To our knowledge, this is the first study to evaluate breast cancer risk in relation to both frequency of drinking and binge drinking. Two other prospective studies have evaluated regularity of drinking and did not find a difference between less and more frequent drinking, but they had fewer breast cancer cases and used less detailed measures.10, 11 In terms of binge drinking, a prospective study showed a non-linear association with the highest risk among those who consumed 4-5 drinks per weekday or 16-21 drinks per weekend and lower risks for those who drank more, but they had few cases in the highest categories and contrary to most studies, non-drinkers had an increased risk of breast cancer.33 A case-control study found a non statistically significant increased risk associated with binge drinking limited to high alcohol consumers.34 After controlling for cumulative average intake, we observed an association with binge drinking, but not frequency of drinking. However, there may still be some residual confounding with the higher cumulative alcohol intake among binge drinkers.
