Effect of breastfeeding on lung function in childhood and modulation by maternal asthma and atopy

In the Tucson Children's Respiratory Study, feeding practices were assessed prospectively based on 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 and before 4 months (n = 336), or at 4 months and older (n = 200, "longer breastfed"). Lung function was measured at age 11 and 16 years. A random-effects model was used to assess the relationship of infant-feeding practices to measures of lung function. FVC by age 16 was increased by 103 +/- 40.0 ml (P = 0.01), and the FEV(1)/FVC ratio was lower (-1.9 +/- 0.6%, P = 0.004) in the longer breastfed children compared with children with early formula introduction. This effect was modified after stratifying by maternal asthma. Compared with children with early formula introduction, longer breastfed children with asthmatic mothers had an FVC that was not increased (P = 0.7) and an FEV(1)/FVC ratio (-5.7 +/- 2.4%, P = 0.02) that was significantly decreased by age 16. Longer breastfed children with nonatopic, nonasthmatic mothers demonstrated an increased FVC (142 +/- 71.1 ml, P = 0.047) and no decrease in FEV(1)/FVC (P = 0.7) 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.