Interactions between breast-feeding, specific parental atopy, and sex on development of asthma and atopy

BackgroundThe influence of breast-feeding on the risk of developing atopy and asthma remains controversial.ObjectiveTo examine asthma and atopy outcomes by sex, reported specific parental history of atopy, and breast-feeding.MethodsIn a birth cohort, we examined childhood asthma and atopy (positive skin prick tests) by sex and breast-feeding in relation to maternal and paternal atopy. Interactions were explored in logistic regression models.ResultsFor boys, breast-feeding (odds ratio [OR], 1.63; 95% CI, 0.93-2.87; P = .09) and maternal atopy (OR, 1.95; 95% CI, 0.93-4.08; P = .08) were each associated with atopy at age 13 years. Breast-feeding increased the risk for atopy among boys with paternal atopy (OR, 7.39; 95% CI, 2.21-24.66) compared with non–breast-fed boys with paternal atopy, but did not significantly further increase risk among subjects with maternal atopy. For girls, breast-feeding (OR, 0.74; 95% CI, 0.41-1.31) and maternal and paternal atopy were not independent risk factors for atopy at age 13 years. However, breast-feeding increased the risk for atopy in girls with maternal atopy (OR, 3.13; 95% CI, 1.20-8.14) compared with non–breast-fed girls with maternal atopy. There was no such effect among subjects with paternal atopy. Results for the outcome of asthma followed a similar pattern.ConclusionThe influence of breast-feeding on development of atopy and asthma differs by sex and by maternal and paternal atopy, and is most significant among subjects at lower baseline risk.Clinical implicationsAnalyses of environmental risk factors for asthma and atopy should be stratified by specific parental atopy and sex.