Epidemiology of rheumatoid arthritis.

Rheumatoid arthritis is a relatively common disorder that affects men and women at the prime of their lives. Only 30% of the causes of rheumatoid arthritis can be attributed to genetic factors; the rest remain unexplained. Descriptive and analytic epidemiologic methods may lead to a better understanding of the causative, precipitating, and modulatory factors in rheumatoid arthritis.