Asthma is the most chronic disease of childhood and the leading cause of morbidity in children globally as measured by emergency department visits, hospitalisations and days of missed school.1 Susceptibility to asthma may be increased by factors present early in life, including low birth weight, preterm birth, young maternal age and male gender. Environmental allergens including household smoking, house dust mite, grasses or pollens are also implicated. Conversely, early exposure to respiratory infections may be protective, although certain infections are suspected to increase the risk. Against this complex aetiological background, there is some evidence that breast feeding may protect against the development of asthma in children.2 3

In this issue of Thorax, a birth cohort study by Scholtens and colleagues assesses whether the association between breast feeding and asthma measured longitudinally from 1 to 8 years of age is influenced by maternal and paternal allergy (see page 604). The main finding of the study confirmed that breast feeding for >16 weeks was significantly associated with reduced asthma prevalence from 3 to 8 years without evidence of attenuation and regardless of family history.4

The study population consisted of 3963 Dutch children born in 1996/1997 who participated in the Prevention and Incidence of Asthma and Mite Allergy (PIAMA) birth cohort study and who were followed every year for 8 years. Asthma was defined as at least one attack of wheeze and/or dyspnoea and/or prescription of inhalation steroids in the last year. Chronic asthma was defined as asthma diagnosis at 8 years with asthma diagnosis in at least two other years. Specific immunoglobulin E (IgE) to common airborne allergens and bronchial hyper-responsiveness were measured according to a standard protocol. Breast feeding was measured at 3 months and at 1 …