Associations of alcohol consumption with breast tissue composition

BACKGROUND: We investigated the associations of alcohol with percentage of epithelium, stroma, fibroglandular tissue (epithelium + stroma), and fat in benign breast biopsy samples. METHODS: We included 857 cancer-free women with biopsy-confirmed benign breast disease within the Nurses’ Health Study (NHS) and NHSII cohorts. Percentage of each tissue was measured on whole slide images using a deep-learning algorithm and then log-transformed. Alcohol consumption (recent and cumulative average) was assessed with semi-quantitative food frequency questionnaires. Regression estimates were adjusted for known breast cancer risk factors. All tests were 2-sided. RESULTS: Alcohol was inversely associated with % of stroma and fibroglandular tissue (recent ≥ 22 g/day vs. none: stroma: β = − 0.08, 95% Confidence Interval [CI] − 0.13; − 0.03; fibroglandular: β = − 0.08, 95% CI − 0.13; − 0.04; cumulative ≥ 22 g/day vs. none: stroma: β = − 0.08, 95% CI − 0.13; − 0.02; fibroglandular: β = − 0.09, 95% CI − 0.14; − 0.04) and positively associated with fat % (recent ≥ 22 g/day vs. none: β = 0.30, 95% CI 0.03; 0.57; cumulative ≥ 22 g/day vs. none: β = 0.32, 95% CI 0.04; 0.61). In stratified analysis, alcohol consumption was not associated with tissue measures in premenopausal women. In postmenopausal women, cumulative alcohol use was inversely associated with % of stroma and fibroglandular tissue and positively associated with fat % (≥ 22 g/day vs. none: stroma: β = − 0.16, 95% CI − 0.28; − 0.07; fibroglandular: β = − 0.18, 95% CI − 0.28; − 0.07; fat: β = 0.61, 95% CI 0.01; 1.22), with similar results for recent alcohol use. CONCLUSION: Our findings suggest that alcohol consumption is associated with smaller % of stroma and fibroglandular tissue and a greater % of fat in postmenopausal women. Future studies are warranted to confirm our findings and to elucidate the underlying biological mechanisms. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s13058-023-01638-z.