The evidence linking bottle feeding to infant and early childhood mortality has been reviewed. Ecological studies of national time trends in infant mortality do not parallel breast feeding trends in those countries, and indicate that falling death rates are more likely to be related to better health care facilities and social conditions. Direct studies of deaths provide some contradictory findings; meta-analyses are not informative because of the many differences in statistical and sample methodology. The methodology exhibited in most studies is more likely to have over- rather than under-estimated a relationship between bottle feeding and infant mortality. Retrospective analyses must take account of changes in feeding pattern due to early signs of illness. Prospective population studies able to account for large numbers of potential confounders provide the best estimates, especially if proportional hazards models are used. Two such studies have been carried out--both showed protective effects of breast feeding.
PIP: The assumption that breast feeding prevents a large number of infant deaths is not consistently supported by the research literature. In general, infant mortality rates in developing countries have declined during the same period that breast feeding rates have fallen. Declining infant mortality has been linked primarily to affordable health services, improvements in women's status, nutrition standards, universal immunization, and the expansion of prenatal and obstetric services. This should not be interpreted as meaning that breast feeding is not relevant as a child survival intervention. The protective effect of breast feeding becomes more evident when deaths from gastroenteritis and respiratory infections are analyzed. For example, a major case-control study conducted in Brazil found that infants who were fed non-milk supplements had a reduced overall risk of death, but after adjustment for confounders, there was a very strong association between diarrhea mortality and lack of breast feeding. In developed countries, most studies have focused on the relationship between breast feeding and sudden infant death syndrome. In this case, maternal smoking appears more salient than infant feeding method. Needed are more prospective population studies able to account for the large numbers of potential confounders in the breast feeding-infant mortality relationship.