Children who are not exclusively breastfed have a higher risk of asthma and atopy, according to a report in the September issue of the American Journal of Public Health.
Dr. Wendy H. Oddy, of the University of Western Australia, West Perth, and colleagues examined the association between breastfeeding, asthma and atopy, and body mass index (BMI) in 2195 children prospectively followed from birth to 6 years.
The team defined asthma as doctor-diagnosed asthma and wheeze in the last year and skin prick tests were used to determine atopy for 1596 children.
A logistic regression model before adjustment revealed a significant association between a shorter duration of any breastfeeding and increased BMI at 6 years. The effect of longer breastfeeding did not significantly decrease a child's risk of being overweight after adjustment for gender, birthweight, and maternal smoking during pregnancy.
The researchers also observed an association between less exclusive breastfeeding and increased asthma and atopy after adjustment for BMI. With each additional month of breastfeeding, there was a 4% reduction in the risk of asthma. No significant effects of breastfeeding on atopy were observed.
After adjusting for known risk factors, increased BMI was significantly associated with asthma risk. "Reasons for an association between increased body weight and asthma are not clear, but an immunological mechanism has been suggested," Dr. Oddy and colleagues write. "In obese individuals, the biological activity of adipose tissue may increase the risk of developing asthma."
The investigators call for additional studies to confirm these findings and to understand the mechanism of the protective effect of breastmilk. In the meantime, they note that "public health interventions to promote exclusive breastfeeding for at least 6 months may reduce the prevalence and subsequent morbidity of asthma and atopy in early childhood."
