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

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.