According to a study in the August 17 issue of JAMA, an analysis of data from almost 500,000 individuals indicates, that the risk of bladder cancer among smokers is higher than reported from previous population data, and that the risk for female smokers is comparable with that of men. According to background information in the article, over 350,000 individuals are diagnosed with bladder cancer per year worldwide; this includes over 70,000 cases per year in the United States. Tobacco smoking is the best-established risk factor for bladder cancer in both men and women. Previous studies suggest that current cigarette smoking triples bladder cancer risk relative to never smoking.

The authors write:

“However, the composition of cigarettes has changed during the past 50 years, leading to a reduction in tar and nicotine concentrations in cigarette smoke, but also to an apparent increase in the concentration of specific carcinogens, including beta-napthylamine, a known bladder carcinogen” adding that “changing smoking prevalence and cigarette composition warrant revisiting risk estimates for smoking and bladder cancer.”

Neal D. Freedman, Ph.D., M.P.H., of the National Cancer Institute, Department of Health and Human Services, Rockville, Md., and their colleagues carried out a study to determine the link between tobacco smoking and bladder cancer. They analyzed data from 281,394 men and 186,134 women in the National Institutes of Health-AARP (NIH-AARP) Diet and Health Study, who filled in a lifestyle questionnaire and were followed up between October 1995 and December 2006. Earlier studies of smoking and incident bladder cancer were identified by a systematic review of the literature available.

During the follow-up period 3,896 men and 627 women were newly diagnosed with bladder cancer, with cigarette smoking being a significant risk factor for bladder cancer in both sexes. In relation to people who never smoked, former and current smokers showed an increased risk of bladder cancer in both, men and women. According to the data results, research suggests, that former smokers have a 2.2 times increased risk of bladder cancer and that the risk was approximately 4 times higher for current smokers in comparison to those who never smoked. The authors commented:

“In contrast, the summary risk estimate for current smoking in 7 previous studies (initiated between 1963 and 1987) was 2.94”.

Current and former smoking is responsible for a similar proportion of bladder cancer in both sexes, posing a 50 percent risk in men and 52 percent risk in women.The researchers write:

“Factors that may have strengthened the cigarette smoking-bladder cancer association include changes in the constituents of cigarette smoke (such as increased concentrations of beta-napthylamine), and increased awareness of bladder cancer risk in smokers, which may prompt earlier diagnostic workup” They continued to conclude, “These results support the hypothesis that the risk of bladder cancer associated with cigarette smoking has increased with time in the United States, perhaps a reflection of changing cigarette composition. Prevention efforts should continue to focus on reducing the prevalence of cigarette smoking.”

Written by Grace Rattue