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

Background: The influence of breast-feeding on the risk of developing atopy and asthma remains controversial. Objective: To examine asthma and atopy outcomes by sex, reported specific parental history of atopy, and breast-feeding. Methods: In 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. Results: For boys, breast-feeding (odds ratio [OR], 1.63; 95% CI, 0.93-2.87; P =.09) and maternal atopy (OR, 1.95; 95% CI, 0.934.08; 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. Conclusion: The 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 implications: Analyses of environmental risk factors for asthma and atopy should be stratified by specific parental atopy and sex.