SAN FRANCISCO, Aug. 4 -- Women with a strong genetic predisposition to rheumatoid arthritis aren't exacerbating the problem by smoking, surprised investigators here discovered.
Smoking doubled the disease risk for women lacking genetic susceptibility, but in those with strong genetic risk factors -- whose odds of getting the disease were already high -- smoking did not significantly boost the odds further, said Lindsay Criswell, M.D., M.P.H., of the University of California San Francisco.
The results were "unexpected," because Dr. Criswell and colleagues had hypothesized that a genetic predisposition would interact with tobacco exposure to raise the risk for RA higher than either factor could alone, the scientists said online today in the Annals of Rheumatic Diseases.
The analysis included more than 600 older white women (average age 60), enrolled in the Iowa Women's Health Study. Information on disease state and smoking status were obtained via surveys given at baseline in 1986 and again in 1992 and 1997.