Being overweight has long been associated with a variety of health problems such as diabetes, high blood pressure, and heart disease. But a new study suggests that it may also increase the risk of rheumatoid arthritis.
Rheumatoid arthritis (RA) is a form of arthritis that causes pain, swelling, stiffness and loss of function in your joints. It is an autoimmune disease, which means the arthritis results from your immune system attacking your body’s tissues. This disease can affect anyone but it is more common in women than men.
According to a study presented at the annual meeting of the American College of Rheumatology in Washington, overweight and obese women were more likely to develop rheumatoid arthritis compared to normal-weight women.
For the new study, researchers analyzed data from more than 238,000 U.S. women who took part in two large cohort studies of women nurses, 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 their body mass index (BMI), a measurement based on weight and height. BMI between 25 to 29.9 are considered overweight and BMI of 30 or higher are considered obese.
The analysis of the data was adjusted for factors such as age, alcohol consumption, smoking, breast-feeding, birth control pill use, menopausal status and postmenopausal hormone therapy.
The results showed that overweight women with BMI of 25 to 29.9 were 19 percent more likely (in the first study) or 78 percent more likely (in the second study) to develop rheumatoid arthritis than women whose BMI less than 25. And those who were obese, with BMI over 30, the risk of developing RA were 18 percent higher in the first study and 73 percent higher in the second study.
“We’ve found that being overweight or obese in women increased the chance of getting RA,” said lead researcher Bing Lu, MD, DrPH, assistant professor of medicine at Harvard Medical School, Brigham and Women’s Hospital. “We also found that the effect was stronger in seronegative type of RA.” Conversely, women with normal weight levels didn’t have a higher risk. He noted that the two different phenotypes may be due to different genetic and environmental studies.
While he could not explain the findings definitively, Lu speculated that inflammatory proteins known as cytokines regulate the immune system. Since rheumatoid arthritis is an inflammatory disease, it is possible that obesity increases the risk of rheumatoid arthritis.
This study found an association between overweight and rheumatoid arthritis risk, but it did not prove cause-and-effect. Lu noted that further studies are needed to confirm these findings in other populations.