Anything that can increase your risk of getting a disease is called a risk factor. Please bear in mind that having one or more of these risk factors doesn't mean you will get non-Hodgkin lymphoma (NHL).
Age and gender
Although NHL can happen at any age, just over a third (35%) of people diagnosed with NHL are aged 75 and over. Overall, NHL is slightly more common in men than in women.
Weakened immune system
People whose immune system is not working as well as it should are more likely to develop a lymphoma. Immunity can be lowered for the following reasons:
- taking drugs to stop organ rejection after a transplant
- HIV or AIDS
- being born with a rare medical condition that affects immunity
- autoimmune diseases
If you have autoimmune disease, your own immune system attacks your body tissue as it would attack a germ. Autoimmune diseases include rheumatoid arthritis, haemolytic anaemia, coeliac disease, Sjogren's syndrome and systemic lupus erythematosus.
A number of viruses and bacteria have been linked with an increased risk of NHL. However, many of these infections are uncommon in the UK. So the actual number of cases caused by infections here is small.
The infection is only part of a complex process for cancer to develop. Most people with these infections don't go on to develop NHL. And NHL itself is not infectious.
A more common bacterial infection called Helicobacter pylori can cause a rare type of lymphoma that starts in the stomach. This type of lymphoma is called MALT lymphoma . MALT stands for mucosa associated lymphoid tissue. This means the lymphoma starts in lymphatic tissue outside the main lymphatic system. In this case, in the lining of the stomach.
Human immunodeficiency virus (HIV)
Having the human immunodeficiency virus (HIV) increases a person's risk of developing NHL. This risk is greater in some types of NHL, such as diffuse large B cell lymphoma (DLBCL). HIV can often be successfully treated with highly active antiretroviral therapy (HAART). The risk of NHL has decreased since the introduction of HAART in 1996.
T cell lymphoma virus 1 (HTLV1)
Infection with a virus called human T cell lymphoma virus 1 (HTLV1) can increase the risk of developing NHL. HTLV1 is most common in Japan and the Caribbean.
Epstein Barr virus
The Epstein Barr virus is linked to an increased incidence of a type of NHL called Burkitt lymphoma. Burkitt lymphoma is more common in Africa than Europe. This is the virus that causes glandular fever (mononucleosis). People who have had mononucleosis might have a higher risk of developing NHL.
People with the hepatitis C virus have an increased risk of developing NHL. But this is a small increased risk for people living in this country. The hepatitis B virus might also increase the risk but the evidence is less clear.
This is a disease of the small bowel. It affects about 1 in every 100 people. People with coeliac disease have an immune reaction to gluten, a protein found in rye, wheat and barley. This reaction causes inflammation of the small bowel.
For some time, coeliac disease has been a known risk factor for a rare type of lymphoma of the small bowel called enteropathy type T cell lymphoma (ETTL).
The risk seems to be higher in people with poorly managed coeliac disease. The risk in people with a diagnosis of coeliac disease has actually reduced over recent decades. If you have coeliac disease, sticking to a gluten free diet might help reduce your risk.
Family history of NHL
Having a parent, brother or sister diagnosed with NHL slightly increases your risk of getting it. But this is not a major risk factor. The general risk is still small, and most people who get NHL don't have a relative who has had it.
Previous cancer and treatment
Some other types of cancer, particularly blood cancers such as Hodgkin lymphoma and leukaemia, have been linked to an increased risk of NHL. You might also be at a higher risk if you've had a melanoma or prostate cancer.
Doctors are unsure whether this increase in risk is because of the effect of treatment for the first cancer, or because of the same risk factors that caused the first cancer. But these are very small increases in risk compared to the risk of not having the treatment for the original cancer.
Breast Implant Associated Anaplastic Large Cell Lymphoma (BIA-ALCL)
Some women who have a breast implant can develop a rare type of lymphoma of the breast called anaplastic large cell lymphoma. This includes women who have breast enlargement or women who have an implant to reconstruct their breast following breast cancer surgery.
The risk of a woman developing an anaplastic large cell lymphoma following a implant is small. This can happen some years later. Doctors believe that, on balance, implants are a safe option for breast reconstruction, but women should be made aware of this risk. This link is associated with textured implants. There have been no women diagnosed with this following a smooth implant.
Those who have had a breast implant are encouraged to contact their doctor if they have a lump of swelling in that breast. This type of lymphoma is usually easy to treat with surgical removal of the lymphoma and the implant.
Other possible causes
Stories about potential causes are often in the media. It isn’t always clear which of the ideas reported are supported by good evidence.
You might have heard about a possible cause which we haven’t included here. This is either because there is no evidence to support it, or because it is not fully clear what the evidence shows.