Those who were overweight or obese were more likely to develop the painful disease, analysis showed.

(HealthDay)—Overweight and obese women are at increased risk for rheumatoid arthritis, a new study suggests.

Rheumatoid arthritis is an autoimmune disease that causes pain, swelling, stiffness and loss of function in the joints, and can also affect other body organs. About 1.3 million Americans have the disease, which occurs in women twice as often as in men.

For the new study, researchers analyzed data from more than 238,000 U.S. women who took part in the large, long-running investigation of women's health known as the Nurses' Health Study (women aged 30 to 55) and the Nurses' Health Study II (women aged 25 to 42).

The women provided information about their lifestyle and health habits and their body mass index (BMI), a measurement based on height and weight. The analysis of the data was adjusted for factors such as age, tobacco and alcohol use, breast-feeding, birth control pill use, menopausal status and postmenopausal hormone treatment.

Compared to normal-weight women, overweight and obese women were more likely to develop rheumatoid arthritis, according to lead investigator Dr. Bing Lu, a researcher at Brigham and Women's Hospital in Boston, and colleagues.

For overweight women (those with a BMI of 25 to 29.9), the risk was 19 percent higher in the first study and 78 percent higher in the second study. For obese women (those with a BMI over 30), the risk was 18 percent higher in the first study and 73 percent higher in the second study, the investigators found.

Previous studies have suggested a link between excess weight and rheumatoid arthritis risk, but the evidence was conflicting, so the study authors sought to learn more about the relationship between weight and the painful disease, according to background information in a news release from the American College of Rheumatology.

While the study found an association between overweight and rheumatoid arthritis risk, it did not prove cause-and-effect.

The study findings are scheduled for presentation Monday at the annual meeting of the American College of Rheumatology in Washington, D.C.

The data and conclusions of research presented at medical meetings should be viewed as preliminary until published in a peer-reviewed journal.

More information: The U.S. National Institute of Arthritis and Musculoskeletal and Skin Diseases has more about rheumatoid arthritis.

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