Epidemiology

Abstract

Hodgkin lymphoma (HL) is a relatively rare malignancy with a complex epidemiology. In addition to clinical and histological complexity, it shows substantial variation in incidence and risk factors across demographic factors and tumor characteristics. This chapter provides an overview of the epidemiology of HL with particular attention to this etiologic heterogeneity in incidence patterns, timing of exposure to common infections, the role of Epstein-Barr virus (EBV), altered immune function, genetic susceptibility, and selected lifestyle practices. Altogether, evidence to date points to HL as an uncommon outcome in genetically susceptible individuals of immune dysfunction provoked by early (i.e., childhood) and subsequent environmental exposures. However, given the variations in incidence rates and risk associations with age and tumor EBV status, among other factors, HL has been proposed to comprise four etiologically distinct entities-EBV-associated childhood HL, EBV-associated young-adult HL, EBV-associated HL in older adults (and in the immunosuppressed), and non-EBV-associated HL (occurring primarily in young adults). With this complexity, and the fact that associations with potential etiologic factors have not been strong and/or have low population prevalence, our understanding of risk factors for HL needs to advance considerably to meet the ultimate goal of disease prevention. Furthermore, to account for the considerable epidemiologic heterogeneity of HL, informative future work must be undertaken in diverse study populations of substantial size.