REVIEW History of Breast-Feeding in Relation to Breast Cancer Risk: a Review of the Epidemiologic Literature

The purpose of this review is to critically evaluate the col-lective epidemiologic evidence that a history of breast-feeding may decrease the risk of breast cancer. Original data for inclusion were identified through a MEDLINE ® search of the English language literature from 1966 through 1998. To date, virtually all epidemiologic data regarding breast-feeding and breast cancer risk are derived from case–control studies, which vary according to classification of breast-feeding history. Overall, the evidence with respect to “ever” breast-feeding remains inconclusive, with results indicating either no association or a rather weak protective effect against breast cancer. An inverse association between in-creasing cumulative duration of breast-feeding and breast cancer risk among parous women has been reported in some, but not all, studies; the failure to detect an association i