부산대학교 도서관

Background: Urinary bladder cancer is very frequent in western countries. Its main risk factors are smoking and certain occupational exposures. The evidence of its association with the textile industry is limited, the link with occupational factors in women has received little recognition and its relationship with social class is controversial. Articles: This thesis comprises 4 articles corresponding to two studies: 1) Study of Vallès Occidental (VO), with the objective to evaluate the risk of bladder cancer in the textile industry; two articles are included, on this association and on social class on the basis of occupation; 2) European pooled analysis, including the previous study, with the objective to evaluate the impact of occupation on bladder cancer in Europe; two articles are included, one on occupation in women and the other on smoking in men.Methods: 1) Study VO: case control design, with 218 incident cases of bladder cancer diagnosed between 1993-1995 in the population living in VO, and 344 controls selected through the municipal lists; lifetime occupational and smoking history was obtained for all; 2) European pooled analysis: primary data from eleven recent case control studies conducted in Europe, with detailed information on occupation and smoking.Results: The adjusted incidence rate for men in VO was among the highest in Europe, whereas for women it was intermediate-low and 10 times lower. No overall excess risk was found associated neither with the textile industry nor for its specific sectors. An elevated risk was found for spinners for more than 20 years (OR 3.28; 95%CI 1.08-9.97) and machine setters between 1960 and 1974 (OR 4.26; 95%CI 1.09-16.7). The association with social class was weak, with the highest risk for highest social classes. Pooling the European data of 700 female cases and 2,425 female controls showed an elevated risk for a few previously identified risk occupations, and for certain for metal workers (OR=2.0, 95%CI 1.1-3.6), tobacco workers (OR=3.1, 95%CI 1.1-9.3), field crop and vegetable farm workers (OR=1.8, 95%CI 1.0-3.1) and dressmakers (OR=1.4, 95%CI 1.0-2.1). About 8% (95%CI 3.1-19.9) of all bladder cancers in women could be attributed to occupation. Cigarette smoking was analysed in European men, including 2,600 cases and 5,524 controls. There was a linear increasing risk with increasing duration of smoking, and a dose-response relationship with number of cigarettes smoked per day up to threshold limit of 15-20 cigarettes/day after which no increased risk was observed. An immediate decrease in risk of bladder cancer was observed for those who gave up smoking, which was over 60% after 25 years (OR=0.37, 95%CI 0.30-0.45), but the risk did not reach the level of never-smokers. The proportion of cases attributable to ever smoking was 0,66 (95%CI 0.66-0.79). Similar results for smoking were obtained in VO study.Conclusions: The incidence of bladder cancer in men of VO is among the highest in Europe, is associated with smoking and certain occupations in the textile industry with highest exposures, but other risk factors remain unknown. The risk associated with previously identified high-risk occupations is now lower. In European women, 1-2 cases among each 20 cases can be attributed to occupation. In European men, smoking can explain a 65% of cases, the risk is mainly associated with duration and an important reduction is observed with cessation. More studies are needed using more accurate methodologies which include other potential risk factors for bladder cancer.