RESUMO
OBJECTIVE: To determine the influence of type of infant feeding on the incidence of lower (LRTI) and upper respiratory tract infections during the first 12 months of life. DESIGN: Historical cohort study. SETTING: Primary care centers. PARTICIPANTS: A total of 250 babies born at term between October 1, 1994 and February 1, 1998. INCLUSION CRITERIA: current medical record available at a participating primary care center, participation in a Healthy Baby Program, residence in the basic health area involved in the study, birth weight #>2500 g. Interventions. Breastfeeding alone or in combination with formula feeding; artificial feeding alone. MAIN OUTCOME MEASURES AND RESULTS: Attending day care, antecedents of atopy, fathers and mothers smoking habit, parents level of education, number of persons in the household, mothers age. There was no association between type of feeding and the incidence of respiratory infections. All 95% confidence intervals (95% CI) of the odds ratios (OR) included the value of 1. At age 3 months, LRTI was associated with the number of persons in the household (OR, 1,87; 95% CI, 1.18-2.95) and with antecedents of atopy (OR, 2.96; 95% CI, 1.19-7.4). At age 6 months, LRTI was associated with the number of persons in the household (OR, 1.62; 95% CI, 1.07-2.44) and with attending day care (OR, 4.52; 95% CI, 1.20-17.1). CONCLUSIONS: In the present study breastfeeding was not effective in lowering the incidence of respiratory infections.