Women with rheumatoid arthritis are already more prone to heart attacks than the general population because of their autoimmune disease.
The researchers followed 813 patients with rheumatoid arthritis and the same number of controls. They also studied other patient data from 1980 to 2007 and found that from 1985 to 2007 the incidence of rheumatoid arthritis rose 9.2 percent per 100,000 women. Obesity accounted for 52.2 percent of the increase.
Rheumatoid arthritis is an inflammatory disease that causes pain, swelling and stiffness in the joints and surrounding tissues. About 1.3 million people in the U.S. have the disease, which occurs in two to three times as many women as men, according to the National Institutes of Health.
Study authors said they had wanted to find the reasons behind an increase in rheumatoid arthritis in the past two decades. They realized obesity had also increased in that time period. "The biological connection is we know that fat cells produce inflammatory proteins and they're active in inflammation," researchers said.
Once the illness becomes severe, the medications needed cost several thousand dollars monthly, according to Dr. Nadera Sweiss, director of rheumatology clinical research at University of Illinois Hospital and Health Sciences System.