Environmental and genetic risk factors in the development of rheumatoid arthritis

New data presented at EULAR 2007, the Annual European Congress of Rheumatology in Barcelona, Spain, sheds light on the role of environmental and genetic risk factors in the development of rheumatoid arthritis (RA).

Two new studies by a team in Sweden have identified smoking, a low formal level of education and certain metabolic indicators as important risk factors in the development of RA. These findings represent a significant step towards better understanding of the risk factors for RA and may contribute to improved future prevention and treatment of this debilitating disease.

The first study showed that smoking (odds ratio 1.77; 95% confidence interval 1.13 to 2.78) and a low level of formal education, such as elementary school education only versus university degree status (odds ratio 2.46 confidence interval 1.20 to 5.02), may independently increase the risk of developing RA.

The second study similarly highlights the link between of smoking and RA but, contrary to previously noted relationships between RA with active inflammation and impaired glucose tolerance, observes better glucose tolerance as a predictor of RA. In the multivariate model, a lower glucose level at 120 minutes after an oral glucose tolerance test (odds ratio 1.19 per mmol/L; confidence interval 1.04 to 1.35) and smoking (odds ratio 1.64; confidence interval 1.08 to 2.48) were both found to be independent predictors of RA. Thus the authors suggest that factors such as diet and genetics influencing metabolism may play an important part in RA development.

Dr Ulf Bergstr'm from the Malm' University Hospital, Sweden, lead investigator on both studies said, "The determinants for developing RA in any population are clearly complex and often unrelated. These studies help us to add more pieces to the giant jigsaw of risk factors for one of the most common autoimmune diseases, affecting approximately 1% of adults worldwide. We hope these findings will contribute to better understanding of future RA prevention and treatment. Whilst the glucose tolerance findings contrast with previous studies linking impaired tolerance to established RA, they suggest that other mechanisms may be important years before RA onset. Our results will pave the way for future debate and research to pinpoint its definitive causes."

The two studies involved people enrolled in the Malm' Diet and Cancer Study (MDCS) (n=30,447) between 1991 and 1996 and a Preventive Medicine Program (PMP) (n=33,346) between 1974 and 1992. Investigators examined lifestyle factors using a self-administered questionnaire and glucose tolerance and lipids readings were taken by health professionals. Individuals who developed RA after participation in the health surveys were compared to controls without RA from the PMP and MDCS, matched for age, sex and year of screening.