Publication date: 25 September 1999
What is already known about this subject:
- Asthma is the leading cause of admission to hospital in Australian children and the number of existing cases is increasing. Susceptibility to asthma may be increased by factors present early in life such as being a boy, low birth weight, preterm birth, young maternal age, maternal smoking and possibly stopping breastfeeding before 6 months of age. Environmental allergens (substances that cause an allergic reaction), including house dust mite, grasses, or pollens may also cause allergic reaction. An allergic reaction may occur when the body's immune system overreacts to an allergen in the environment. On the other hand, early exposure to respiratory infections may protect against allergic reactions.
- Environmental exposures in the early months of life are critical for the development of the immune system (the organs and processes of the body that provide resistance to infection and toxins: organs include the thymus, bone marrow, and lymph nodes). However, exposure to allergens has the potential to predispose the infant to allergy. Breastfeeding may be an important determinant of the immune response (the reaction of the cells and fluids of the body to the presence of a substance which is not recognized as a constituent of the body itself) but whether breastfeeding protects against asthma or allergy, or both, is controversial. If exclusive breast feeding is protective against childhood asthma it requires investigation in a large childhood study followed forward in time from birth, with assessment of both breastfeeding in infancy and asthma later in childhood.
What this study adds
- The Raine Study children were recruited through prenatal clinics at the major tertiary obstetric hospital in Perth and 2187 were followed to 6 years. The introduction of milk other than breast milk before 4 months of age was a significant risk factor for factors related to asthma and allergy in children at 6 years, such as asthma diagnosed by a doctor; wheeze three or more times since 1 year of age; wheeze in the past year; sleep disturbance due to wheeze within the past year; age when doctor diagnosed asthma; age at first wheeze; and positive allergy test.
- A significant reduction in the risk of childhood asthma at age 6 years occurs if exclusive breast feeding is continued for at least the 4 months after birth. These findings are important for our understanding of the cause of childhood asthma and suggest that public health interventions to promote breastfeeding may help to reduce the community burden of childhood asthma and its associated traits.