Rheumatoid arthritis may soon be added to the growing list of health risks associated with obesity. According to a recent Mayo Clinic study, women with a history of obesity are at a higher risk of developing rheumatoid arthritis.
To study the association, the researchers analyzed medical records from 1980 to 2007 that were part of the Rochester Epidemiology Project. The team looked at data on 813 adults with rheumatoid arthritis and 813 disease-free adults, matched for age and gender, as the controls. About 30% of the participants were obese and 68% were women.
The researchers found that rheumatoid arthritis cases rose by 9.2 per 100,000 women from 1985 to 2007 and that obesity accounted for 52% of that increase. Women are more likely to get rheumatoid arthritis, which could explain why the association was more significant for them. In 2007, an estimated 1.5 million Americans had rheumatoid arthritis.
“The data suggests a significant portion of rheumatoid arthritis cases could be due to obesity,” says study author Dr. John Davis, a rheumatology consultant at the Mayo Clinic in Rochester, Minn. “Unless we are able to change the course of the obesity epidemic, we can expect to see a rise in the incidence of rheumatoid arthritis.”
Exactly how obesity causes rheumatoid arthritis is unclear, but the researchers speculate that it could have something to do with inflammation. Rheumatoid arthritis is an autoimmune disorder that causes inflammation of the joints and also affects other organs in the body. Having excess fat can also contribute to chronic inflammation — a condition that is known to increase the risk for diseases like heart disease and diabetes, and potentially also arthritis. Extra weight around the joints may further accelerate arthritis progression.
“Having inflammation from arthritis can also cause a decrease of lean body mass and an increase in other fat in the body,” says Dr. Davis. “It’s a bit of a chicken-or-the-egg problem.”
Another possibility could be a lack of vitamin D — a deficiency that is commonly found in both obese and rheumatoid arthritis patients.
Smoking is also a risk factor for rheumatoid arthritis, but the researchers ruled it out as a contributing factor in the current study because the rate of smoking remained constant throughout the study period while cases of rheumatoid arthritis rose.
Further research is still needed to determine the biological mechanisms connecting obesity and arthritis and how weight loss can influence progression of the disease.
“Curing obesity won’t cure arthritis for people who have it, but it could alleviate symptoms,” says Dr. Davis. “Obviously this suggests that from a public health perspective, achieving weight loss is important for other health complications. If we could eliminate obesity, we could substantially decrease arthritis.”
The study was published online in the American College of Rheumatology’s journal Arthritis Care & Research.