The hypothesis has been raised that
coffee consumption may increase the incidence of
breast cancer, based on the report that
fibrocystic breast disease, a risk factor for
breast cancer, regresses after abstention from
coffee and other methylxanthines. The relation between recent
coffee consumption and the risk of
breast cancer was evaluated in a case-control study, based on interviews conducted 1975-1982 at several mainly eastern US teaching and community hospitals. The responses of 2,651 women with newly diagnosed
breast cancer were compared with those of 1,501 controls with nonmalignant conditions and 385 controls with
cancers at other sites. The relative risk estimates for levels of
coffee drinking up to seven or more cups daily, relative to none, approximated 1.0 with narrow 95% confidence intervals. After allowance for confounding, the relative risk estimate for drinking at least five cups a day was 1.2 (95% confidence interval, 0.9-1.6) using the noncancer controls and 1.1 (0.7-1.6) using the
cancer controls.
Coffee consumption was not associated with an increase in the risk of
breast cancer among women with a history of
fibrocystic breast disease, nor were
tea or decaffeinated
coffee associated with an increase in the risk of
breast cancer. The results suggest that the recent consumption of
coffee does not influence the incidence of
breast cancer.