Alcohol consumption and mammographic density in a multiethnic population.

This report examined the association between alcohol intake and breast cancer risk as assessed by mammographic densities in a multiethnic population. Information for this analysis was available from 2 previous investigations: a nutritional intervention study (The Breast, Estrogens, and Nutrition Study; BEAN) with 217 premenopausal women and a nested case-control study within The Multiethnic Cohort (MEC) with 1,250 primarily postmenopausal women. On the basis of self-reported alcohol intake from a validated food frequency questionnaire, women were categorized into abstainers (<1 drink/month), low (<1 drink/day) and high (>or=1 drink/day) alcohol consumers. On average, 3 mammograms were available per woman. Using mixed models, we calculated mean percent densities for each alcohol consumption category while adjusting for covariates. Mean alcohol intakes for women in the BEAN study and for cases and controls in the MEC study were 2.0, 2.7 and 1.8 drinks/week, respectively. Overall, the difference in densities between abstainers and the highest alcohol intake category was only 1-2% and the differences were not statistically significant. However, the difference was 3-5% for women aged 55-65 years and for breast cancer cases. In postmenopausal women without hormone replacement therapy (HRT), breast density increased by 2% for each higher alcohol intake category. Breast densities were also elevated for high alcohol consumers on estrogen-only therapy as compared to abstainers and low consumers, whereas combined HRT use was associated with higher mammographic densities independent of alcohol use. In conclusion, despite the low alcohol intake in our population, alcohol consumers had higher percent breast densities than did abstainers. The larger difference in some subgroups suggests that women with certain characteristics may be more susceptible to the influence of alcohol on breast density than others.