ALCOHOL, SMOKING, PASSIVE SMOKING AND CAFFEINE IN RELATION TO BREAST-CANCER RISK IN YOUNG-WOMEN

The UK National Case-Control Study Group has examined the relationship between smoking (both own smoking and passive), alcohol consumption a nd caffeine consumption and the risk of breast cancer. A total of 755 women with breast cancer diagnosed before the age of 36, each with an age-matched general population control, were interviewed, and detailed information on reproductive, contraceptive and medical history, perso nal attributes and habits were obtained. Additional data on passive sm oking were obtained from a subgroup of women. There was no evidence of a statistically significant difference in breast cancer risk between subjects who had ever smoked as much as one cigarette per day and thos e who had not [relative risk (RR)= 1.01, 95% confidence interval (CI) 0.81-1.26]. Most relative risks for passive smoking exceeded unity, bu t there was little evidence of significant trends with increasing expo sure. The lack of effect of own smoking, and the fact that such smoker s are also themselves exposed to the effects of passive smoking, makes any relationship between exposure to others' smoking and breast cance r risk implausible. Alcohol consumption during the year prior to diagn osis and at ages 18 and 25 was examined. Consumers of 0.1-4.9 and 5.0- 14.9 g per day generally had non-significantly increased risks compare d with never drinkers, but consumers of more than 15 g per day had red uced risks.