Longer duration of breastfeeding may be protective against asthma. However, early manifestations of allergic disease, such as eczema, are risk factors for asthma and can influence duration of breastfeeding, hence may bias observable associations.
We examined the relationship between breastfeeding ever and duration on the development of asthma and allergic asthma phenotypes, stratified by a diagnosis of eczema during or after the breastfeeding period.
3663 children participated in the 6-year-old follow-up of the HealthNuts study, a population-based, longitudinal study of allergic diseases in Australia. At age 1, breastfeeding and eczema data was collected and at age 6, information on wheeze, medication use and parental-report of doctor-diagnosed asthma were obtained, both via questionnaire. Skin prick test responses to food and aeroallergens at age 6 further distinguished asthmatic children into allergic and non-allergic phenotypes.
Breastfeeding initiation was not associated with current asthma at age 6 (aOR 0.76; 95% CI 0.45-1.29) when compared to never breastfeeding. Results were similar for length of exclusiveness and overall duration of breastfeeding, and allergic and non-allergic asthma phenotypes. However, increased duration of breastfeeding among children without eczema in infancy, was associated with reduced odds of asthma, (per month increase, aOR 0.98, 95% CI 0.95-1.0 p=0.05) which equates to a 0.86 (95% CI 0.74-1.0) reduced odds of asthma for a 6-month increase in breastfeeding. This association was not apparent in children who were diagnosed with eczema during breastfeeding (aOR 1.03 (95%CI 0.98-1.08, p=0.3).
Longer duration of breastfeeding was associated with a reduced odds of asthma among children without eczema in the first year of life; this association was masked prior to stratification by eczema in infancy. Future studies examining breastfeeding practices and the risk of allergic outcomes in later childhood need to consider the presence of early life allergic manifestations impacting on breastfeeding behaviour.

Copyright © 2020. Published by Elsevier Inc.