5/8/09 A new study suggests that people with rheumatoid arthritis are more sensitive to pain than those without the condition.
Researchers at Johns Hopkins University in Baltimore, found that people who live with rheumatoid arthritis are more reactive to pain in two ways – as a group they’re more sensitive to painful stimulation and appear to feel pain more strongly. And in the presence of pain, the immune systems of people with rheumatoid arthritis seem to react more vigorously, mounting a powerful inflammatory response.
The study was published in the May 2009 issue of Arthritis Research and Therapy.
Pain is the most commonly reported and debilitating complaint of people who have rheumatoid arthritis. But scientists say that given the scope of the problem for patients, there has been a relatively small amount of research into the topic of pain.
Robert Edwards, PhD, is a clinical psychologist working in the Pain Management Center at Brigham and Women’s Hospital in Boston. He led the research team while he was at Johns Hopkins University.
“The focus is often on getting inflammatory processes under control and thinking that once that gets done, everything will be fine. It often means that pain in RA patients is not quite ignored, but it’s relatively under targeted as an important symptom,” Edwards explains.
For this study, researchers conducted a battery of pain tests involving pressure, heat and cold stimulation. Study participants had the power to stop the pain at any time. Scientists compared pain experiences and blood samples of 19 rheumatoid arthritis patients with similar data from 21 healthy individuals. Participants each had one testing session in which their responses to a variety of painful stimuli were recorded and blood samples were taken multiple times to test their reactivity to the stress hormone cortisol as well as interleukin-6 (IL-6) and tumor necrosis factor-alpha (TNF-alpha) chemicals.
The study found that people with rheumatoid arthritis had a fairly general increased sensitivity to pain and to mechanical and thermal stimuli across several body sites. They also complained of pain from heat and cold more quickly and felt it more intensely than those without rheumatoid arthritis.
They felt pain from heat, for example, at a temperature about three to four degrees cooler than those without rheumatoid arthritis.
“I’d estimate that in general and on average, RA patients are 20 percent more sensitive to a painful stimuli than the controls,” Edwards says.
The implications for daily life are obvious.
“If you are more sensitive to pain and you do something like stub your toe, it’s going to hurt worse and bother you more than it would someone who’s less pain sensitive,” he says.
And there may be other long-term, negative consequences to be more pain sensitive. For example, a good amount of literature now suggests that the more sensitive to pain you are, the more you are at risk for things like long-term post surgical pain.
People with rheumatoid arthritis and those in the control group had the same TNF-a in their blood stream before pain. But after scientists applied plain, the levels in people with rheumatoid arthritis went up by a factor of three or four, where as levels in the control group did not change. Edwards says it’s not clear how pain turns up inflammation.
Daniel Clauw, MD, is a professor of anesthesiology at the University of Michigan and serves as the Director of the Chronic Pain and Fatigue Research Center. He says several factors could be causing the pain. He points out that this study shows the pressure difference was most varied in the thumb, which is the area that is most likely to be closest to inflamed joints. He says that suggests in the future, researchers should look at precisely what regions have the increased pain sensitivity to see if it’s due to inflammation of the joints or something more widespread.
Until then, Edwards says there are things that people with rheumatoid arthritis can do to minimize their pain.
“There’s pretty good evidence out there that the way a lot of people respond to pain is they wait until it gets really bad before they do anything about it. And at this point, there’s very good reason to think that even mild pain should be treated as early as possible,” he says.
Edwards also points out that there is evidence that regular exercise and alternative approaches like yoga, hypnosis and acupuncture may help to improve pain. “So I’d strongly encourage RA patients to take advantage of these.”
