People with rheumatoid arthritis (RA) who are obese are less likely to achieve disease remission than their non-obese counterparts, according to a meta-analysis published in May in Arthritis Care and Research. The review also found that obesity was associated with higher levels of disease activity and pain, suggesting excess weight may negatively affect overall outcomes in RA. This meta-analysis supports earlier research, including a study presented at the 2015 annual meeting of the American College of Rheumatology.
There is strong evidence that obesity increases the risk of developing RA, but less is known about its effect on people living with the disease. So researchers reviewed more than 3,500 studies about the relationship between obesity and four key measures: remission rates, disease activity, patient-reported outcomes at follow-up, and mortality.
They identified 20 studies meeting their inclusion criteria; eight focused solely on remission rates. These studies varied in size (some included a relatively small number of obese patients), design and timeliness (all were published in the past five years, but some relied on data going back decades). Still, the results were similar.
After adjustments for factors that might influence the results, such as age, sex and symptom duration, patients who were obese were found to be 43 percent less likely to achieve remission and 51 percent less likely to achieve sustained remission than people who were normal weight or overweight. Obesity was defined as a body mass index (BMI) greater than 30 and overweight as a BMI of 25 to 29.9 – classifications used by the World Health Organization.
Although remission was defined slightly differently by the authors of the individual studies, it generally means having very few or no signs of clinical disease – including few tender or swollen joints; low blood markers of inflammation such as C-reactive protein (CRP) or erythrocyte sedimentation rate (ESR or “sed rate”); and improved pain and function. For the purposes of the meta-analysis, sustained remission meant remission that occurred at several consecutive time points during a particular study – for example, at six months, nine months and one year.
More disease activity, pain
When the researchers looked at other measures, including disease activity, patient-reported outcomes and mortality, they again found that many studies, though not all, reached similar conclusions. In general, obesity was associated with worse disease activity and pain as well as higher counts of tender (but not swollen) joints and inflammation markers.
The researchers did not see higher mortality rates in obese patients – in fact, just the opposite. But that finding may be skewed, according to co-author Gilaad G. Kaplan, MD, an associate professor in the departments of medicine and community health sciences at the University of Calgary, in Alberta, Canada. Dr. Kaplan explains that the studies he and his colleagues reviewed showed inconsistent results; ultimately there wasn’t enough data to know definitively whether obesity has a negative effect on mortality. It also wasn’t possible to determine if a particular treatment plan or medication affected outcomes (some RA medications are known to be less effective in overweight and obese patients) because different studies used different drug regimens and/or switched patients between medications during the study period.
Why obesity produces such poor outcomes isn’t clear, although the researchers point out that fat releases proteins (cytokines) that drive inflammation throughout the body; many of these cytokines are identical to those produced by inflamed joint tissue. They also note that obesity may make some arthritis drugs less effective. People who are obese may also have other health issues that restrict which medications can be used.
Whatever the reason, it’s clear that people with RA who are obese fare worse than those who are not. In one sense, this is good news because weight is something people can try to change. However, more studies are needed to determine if weight loss will, indeed, improve outcomes for obese patients with RA, Dr. Kaplan says.
Vivian Bykerk, MD, a rheumatologist at Hospital for Special Surgery (HSS) in New York City, thinks obese and overweight patients need to start losing weight now. Dr. Bykerk was not involved in the meta-analysis, but she and her colleagues at HSS recently studied obesity in 1,000 newly diagnosed RA patients. They found that only 28 percent of those who were obese achieved sustained remission compared to 48 percent of normal-weight patients, despite receiving similar, guideline-based treatments.
The key message from both investigations, she says, is that “modifiable lifestyle factors such as smoking and obesity must be addressed in order for people with rheumatoid arthritis to achieve their treatment targets. Obesity rates in RA are approaching [those] of the general population and are having a significant negative impact in patients with rheumatoid arthritis.” (According to just-released statistics from the Centers for Disease Control and Prevention, 40 percent of U.S. women and 35 percent of men are obese).
Dr. Bykerk says it’s essential to put in place strategies to help people with RA lose weight, but that “those who have lived with long-standing RA and accumulated joint damage that has reduced mobility may find it even more difficult to achieve a healthier weight.”
Author: Linda Rath for the Arthritis Foundation
- Being Overweight Can Hurt Rheumatoid Arthritis Remission
- Learn More About Rheumatoid Arthritis
- For more content like this, subscribe to Arthritis Today magazine