Cigarette smoking was first evaluated as a risk factor for bladder cancer more than 50 years ago. As early as 1964, the Surgeon General's report summarized results from four case-control studies and seven prospective cohort studies. In the case-control studies, the odds ratios in men ranged from 2.0 to 3.3. In the cohort studies, the mean relative risk of bladder cancer mortality in smokers, relative to nonsmokers, was 1.9. The data suggested that the association of smoking with bladder cancer increased according to smoking frequency and depth of inhalation. This evidence led to the conclusion that "... available data suggest an association between cigarette smoking and urinary bladder cancer in the male but are not sufficient to support a judgment on the causal significance of the association".
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