Population-based study of lymphoma in Germany: rationale, study design and first results

Abstract A multi-centre, population-based case–control study of lymphoma among adults was conducted in Germany from 1999–2003. The study comprised 700 incident cases (Hodgkin lymphomas and non Hodgkin’s lymphoma, NHL) in the age range 18–80 years and 700 age-, sex- and area-matched controls obtained from population registries. Diagnosis was based on the REAL/WHO classification. Information on demographic characteristics, lifestyle, medical history and occupation was obtained by in-person interviews. Each participant was asked for a 24 ml blood sample. First results are focused on basic demographic characteristics, contact to animals, childhood diseases and vaccinations. Odds ratios (ORs) and 95% confidence intervals (CIs) were estimated using conditional logistic regression. The ORs for lymphoma were decreased for exposure to sheep and goats (OR=0.7; 95% CI=0.5–0.9), for rabbits and hare (OR=0.7; 95% CI=0.5–0.9), measles infection (OR=0.6; 95% CI=0.5–0.9), Bordetella pertussis infection (OR=0.7; 95% CI=0.6–0.95), and tetanus vaccination (OR=0.5; 95% CI=0.3–0.9). Increased risk of lymphoma was associated with exposure to cattle (OR=1.3; 95% CI=1.03–1.7) and immunization for tuberculosis (OR=1.5; 95% CI=0.997–2.4). The results of this study are partly consistent with the hygiene hypothesis. The inconsistencies of some of the findings with an explanation by the Th1/Th2 paradigm, however, warrant further research and may indicate that broader explanatory concepts are needed.