Meta-analyses of non-Hodgkin's lymphoma and farming

Objectives This study examined the association between non-Hodgkin's lymphoma (NHL) and farming. Methods A series of meta-analyses of peer-reviewed studies was performed using 36 studies published between 1982 and 1997. Prior to the meta-analyses, all the studies were reviewed and evaluated for heterogeneity and publication bias. Combined relative risks (RR) were calculated using the random effect model. Results The combined RR was 1.10 [95% confidence interval (95% CI) 1.03-1.19] for all the studies and 0.93 (95% CI 0.82-1.06) for studies involving female farmers. Significant heterogeneity was detected for study design and country of study among the studies. Significantly elevated RR values were obtained for case-referent studies (combined RR 1.19, 95% CI 1.06-1.33) and for studies conducted on farmers residing in the United States (combined RR 1.26, 95% CI 1.15-1.37). These findings were not influenced by a publication bias. Conclusions The findings suggest that male farmers residing in the United States have a slightly elevated risk of contracting NHL. Commonly experienced exposures that might contribute to the occurrence of MIL in this group include infectious microorganisms, herbicides, and insecticides.