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 that person developing 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), Sjogren (Sjögren) disease, 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 make lymphocytes grow and divide more often than normal. This might increase the risk of them developing into lymphoma cells.
Some types of infections may raise the risk of non-Hodgkin lymphoma in different ways.