Association between breastfeeding and allergic disorders in Japanese children.

Setting: Data on the association between breastfeeding and allergies are conflicting.
Objective: To investigate the relationship between the duration and exclusivity of breastfeeding and the prevalence of wheeze, asthma and eczema in young Japanese children.
Design: Study subjects were 1957 children aged 3 years. Data on breastfeeding, allergic symptoms and potential confounders were collected using a questionnaire. Outcomes were defined according to the criteria of the International Study of Asthma and Allergies in Childhood. Adjustment was made for sex, number of siblings, household smoking, paternal and maternal history of asthma, atopic eczema and allergic rhinitis, and paternal and maternal educational levels.
Results: The prevalence values of symptoms of wheeze, asthma and eczema in the previous 12 months were respectively 22.1%, 8.9% and 17.3%. Exclusive breastfeeding for > or =4 months vs. <4 months was associated with a lower prevalence of asthma. The duration of breastfeeding, regardless of exclusivity, for > or =6 months tended to be associated with a lower prevalence of asthma. There was no appreciable association between breastfeeding and wheeze or eczema.
Conclusions: Data from this study indicate that breastfeeding may be associated with a lower prevalence of asthma among young Japanese children.