To evaluate the association between breastfeeding and asthma in young Canadian children.
Baseline data from the National Longitudinal Survey of Children and Youth (a population-based study of child health and well-being) were used. A weighted sample of 331 100 (unweighted n = 2184) children between the ages of 12 and 24 months, whose biological mother reported data on breastfeeding and asthma, were included. Outcomes included parental report of physician-diagnosed asthma and wheeze in the previous year. Breastfeeding was categorized by duration as follows: less than 2 months, 2 to 6 months, 7 to 9 months, and longer than 9 months. Logistic regression analyses were conducted with breastfeeding duration dichotomized at various cutoffs. Important potential confounders were considered in the adjusted analyses. Published statistical methods appropriate for the sampling strategy were used.
The prevalence of asthma was 6.3%; and wheeze, 23.9%. Almost half of the children (44.0%) were breastfed for less than 2 months. After adjustment for smoking, low birth weight, low maternal education, and sex, a duration of breastfeeding for 9 months or less was found to be a risk factor for asthma (odds ratio, 2.39; 99% confidence interval, 0.95-6.03) and wheeze (odds ratio, 1.54; 99% confidence interval, 1.04-2.29). A dose-response effect was observed with breastfeeding duration.
A longer duration of breastfeeding appears to be protective against the development of asthma and wheeze in young children. More public health efforts should be directed toward increasing the initiation and duration of breastfeeding.