For current cigarette smokers without the SE gene, the risk factor was comparable--2.4 times. These findings affirm the SE gene and smoking as independently related to the development of rheumatoid factor positive RA. Among current smokers with the SE gene, however, the disease risk increased to 7.5 times. "The interaction was even more pronounced in smoking subjects with double SE genes, whose relative risk of rheumatoid factor positive RA was 15.7 times higher," observes one of the authors Leonid Padyukov, M.D., Ph.D. However, no risk was found for rheumatoid factor negative RA in this study.
Beyond strengthening the case against cigarette smoking as a health hazard, this study has important implications for ongoing research into the factors contributing to RA and other autoimmune diseases. "Our study also emphasizes the need to include data on environmental exposures in genetic analyses of a complex disease," the authors note.