Cigarette smoking and benign breast disease.

The association between cigarette smoking and the occurrence of benign breast disease was assessed in a hospital-based case-control study conducted in Connecticut during 1979-81. Current smokers, but not former smokers, were at reduced risk for all benign breast diseases. The odds ratios associated with current smoking were 0.7 (95% confidence intervals = 0.6, 0.9) for fibrocystic breast disease, 0.6 (95% confidence intervals = 0.5, 0.9) for fibroadenoma, 0.6 (95% confidence intervals = 0.4, 1.0) for fibrocystic breast disease concomitant with fibroadenoma, and 0.6 (95% confidence intervals = 0.5, 0.9) for other benign breast disease. Adjustments for potentially confounding variables, including indices of medical care utilisation, affected these odds ratios only slightly. There was no convincing evidence of an association, either negative or positive, between current cigarette smoking and the degree of epithelial atypia of the fibrocystic lesions. However, the negative association between fibrocystic disease and current cigarette smoking was strongest for atypical lobular hyperplasia, which in turn has been associated with a particularly elevated risk of subsequent breast cancer.