A LONGITUDINAL ANALYSIS OF INFANT MORBIDITY AND THE EXTENT OF BREAST-FEEDING IN THE UNITED-STATES

Background. Studies on the health benefits of breastfeeding in develop ed countries have shown conflicting results. These studies often fail to account for confounding, reverse causality, and dose-response effec ts. We addressed these issues in analyzing longitudinal data to determ ine if breastfeeding protects US infants from developing diarrhea and ear infections. Methods. Mothers participating in a mail panel provide d information on their infants at ages 2, 3, 4, 5, 6, and 7 months. In fants were classified as exclusively breastfed; high, middle, or low m ixed breast- and formula-fed; or exclusively formula-fed. Diarrhea and ear infection diagnoses were based on mothers' reports. Infant age an d gender; other liquid and solid intake; maternal education, occupatio n, and smoking; household size; family income; and day care use were a djusted for in the full models. Results. The risk of developing either diarrhea or ear infection increased as the amount of breast milk an i nfant received decreased. In the full models, the risk for diarrhea re mained significant only in infants who received no breast milk compare d with those who received only breast milk (odds ratio = 1.8); the ris k for ear infection remained significant in the low mixed feeding grou p (odds ratio = 1.6) and among infants receiving no breast milk compar ed with those who received only breast milk (odds ratio = 1.7). Conclu sions. Breastfeeding protects US infants against the development of di arrhea and ear infection. Breastfeeding does not have to be exclusive to confer this benefit. In fact, protection is afforded in a dose-resp onse manner. The more breast milk an infant receives in the first 6 mo nths of life, the less likely that he or she will develop diarrhea or ear infection.