Categorized | Bladder Cancer, Feature

Study Finds Strong Association Between Smoking and Risk for Bladder Cancer

Data from a large cohort study showed that smoking’s contribution to bladder cancer risk increased over the past 25 years, and the attributable risk in women caught up with that of men.

Current smokers increased risk of bladder cancer by four times compared to people who never smoked.  The risk among former smokers two times that of people who never smoked.  Previous cohort studies had shown about a threefold increased risk of bladder cancer among current smokers.

According to a recent article published in JAMA, smoking accounted for about half of the population-attributable risk of bladder cancer in men and women alike.

This apparent association between smoking and bladder cancer could reflect changes in cigarette manufacturing.

From the 1980s, the rates of bladder cancer in the U.S. has remained stable, ranging from 123.8 to 142.2 cases per 100,000 person-years in men, and from 32.5 to 33.2 cases per 100,000 person-years in women.

The authors noted in their introduction that the prevalence of smoking and cigarette composition have changed considerably during the same period, which perhaps changes the nature of the association between smoking and bladder cancer.

Neal D. Freedman, PhD, of the National Cancer Institute in Bethesda, Md., and co-authors revisited risk estimates for smoking and bladder cancer by examining data from the National Institutes of Health-American Association of Retired Persons (NIH-AARP) Diet and Health Study.

The NIH-AARP cohort study had follow-up data through December 31, 2006.  The participants, who were ages 50 to 71 at enrollment, completed a lifestyle questionnaire during 1995 and 1996.  This follow-up continued until the end of the study, a diagnosis of bladder cancer, a move outside the study’s catchment area, or death.

State cancer registries provided bladder cancer diagnoses information.  The foma; analysis included 281,394 men and 186,134 women.  During 4,518,941 person-years of follow up, 3,896 men had new diagnoses of bladder cancer, resulting in an incidence of 144 per 100,000 person-years.  During this same follow-up period, 627 women had a new diagnosis of bladder cancer for an incidence of 34.5 per 100,000 person-years.  Rates among people who never smoked were 69.8 and 16.1 per 100,000 person-years in men and women, respectively.  These rates increased to 154.6 and 276.4 per 100,000 person-years among men who were former or current smokers. Corresponding rates in women were 40.7 and 73.6 per 100,000 person-years.

The research team performed a systematic review and meta-analysis of prospective cohort studies of current smoking and bladder cancer started between 1963 and 1987.

Limitations of the study included lack of information on the year smoking had started and lack of follow-up data on smoking after the baseline survey to know how many people may have quit.

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