Whether or not breast-feeding is protective against asthma among children is still controversial. Therefore, we examined the effects of breast-feeding on hospitalization for asthma in early childhood.

Secondary data analyses of a nationwide longitudinal survey of children in Japan ongoing since 2001, with results collected from 2001 to 2004. We used logistic regression models to evaluate the associations of breast-feeding with hospitalization for asthma in children between the ages of 6 and 42 months, adjusting for children’s factors (sex, day-care attendance and presence of older siblings) and maternal factors (educational attainment and smoking habit).

All over Japan.

Term singleton children with information on feeding practices during infancy (n 43367).

After adjusting for maternal factors and children’s factors, exclusive breast-feeding at 6–7 months of age was associated with decreased risk of hospitalization for asthma in children. The adjusted odds ratio was 0·77 (95 % CI 0·56, 1·06). One-month longer duration of breast-feeding was associated with a 4 % decreased risk of hospitalization for asthma (OR=0·96; 95 % CI 0·92, 0·99).

The protective effects of breast-feeding on hospitalization for asthma were observed in children between the ages of 6 and 42 months.