Objectives: To examine the combined effect of alcohol and folate intake during adolescence on the risk of proliferative benign breast disease (BBD).
Methods: We used data from 29 117 women in the Nurses' Health Study II who completed both adolescent alcohol consumption questions in 1989 and an adolescent diet questionnaire in 1998. A total of 659 women with proliferative BBD diagnosed between 1991 and 2001 were confirmed by central pathology review. Cox proportional hazards models were used to estimate hazard ratios and 95% confidence intervals (CIs), adjusted for established risk factors of breast cancer.
Results: Adolescent alcohol consumption was dose-dependently associated with an increased risk of proliferative BBD (hazard ratio = 1.15 per 10 g/day consumption; 95% CI, 1.03-1.28). There was no significant association between adolescent folate intake and the risk of proliferative BBD. Stratified analyses showed that each 10-g/day alcohol intake during adolescence was associated with a 21% (95% CI, 1.01-1.45) increase in the risk of proliferative BBD among women with low folate intake during adolescence, which was not significantly different from the alcohol-associated risk among women with moderate and high folate intake during adolescence (P for interaction = 0.18).
Conclusions: Adolescent alcohol consumption is associated with increased risk of proliferative BBD, which may not be reduced by increased folate intake during adolescence.