The importance of smoking-related variables in the development of bladder cancer was examined in data from a hospital-based case-control study of 1316 male and 505 female cases, and 3940 male and 1504 female age-matched controls interviewed in 20 hospitals from 9 United States cities between 1969 and 1984.
For male current smokers, odds ratios for number of cigarettes smoked per day (cpd) increased to approximately 2.5 for smokers of more than 20 cpd, after adjustment for duration and nonsmoking-related covariates. Above 20 cpd, no further increase in odds ratio was observed. In females, the adjusted odds ratios showed no significant effect of increasing cpd level. In males, the odds ratios for duration increased from 1.18 (0.52–2.72) in those who smoked for less than 20 years to 2.31 (1.65–3.24) in those who smoked for greater than 40 years. In females, the corresponding odds ratios were 0.97 (0.27–3.44) and 1.62 (1.00–2.62). The results did not suggest an increased risk with early age at start of smoking in either sex. Ex-cigarette smokers, as a whole, had reduced odds ratios for bladder cancer, but the extent of the reduction was similar in short-term and longer-term quitters.
The findings of this investigation support an association between smoking and bladder cancer. The pattern of risk associated with cpd and duration among current smokers and the early decline in risk associated with quitting are discussed in relation to possible mechanisms of bladder carcinogenesis.
This research was supported by National Cancer Institute Program Project Grant CA32617 and Center Grant CA17613, and American Cancer Society Special Institutional Grant SIG-8.