SAN DIEGO – In what may be the largest study of its kind, British researchers have linked obesity to significantly higher odds of rheumatoid arthritis disease activity and disability.
“This study emphasizes that obesity can have a profound effect on treatment goals in rheumatoid arthritis,” says Elena Nikiphorou, MD, of King’s College London, who presented the study findings at the annual meeting of the American College of Rheumatology. “Obesity reduced the odds of achieving remission or low disease activity by around 30%. And the odds of having disability were increased by 63%. This confirms what’s been shown in other, smaller studies.”
Dr. Elena Nikiphorou
Despite obesity having been tied to decreased joint damage in established RA, Eric L. Matteson, MD, noted in an interview, that“the biomechanical effect of [being] overweight, especially on the weight-bearing joints” is one of the two “especially important” mechanisms explaining the link between RA and obesity. “The other is that fat cells produce inflammatory proteins, which contribute to the disease process and make it more difficult to treat,” said Dr. Matteson, a rheumatologist at the Mayo Clinic, Rochester, Minn.
“In my view the mechanical risk to the joint outweighs any possible ‘protective’ effect of RA,” Dr. Matteson added in an interview.
For the new study, Dr. Nikiphorou and colleagues compiled statistics from two consecutive United Kingdom RA inception cohorts. One tracked 1,465 patients for up to 25 years (median follow-up, 10 years), and the other tracked 1,236 patients for as many as 10 years (median follow-up, 6 years).
At baseline, 37.2% of 2,420 patients (90% of total) were overweight, and 21.3% were obese. Average body mass index (BMI) rose between the two consecutive studies from 25.5 to 27.6.
The researchers found that obesity was linked to lower likelihoods of remission and low disease activity status (odds ratio, 0.71; 95% confidence interval, 0.55-0.93 and OR, 0.69; 95% CI, 0.55-0.87, respectively.) After controlling for factors such as age and gender, they also saw slightly lower odds of remission in those with higher BMI (OR, 0.97; 95% CI, 0.95-0.99). But there was no statistically significant link between higher BMI and low disease activity status.
The study also connected obesity to higher odds of disability (OR, 1.63; 95% CI, 1.20-2.23). Furthermore, higher BMI was linked to higher odds of disability (OR, 1.04; 95% CI, 1.01-1.06).
Study lead author Dr. Nikiphorou, who spoke in an interview and in comments at an ACR press conference, said “this study emphasizes that obesity can have a profound effect on treatment goals in rheumatoid arthritis. It creates a strong case for addressing BMI and addressing obesity, flagging it up to primary care.”
She added that rheumatologists too often focus on only rheumatoid conditions. “We place so much evidence on disease activity scores,” she said. “How often do we really address the patient in terms of other things going on, including obesity? What we can do is include discussion of BMI, exercise, nutrition.”
Dr. Nikiphorou and Dr. Matteson report no relevant disclosures. No specific study funding is reported.
This article was updated 11/10/17.