Table 11.2 Risk factors for bladder cancer, by direction of association and strength of evidence
| Increases risk | Decreases risk |
Convincing or probable | Tobacco smoking1 | |
| Various occupations and employment in particular industries and product manufacture2-8 | |
| Occupational exposure to aromatic amines and polycyclic aromatic hydrocarbons 3,4 | |
| Ionizing radiation9 | |
| Arsenic and inorganic arsenic compounds10 | |
Possible | Volume of tap water consumed11 | Having had children16 |
| Disinfection by-products in drinking water12,13 | Non-steroidal anti-inflammatory drugs (other than aspirin)17 |
| Type II diabetes14 | Selenium18 |
| Infection with human papilloma viruses (HPV)15 | |
| Early menopause16 | |
|
1 Secretan et al., 2009; 2 Reulen et al., 2008; 3 Scélo and Brennan, 2007; 4 Baan et al., 2009; 5 Reulen et al., 2008; 6 Manju et al., 2009; 7 Guha et al., 2010; 8 Harling et al., 2010; 9 El Ghissassi et al., 2009; 10 Straif et al., 2009 11 Villaneuva et al., 2006; 12 Villanueva et al., 2004; 13 Costet et al., 2011; 14 Larsson et al., 2006; 15 Li et al., 2011; 16 Dietrich et al., 2011; 17 Daugherty et al., 2011; 18 Amaral et al., 2010 |
The leading known cause of cancer of the bladder is tobacco smoking (Table 11.2). Two-thirds of bladder cancers in men and one-third in women are considered to be due to smoking (Brennan et al., 2000; Brennan et al., 2001). Risk increases with duration of cigarette smoking and number of cigarettes smoked (International Agency for Research on Cancer, 2004b). Risk is also increased in those who smoke pipes or cigars, but do not smoke cigarettes (Pitard et al., 2001). Stopping smoking results in an immediate decrease in risk (Scélo and Brennan, 2007).
A range of occupations (including painting, mining, bus driving, motor mechanic, blacksmith, machine setter and hairdressing) and employment in various industries or in manufacturing of specific products (including rubber manufacturing, aluminium production and magenta manufacture) are associated with bladder cancer. In terms of specific occupational exposures which cause bladder cancer, the most consistent evidence relates to aromatic amines and polycyclic aromatic hydrocarbons.
Other than smoking and occupational exposures, the factors involved in bladder cancer aetiology are largely unknown, although several putative relationships have been suggested. Positive associations have been reported between volume of tap water consumed and bladder cancer risk. This may be due to increased intake of carcinogenic chemicals contained in the water, such as arsenic (which is a recognised cause of bladder cancer) or disinfection by-products (e.g. trihalomethanes, the main by-product of chlorinated water), but the results of studies are not consistent.
Individuals with type II diabetes may have a modest increased risk of developing bladder cancer. A meta-analysis of studies investigating human papilloma virus (HPV) infection and bladder cancer estimated that risk could be increased by almost 3-fold in infected individuals. In another meta-analysis, bladder cancer risk was reduced by one-third in ever parous women (those who had had one or more children), and was elevated among those undergoing an early menopause. Non-smokers who regularly use non-steroidal anti-inflammatory drugs other than aspirin may have reduced bladder cancer risk, although aspirin use itself does not appear to be associated with risk. Those with higher levels of selenium measured in serum or toenails may also have lower risk.
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