Background: Using a combined analysis of 11 case-control studies from Europe, we have investigated the relationship between cigarette smoking and bladder cancer in women.
Methods: Available smoking information on 685 female bladder cancer cases and 2416 female controls included duration of smoking habit, number of cigarettes smoked per day, and time since cessation of smoking habit for ex-smokers.
Results: There was an increasing risk of bladder cancer with increasing duration 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 interval (CI) 1.1-3.1) to over a four-fold increased risk for a duration of greater than 40 years (OR = 4.1, 95% CI 3.0-5.5). A dose-response relationship was observed between number of cigarettes smoked per day and bladder cancer 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 in risk of bladder cancer was observed for those who gave up smoking. This decrease 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 not 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 (0.14-0.22). These attributable proportions are less than those observed among men, although they are likely to increase in the future as the smoking-related disease epidemic among women matures.