Evidence for protection by breast-feeding against infant deaths from infectious diseases in Brazil

In a population-based case-control study of infant mortality in two urban areas of southern Brazil, the type of milk in an infant's diet was found to be an important risk factor for deaths from diarrhoeal and respiratory infections. Compared with infants who were breast-fed with no milk supplements, and after adjusting for confounding variables, those completely weaned had 14.2 and 3.6 times the risk of death from diarrhoea and respiratory infections, respectively. Part-weaning was associated with corresponding relative risks (RR) of 4.2 and 1.6. The risk of death from infections other than diarrhoea or respiratory infection was less clearly associated with breast-feeding (completely weaned, RR = 2.5; partly weaned, RR = 0.4). Cow's and formula milk seemed to be equally hazardous. For deaths due to diarrhoea the increased risk associated with not breast-feeding was greatest in the first two months of life (RR for completely weaned vs breast-fed without supplementary milk = 23.3).