PURPOSE: We examined the association between alcohol consumption and mammographic density (MD) considering in detail the time of exposure and the type of alcohol.

METHODS: Of 5,356 women (4,489 post-menopausal) from the Danish Diet, Cancer and Health cohort (1993-1997) who attended mammographic screening in Copenhagen (1993-2001), we used MD (mixed/dense or fatty) assessed at the first screening after cohort entry. Alcohol consumption was assessed at the time of recruitment. Logistic regression was used to estimate associations [odds ratios (OR), 95% confidence intervals (CI)] between alcohol consumption and MD.

RESULTS: The mean age was 56.2 years, 56.5% of women had mixed/dense MD, and 91.8% were alcohol consumers. There was no association between current alcohol consumption and MD at baseline (age 50-65, on average 1 year before MD assessment) neither between age at drinking initiation and MD, in the fully adjusted model. There was a borderline statistically significantly increased OR of having mixed/dense MD in women who consumed > 7 drinks/week at age 20-29 (1.31, 95% CI 1.00-1.72) compared to non-drinkers in this age group, and no effect of drinking at age 30-39, 40-49 or after > 50 years, when adjusting for current drinking. However, when considering different types of alcohol, drinking spirits at age 20-29 was positively associated with mixed/dense breast (3-7 drinks/week: OR 1.74, 95% CI 1.12-2.72); >7 drinks/week: (OR 1.76, 95% CI 0.73-4.23). No consistent pattern was found with beer, wine, or fortified wine.

CONCLUSIONS: We found higher MD among women with high alcohol consumption in early adulthood (ages 20-29), in those drinking spirits.