Background: Most studies of the relation between alcohol consumption and breast cancer have shown a modestly increased risk, although the results are still conflicting.

Methods: The aim of this prospective population-based cohort study was to assess the influence of alcohol intake and type of beverage (beer, wine, or spirits) on breast cancer risk in relation to menopausal status. Among 13,074 women aged 20 to 91 years, we examined the relationship between breast cancer risk, total alcohol intake, and type of alcohol in relation to menopausal status. The women were classified as premenopausal or as postmenopausal at younger than 70 years or 70 years or more.

Results: During follow-up, 76 premenopausal and 397 postmenopausal women developed breast cancer. Premenopausal women who had an intake of more than 27 drinks per week had a relative risk of breast cancer of 3.49 (95% confidence limits, 1.36-8.99) compared with light drinkers (p = 0.011), whereas there were no differences in risk in the lower-intake categories. The increased risk of breast cancer among premenopausal women was independent of the type of alcohol. Postmenopausal women older than 70 years of age who had an intake of more than six drinks per week of spirits had a relative risk of breast cancer of 2.43 (95% confidence limits, 1.41-4.20) compared with women who consumed less than one drink of spirits per week (p = 0.0014).

Conclusions: Total alcohol intake of more than 27 drinks per week increases breast cancer risk in premenopausal women independently of the type of alcohol. Among postmenopausal women, an intake of spirits of more than six drinks per week increases breast cancer risk.