Bladder cancer risks and causes | Cancer Research UK
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Bladder cancer risks and causes

Bladder cancer is more common in men than women. Bladder cancer usually takes a long time to develop and is most common in older people. It is rare in people under 40.

Main risk factors

The two main risk factors for bladder cancer are smoking and exposure to chemicals at work. Your risk if you smoke is up to 4 times higher than a non smoker. Chemicals in cigarette smoke get into the bloodstream and end up in the urine. This brings them into contact with the bladder. Chemicals used in some industries can also cause bladder cancer. Some have been banned in the UK for over 50 years, but you may have been exposed to them in the past.

Other risk factors

Parasitic bladder infections such as bilharzia increase the risk of bladder cancer in many developing countries. But this is not a major cause in the UK. Past cancer treatment with pelvic radiotherapy or chemotherapy drugs called cyclophosphamide also increases the risk.

 

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What risk factors are

A risk factor is anything that can increase your chance of developing cancer. Different cancers have different risk factors.

Remember that having one or more risk factors does not mean that you will definitely get bladder cancer. Many people who have one or more of the risk factors never get bladder cancer and some people who have none of the risk factors do develop bladder cancer. Risk factors are only a guide to what may increase risk.

 

How common bladder cancer is

Around 10,400 people are diagnosed with bladder cancer each year in the UK. Not counting non melanoma skin cancer, bladder cancer is the 7th most common cancer in the UK.  It is the 4th most common cancer in men.

More men than women get bladder cancer. This may just be because more men than women have smoked in the past few decades. And more men have been exposed to chemicals at work.

Your ethnic background is also related to your risk. Black or Asian men have around half the risk of bladder cancer as White men. Black or Asian women have around two thirds the risk of White women. 

Bladder cancer usually takes a long time to develop and it is most common in older people. Most people with bladder cancer are older than 60 years old. It is rare in people under 40.

 

Smoking

Smoking cigarettes definitely increases the risk of bladder cancer. Your risk if you currently smoke is up to 4 times that of someone who has never smoked. People with the highest risk are those who smoke heavily, or started smoking at a young age, or who have smoked for a long time. Smoking cigars and pipes also increases bladder cancer risk. In the UK, a large Cancer Research UK study in 2010 looking at lifestyle factors found that over a third of all bladder cancers are caused by smoking. 

The chemicals in the smoke get into the bloodstream. They are then filtered out of the blood by the kidneys and end up in the urine. When the urine is stored in the bladder, these chemicals are in contact with the bladder lining. Chemicals called arylamines in cigarette smoke may be the cause of the increased bladder cancer risk in smokers. In people who smoke, passing urine more frequently may, in some cases, reduce bladder cancer risk. But there is not enough evidence to support this for everyone.

A paper looking at second hand smoking (passive smoking) and bladder cancer risk did not find a link.  Some studies have tried to find a link between second-hand smoke in children and bladder cancer risk but the results have varied.

 

Chemicals at work

A group of chemicals called arylamines are known to cause bladder cancer. Some of these chemicals have been banned in the UK for over 50 years. But it can take up to 25 years for a bladder cancer to develop. You may have been exposed to them a long time ago if you work in industries such as rubber or plastics manufacture. Arylamines that increase risk of bladder cancer include

  • Aniline dyes
  • 2-Naphthylamine
  • 4-Aminobiphenyl
  • Xenylamine
  • Benzidine
  • O-toluidine

Another group of chemicals called polycyclic aromatic hydrocarbons (PAHs) increase the risk of bladder cancer. Exposure to these chemicals is possible in industries where people handle carbon or crude oil, or substances made from them. You may also come into contact with them in any industry involving combustion, such as smelting.

If you have a diagnosis of bladder cancer, it is worth finding out if you have ever been exposed to any of these chemicals. If you have, talk to your urologist or cancer doctor. You may be able to claim an allowance called Industrial Disease Benefit from the government Department for Work and Pensions.

