Brain tumour risks and causes

In most cases, we do not know what causes a brain tumour. We do know that they are not infectious. You can't catch a brain tumour. There are a few risk factors that we do know about.

Brain tumours are relatively rare. In the UK, almost 5,000 people are diagnosed each year with cancerous (malignant) brain and central nervous system tumours. This makes them the 16th most common cancer in the UK (not counting non melanoma skin cancer).

Around 4,300 people are diagnosed with non cancerous (benign) brain and other central nervous system tumours.

Brain tumours are slightly more common in males than females. But one type, meningioma, is slightly more common in women.

People can get brain tumours at any age. Generally speaking, as we get older our risk of brain tumours increases. But there are many different types of brain tumours and some are more common in younger adults. Overall, more brain tumours are diagnosed than in the past. But this is mostly because we are living longer and brain tumours are more common in older people.

About 300 children are diagnosed with brain tumours in the UK each year, so they are quite rare. But brain tumours are the most common type of solid tumour found in children.

Up to 5 out of every 100 brain tumours (5%) are related to known genetic conditions. If you have one of these syndromes, you are more likely to get a brain tumour. These syndromes cause a number of different medical problems and you may already know if any of these run in your family. Examples are neurofibromatosis type 1 and 2, tuberous sclerosis, Li-Fraumeni syndrome, Von Hippel-Lindau syndrome or Turner syndrome. If you have a parent, brother or sister diagnosed with a tumour of the nervous system, your risk is higher than other people in the general population. Jewish people have a higher risk of meningiomas than other groups, which may be due to genetic factors.

In our environment, the only definite risk we know of is exposure to radioactivity (ionising radiation). Meningiomas and malignant gliomas are more common in people who have had radiotherapy to the head in the past. Children who have had radiotherapy to the head as a treatment for acute lymphoblastic leukaemia (ALL) are known to be at a slightly increased risk of brain tumours. The risk is highest if the radiotherapy was given before the age of five. Modern radiotherapy techniques are less likely to cause brain tumours than the old style of giving a single high dose. The risk of a brain tumour is increased if some chemotherapy drugs called 'anti-metabolites' are given at the same time as the radiotherapy to the head. So, chemotherapy and radiotherapy are usually no longer given together to children with ALL.

Women who have had breast cancer have a slightly increased risk of having a glioma. One study has shown that people with a previous nasopharyngeal cancer have an increased risk of brain tumours, which may be due to unknown shared environmental causes between nasopharyngeal cancer and brain tumours. One study has shown that people who have had melanoma have a small increase in their risk of brain tumours. An analysis of studies showed that people who have had thyroid cancer also have an increased risk.

There is some evidence that people with food or respiratory allergies may have a slightly reduced risk of brain tumours, although it is not clearly understood why this should be. And one recent study did not show this decrease in risk so we need more research to check this. People with autoimmune conditions such as diabetes may also have a reduced risk.

People with HIV or Aids have a slightly increased risk of brain cancer. A specific rare type of brain tumour called primary cerebral lymphoma is more likely to develop in people whose immune system doesn't work properly due to AIDS or medicines taken after an organ transplant. Even in these groups of people, cerebral lymphoma is still very rare.

Many other possible causes have been investigated, but none of these have been proven. 

It is thought that female hormones may affect brain tumour development. Three studies have shown that women whose periods started before the age of 12 have a slightly lower risk of glioma than women whose periods started after the age of 14. More research is needed though to find out the exact role of hormones.

Long term use of brown permanent hair dye slightly increased the risk of gliomas in one study but more research is needed to confirm this.

Some studies have looked at the idea that the risk of childhood brain tumours is related to the mother’s diet during pregnancy. Some studies have shown a higher risk of brain tumours in children whose mothers ate cured meats during pregnancy. Other studies have seemed to show that eating more vegetables, or use of vitamin supplements by the mother, during pregnancy may reduce the risk of childhood brain cancer. The results of studies examining the link between maternal diet and childhood brain cancer can be unreliable if the people taking part forget what they ate during pregnancy. So more results are needed to confirm these findings.

Researchers have looked into whether coffee or tea intake might increase the risk of brain tumours. A large study in 2010 as part of the European Prospective Investigation into Cancer and Nutrition (EPIC) reported that caffeine intake had no effect on brain tumour risk.

People do worry about other possible causes of brain tumours. There is no evidence that brain tumours may be caused by power lines or mobile phones but we have included this information here because people ask about them. They are still being researched.

Several studies have looked at whether living near power lines, or being exposed to electromagnetic fields in your work, increases the risk of brain cancer, but they have not found an increased risk for either.

Mobile phones are being investigated to see how much low level (non ionising) radiation they produce. From the evidence we have so far, we still can't say that mobile phones pose a problem to health.  There has been some concern about them causing brain tumours in particular.  But there is no strong evidence that there is any link.  There is more detailed information about research into mobile phones and brain tumours on CancerHelp UK.

Researchers in 2010 reviewed research which had compared people who had taken aspirin daily with those who hadn't and the health conditions they developed. They found that the people who took aspirin everyday for at least 5 years had a lower risk of dying from a brain tumour. We need more research to confirm this. Remember aspirin can be dangerous because they can irritate the stomach lining and cause bleeding. You should not start to take aspirin or other anti inflammatory drugs without checking with your doctor first.