Domestic and Farm-Animal Exposures and Risk of Non-Hodgkin's Lymphoma in a Population-Based Study in the San Francisco Bay Area

OBJECTIVE: To assess the association between animal exposures and non-Hodgkin's lymphoma (NHL). METHODS: Exposure data were collected from 1,591 cases and 2,515 controls during in-person interviews in a population-based case-control study of NHL in the San Francisco Bay Area. Odds ratios (OR) and 95% confidence intervals (95% CI) were adjusted for potential confounders. RESULTS: Pet owners had a reduced risk of NHL (OR, 0.71; 95% CI, 0.52-0.97) and diffuse large-cell lymphoma large cell (DLCL; OR, 0.58; 95% CI, 0.39-0.87) compared with those who never had owned a pet. Ever having owned dogs and/or cats was associated with reduced risk of all NHL (OR, 0.71; 95% CI, 0.54-0.94) and of DLCL (OR, 0.60; 95% CI, 0.42-0.86). Longer duration of cat ownership (P(trend) = 0.008), dog ownership (P(trend) = 0.04), and dog and/or cat ownership (P(trend) = 0.004) was inversely associated with risk of NHL. Ownership of pets other than cats and dogs was associated with a reduced risk of NHL (OR, 0.64; 95% CI, 0.55-0.74) and DLCL (OR, 0.58; 95% CI, 0.47-0.71). Exposure to cattle for >or=5 years was associated with an increased risk of NHL (OR, 1.6; 95% CI, 1.0-2.5) as was exposure to pigs for all NHL (OR, 1.8; 95% CI, 1.2-2.6) and for DLCL (OR, 2.0; 95% CI, 1.2-3.4). CONCLUSIONS: The association between animal exposure and NHL warrants further investigation in pooled analyses.