A pooled analysis of bladder cancer case-control studies evaluating smoking in men and women

Objective: A recent study suggested that risk of bladder cancer may be higher in women than in men who smoked comparable amounts of cigarettes. We pooled primary data from 14 case-control studies of bladder cancer from Europe and North America and evaluated differences in risk of smoking by gender. Methods: The pooled analysis included 8316 cases (21% women) and 17,406 controls (28% women) aged 30-79 years. Odds ratios (ORs) and 95% confidence intervals (95% CI) for smoking were adjusted for age and study. Exposure-response was evaluated in a stratified analysis by gender and by generalized additive models. Results: The odds ratios for current smokers compared to nonsmokers were 3.9 (95% CI 3.5-4.3) for males and 3.6 (3.1-4.1) for females. In 11 out of 14 studies, ORs were slightly higher in men. ORs for current smoking were similar for men (OR = 3.4) and women (OR = 3.7) in North America, while in Europe men (OR = 5.3) had higher ORs than women (OR = 3.9). ORs increased with duration and intensity in both genders and the exposure-response patterns were remarkably similar between genders. Conclusion: These results do not support the hypothesis that women have a higher relative risk of smoking-related bladder cancer than men.