The contribution of cigarette smoking to bladder cancer in women (pooled European data)

Background: Using a combined analysis of 11 case-control studies from Europ e, we have investigated the relationship between cigarette smoking and blad der cancer in women. Methods: Available smoking information on 685 female bladder cancer cases a nd 2416 female controls included duration of smoking habit, number of cigar ettes smoked per day, and time since cessation of smoking habit for ex-smok ers. Results: There was an increasing risk of bladder cancer with increasing dur ation of smoking, ranging from approximately a two-fold increased risk for a duration of less than 10 years (odds ratio (OR) = 1.9, 95% confidence int erval (CI) 1.1-3.1) to over a four-fold increased risk for a duration of gr eater than 40 years (OR = 4.1, 95% CI 3.0-5.5). A dose-response relationshi p was observed between number of cigarettes smoked per day and bladder canc er up to a threshold limit of 15-20 cigarettes per day, OR = 3.8 (95% CI 2. 7-5.4), after which no increased risk was observed. An immediate decrease i n risk of bladder cancer was observed for those who gave up smoking. This d ecrease was over 30% in the immediate 1-4 years after cessation, OR = 0.68 (95% CI 0.38-1.2). However, even after 25 years the decrease in risk did no t reach the level of the never-smokers, OR = 0.27 (95% CI 0.21-0.35). Conclusion: The proportion of bladder cancer cases among women attributable to ever smoking was 0.30, (0.25-0.35) and to current smoking was 0.18 (0.1 4-0.22). These attributable proportions are less than those observed among men, although they are likely to increase in the future as the smoking-rela ted disease epidemic among women matures.