Alcohol drinking and risk of breast cancer

Using a case-control design, the authors studied female residents of five Massachusetts towns between 1983 and 1986. The objective was to measure the association between breast cancer occurrence and drinking alcohol. Cohort and case-control studies have often observed an association between drinking alcohol and breast cancer risk. In this study, women with any history of drinking alcohol had a risk of breast cancer 1.2-fold greater than women who never drank alcohol (95% confidence interval 0.7-1.8). The relative risk of breast cancer did not depend on the usual number of drinks per day or drinking history relative to time of diagnosis. Women who reported ever having a period of 6 months or more during which they drank more than average had an adjusted relative risk of breast cancer equal to 2.6 (95% confidence interval 1.1-5.8). The estimates of effect are consistent with the positive dose-response trends reported in a pooled analysis of large cohort studies and a meta-analysis of a broader spectrum of studies. Alcohol drinking remains one of the few risk factors for breast cancer amenable to intervention.