Rheumatoid arthritis affects up to 1% of adults.
It tends to be worse in smokers than in nonsmokers.
The only known risk factor for rheumatoid arthritis is a possible inherited factor in some families (genetic predisposition). A genetic factor may affect how the immune system functions, causing inflammation and eventual destruction of the membranes lining the joints.
Citations
Firestein GS (2005). Rheumatoid arthritis. In DC Dale, DD Federman, eds., ACP Medicine, section 15, chap. 2. New York: WebMD.
O'Dell JR (2005). Rheumatoid arthritis: The clinical picture. In WJ Koopman, LW Moreland, eds., Arthritis and Allied Conditions: A Textbook of Rheumatology, 15th ed., vol. 1, pp. 1165-1194. Philadelphia: Lippincott Williams and Wilkins.
WebMD Medical Reference from Healthwise