Background: Non-Hodgkin's lymphoma (NHL) are among the small number of malignant tumors with markedly increasing incidence and mortality rates in the recent past. This trend is particularly obvious in industrialized countries. The causes of the observed increase remain unclear.
Methods: We conducted a Medline search to identify case control and cohort studies on medical, biological and selected environmental risk factors of non-Hodgkin's lymphoma published between 1992 and 1998. Methodological aspects and results of identified studies are presented in tabular form. We furthermore discuss the role of various risk factors for the observed trends in non-Hodgkin's lymphoma.
Results: We identified a total of 64 studies. Iatrogenic immunosuppression as well as numerous diseases associated with an impaired immune system have clearly been recognized as etiological factors for non-Hodgkin's lymphoma. However, they can explain only a small percentage of the rate increases of non-Hodgkin's lymphoma. Similarly, the HIV/AIDS epidemic in Germany is responsible only for a small proportion of the rising figures of non-Hodgkin's lymphoma; other viral agents are currently being associated with a few distinct subtypes of non-Hodgkin's lymphoma. Smoking and nutritional factors are weakly or not at all associated with non-Hodgkin's lymphoma and can not account for the disease trends.
Conclusion: The observed secular rise in incidence and mortality of non-Hodgkin's lymphoma can only partly be explained. New epidemiologic studies should focus on risk factors associated with the function of the immune system and on possible interactions between different etiological factors.