Alcohol and breast cancer.

We examined breast cancer incidence in a cohort of about 69,000 women who answered detailed questions about alcohol consumption from 1979 to 1984. Among women with no prior cancer, breast cancer had developed in 303 by the end of 1984 for an age-adjusted incidence of 1.3/1,000 person years of follow-up. In analysis controlling only for age there was a progressive increase in breast cancer incidence corresponding to each higher level of reported alcohol consumption. In multivariate analyses controlling for age, race, body mass, and smoking, the relative risk at 1-2 drinks/day was 1.5 (95% confidence interval (CI) 1.0-2.3), at 3-5 drinks/day was 1.5 (95% CI 0.8-2.8), and at 6 or more drinks/day was 3.3 (95% CI 1.2-9.3). Past drinkers tended to have been heavier drinkers than current drinkers and had a relative risk of 2.2 (95% CI 1.2-3.9). Study of wine, beer, and liquor use did not suggest that any particular alcoholic beverage was responsible. Significant associations with heavy alcohol consumption were strongest among white and postmenopausal women. This study adds support to the growing evidence that alcohol may be a risk factor for development of breast cancer.