Changes in alcohol consumption and the risk of postmenopausal breast cancer in the European Prospective Investigation into Cancer and Nutrition cohort.

PURPOSE: Alcohol consumption is a cause of breast cancer (BC), yet the association between changes in alcohol consumption during adulthood and the risk of BC has been examined little. This study aimed to investigate the association between midlife changes in alcohol consumption and the risk of BC. METHODS: Within the European Prospective Investigation into Cancer and Nutrition cohort including 123,679 women, changes in alcohol intake were obtained by comparing middle-aged participants' alcohol intake assessed at recruitment and during follow-up, 9.8 years (median) later. Missing information about follow-up alcohol intake and covariates was multiple imputed. In the primary analysis, changes in alcohol consumption were investigated continuously as a change in alcohol intake of 10 g/day, calculated by subtracting the baseline intake (g/day) from the follow-up intake (g/day) and divided by 10 in relation to the risk of subsequent postmenopausal BC, overall, and by hormonal receptor status: estrogen receptor (ER), progesterone receptor (PR), and human epidermal growth factor receptor 2 (HER2). In a secondary analysis, changes in alcohol intake were categorized in nine combinations of three intake groups at baseline and follow-up (≤1 g/day, >1-8 g/day, and >8 g/day)., Multivariable Cox proportional hazards regression models were used to estimate hazard ratios (HRs) with 95% confidence intervals (CIs). RESULTS: During a median follow-up time of 4.0 years after the follow-up assessment, 2,173 cases of postmenopausal BC were diagnosed. No associations were observed between alcohol changes and BC risk (HR: 0.97, 95% CI 0.93, 1.01) per 10 g/day nor with ER-/PR-, ER+/PR, ER+/PR+, HER2-, or HER2+ specific BC. CONCLUSION: Changes in alcohol consumption during midlife were not associated with the risk of postmenopausal BC, either overall or by hormonal receptor status.