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Cigarette Smoking Implicated in Half of Bladder Cancers in Women


In 2011, approximately 69,250 people will be diagnosed with bladder cancer in the US, and 14,990 will die from the disease.


Previous studies indicate that the population attributable risk (PAR) of bladder cancer for tobacco smoking is 50% to 65% in men and 20% to 30% in women and that current cigarette smoking triples bladder cancer risk relative to never smoking. During the last 30 years, incidence rates have remained stable in the United States in men (123.8 per 100 000 person-years to 142.2 per 100 000 person-years) and women (32.5 per 100,000 person-years to 33.2 per 100,000 person-years).


Although there have been reductions in the concentrations of tar and nicotine in cigarette smoke, there have been apparent increases in the concentrations of certain carcinogens associated with bladder cancer. A 2009 NCI/DCEG study was the first to suggest a higher risk for smoking-induced bladder cancer than previously reported. That report, based on data from the New England Bladder Cancer Study, found that the association between cigarette smoking and risk of bladder cancer appeared to be stronger than it was in the mid-1990s.


According to an article published in the Journal of the American Medical Association (2011;306:737-745), it was shown that current cigarette smokers have a higher risk of bladder cancer than previously reported, and the risk in women is now comparable to that in men. The study used data from over 450,000 participants in the NIH-AARP Diet and Health Study, a questionnaire-based study that was initiated in 1995, with follow-up through the end of 2006.


While previous studies showed that only 20 to 30% of bladder cancer cases in women were caused by smoking, these new data indicate that smoking is responsible for about half of female bladder cancer cases – similar to the proportion found in men in current and previous studies. The increase in the proportion of smoking-attributable bladder cancer cases among women may be a result of the increased prevalence of smoking by women, so that men and women are about equally likely to smoke, as observed in the current study and in the U.S. population overall, according to surveillance by the CDC. The majority of the earlier studies were conducted at time periods or in geographic regions where smoking was much less common among women.


In the current study, former smokers were twice as likely to develop bladder cancer as never smokers, and current smokers were four times more likely than those who never smoked. As with many other smoking-related cancers, smoking cessation was associated with reduced bladder cancer risk. Participants who had been smoke-free for at least 10 years had a lower incidence of bladder cancer compared to those who quit for shorter periods of time or who still smoked.


According to the authors, even though smoking carries the same risk for men and women, men are still about four times more likely to be diagnosed with bladder cancer, and that the study results suggest that difference in smoking rates explain only part of the higher incidence rates in American men. The authors added that occupational exposures, as well as physiologic differences, may contribute to the gender disparity.


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