Atopic disease and breast-feeding - cause or consequence?

Background: A number of studies have observed an association between breast-feeding and increased risk of development of asthma and eczema. It has been proposed that these results might be due to early signs of atopic disease in the infant causing mothers to prolong breast-feeding. Objective: We sought to determine whether early symptoms of atopic disease (eczema, food reaction, or asthma) or positive skin prick test responses reduce the likelihood of ceasing breast-feeding. Methods: A prospective birth cohort of 620 infants from Melbourne, Australia, was used. Telephone interviews every 4 weeks were conducted until 64 weeks and then again at 78 and 104 weeks to determine duration of breast-feeding (both exclusive and total) and evidence of atopic disease. Because of the varying time of onset of atopic symptoms, they were modeled as time-varying covariates in Cox models. Results: Only 52 (8.4%) infants did not establish breast-feeding, whereas an additional 103 (25.0%) did not establish exclusive breast-feeding. Early signs of atopic disease or sensitization were independently associated with an approximately 28% reduction in risk of ceasing exclusive breast-feeding (adjusted hazard ratio, 0.72; 95% CI, 0.53-0.97; P = .029), but there was no evidence for a relationship with risk of ceasing breast-feeding completely (adjusted hazard ratio, 1.12; 95% CI, 0.92-1.37; P = .262). Conclusion: Early signs of atopic disease might prolong the duration of exclusive breast-feeding. This could mask a protective effect of breast-feeding or even result in breast-feeding appearing to be a risk factor for the development of atopic diseases. Future investigation of the relationship between breast-feeding and atopic diseases should consider this possibility.