Association between alcohol consumption and postmenopausal breast cancer: results of a case-control study in Montreal,Quebec, Canada

OBJECTIVES: To determine the association between postmenopausal breast cancer and prior consumption of alcoholic beverages.METHODS: This case–control study, conducted in all Montreal hospitals between 1996 and 1997, included 556 postmenopausal women (age 50–75 years) who had a new histologically confirmed diagnosis of primary, malignant breast cancer. Control subjects (577) were selected from other histologically confirmed sites of cancer. A detailed history of alcohol consumption and other risk factors was obtained by interview. Indices reflecting alcohol consumption were developed and unconditional logistic regression was used to estimate adjusted odds ratios (OR) and 95% confidence intervals (CI).RESULTS: Current regular drinkers of any type of alcohol were at an increased risk of breast cancer (OR = 1.5; 95% CI 1.0–2.2). For all beverages considered, current regular drinkers showed higher risks than ever regular drinkers. The risk of breast cancer was highest among women who reported exclusive drinking of wine on a weekly or daily basis (e.g. current regular drinking: OR = 2.3; 95% CI 1.2–4.3). Women who started to drink wine on or before the age of 40 were at a 2.5 times increased risk (95% CI 1.4–4.4).CONCLUSIONS: Our findings provide further support for a positive association between the risk of postmenopausal breast cancer and alcohol consumption.