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Smoking Linked to Increased Risk of Rheumatoid Arthritis in Men

NEW YORK (Reuters Health) Mar 31 - Smoking may double the risk of rheumatoid arthritis (RA) in men, but it does not seem to affect women's risk of the disease, according to a report published in the March issue of Arthritis Research and Therapy.

Researchers suspect that hormone difference may explain why smoking does not raise the risk of RA in women, although they stress that further studies are needed to understand the different effects of smoking in men and women.

Previous reports have suggested that smoking increases the risk of RA. The cause of rheumatoid arthritis is not very well understood, but research suggests that age, smoking, obesity and genetic factors appear to play a role in the development of the disease.

Dr. Eswar Krishnan, from Stanford University in Palo Alto, California, and colleagues compared the smoking histories and other demographic variables of 1095 RA patients with that of 1530 healthy adults.

Men with a history of smoking were twice as likely as other men to be diagnosed with RA, Dr. Krishnan's team reports. Further analysis revealed that the increased risk was only associated rheumatoid factor-positive RA.

The investigators note that past research has shown that smoking boosts the production of rheumatoid factor, which often precedes clinical disease.

Smoking was not associated with RA in women. This suggests that estrogen or other hormone differences may counteract the effects of smoking, according to the researchers.

Hormone changes during the menstrual cycle may help block the effect of smoking on rheumatoid factor and RA, the authors state. However, the researchers add, they did not have enough information on the female participants' menopausal status to address this issue.

"Data presented in this report suggest that factors related to the sex of an individual modify the effect of smoking on the risk of rheumatoid arthritis," the authors conclude.

Arthritis Res Therapy 2003;5:158-162.