorized as having occurred before 2 months (n = 143, “early formula introduction”), from 2 to before 4 months (n = 336), or at ≥4 months (n = 200, “longer breastfed”). Lung function was measured at ages 11 and 16 years. A random-effects model was used to assess the relationship of infant-feeding practices to measures of lung function.
RESULTS. Forced vital capacity (FVC) by age 16 was increased by 103 ± 40 mL (P = .01), and the forced expiratory volume in 1 second (FEV1)/FVC ratio was lower (−1.9 ± 0.6%; P = .004) in the longer-breastfed children compared with children with early formula introduction. This effect was modified after stratifying according to maternal asthma. Compared with children with early formula introduction, longer-breastfed children with asthmatic mothers had an FVC that was not increased (P = .7) and an FEV1/FVC ratio (−5.7 ± 2.4%; P = .02) that was significantly decreased by age 16. Longer-breastfed children with nonatopic, nonasthmatic mothers demonstrated an increased FVC (142 ± 71 mL; P = .047) and no decrease in FEV1/FVC (P = .7) compared with children with early formula introduction.
CONCLUSIONS. Longer duration of breastfeeding favorably influences lung growth in children. However, in the presence of maternal asthma, longer breastfeeding is associated with decreased airflows.
REVIEWER COMMENTS. There seems to be a differential effect of the relation of breastfeeding to lung function on the basis of the asthmatic background of the mother. Breastfed children with nonatopic, nonasthmatic mothers had an increased FVC and no decrease in their airflows. However, children of mothers with asthma with longer breastfeeding did not demonstrate any improvement in FVC but had a significant reduction in airflows, suggesting that the risk for increased asthma in this group may be partly a result of altered lung growth. Children with longer breastfeeding who had atopic but nonasthmatic mothers had intermediate findings, and they showed a similar increase in FVC compared with those with nonatopic, nonasthmatic mothers but a decrease in airflows similar to children with asthmatic mothers. These findings may support the speculation that the milk of mothers with atopy or asthma may differ with regard to immunologically active substances; thus, breastfeeding in these groups may have a different effect on growth and/or development of the airways. It goes without saying that the clinical significance of these findings is unknown. Human milk is uniquely suited to the feeding of infants. There are many well-documented benefits of breastfeeding. For children of nonasthmatic mothers, this study demonstrates a further benefit of breastfeeding. Additional study is needed draw firm conclusions for other infants.