Non-Hodgkin's Lymphoma - Risk Factors

Studies are reporting a higher prevalence of viral hepatitis C and B in patients with lymphomas, although such viruses do not appear to play a major role in triggering lymphoma.

Note: One study reported a lower risk for certain lymphomas in people with a history of receiving five or more different vaccines.

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Disorders of the Immune System

Patients with diseases or conditions that affect the immune system may be at higher risk for lymphomas.

HIV-positive patients and those with full-blown AIDS are at higher risk for NHL, and the disease is more likely to be widespread in these patients than in those without the immune disease. Most AIDS-related NHLs are high-grade lymphomas. Burkitt's lymphoma is often seen in AIDS patients. Although these patients have had a very poor prognosis, advances in antiviral therapy for HIV now allow better management of NHL with some success in achieving favorable outcomes. Part of the dramatic increase in NHL incidence over the past decades can, in fact, be traced to AIDS. However, one 2002 study observed that AIDS is now declining in the US, but non-AIDS-related NHL continues to increase.
Patients with a history of autoimmune diseases, including rheumatoid arthritis (RA), Hashimoto's thyroiditis, Crohn's disease, and Sjögren's syndrome are at an increased risk for certain NHLs, such as marginal zone lymphomas. [See section: Other Conditions Associated with Non-Hodgkin's Lymphomas.]
People who have organ transplants are at higher risk for NHL, probably due to multiple factors, including the drugs used to suppress the immune system and the transplanted organ itself.
Patients who have had high-dose chemotherapy with stem-cell transplantation are at higher risk.
Other immunodeficiency syndromes that put people at risk for NHL include Chediak-Higashi syndrome, ataxia-telangiectasia, B-cell lymphoproliferative syndrome, Bruton agammaglobulinemia, common variable immunodeficiency, and Wiskott-Aldrich syndrome.

Note on Allergies: There appears to be no adverse association between NHL and allergy, which is an overactive response of the immune system and is the most common immune disorder. In fact, one study found a decreased risk for certain lymphomas in people with plant or pet allergies or a history of bee or wasp stings.

Industrial Chemicals and Other Environmental Risk Factors

Overexposure to a number of industrial and agricultural chemicals have been frequently linked to an increased risk for lymphomas. The data, however, is not consistent.

Organochlorines are chemicals produced when solid waste is burned. These by-product chemicals include dioxin, polychlorinated biphenyls (PCBs), and furans. Many studies have indicated that exposure to these chemicals increases the risk of developing NHL.
A number of studies have found an association between NHL and certain pesticides and herbicides, although more research is needed to confirm any risk.
White spirits, thinners, phenoxy herbicides, wood preservative, aviation gasoline, plastic, and rubber chemicals have been associated with a higher risk for lymphomas. Specifically, in one study, painters and lumberjacks had a higher risk for NHL, while office and house workers had a lower risk. (In this study, farmers also had a lower risk than others.)
Some studies have found an association with long duration and early use of permanent dark hair dyes. There is no consistent evidence, however, that hair dye increases the risk for lymphomas.