Background Alcohol consumption and breast density are both established risk factors for breast cancer. Although it has been suggested that the effect of alcohol on breast cancer is via altered breast density, few studies examine whether alcohol consumption at particular life-stages is associated with subsequent mammographic breast density. Average breast density decreases with age and at menopause however women with high alcohol consumption have been shown to have higher breast density. The aim of the study was to examine the association between alcoholic consumption during mid-life and breast density in a population based sample of postmenopausal women.

Methods Data on alcohol consumption and breast density were examined among 833 postmenopausal women from the National Survey of Health and Development, a cohort followed up since their birth in 1946. Mammograms were obtained from routine screening programmes (at approximately age 50 years), from which breast density was calculated. Alcohol intake was self -reporting during mid-life (36, 43 & 53 years). Linear regression was used to evaluate the association between weekly grams of alcohol intake at each age and breast density. Regression was used to evaluate the association between alcohol consumption and breast density. This was then adjusted for body mass index (BMI), a known confounder. Then adjusted for BMI and additional confounders; parity, age at first child, age at menstruation, smoking status, physical activity, social status. Age at mammogram and menopause status were constant for all women, therefore no adjustment necessary.

Results In unadjusted analysis a unit increase in weekly alcohol consumption at age 36, 43 and 53 was associated with 4.1% & 3.4% increase and 0.3% decrease in breast density respectively. After adjustment for BMI, association remained age 36 with a 2.7% increase, and lost age 43 & 53. All association was lost when adjusted for potential confounders.

Conclusion A 2017 systematic review by Zimbicki and colleagues found a positive association between high alcohol intake and breast density, with a stronger effect seen in premenopausal women. This study suggests that there is no association between alcohol consumption in mid-life and postmenopausal breast density.