Two new studies have found that smoking, low formal level of education and certain metabolic indicators are high risk factors in the development of rheumatoid arthritis (RA).
The study was conducted by a team of researchers led by Dr Ulf Bergstrom at the Malmo University Hospital, Sweden.
As part of the studies, researchers examined people enrolled in the Malmo Diet and Cancer Study (MDCS) between 1991 and 1996 and in a Preventive Medicine Program (PMP) between 1974 and 1992 to study the link between smoking and RA and glucose level as a predictor of RA.
Investigators examined lifestyle factors using a self-administered questionnaire and took glucose tolerance and lipids readings.
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.
The first study found that smoking and a low level of formal education, such as elementary school education only versus university degree status, might independently increase the risk of developing RA.
The second study highlighted the link between smoking, glucose levels and RA and found that both smoking and glucose levels to be independent predictors of RA.
The authors suggested that factors such as diet and genetics influencing metabolism might play an important part in RA development.
"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," Bergstrom said.
"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," Bergstrom added.
The findings of the study were presented at EULAR 2007, the Annual European Congress of Rheumatology in Barcelona, Spain.