Cigarette smoking and bladder cancer in men: A pooled analysis of 11 case-control studies

The primary risk factor for bladder cancer is cigarette smoking. Using a co mbined analysis of 11 case-control studies, we have accurately measured the relationship between cigarette smoking and bladder cancer in men. Availabl e smoking information on 2,600 male bladder cancer cases and 5,524 male con trols included duration of smoking habit, number of cigarettes smoked per d ay and time since cessation of smoking habit for ex-smokers. There was a li near increasing risk of bladder cancer with increasing duration of smoking, ranging from an odds ratio (OR) of 1.96 after 20 years of smoking (95% con fidence interval [CI] 1.48-2.61) to 5.57 after 60 years (CI 4.18-7.44). A d ose relationship was observed between number of cigarettes smoked per day a nd bladder cancer up to a threshold limit of 15-20 cigarettes per day, OR = 4.50 (CI 3.81-5.33), after which no increased risk was observed. An immedi ate decrease in risk of bladder cancer was observed for those who gave up s moking. This decrease was over 30% after 1-4 years, OR = 0.65 (0.53-0.79), and was over 60% after 25 years of cessation, OR = 0.37 (0.30-0.45), Howeve r, even after 25 years, the decrease in risk did not reach the level of the never-smokers, OR = 0.20. (0.17-0.24). The proportion of bladder cancer ca ses attributable to ever-smoking was 0.66 (0.61-0.70) for all men and 0.73 (0.66-0.79) for men younger than 60. These estimates are higher than previo usly calculated. Int. J. Cancer 86: 289-294, 2000. (C) 2000 Wiley-Liss, Inc .