The association between alcohol consumption and breast density: A systematic review and meta-analysis

Background: Percent breast density (PBD) is a strong risk factor for breast cancer that is influenced by several other risk factors for the disease. Alcohol consumption is associated with an increased risk of breast cancer with an uncertain association with PBD. We have carried out a systematic review and metaanalysis to examine the association of alcohol consumption with PBD. Methods: We searched nine databases to identify all relevant studies on the association between alcohol intake and breast density. Two independent investigators evaluated and selected 20 studies that were included in our analyses. We divided the studies into three groups according to the methods used to measure and analyze the association of breast density with alcohol consumption. Results: Meta-analysis of the 11 studies that used quantitative methods to measure and analyze PBD as a continuous variable found a statistically significant difference in PBD when comparing the highest with the lowest alcohol level [β = 0.84; 95% confidence interval (CI), 0.12-1.56]. Three studies that used quantitative methods to measure PBD and categories of PBD for analysis had a summary OR = 1.81 (95% CI, 1.07-3.04). Five studies that used categories to classify PBD and analyze their association with alcohol intake had a summary OR = 1.78 (95% CI, 0.90-3.51). Conclusions: These results suggest that there is a positive association between alcohol intake and PBD. Impact: Alcohol may increase the risk of breast cancer associated with PBD.