Objective.— To assess the risk of invasive breast cancer associated with total and
beverage-specific alcohol consumption and to evaluate whether dietary and
nondietary factors modify the association.
Data Sources.— We included in these analyses 6 prospective studies that had at least
200 incident breast cancer cases, assessed long-term intake of food and nutrients,
and used a validated diet assessment instrument. The studies were conducted
in Canada, the Netherlands, Sweden, and the United States. Alcohol intake
was estimated by food frequency questionnaires in each study. The studies
included a total of 322647 women evaluated for up to 11 years, including 4335
participants with a diagnosis of incident invasive breast cancer.
Data Extraction.— Pooled analysis of primary data using analyses consistent with each
study's original design and the random-effects model for the overall pooled
Data Synthesis.— For alcohol intakes less than 60 g/d (reported by >99% of participants),
risk increased linearly with increasing intake; the pooled multivariate relative
risk for an increment of 10 g/d of alcohol (about 0.75-1 drink) was 1.09 (95%
confidence interval [CI], 1.04-1.13; P for heterogeneity
among studies, .71). The multivariate-adjusted relative risk for total alcohol
intakes of 30 to less than 60 g/d (about 2-5 drinks) vs nondrinkers was 1.41
(95% CI, 1.18-1.69). Limited data suggested that alcohol intakes of at least
60 g/d were not associated with further increased risk. The specific type
of alcoholic beverage did not strongly influence risk estimates. The association
between alcohol intake and breast cancer was not modified by other factors.
Conclusions.— Alcohol consumption is associated with a linear increase in breast cancer
incidence in women over the range of consumption reported by most women. Among
women who consume alcohol regularly, reducing alcohol consumption is a potential
means to reduce breast cancer risk.