A risk factor is something that increases the risk of developing cancer. It could be a behaviour, substance or condition. Most cancers are the result of many risk factors. But sometimes non-Hodgkin lymphoma (NHL) develops in people who don’t have any of the risk factors described below.
The risk of developing NHL increases with age. It is more common in people who are in their 60s and older. Overall, NHL is more common in men than women, but some specific types of NHL are more common in women.
The following are risk factors for NHL. Most of the known and possible risk factors are not modifiable. This means that you can’t change them. Until we learn more about these risk factors, there are no specific ways you can reduce your risk.
Risk factors are generally listed in order from most to least important. But in most cases, it is impossible to rank them with absolute certainty.
There is convincing evidence that the following factors increase your risk for NHL.
People who have a weakened immune systemimmune systemThe complex group of cells and organs that defend the body against infection, disease and foreign substances. have a higher risk of developing NHL. Your immune system can already be damaged when you are born (called congenital immune system damage). It can also be damaged over the course of your life (called acquired immune system damage). No matter when your immune system is damaged, it doesn’t change your risk for developing NHL.
The following can weaken your immune system.
Immunosuppressant drugs affect the immune system so it doesn’t react as it normally would. These drugs are given after an organ transplant so the person’s immune system doesn’t attack the donated organ.
People who take immunosuppressant drugs after a solid organ transplant (such as a kidney, heart or liver transplant) have a higher risk for NHL. People who take these drugs for other conditions, such as rheumatoid arthritis, lupus or inflammatory bowel disease, also have a higher risk of developing NHL. But their risk is lower than for people who take immunosuppressant drugs after an organ transplant.
HIV and AIDS weaken the body’s immune system. People with HIV (human immunodeficiency virus) or AIDS (acquired immunodeficiency syndrome) have a greater risk of developing some types of NHL. Fewer lymphomas are related to AIDS and HIV infection as drugs are developed to treat them.
An immunodeficiency disorder affects the immune system’s natural ability to defend the body against infection. People with immunodeficiency disorders often have frequent infections, which can be severe or unusual. They also have a higher risk of developing certain types of cancer.
You can have an immunodeficiency disorder when you are born. These disorders are usually inherited, which means they are passed from parents to children. Immunodeficiency disorders can also develop over the course of your life. These are called acquired immunodeficiency disorders. They can be caused by another disorder or treatments that suppress the immune system. Inherited immunodeficiency disorders are very rare, but acquired ones are a little more common.
How NHL develops is related to the specific disorder and which part of the immune system it affects. The following immunodeficiency disorders increase the risk of developing NHL.
Ataxia-telangiectasia (AT) is a rare inherited disorder. It causes abnormalities in a part of the brain called the cerebellum, which lead to problems with muscle coordination (called ataxia). People with AT have nervous system problems that gradually get worse over time. AT also causes small blood vessels to widen (called dilated capillaries or telangiectasia) or spider veins to appear, especially in the eyes and on the ears.
Wiskott-Aldrich syndrome is a rare inherited disorder. It usually only affects boys. Wiskott-Aldrich syndrome causes low platelet counts (called thrombocytopenia), which leads to bleeding problems. It also causes infections in the respiratory system and a skin condition called eczema.
Common variable immunodeficiency (CVID) is an acquired disorder. It can cause autoimmune diseases (such as rheumatoid arthritis) to develop. It can also cause problems with the gastrointestinal (GI) tract and repeated lung infections.
Severe combined immunodeficiency (SCID) is a very rare inherited immunodeficiency disorder, and it is the most serious. It causes yeast infections in the mouth (also called thrush), diarrhea and pneumonia in infants and young children.
X-linked lymphoproliferative disorder is a very rare inherited disorder. Children with this disorder develop very serious infectious mononucleosis because of infection with the Epstein-Barr virus. They can later develop liver failure, bone marrow failure and other conditions.
An autoimmune disorder causes the immune system to attack the body’s own tissue. Some autoimmune disorders have been linked to a higher risk of NHL. But only a small number of cases of NHL are linked with autoimmune disorders. People with autoimmune disorders may be treated with immunosuppressant drugs, which can also increase the risk of developing NHL.
The following autoimmune disorders have been linked with NHL.
Sjogren’s syndrome is a chronic disorder that damages the salivary glands and tear glands, which causes a very dry mouth and dry eyes. It can affect other organs and parts of the body such as joints, muscles, nerves, lungs, kidneys, liver, pancreas, stomach, brain and thyroid. Sjogren’s syndrome is linked with marginal zone lymphomas that develop in the salivary glands or other sites, such as the stomach or lungs. It is also linked with diffuse large B-cell lymphoma.
Rheumatoid arthritis causes inflammation, pain and stiffness in the joints. It can also cause inflammation in other organs, such as the eyes, lungs or heart. Rheumatoid arthritis is linked with diffuse large B-cell lymphoma and lymphoplasmacytic lymphoma.
Systemic lupus erythematosus (SLE, or lupus) can cause inflammation of the skin, joints, blood vessels and nervous system in different parts of the body. It can also affect internal organs such as the heart, lungs or kidneys. SLE is linked with diffuse large B-cell lymphoma.
