Background: Risk of Hodgkin's lymphoma in young adults has previously been associated with higher childhood socioeconomic status (SES) and other markers of delayed infection with common childhood pathogens, especially the Epstein-Barr virus. This study examines the current role of childhood social environment in the development of Hodgkin's lymphoma.
Methods: A population-based case-control study of 565 Hodgkin's lymphoma cases and 679 controls was conducted in the Boston, MA metropolitan area and the state of Connecticut to investigate the viral etiology of Hodgkin's lymphoma.
Results: A novel association was detected between attendance of nursery school or day care and reduced risk of Hodgkin's lymphoma among individuals ages 15 to 54 years. The odds ratio (95% confidence interval) for having attended preschool for at least 1 year was 0.64 (0.45-0.92). Risk of young-adult Hodgkin's lymphoma was also associated with family history of hematopoietic cancer, Jewish ethnicity, and cigarette smoking. Other indicators of childhood SES were not associated with young-adult Hodgkin's lymphoma. Among older adults ages 55 to 79 years, Hodgkin's lymphoma was associated with lower childhood SES but not with preschool attendance.
Conclusions: Early exposure to other children at nursery school and day care seems to decrease the risk of Hodgkin's lymphoma in young adults, most likely by facilitating childhood exposure to common infections and promoting maturation of cellular immunity. This finding supports the delayed infection model of Hodgkin's lymphoma etiology in young adults while introducing a new major determinant of age at infection. Hodgkin's lymphoma seems to have a separate pathogenesis among older adults.