Cigarette smoking may be contributing not only to lung cancer, but also to steady rates of bladder cancer, according to new research.
Scientists have known that tobacco, among other environmental exposures to carcinogens, is a strong risk factor for bladder cancer. But despite declines in cigarette smoking over the past three decades, rates of bladder cancer in the U.S. have remained steady.
What’s responsible for the consistently high rates? Reporting in the Journal of the American Medical Association, Neal Freedman and his colleagues at the National Cancer Institute suggest that the changing make-up of cigarettes may have something to do with it.
Freedman believes that the lack of decline in bladder cancer rates indicates that cigarettes today may contain even more dangerous concentrations of carcinogens than in the past, thus off-setting whatever benefits the drop in smoking rates might have had on a population level. Over the past few decades, says Freedman, there is evidence that while concentrations of nicotine and tar have decreased in cigarettes, changes in the way cigarettes are made may have boosted levels of other carcinogens.
“It’s a hypothesis, that it does seem like perhaps one of the reasons the risks of bladder cancer stayed constant is that the strength of association between smoking and the cancer became stronger,” Freedman says.
In the study, in which more than 560,000 men and women in the National Institutes of Health-AARP Diet and Health Study completed questionnaires about their smoking history and experience with bladder cancer over a 10-year period, former smokers were two times as likely to develop bladder cancer as nonsmokers, and current smokers were four times as likely to report cases of bladder cancer.
Smoking, which accounts for about half of bladder cancer cases, is an important, modifiable factor. “The most important message of the study is that one of the best ways to prevent bladder cancer is to not smoke at all. But if someone is a smoker, stopping smoking can reduce the risk,” he says.