Smoking habits and risk of benign breast disease.

The relationship between smoking habits and the risk of benign breast disease (BBD) was analyzed using data from a case-control study conducted between 1981 and 1983 in the greater Milan area, Northern Italy. Cases (n = 288) were women with histologically confirmed BBD (203 dysplasia, 85 benign tumours) referred to the National Cancer Institute of Milan for biopsies. Controls were women (n = 291) seen on selected days for a cytological smear for cervical cancer in outpatient clinics of the same Institute. No consistent association emerged between various indicators of smoking habits (smoking status, number of cigarettes smoked per day, duration of smoking) and the risk of BBD. Compared with never smokers the relative risk (RR) of all BBD combined was 0.7 (95% confidence interval, Cl: 0.4-1.3) in exsmokers, 1.4 (95% Cl: 0.8-2.5) in smokers of less than 10 cigarettes per day, and 1.1 (95% Cl: 0.7-1.7) in smokers of 10 or more cigarettes per day. There was some suggestion that the risk may be below unity post-menopause, but the relative risks for smokers were not statistically different in pre- (RR = 1.2; 95% Cl: 0.8-1.8) and post-menopausal (RR = 0.6; 95% Cl: 0.2-1.7) women. The risk of benign tumours (chiefly fibradenoma) was higher in current smokers, but this finding was not statistically significant (RR = 1.5; 95% Cl: 0.9-2.6) and the highest risks were observed in the strata of lighter smokers and those with shorter duration of smoking. Overall these results fail to support a negative association between smoking habits and benign breast disease.