Breast feeding, parental allergy and asthma in children followed for 8 years. The PIAMA birth cohort study
Background: It is unclear how the association between breast feeding and asthma develops with age of the child and how this association over time is influenced by maternal or paternal allergy. These factors - the age of the child and maternal or paternal allergy - might partly explain the conflicting results observed in cross-sectional studies. Methods: The study population consisted of 3115 Dutch children born in 1996/1997 who participated in the PIAMA (Prevention and Incidence of Asthma and Mite Allergy) birth cohort study. Data on breast feeding and asthma (based on wheeze, dyspnoea and prescription of inhaled steroids) were collected by yearly questionnaires. At 8 years, specific immunoglobulin E (IgE) to airborne allergens and bronchial responsiveness were measured. Data were analysed by logistic regression and generalised estimating equations (GEEs), and stratified by maternal and paternal allergic status. Results: 35% (n=1081) of the children were breast fed for >16 weeks. At 8 years of age, 12.6% (n=392) had asthma. Breast feeding (>16 weeks vs no breast feeding) was significantly associated with a lower asthma prevalence from 3 to 8 years of age, in children of both non-allergic and allergic mothers. The inverse association between breast feeding and sensitisation to airborne allergens at 8 years was non-significant. Breast feeding was not associated with bronchial hyper-responsiveness. No interaction between breast feeding and gender, maternal allergy or paternal allergy was observed in any of the associations. Conclusions: Breast feeding is associated with a lower asthma risk in children until 8 years of age without evidence of attenuation and regardless of the family history of allergy.