Some other jobs have been linked to an increased risk of bladder cancer. These include

  • Bus and taxi drivers and railroad workers
  • Metal casters, machine setters and operators
  • Leather workers
  • Blacksmiths
  • Hairdressers
  • Mechanics
  • Miners
  • Painters

In all these occupations the increase in risk of bladder cancer is below 35%.

 

Water disinfection chemicals

When chlorine is used to disinfect water it can break down into chemicals called trihalomethanes (THMs). Chlorine is used to disinfect drinking water and swimming pools. It stops the growth of bacteria that can harm us. Some studies have looked at whether exposure to THMs by drinking chlorinated water can increase bladder cancer risk. 

Some studies seem to show that long term drinking of tap water with high levels of THMs may increase the risk of bladder cancer but findings are mixed. In some studies the increase in risk was only seen in men, and bladder cancer risk in women was not linked to drinking tap water. Other studies have shown a reduced risk of bladder cancer in people who drink a lot of water, especially if they empty their bladder often. But these studies also have limitations so we don't know for certain. 

There is some evidence that swimming in, or bathing or showering in, chlorinated water can also increase the risk when the chemicals are absorbed through the skin or breathed in as water droplets. But it is important to remember that disinfecting water reduces the risk of serious infectious diseases, so the risk of not chlorinating water is likely to be higher than that of exposure to THMs.

 

Treatment for other cancers

Treatment with radiotherapy to the pelvic area for cancers such as cervical cancer, prostate cancer, fallopian tube cancer, testicular cancer and womb cancer can increase your risk of bladder cancer. Treatment for some other cancers may also increase risk, including head and neck cancers, lung cancer and kidney cancer. This is probably to do with radiotherapy or chemotherapy, or these cancers may share risk factors with bladder cancer. Treatment with the chemotherapy drug cyclophosphamide also increases the risk.

 

Medical conditions

People who have diabetes have been found to have an increase in their risk of developing bladder cancer of around a third compared to people who do not have diabetes. This is likely to be due to a particular drug used in type 2 diabetes treatment called pioglitazone (which is a type of thiazolidinedione). This drug has been found to increase the risk of bladder cancer. But other drugs in the same group do not seem to increase the risk. Also, the type of treatment used depends on the stage of diabetes. The diabetes stage may also affect these findings. 

Some other medical conditions may affect the risk of bladder cancer. People with a spinal cord injury have a higher risk. This may be because they are more likely to have a urinary catheter, bladder or urine infections or bladder stones. Women who have systemic sclerosis also have a higher risk . The risk increase may be due to treatment with a drug called cyclophosphamide. 

Bladder cancer risk is higher in people after they have had a kidney transplant compared to the general public. And it is also higher for people with Crohn's disease, compared to people who do not have Crohn's. 

 

Chronic bladder irritation and infections

Some studies in the past have seemed to show that if you have had many bladder infections, or suffer from chronic bladder infection, you may be more at risk of bladder cancer. The risk is particularly high for a type called squamous cell cancer of the bladder. But one recent study did not find an increase in risk for people with a history of common bladder infections. Another study actually showed a decrease in risk in women. So we need more research to find out if there is a link between bladder infections and bladder cancer.

A study in 1991 showed that smokers who have repeated bladder infections may have a risk of bladder cancer 10 times higher than the general population. But there have not been any more recent studies to confirm this. Other studies have found that men who have had gonorrhoea infection also have an increased risk of bladder cancer. And for those men who smoke and have gonorrhoea, the risk may be even higher. 

In the developing world, parasitic infection is the main cause of bladder cancer. A parasite called bilharzia or schistosomiasis is widespread in many countries and increases the risk of squamous cell bladder cancer. But in the UK, parasitic infection is extremely rare and infection is a much less common cause of bladder cancer than smoking or workplace chemicals.

Bladder stones are little lumps of calcium that can form in the urinary system. You can get kidney or bladder stones. If you have stones in the bladder (sometimes called bladder calculi), you may be more at risk from a type of bladder cancer called squamous cell bladder cancer. This is because stones can cause chronic infection. But you would need to suffer from this for a long time before it would increase your risk of bladder cancer.

