Study: Smoking, bladder cancer link higher in women than previously thought
Cigarettes may be the smoking gun behind half of the bladder cancer cases for women in the United States, scientists from National Cancer Institute announced Tuesday.
Published in the Journal of the American Medical Association, the new findings show that -- at least in terms of developing bladder cancer -- smoking cigarettes is just as risky for women as it is for men.
That flies in the face of previous reports that concluded that only 20 to 30 percent of bladder cancer cases in women were linked to smoking. "Ours is the first study to indicate the proportion of bladder cancer linked to smoking is, in fact, the same," said Neal Freedman, author of the study.
According to Freedman, previous studies were conducted in time periods and geographic locations where women smoked less than men. Today in the United States, both sexes are lighting up in equal proportions and the risk factor has also evened out, he said.
One in five adults smokes, and approximately 69,250 people will be diagnosed with bladder cancer in the United States this year, the NCI reports. About 14,990 will die from the disease.
Even though the risk factor is now about the same, men are still diagnosed with the disease four times more often than women, for unknown reasons.
After examining data from more than 450,000 participants in a questionnaire-based study that began in 1995, the NCI researchers also concluded that the risk for bladder cancer was four times higher for smokers than their non-smoking peers. Past studies showed the risk to be three times more.
But the findings weren't all grim. The report also indicates that smokers who kicked the habit were much less likely to develop bladder cancer.
Former smokers were twice as likely to develop bladder cancer as those who never started. But those currently smoking are four times more likely to get the disease.
That could be good news in the United States, where the number of smokers has declined steadily in the past three decades. But there's a caveat that still troubles researchers: the number of people diagnosed with the disease doesn't seem to be falling in conjunction with the smoking rate. Rather, it's remained fairly steady in the last three decades.
Freedman and his colleagues believe it could be due to the fact that cigarettes may be more toxic than they used to be for those who continue to smoke. Recently, he said, there have been a number of changes in the composition of cigarettes, the way the tobacco is cured, and the concentrations of tar and nicotine. More powerful filters may even be changing the way people smoke by causing them to inhale more deeply. "But we can only speculate which of these changes is related to bladder cancer," he said.
Dr. Bernard Bochner, an attending surgeon specializing in bladder cancer at Memorial Sloan-Kettering Cancer Center in New York, called the findings "significant" and said the figures will be a powerful tool in convincing people to stop smoking or to avoid the habit altogether.
"People have the impression that once they stop smoking, their risks for cancer immediately go away. And that simply is not the case," he said.
But the report also brings to the forefront an important question, he said. If smoking only causes 50 percent of bladder cancer cases, what's driving the other half?
"There must be other environmental factors involved. It still remains a little bit of a mystery in that some people can smoke two packs a day and not develop bladder cancer while marathon runners who eat well and have never picked up a cigarette are still being diagnosed," he said.
"But to have such a well-recognized agent causing half of these cases, it's critical to get people to understand bladder cancer is directly tied to smoking."