Opportunities for exposure to infection and risk of young adult Hodgkin lymphoma (HL) in twins

Risk factors for Hodgkin lymphoma diagnosed before age 50 (young adult Hodgkin lymphoma, YAHL) include lack of close siblings, high socioeconomic status of parents, and single family residence. These risk factors suggest that relative social isolation and protection from exposure to common childhood infections that leads to increased susceptibility. A matched case-control study was conducted in twins discordant for Hodgkin lymphoma to test the hypothesis that the twin with more opportunities for exposure to infections as a child would have lower risk. Statistical analysis was performed using conditional logistic regression (SAS, Version 8.1). The twin who put things into their mouth more as a young child was at a significantly lower risk for YAHL (OR = 0.39, 95% CI = 0.20--0.75), as was the twin who kissed more on the mouth during high school (OR = 0.8, 95% CI = 0.44--1.44), or had more contact with pets (OR = 0.81, 95% CI = 0.48--1.36).