OBJECTIVE. The American Academy of Pediatrics recommends exclusive breastfeeding for an infant's first 6 months of life. When compared with exclusive breastfeeding for 4 months, greater protection against gastrointestinal infection, but not respiratory tract infection, has been demonstrated for the 6-month duration. The objective of this study was to ascertain if full breastfeeding of 9 >= 6 months compared with 4 to < 6 months in the United States provides greater protection against respiratory tract infection. METHODS. Secondary analysis of data from the National Health and Nutrition Examination Survey III, a nationally representative cross-sectional home survey conducted from 1988 to 1994, was performed. Data from 2277 children aged 6 to < 24 months, who were divided into 5 groups according to breastfeeding status, were compared. Children who required neonatal intensive care were excluded. SUDAAN software was used to account for the complex sampling design. Logistic regression adjusted for confounding factors. Outcome measures included adjusted odds of acquiring pneumonia, >= 3 episodes of cold/influenza, >= 3 episodes of otitis media (OM), or wheezing in the past year or acquiring first OM at < 12 months of age. RESULTS. In unadjusted analyses, infants who were fully breastfed for 4 to >= 6 months (n = 223) were at greater risk for pneumonia than those who were fully breastfed for >= 6 months (n = 136) (6.5% vs 1.6%). There were not statistically significant differences in >= 3 episodes of cold/influenza (45% vs 41%), wheezing (23% vs 24%), >= 3 episodes of OM (27% vs 20%), or first OM at < 12 months of age (49% vs 47%). Adjusting for demographic variables, childcare, and smoke exposure revealed statistically significant increased risk for both pneumonia (odds ratio [OR]: 4.27; 95% confidence interval [CI]: 1.27-14.35) and >= 3 episodes of OM (OR: 1.95; 95% CI: 1.06-3.59) in those who were fully breastfed for 4 to >= 6 months compared with >= 6 months. CONCLUSIONS. This nationally representative study documents increased risk of respiratory tract infection including pneumonia and recurrent OM in children who were fully breastfed for 4 vs 6 months. These findings support current recommendations that infants receive only breast milk for the first 6 months of life.
