The relationship of breast-feeding, overweight, and asthma in preadolescents.

Background: Breast-feeding is suggested to be associated with overweight or asthma in children. Overweight and asthma may share common environmental influences of which breast-feeding may be one.
Objective: We evaluated whether short duration of exclusive breast-feeding and subsequent overweight were associated with asthma.
Methods: A nested case-control study included 246 children with pediatric allergist-diagnosed asthma and 477 controls without asthma at age 8 to 10 years. Information on exclusive breast-feeding was obtained from questionnaire data. Overweight at 8 to 10 years of age was defined as body mass index >/=85th percentile of age and sex-specific growth charts. The association between asthma and exclusive breast-feeding <12 weeks plus overweight, adjusted for sex, parental asthma, aboriginal origin, passive smoking at birth, residence location, and family income, was determined in logistic regression analyses.
Results: Exclusive breast-feeding <12 weeks was closely associated with overweight at age 8 to 10 years (P < .001). Exclusive breast-feeding <12 weeks plus overweight was significantly associated with asthma (adjusted OR, 1.81; 95% CI, 1.11-2.95; P = .018). This association appeared to be strong in children whose mothers had asthma (adjusted OR, 3.93; 95% CI, 1.17-13.2) and also in boys (adjusted OR, 2.22; 95% CI, 1.14-4.34). Asthma was not associated with either exclusive breast-feeding <12 weeks or overweight in the absence of the other.
Conclusion: Short duration of exclusive breast-feeding and subsequent overweight are associated with asthma in susceptible children, suggesting a common pathway.
Clinical Implications: This finding adds to the importance of promoting prolonged breast-feeding for the prevention of overweight and asthma.