New epidemiologic leads in the etiology of non-Hodgkin lymphoma in the elderly: the role of blood transfusion and diet

The incidence of non-Hodgkin lymphoma (NHL) in persons over the age of 65 years has increased dramatically since the 1950s in western countries. The strongest known risk factors for NHL are primary or acquired immunosuppression, but these severe deficiencies are relatively rare and cannot explain the rapid increase observed in the elderly. Recent work suggests that common exposures which influence immunocompetence, albeit at a much weaker level, may also be risk factors for NHL. Two such risk factors recently associated with NHL are prior history of blood transfusion and certain aspects of diet. In four out of four studies, prior history of blood transfusion was associated with approximately a doubling in NHL risk, even for a transfusion first received a decade or more before diagnosis. Other studies suggest that diets high in animal proteins and fats may increase the risk of NHL while fruit and vegetable consumption may decrease risk. Allogeneic blood transfusion is known to suppress the immune system, and diets high in protein and fat may also lead to altered immunocompetence, although other mechanisms such as viral transmission or the effects of heterocyclic amines and N-nitroso compounds may also play a role. Follow-up of these observations may lead to a better understanding of the NHL epidemic and new approaches to the prevention of NHL.