Background: Because of unique exposures, studies among farmers may yield insights into the relationship between allergies and non-Hodgkin lymphoid (NHL) neoplasms. We evaluated farm characteristics, allergic symptoms and conditions, and risk of NHL including specific subtypes in the Agricultural Health Study, a prospective cohort of farmers and spouses from North Carolina and Iowa. Methods: We identified 710 incident cases of NHL (including chronic lymphocytic leukemia and multiple myeloma) among 82,370 participants with baseline data on crop and animal exposures, including 454 cases among 52,850 participants with baseline data on recent allergy symptoms (rhinitis) and living on a farm during childhood. HR and 95% confidence intervals (CI) were calculated using multivariable-adjusted proportional hazards models. Results: We observed reduced risks of NHL among farmers and spouses with rhinitis at baseline (HR, 0.63; 95% CI, 0.51-0.79), related to growing soybeans (HR, 0.80; 95% CI, 0.67-0.96), and among farmers who handled stored grains or hay (HR, 0.66; 95% CI, 0.52-0.82). Growing up on a farm was associated with increased NHL risk (HR, 1.51; 95% CI, 1.15-1.98). Results did not differ significantly by NHL subtype. Conclusions: Both the reduced risk of NHL among those with allergy symptoms and specific farm exposures in adulthood, and the increased risk among those who grew up on a farm suggest that the host immune response to agricultural allergens may influence NHL development. Impact: This prospective study is, to our knowledge, the first to investigate the relationship between allergy symptoms and NHL risk in farmers; confirmation of these findings in other farming populations is warranted.
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