Issues Magazine

Pain association for arthritis and fibromyalgia compared

By Lily Yeang

Pain at rest is associated with depression scores in patients with rheumatoid arthritis, and is associated with stress in patients with fibromyalgia, a Perth study has found.

Fibromyalgia is a chronic disorder characterised by widespread pain and tenderness.While it is considered a rheumatic condition like arthritis, it is not considered the same because it doesn’t cause damage to the joints, but impairs them and causes chronic pain.

Findings from the study suggest that distress aggravated pain processes are linked with rheumatoid arthritis, whereas another mechanism triggers stress-induced pain in fibromyalgia.

Murdoch University Professor Peter Drummond from the Center for Research on Chronic Pain and Inflammatory Disease says depression is associated with arthritis while stress is associated with fibromyalgia because people may regard arthritis as an inescapable result of aging, whereas fibromyalgia is more reactive to stress (e.g. through stress-evoked cytokine release).

“We speculate in the journal article that disruption of inhibitory pain modulation processes and an aberrant interaction between the sympathetic and nociceptive systems contributes to pain in fibromyalgia,” Prof Drummond says.

“In arthritis, pains increased during stressful tests, in-line with increases in distress, possibly because the discomfort evoked by the stressful tests made everything seem worse, including their arthritic pain.”

Prof Drummond says in patients with fibromyalgia, clinical pain increased after the acoustic startle stimulus and painful forehead cooling, and increased during stressful mental arithmetic.

Arthritic pain also increased during forehead cooling and mental arithmetic in association with indices of psychological distress.

“Each of these stimuli increases activity in the sympathetic nervous system,” he says.

“The acoustic startle stimulus briefly, forehead cooling in association with pain, and mental arithmetic in association with negative emotions such as anxiety.”

The study aimed to determine whether clinical pain associated with rheumatoid arthritis or fibromyalgia would increase during standard laboratory tasks and, if so, whether these increases were linked with individual differences in psychological distress.

Twenty-three patients with fibromyalgia and 16 patients with rheumatoid arthritis rated changes in clinical pain after being exposed to the different stimuli.

In addition, pain tolerance was assessed during a sub maximal effort tourniquet (constriction) test, and patients provided ratings of distress on a standard Depression, Anxiety and Stress Inventory.

It was found that pain tolerance was unrelated to individual differences in psychological distress in either group.

Prof Drummond says interactions between the sympathetic and immune systems that heighten inflammatory response might be important both in arthritis and fibromyalgia, and should be further examined.

He also says future studies should look into stress management which could help people with arthritis to more effectively control their pain.