How Does Obesity Affect Arthritis Outcomes?
Obesity may affect risk of developing osteoarthritis and rheumatoid arthritis, and it has been linked with increased disease activity and adverse clinical outcomes.
According to the Centers for Disease Control and Prevention, obesity affects more than one-third of Americans, and it has been associated with a range of negative health outcomes, including cardiovascular disease (CVD), diabetes, and cancer.1 A large body of evidence has also linked obesity with osteoarthritis and rheumatoid arthritis, suggesting that it may both influence the pathogenesis of the disease as well as clinical outcomes, disability, and quality of life.
“There is a high degree of interaction between obesity and arthritis, with over 80% of obese patients having some form of joint disease,” according to John Morton, MD, MPH, FACS, chief of bariatric and minimally invasive surgery at Stanford University School of Medicine in California. “Increased weight upon joints, impaired bone and cartilage metabolism, and heightened inflammation associated with obesity are all contributors to this interaction,” he said in an interview.
Obesity and Osteoarthritis
The relationship between excess weight and osteoarthritis is well-established. In fact, obesity appears to be the top modifiable factor that influences osteoarthritis risk, with one study reporting that individuals whose body mass index (BMI) was higher than 30 kg/m2 having a nearly 7-fold increased risk of developing knee osteoarthritis.2
Two recent meta-analyses found a dose-response relationship between increasing BMI and incidence of both knee and hip osteoarthritis. Specifically, for each 5-unit increase in BMI, the risk of knee osteoarthritis increased by 35%, and the risk of hip osteoarthritis increased by 11%.3,4
“Obesity is a major risk for degenerative arthritis of the lower extremities, especially knees and hips, due to excessive mechanical loading,” Eric L. Matteson, MD, MPH, chair of the department of rheumatology at the Mayo Clinic in Rochester, Minnesota, said in an interview. The joints are subjected to force of up to 10 times one's body weight during physical activity such as walking, and of course, the higher the weight, the greater the joint load will be.
Other findings indicate that obesity greatly increases the odds of needing arthroplasty—and at much younger ages. Findings of a prospective study published in Rheumatology attributed 69% of total knee replacements and 27% of total hip replacements to excess weight and obesity, with further research suggesting that obesity may impede recovery from arthroplasty.2
Obesity and Rheumatoid Arthritis
More recently, attention has turned toward an apparent connection between obesity and rheumatoid arthritis. “There is evidence that obesity is a risk factor for development of rheumatoid arthritis, and this is more evident in women than men,” said Larry W. Moreland, MD, the Margaret Jane Miller Endowed Professor of Arthritis Research and chief of the division of rheumatology and clinical immunology at the University of Pittsburgh School of Medicine.
“Adipose tissue is an ‘active' organ in that it [produces] pro-inflammatory molecules such as cytokines, and there are possibly other factors that have not yet been clearly identified as to why obesity has now been identified as a risk factor for developing rheumatoid arthritis,” he said.
A significant treatment challenge that remains is the standard dose of rheumatoid arthritis medications may not attain the same concentrations at sites of inflammation in obese vs nonobese patients, thus rendering them less effective. In recently published data, obese patients with chronic inflammatory rheumatic diseases demonstrate an altered response to disease-modifying antirheumatic drugs (DMARDs) and tumor necrosis factor (TNF) inhibitors.5
“Control of the underlying inflammatory disease is essential to [improving] function and well-being in patients with inflammatory arthritis,” said Dr Matteson. “As well, rheumatologists are part of the patient's multidisciplinary health team, and must work with other health care providers in managing medically-complicated obesity by making appropriate referrals and limiting the use of glucocorticoids which [further] contributes to obesity and its complications.”