What are the risk factors for non-Hodgkin lymphoma?
A risk factor is something that affects your chance of getting a disease such as cancer. Different cancers have different risk factors. Some risk factors, like smoking, can be controlled. Others, like a person’s age or family history, can’t be changed.
But risk factors don’t tell us everything. Having a risk factor, or even many risk factors, does not mean that you will get the disease. And many people who get the disease may have few or no known risk factors. Even if a person with non-Hodgkin lymphoma has a risk factor, it’s often very hard to know how much that risk factor may have contributed to the lymphoma.
Researchers have found several factors that may affect a person’s chance of getting non-Hodgkin lymphoma. There are many types of lymphoma, and some of these factors have been linked only to certain types.
Getting older is a strong risk factor for lymphoma overall, with most cases occurring in people in their 60s or older. But some types of lymphoma are more common in younger people.
Overall, the risk of non-Hodgkin lymphoma is higher in men than in women, but there are certain types of non-Hodgkin lymphoma that are more common in women. The reasons for this are not known.
Race, ethnicity, and geography
In the United States, whites are more likely than African Americans and Asian Americans to develop non-Hodgkin lymphoma.
Worldwide, non-Hodgkin lymphoma is more common in developed countries, with the United States and Europe having the highest rates. Some types of lymphoma that have been linked to specific infections (described further on) are more common in certain parts of the world.
Exposure to certain chemicals
Some studies have suggested that chemicals such as benzene and certain herbicides and insecticides (weed- and insect-killing substances) may be linked with an increased risk of non-Hodgkin lymphoma. Research to clarify these possible links is still in progress.
Some chemotherapy drugs used to treat other cancers may increase the risk of developing non-Hodgkin lymphoma many years later. For example, patients who have been treated for Hodgkin disease have an increased risk of later developing non-Hodgkin lymphoma. But it’s not totally clear if this is related to the disease itself or if it is an effect of the treatment.
Studies of survivors of atomic bombs and nuclear reactor accidents have shown they have an increased risk of developing several types of cancer, including leukemia, thyroid cancer, and non-Hodgkin lymphoma.
Patients treated with radiation therapy for some other cancers, such as Hodgkin disease, have a slightly increased risk of developing non-Hodgkin lymphoma later in life. This risk is greater for patients treated with both radiation therapy and chemotherapy.
Immune system deficiency
People with weakened immune systems have an increased risk for non-Hodgkin lymphoma. For example, people who receive organ transplants (kidney, heart, liver) are treated with drugs that suppress their immune system to prevent it from attacking the new organ. These people have a higher risk of developing non-Hodgkin lymphoma.
The human immunodeficiency virus (HIV) can also weaken the immune system, and people infected with HIV are at increased risk of non-Hodgkin lymphoma.
Some genetic (inherited) syndromes can cause children to be born with a deficient immune system. Along with an increased risk of serious infections, these children also have a higher risk of developing non-Hodgkin lymphoma. These inherited immune deficiency diseases can be passed on to children, but people with non-Hodgkin lymphoma who don’t have these inherited diseases do not pass an increased risk of lymphoma on to their children.
Some autoimmune diseases such as rheumatoid arthritis, systemic lupus erythematosus (SLE or lupus), celiac sprue (gluten-sensitive enteropathy), and others have been linked with an increased rate of non-Hodgkin lymphoma.
In autoimmune diseases, the immune system sees the body’s own tissues as foreign and attacks them, as it would a germ. Lymphocytes (the cells from which lymphomas start) are part of the body’s immune system. The overactive immune system in autoimmune diseases may cause lymphocytes to grow and divide more often than normal. This may increase the risk of them developing into lymphoma cells.
Some types of infections may raise the risk of non-Hodgkin lymphoma in different ways.
Infections that directly transform lymphocytes
Some viruses can directly affect the DNA of lymphocytes, helping to transform them into cancer cells. The human T-cell leukemia/lymphoma virus (HTLV-1) and the Epstein-Barr virus (EBV) seem to work in this way.
Infection with HTLV-1 increases a person’s risk of developing certain types of T-cell lymphoma. This virus is most common in some parts of Japan and in the Caribbean region, but is found throughout the world. In the United States, it causes less than 1% of lymphomas. HTLV-1 spreads through sex and contaminated blood and can be passed to children through breast milk from an infected mother.
Infection with the Epstein-Barr virus (EBV) is an important risk factor for Burkitt lymphoma in areas of Africa where this type of lymphoma is common. In developed countries such as the United States, EBV is more often linked with lymphomas in patients also infected with HIV, the virus that causes AIDS. It has also been linked with developing nasal-type extranodal natural killer/ T-cell lymphoma, lymphomatoid granulomatosis (a form of B-cell lymphoma), and post-transplant lymphoproliferative disorder.
Human herpes virus 8 (HHV8) can also infect lymphocytes, leading to a rare type of lymphoma called primary effusion lymphoma. This lymphoma is most often seen in patients who are infected with HIV. HHV8 infection is also linked to another cancer, Kaposi sarcoma. For this reason, another name for this virus is Kaposi sarcoma-associated herpes virus (KSHV).
Infections that weaken the immune system
Infection with human immunodeficiency virus (HIV), also known as the AIDS virus, commonly causes immune system deficiency. HIV infection is a risk factor for developing certain types of non-Hodgkin lymphoma, such as Burkitt lymphoma and diffuse large B-cell lymphoma.
Infections that cause chronic immune stimulation
Some long-term infections may increase the risk of lymphoma by forcing a person’s immune system to be constantly activated. As more lymphocytes are made to fight the infection, there is a greater chance that genetic mistakes can occur, which might eventually lead to lymphoma.
Helicobacter pylori, a type of bacteria known to cause stomach ulcers, has also been linked to mucosa-associated lymphoid tissue (MALT) lymphoma of the stomach. The body’s immune reaction to this infection increases the risk of lymphoma. This is important because antibiotics can help treat some patients who have MALT lymphomas of the stomach that test positive for H. pylori.
Chlamydophila psittaci (formerly known as Chlamydia psittaci) is a bacteria that can infect both human and animals. In humans, it can cause a lung infection called psittacosis. DNA from this bacterium has been found in biopsies of MALT lymphoma in the tissues around the eye (called ocular adnexal marginal zone lymphoma). This is a sign of infection. A recent study has shown that treating the infection with an antibiotic (doxycycline) can make this lymphoma get better and even go away.
Infection with the bacterium Campylobacter jejuni has been linked to a type of MALT lymphoma called immunoproliferative small intestinal disease. This type of lymphoma, which is also sometimes called Mediterranean abdominal lymphoma, typically occurs in young adults in eastern Mediterranean countries. Antibiotics can be helpful in treating this lymphoma, especially in early stages.
The hepatitis C virus (HCV) can also cause long-term infections. Infection with HCV seems to be a risk factor for certain types of lymphoma. In splenic marginal zone lymphoma, successful treatment of the HCV infection can lead to the lymphoma getting better and even going away.
Body weight and diet
Some studies have suggested that being overweight or obese may increase your risk of non-Hodgkin lymphoma. Other studies have suggested that a diet high in fat and meats may raise your risk. More research is needed to confirm these findings. In any event, staying at a healthy weight and eating a healthy diet have many known health benefits outside of the possible effect on lymphoma risk.
Last Medical Review: 03/27/2013
Last Revised: 11/14/2013