Celiac disease damages the small intestine so that it can’t take up nutrients from food as it normally would. People with celiac disease have an immune response to gluten, which is a protein found in wheat, rye and barley. Celiac disease is linked with a higher risk for a rare type of T-cell lymphoma called enteropathy-associated T-cell lymphoma (EATL).
Hashimoto’s thyroiditis is an autoimmune disease that affects the thyroid and causes lowered thyroid function (called hypothyroidism). Symptoms of Hashimoto’s thyroiditis include fatigue, aches and pain, constipation, dry skin and depression. It is linked with a higher risk of developing primary thyroid lymphomas.
The following viral and bacterial infections can increase the risk of developing NHL. They may damage lymphocyteslymphocytesA type of white blood cell that fights viruses, bacteria, foreign substances or abnormal cells (including cancer cells). or constantly stimulate the immune system so it doesn’t work properly.
Epstein-Barr virus (EBV) is a type of herpes virus that causes infectious mononucleosis (also called mono, or the kissing disease). It is linked to Burkitt lymphoma and to lymphomas in people with a weakened immune system because of HIV/AIDS or immunosuppressant drugs. EBV is also linked to some other types of cancer. This virus and Burkitt lymphoma occur most commonly in Africa.
Human T-cell leukemia/lymphoma virus, type 1 (HTLV-1) increases the risk of developing adult T-cell lymphoma and leukemia. It is most common in southern Japan and the Caribbean.
Helicobacter pylori (H. pylori) is a type of bacteria that causes stomach ulcers and inflammation of the stomach lining (called gastritis). It is linked with gastric lymphomas, particularly a type of lymphoma that occurs in the stomach called mucosa-associated lymphoid-tissue (MALT) lymphoma. H. pylori also increases the risk of stomach cancer.
Kaposi sarcoma herpes virus (KSHV) is also called Human herpesvirus 8 (HHV-8). It is linked with primary effusion lymphoma, body cavity lymphomas and AIDS-related lymphomas.
Hepatitis C virus (HCV) and hepatitis B virus (HBV) are 2 of a group of viruses that can cause inflammation of the liver (called hepatitis). People with HCV or HBV infection have a higher risk of developing some types of NHL.
Campylobacter jejuni (C. jejuni) is a type of bacteria that can cause gastrointestinal (GI) infections. It is linked with a type of lymphoma called mucosa-associated lymphoid-tissue (MALT) lymphoma.
People who have received chemotherapy, with or without radiation therapy, for another type of cancer have a higher risk of developing NHL. This is especially true for people who were treated for Hodgkin lymphoma. But the benefit of being treated for cancer usually far outweighs the risk of developing a second cancer.
The risk of developing NHL is greatest in the first 5 years after treatment. But people who have been treated for cancer have a higher risk of developing NHL for the rest of their lives.
The following factors have been linked with NHL, but there is not enough evidence to show they are known risk factors. Further study is needed to clarify the role of these factors for NHL.
NHL is not generally considered to be familial, which means occurring in families more often than would be expected by chance. But some studies show a higher risk of NHL in people with a first-degree relative (a parent, brother, sister or child) who has been diagnosed with lymphoma. Further studies are needed to determine the risk of developing NHL when a first-degree relative has had the disease.
Pesticides include a large number of different chemicals, some of which may be related to NHL risk. Some studies suggest that exposure to certain pesticides, such as Agent Orange, may be linked with a higher risk of developing NHL. The evidence has not been consistent, so further research is needed to help clarify the possible link between pesticides and cancer, and to identify which ones may increase the risk of NHL.
Trichloroethylene (TCE) is a solvent used mostly to remove grease from metal. Some studies suggest that exposure to TCE may increase the risk of developing NHL.
The link between NHL and diet is very complex. Researchers are trying to find out if diet may increase the risk for NHL. Some studies suggest that diets high in meat, dairy products and saturated fat may increase the risk of developing NHL. Other studies show that diets low in vegetables increase the risk of NHL.
Some studies suggest that being obese may increase the risk of developing NHL, particularly large B-cell lymphoma.
Studies have shown a higher risk of NHL in people who used hair dye before 1980. The chemical composition of hair dyes is different now than before 1980, and some of the harmful ingredients have been removed. The risk affects people who used permanent dyes with dark colours in particular. This risk may also be higher in hair dressers and barbers, who were exposed to the dye at work.
A number of studies suggest that people working in certain jobs have a higher risk of NHL. These occupations include farming, the rubber industry, wood and forestry, printing and welding. Researchers haven’t identified specific exposures to explain these risks. More research is needed.
It isn’t known whether or not exposure to ionizing radiation is linked with NHL. It may be that researchers can’t show a definite link or that studies have had different results. Further study is needed to see if ionizing radiation is a risk factor for NHL.
People who survived nuclear industry accidents or the atomic bombs used during World War II were exposed to large amounts of ionizing radiation. People who are treated with radiation therapy are exposed to smaller amounts of ionizing radiation. Medical imaging, such as x-rays, also uses very small doses of ionizing radiation.
To make the decisions that are right for you, ask your healthcare team questions about risks.