Alcohol and breast cancer mortality in a cohort study

Available epidemiological evidence indicates that alcohol intake is associa ted with a higher risk of developing breast cancer. Plausible biological pa thways include its effect on levels of estrogens, cell membrane integrity a nd cell-to-cell communication, inhibition of DNA repair, and congener effec t. The present study evaluated the impact of alcohol on mortality from brea st cancer, an area with relatively few studies in the literature. The subje cts were participants in a Canadian prospective cohort study, the National Breast Screening Study (NBSS). Women were enrolled in the cohort from 1980 to 1985 to evaluate the efficacy of mammographic screening. Information on usual diet and alcohol intake at enrolment and other epidemiological variab les was collected by means of a mailed, self-administered questionnaire. Mo rtality from breast cancer during follow- up to 31 December, 1993 was ascer tained by record linkage to the Canadian Mortality Data Base maintained by Statistics Canada. During the follow-up period of 1980-1993 (average 10.3 y ears), 223 deaths from breast cancer were identified for this analysis. The hazard ratios for the risk of death from breast cancer increased with inta kes of total alcohol of 10-20 g/day (1.039, 1.009-1.071) and > 20 g/day (1. 063, 1.029-1.098). This increase was contributed largely by the intake of w ine, a 15% increase in risk at intakes higher than 10 g/day of alcohol from wine. Alcohol from spirits was associated with a small decrease in risk of death (hazard ratio at 10 g/day, 0.945, 0.915-0.976). The effect of alcoho l from beer was not significant in the two categories studied. Although our results were statistically significant, the magnitude of the change in ris k was small.