Each year in the United States, approximately 71,000 people are diagnosed with bladder cancer. One of the most important risk factors for bladder cancer is smoking.
New data continue to define the risk of smoking and the development of bladder cancer. Women were initially thought to have a lower rate of smoking-attributable bladder cancer than men, but it now appears that smoking accounts for half of all cases of bladder cancer in both men and women.1,2 and research suggests that childhood exposure to second hand smoke increases the risk of developing bladder cancer.3
One of the most important risk factors for bladder cancer is smoking. Initial research suggested that smoking was linked with a three-fold increase in the risk of bladder cancer. These studies also found that 20 to 30 percent of bladder cancers in women and roughly 50 percent of bladder cancers in men were caused by smoking. Changes in smoking habits and the composition of cigarettes, however, may have caused these numbers to shift.
Although there is limited information about how the composition of cigarettes has changed over time, evidence suggests that the level of some carcinogens has increased. Furthermore, the introduction of low-nicotine cigarettes appears to have contributed to deeper and more frequent inhalation among smokers. As a result of these changes, smokers may now have a higher risk of bladder cancer than in the past.
To evaluate more recent data regarding smoking and bladder cancer, researchers at the National Cancer Institute used the NIH-AARP Diet and Health Study. Information was available about more than 450,000 people.
- Smoking accounted for a higher proportion of bladder cancer among women than previously reported: Roughly half of all bladder cancers among women were attributable to smoking, which is similar to what is seen among men.
- Current smokers had a four-fold increase in risk of bladder cancer, which is higher than previous estimates.
- Risk of bladder cancer was lower among former smokers than among current smokers. Nevertheless, the risk of bladder cancer in former smokers was twice as high as the risk in people who had never smoked.
The study highlights the important role that smoking plays in bladder cancer among both men and women. Never-smokers have the lowest risk, but current smokers can reduce their risk by quitting.
It’s also important to be aware that roughly half of all bladder cancers are due to factors other than smoking. This means that everyone (regardless of smoking status) should seek care for symptoms of bladder cancer such as blood in the urine.
What do other studies show?
To explore whether the risk of bladder cancer among smokers has increased over time, researchers evaluated information from studies conducted in New Hampshire during 1994-1998, 1998-2001, and 2001-2004.
- The link between smoking and bladder cancer appears to have grown stronger over time. Current smoking was linked with a threefold increase in risk during 1994-1998, a more than fourfold increase in risk during 1998-2001, and a 5.5-fold increase in risk during 2001-2004.
- Risk among former smokers was lower than risk among current smokers but also increased over time.
- The study also reported that for individuals with a similar total number of cigarettes smoked, smoking fewer cigarettes for a longer period of time appeared to pose a greater risk than smoking a greater number of cigarettes for a shorter period of time.
This study suggests that the risk of bladder cancer among smokers has increased over time. This may be the result of changes in the composition of cigarettes, changes in inhalation behavior among smokers, or both.4
According to a study published in the journal Cancer Epidemiology, Biomarkers and Prevention, risk of bladder cancer increases with duration and amount of smoking.
Risk of bladder cancer increases with age, and men are more commonly affected than women. Because smoking has been linked with an increased risk of bladder cancer, researchers continue to evaluate specific aspects of smoking in relation to bladder cancer risk.
To further evaluate the link between smoking and bladder cancer, researchers in Spain conducted a study among 1,219 patients with newly diagnosed bladder cancer and 1,271 individuals without bladder cancer.
- Current smoking increased the risk of bladder cancer by more than seven-fold in men and by roughly five-fold in women.
- Former smokers also had an increased risk of bladder cancer, but the strength of the link was stronger for men than for women.
- Risk of bladder cancer increased with duration and amount smoked.
- After accounting for duration of smoking, risk of bladder cancer did not vary significantly by type of tobacco (black vs. blond). However, the decline in risk after quitting smoking was greater for smokers of blond tobacco than smokers of black tobacco.
- Compared to men who inhaled into the mouth, men who inhaled into the throat or chest had an increased risk of bladder cancer.
- Most of the difference in bladder cancer rates between men and women in Spain appeared to be due to differences in smoking.
Children's Exposure to Second Hand Smoker Increases Risk of Bladder Cancer
According to an article published in the International Journal of Cancer, individuals who smoke and children who are exposed to second-hand smoke are at an increased risk of developing bladder cancer.
To assess the relationship between bladder cancer and smoking, researchers from Europe recently conducted a study involving nearly 430,000 individuals who participated in the European Prospective Investigation into Cancer and Nutrition (EPIC). During the follow-up period, 633 of the participants had developed bladder cancer.
- A significantly increased risk of bladder cancer occurred in individuals who were smokers or former smokers compared to never-smokers.
- The risk of bladder cancer increased even further among current smokers if they smoked more cigarettes, smoked for a longer duration of time, or started smoking earlier in their life.
- Exposure to second-hand smoke during childhood increased the risk for the development of bladder cancer later in life; however, exposure to second-hand smoke during adulthood did not appear to increase the risk of developing bladder cancer.
The researchers concluded that not only are smokers at an increased risk of developing bladder cancer, but children who are exposed to second-hand smoke also have an increased risk of developing bladder cancer within their lifetime.3
- Freedman ND, Silverman DT, Hollenbeck AR, et al. Association between smoking and risk of bladder cancer among men and women. JAMA. 2011;306(7):737-745. doi:10.1001/jama.2011.1142
- Samanic C, Kogevinas M, Dosemeci M et al. Smoking and Bladder Cancer in Spain: Effects of Tobacco Type, Timing, Environmental Tobacco Smoke, and Gender. Cancer Epidemiology, Biomarkers and Prevention . 2006;15:1348-1354.
Bjerregaard B, Raaschou-Nielsen O, Sorensen M, et al. Tobacco Smoke and Bladder Cancer – in the European Prospective Investigation into Cancer and Nutrition. International Journal of Cancer. 2006;119:2412 – 2416.
Baris D, Karagas MR, Verrill C et al. A case-control study of smoking and bladder cancer risk: emergent patterns over time. Journal of the National Cancer Institute. 2009;101:1553-1561.
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