Alcohol consumption and risk of breast cancer.

In a population-based case-control study conducted in Adelaide, South Australia, and involving 451 case-control pairs aged 20-74 years, the risk of breast cancer for women consuming more than 9.3 g of alcohol per day was 50% higher than for non-drinkers (unadjusted RR 1.46, 95% CI 1.00-2.13). The increase in risk persisted upon control for potential confounding variables including dietary or diet-related factors, and was not restricted to any particular type of beverage. Lower levels of alcohol consumption were not associated with substantial alterations in risk of breast cancer. When examined within menopausal strata, the effect of alcohol was more pronounced in pre-menopausal women, although none of the estimates of effect within menopausal strata were statistically significant. Although positive associations between alcohol consumption and risk of breast cancer have been observed in previous studies, support for a causal association is, at most, qualified. However, given the widespread nature of this exposure, at least in developed countries, further and more detailed investigations of this association are required.