NEW YORK (Reuters Health) - People who are overweight when they are diagnosed with rheumatoid arthritis are less likely to be able to control the disease well in its early stages than people of a healthy weight, according to a new study.
In rheumatoid arthritis, the body’s immune system attacks its own connective tissue, destroying the cartilage that protects joints. The condition leads to stiffness, joint swelling and whole-body fatigue.
Unlike the more common osteoarthritis, or “wear-and-tear” arthritis, which affects people as they get older, rheumatoid arthritis can happen at any age. It affects less than one percent of adults, or 1.3 million people in the U.S., according to the American College of Rheumatology.
Most patients will experience improvement when they start treatment, but only a minority will go into remission, said Dr. Paul-Peter Tak of the Academic Medical Center at the University of Amsterdam, who was not part of the new research.
The study included almost 500 adults in the early stages of rheumatoid arthritis between 2006 and 2009.
Researchers reviewed a Swedish rheumatology database that included each patient’s self-reported height and weight at diagnosis and information on how the disease had progressed over the next six months.
More than 90 percent of the patients were put on so-called disease-modifying antirheumatic drugs (DMARDs) at the time of their diagnosis, usually methotrexate.
Generic versions of methotrexate cost $1 or $2 per tablet.
Overweight patients were 33 percent less likely to have low disease activity, a sign that medication is keeping the condition in check, at the three-month point than those with a healthy weight.
They also tended to report more pain at three and six months and were less likely to be in remission than patients with a healthy weight, according to results published in the Annals of the Rheumatic Diseases.
Having more body fat could affect the course of rheumatoid arthritis itself or how well medications work to treat it, possibly by leading to more inflammation, Maria E. C. Sandberg told Reuters Health by email.
Sandberg worked on the study at the Karolinska Institutet in Stockholm.
“Our study shows that on a group level overweight and obese patients have less chance of achieving good disease control within the first six months, compared to normal-weight patients,” Sandberg said. “However, obviously, there will be obese patients with good response and normal-weight patients without good response.”
A smaller study published in 2011 found that obese rheumatoid arthritis patients were less likely to see clinical improvement with more expensive second-line medications, which are used when methotrexate doesn’t work, even when the medication dosage was adjusted for weight.
The new study found essentially the same thing in a larger group of patients receiving their first round of treatment, Tak said.
“This is an important observation, which highlights the importance of lifestyle factors, and supports the importance of a healthy diet and active lifestyle in patients with rheumatoid arthritis,” he told Reuters Health in an email.
Rheumatoid arthritis itself is a risk factor for heart disease, which makes a healthy lifestyle even more important, he said.
Weight is probably not the only factor that can affect rheumatoid arthritis prognosis, Sandberg said.
“There are likely very many factors affecting the therapy response by different mechanisms and research is ongoing to find and confirm them,” she said. “Hopefully these factors can then be combined into a model which can predict which medication can best help the different patient groups.”
SOURCE: bit.ly/1jINOj3 Annals of the Rheumatic Diseases, online May 12, 2014.