While the study wasn't designed to investigate why this is happening, the speed of the change points to environmental, rather than genetic, factors, Dr. Sherine E. Gabriel of the Mayo Clinic College of Medicine in Rochester, Minnesota, one of the study's authors, told Reuters Health.
"It's pretty unlikely that the genetic makeup of a population changed that quickly." In rheumatoid arthritis, or RA, a person's immune system attacks the joints, leading to inflammation, pain, stiffness and in some cases erosion of the bone and joint deformity.
Reuters, by Anne Harding, 3/26/2010
Additional coverage: The Vancouver Sun