 

Diet and alcohol intake

Researchers have looked at many different factors in our diet to see if any of them affect bladder cancer risk. Most of the research findings do not provide any clear evidence about this. 

Selenium is a nutrient found in various foods and has also been shown to protect against bladder cancer in some studies. Bladder cancer risk has also been found to be lower in people with higher levels of vitamin D. Some studies suggest that having a higher intake of fruit and vegetables may lower your bladder cancer risk. 

Drinking alcohol does not have an effect on bladder cancer risk. It is important to remember though that alcohol increases the risk of several other cancers including breast and bowel cancer. 

 

Having had bladder cancer before

If you have already been successfully treated for a bladder cancer in the past then your risk of developing another cancer anywhere in the urinary tract is higher. This includes

  • Any part of your bladder that is still there after your treatment
  • The tubes that connect the kidney and the bladder (the ureters), including the part within the kidney (the renal pelvis)
  • The tube leading from the bladder to the outside of the body (urethra)

For this reason your specialist will keep a close eye on you and you will have regular checkups to find any new cancer at its earliest stage. If you have had transitional cell cancer of other parts of the urinary tract (such as the ureters, urethra or renal pelvis) your risk of bladder cancer is also higher than other people in the population.

 

Family history

In a few families, bladder cancer is associated with an inherited faulty gene. But this is very rare. If your relative was diagnosed before the age of 45, it is more likely that their cancer was caused by a gene fault. But family cancer patterns are influenced by behaviour too. Often cancers may seem to run in families because the family members share behaviours such as smoking, which increase the risk of cancer. 

Overall, you are statistically more at risk if you have a first degree relative with bladder cancer (a parent, child, sister or brother). But remember, this is a statistical risk and can only tell you about risk in a whole population, not your risk as an individual person.

 

Early menopause and having children

Some studies show that women who have an early menopause (before the age of 45) have their risk of bladder cancer increased by around half compared to women who have their menopause at the age of 45 or later. The increase in risk is higher in women who have early menopause after having both their ovaries removed for medical reasons.

Women who have had children have a lower risk of getting bladder cancer than women who have not had any children. 

 

Bladder development before birth

As a baby develops inside the mother there is a connection between the baby's bladder and belly button (umbilicus). This connection is called the urachus and usually disappears before the baby is born. The connection can remain after birth. This is extremely rare but can increase the risk of a rare type of bladder cancer called adenocarcinoma.

Another very rare birth defect called extrophy can also increase a person’s risk of developing bladder cancer later in life. Extrophy occurs when the bladder and urethra do not form properly. The bladder does not form its normal round shape but becomes flat and exposed to the outside of the body. It is turned inside out. With the bladder outside the body and not protected by skin covering, it can easily become infected. This can eventually lead to adenocarcinoma of the bladder.

 

Hair dye

Some research has suggested that using hair dye to colour your own hair may lead to an increased risk of bladder cancer, while other research has suggested it doesn’t. Several papers have looked into all the research on hair dye causing cancer. One of these papers, published in 2014, concluded that dyeing your own hair does not have any effect on your risk of bladder cancer. 

There is some evidence that hair dye can increase the risk of bladder cancer for hairdressers and barbers who have been working in the industry for 10 or more years. This is because they are working with these chemicals all the time. But this risk can be reduced by using non touch hairdressing techniques. Also, some of the chemicals that can increase the risk of bladder cancer have been banned. 

 

Down syndrome

One research study has shown that people who have Down Syndrome have a lower risk of bladder cancer. But this is only one study so more research is needed.

 

Being overweight

Some studies have shown no difference in risk of bladder cancer between people who are a normal weight and people who are overweight. But a recent study showed that overweight men were more at risk of developing bladder cancer. The researchers concluded that these results may have been affected by smoking.

 

Physical activity

Research has shown that people who are more physically active have a lower risk of bladder cancer than those who are less physically active.

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Updated: 20 July 2015