Lifetime Alcohol Intake, Binge Drinking Behaviors, and Breast Cancer Risk

The prevalence of binge drinking is rising in the United States. While alcohol is a breast cancer risk factor, less is known about the impact of episodic heavy drinking. Breast cancer-free women, ages 35-74, were enrolled in the Sister Study from 2003-2009 (n = 50,884). United States or Puerto Rico residents who had a sister with breast cancer were eligible. Multivariable Cox regression was used to estimate adjusted hazard ratios (HRs) and 95% confidence intervals (CIs) for breast cancer. 1,843 invasive breast cancers were diagnosed during follow-up (mean = 6.4 years). Increased breast cancer risk was observed for higher lifetime alcohol intake (≥230 drinks/year, HR = 1.35, 95% CI: 1.15, 1.58 versus <60 drinks/year). Relative to low drinkers, HRs were increased for ever binge drinking (HR = 1.29, 95% CI: 1.15, 1.45) or blacking out (HR = 1.39, 95% CI: 1.17, 1.64). Compared to low drinkers who never binged, moderate drinkers who binged had a higher risk (HR = 1.25, 95% CI: 1.08, 1.44). There was evidence of effect modification between moderate lifetime drinking and binging (relative excess risk due to interaction (RERI) = 0.33, 95% CI: 0.10, 0.57). Our findings support the established association between lifetime alcohol and breast cancer and provide evidence for an increased risk associated with heavy episodic drinking, especially among moderate lifetime drinkers.