Sarcopenic Obesity Complicates Rheumatoid Arthritis

Dr Baker describes his research on how patients with obesity and rheumatoid arthritis may also suffer from sarcopenia and how clinicians can work with patients to improve their condition.

Joshua Baker, MD, is a rheumatologist and an associate professor at the University of Pennsylvania.

TRANSCRIPT:

Hi everyone. My name's Josh Baker. I am an associate professor at the University of Pennsylvania and also work at the Philadelphia VA in Philadelphia. I'm going to talk to you a little bit today about our study looking at the prevalence of sarcopenia and sarcopenic obesity in patients with RA.

Just to give you a little bit of background, our study was interested in sarcopenia, which is really just a term that means loss of muscle and muscle strength. When we think of sarcopenia, we typically think of older patients who are very thin and frail, and for a long time that's really how people thought of sarcopenia—as just a disease of aging with really very thin people. But, more recently, it's become clear that a lot of people who are obese and overweight have also lost a lot of muscle and lost a lot of muscle strength. So it is possible to have excess body fat and also have muscle weakness—in particular, muscle weakness that is out of proportion to what you should have for your body habitus. People that are more obese tend to be stronger because they need to carry around this weight.

Recently, there's been a new term called sarcopenic obesity, and sarcopenic obesity is just the general idea that people can be overweight or have excess body fat and also be sarcopenic or have low muscle mass or low muscle strength. So one of the problems with this construct or this idea is that there are not great definitions or there's not a widely accepted definition of what sarcopenic obesity is. The reason for that is that there are a lot of methodologic difficulties with how we define sarcopenic obesity, for a variety of reasons, but I won't go into a lot of detail today. But as a result, we don't really have a true sense of the extent of this problem in our patients, partly because we don't really know how to define it.

What's new about our study that I'm going to tell you about is that we used a new definition of sarcopenic obesity that we've validated, that's really defined as excess body fat and relatively low muscle mass for that level of adiposity. Essentially, we defined this entity being present if someone had high levels of fat and also had low muscle mass compared to what you'd expect for their age, sex, race and fat mass.

We took 3 RA cohorts that we collected in collaboration with other investigators and we compared those 3 cohorts of patients with RA to 2 reference populations. And what we found was that the rates of sarcopenic obesity were indeed much higher in patients with RA, about 3 times as high in patients with RA. In addition, patients with RA had higher rates of low lean mass without excess body fat. So both were increased, but sarcopenic obesity, in particular, was a fair amount higher in patients with RA. So this is probably the most important observation and it gave us a sense that there was a high prevalence of this particular problem in patients with RA.

Second thing that our study did was we looked at how sarcopenic obesity correlated with function and predicted worsening of function, and patients with sarcopenic obesity essentially had the worst function. So you can imagine, they have low muscle mass and also have excess body fat, both of which can contribute to poor physical functioning, so more disability, higher health assessment questionnaire scores. Secondly, the worsening of each of these things was observed in patients with both low muscle mass and sarcopenic obesity.

The takeaway is that prevalence of sarcopenic obesity is much higher in patients with RA and is correlated with worse function and worsening function. So it's an important problem. It's prevalent in RA. The question is, how do we deal with it? That's not what the purpose of my study was, but my hope is that we take away from these kinds of reports that we do need interventions that can effectively manage these problems and they may have important impact on our patients and that this is an ongoing area of investigation. I think in the next 10 years we should have more and more effective ways of dealing with sarcopenia and sarcopenic obesity, and I look forward to the improvements in patient function that we may see, as those become available to our patients.