By Lisa Rapaport

(Reuters Health) – People with rheumatoid arthritis and obesity may be more likely to become disabled than their counterparts who maintain a healthier weight, a U.S. study suggests.

Researchers examined data more than 25,000 patients with rheumatoid arthritis. Most were overweight or obese when they joined the study. Those who were severely obese were more likely to report some disability to start with.

Over the course of the study, for up to about 15 years, obesity was associated with more progression of disability.

Their worsening disability “was not explained by worse disease activity,” said lead study author Dr. Joshua Baker of the University of Pennsylvania and the Philadelphia VA Medical Center. “This suggests that obesity causes disability in patients with rheumatoid arthritis and provides yet another reason for patients to try to take off a few pounds.”

In contrast to the more common osteoarthritis, which happens when cartilage on the ends of bones wears down over time, rheumatoid arthritis is an immune system disorder that causes debilitating swelling and pain in the joints.

In the current study, weight loss was also associated with disability, but it’s possible this is because people lost weight due to poor health or frailty as they aged, and not because of a conscious effort to eat right, exercise more and get in shape, researchers speculate in Arthritis Care and Research.

The study wasn’t designed to prove whether or how obesity might directly contribute to disability in rheumatoid arthritis patients. Still, the results suggest that rheumatoid arthritis patients might feel better if they lose weight, even if it’s not enough to stop being obese, said Dr. Axel Finckh, a researcher at Hopital Beau Sejour in Geneva, Switzerland, who wasn’t involved in the study.

“I would say to my patients that they should aim for a slow, progressive weight loss, associated with increased physical activity, rather then aiming for unrealistic aims such as reaching normal weight,” Finckh said by email.

While obesity may lead to worsening disability for rheumatoid arthritis patients, it’s also possible that some people with the immune system disorder might become obese as a result of this disease, noted Dr. Predrag Ostojic, a researcher at the University of Belgrade in Serbia who wasn’t involved in the study.

“Due to disability and chronic pain, patients with rheumatoid arthritis are less active, and inactivity may contribute in gaining weight,” Ostojic said by email. “On the other hand, obesity may cause joint damage independently of rheumatoid arthritis, by excessive joint loading and accelerated degeneration of the joint cartilage (osteoarthritis), especially on lower limbs and spine.”

“Any weight reduction will have positive effect on functional ability,” Ostojic added. “Healthy weight is ideal, but overweight is also an acceptable target, especially in rheumatoid arthritis patients who are severely obese.”

SOURCE: Arthritis Care and Research, online April 29, 2018.