Joint effects of smoking and body mass index on prostate cancer risk

Between 1979 and 1985, a population-based case,control study of cancer at m ultiple sites was carried out in Montreal. A total of 399 cases with histol ogically confirmed prostate cancer and 476 population controls, 45-70 years of age, gave face-to-face interviews and provided adequate smoking histori es. We analyzed the effects of smoking cigarettes only and of smoking cigar s, or pipes, or both, with or without cigarettes, on the risk of prostate c ancer. Overall, the associations between smoking cigarettes and prostate ca ncer were weak and compatible with no effect; the associations with cigar a nd pipe smoking were stronger. Among men with high body mass index, however , we found appreciable associations between cigarette smoking and prostate cancer risk. A history of ever smoking daily was associated with an odds ra tio of 2.31 (95% confidence interval = 1.09-4.89). Risk increased with the amount smoked per day and with the duration of smoking. Taken together, the findings of increased risk associated with cigar and pipe smoking and the findings of increased risk associated with cigarette smoking among obese me n suggest that tobacco smoking may be a risk factor for prostate cancer.