Childhood infectious diseases and risk of non-Hodgkin's lymphoma according to the WHO classification: A reanalysis of the Italian multicenter case-control study

Since 1960, incidence of non-Hodgkin's lymphoma (NHL) has been increasing in most industrialized countries, but causes of this trend remain unclear. A role of the decreased exposure to infectious agents during childhood has been proposed. Our study evaluates the association between common childhood infectious diseases and the risk of NHL and its major subtypes by a reanalysis of the Italian multicenter case-control study. After exclusion of next-of-kin interviews, 1,193 cases, diagnosed between 1990 and 1993, and 1,708 population-based controls were included in the analyses. OR estimates were obtained by logistic regression, adjusting for gender, age, residence area, education, smoking habit and exposure to radiations, pesticides and aromatic hydrocarbons. Among B-cell lymphomas (n = 1,102) an inverse association was observed for rubella (OR = 0.80, 95% CI: 0.65-0.99), pertussis (OR = 0.74, 95% CI: 0.62-0.88) and any infection (OR = 0.75, 95% CI: 0.61-0.93). A negative trend by number of infections was observed, which was more evident among mature B-cell lymphoma (OR = 0.66 for three infections or more, 95% CI: 0.48-0.90). Our results indicate a potential protective role of common childhood infections in the etiology of B-cell NHL.