Long-term relation between breastfeeding and development of atopy and asthma in children and young adults: a longitudinal study

Breastfeeding is widely advocated to reduce risk of atopy and asthma, but the evidence for such an effect is conflicting. We aimed to assess long-term outcomes of asthma and atopy related to breastfeeding in a New Zealand birth cohort. Our cohort consisted of 1037 of 1139 children born in Dunedin, New Zealand, between April, 1972, and March, 1973, and residing in Otago province at age 3 years. Children were assessed every 2–5 years from ages 9 to 26 years with respiratory questionnaires, pulmonary function, bronchial challenge, and allergy skin tests. History of breastfeeding had been independently recorded in early childhood. 504 (49%) of 1037 eligible children were breastfed (4 weeks or longer) and 533 (51%) were not. More children who were breastfed were atopic at all ages from 13 to 21 years to cats (p=0·0001), house dust mites (p=0·0010), and grass pollen (p