BIRMINGHAM, AL — Fibromyalgia, a disorder characterized by chronic muscle pain and unusually high pain sensitivity, is the focus of two ongoing studies funded by the National Institutes of Health at the University of Alabama at Birmingham (UAB).

One study is investigating the association between emotional stress and pain. “We’re interested in examining the effects of stress on pain experienced by people with fibromyalgia compared to healthy people,” said Laurence A. Bradley, Ph.D., professor of medicine with the Division of Immunology and Rheumatology at UAB.

The first part of the study involves applying varying levels of heat to a small area on the wrist to produce perceptions ranging from warmth to mild or moderate pain. “Before the heat stimulus is applied, participants are asked to vividly imagine either a neutral or stressful event from their life experience and then rate both the intensity and unpleasantness of the heat stimulus they receive,” Bradley said.

Before and after each exercise, participants’ physiologic responses to stress are assessed by measuring heart rate, blood pressure, and cortisol, a hormone that is released into the blood in response to stress. “It usually takes about 30 minutes for cortisol levels to peak following a stressful event,” Bradley said. “So one-hour rest periods follow each test. It takes about eight hours on a single day to complete all the exercises, although the participants receive the heat stimuli only for brief periods of time.”

The second part of the study, which takes about four hours the following day, entails neuroimaging. “Using the same procedures, images are taken of the brain that vividly depict brain blood flow responses to the influences of stressful and non-stressful events on pain,” Bradley said.

The four-year study is scheduled to conclude this summer. Researchers hope to gain a better understanding of factors that influence pain perception. “There are many biological and social factors, like stress, that interact with one another to alter pain perception,” Bradley said. “Understanding how these factors interact will help us better understand the pain experienced by people with fibromyalgia and may help us develop better, more targeted treatments for these patients.”

Another chronic pain study led by Bradley aims to determine if sisters of women with fibromyalgia, compared to the brothers and sisters of healthy women, exhibit greater sensitivity to pain and if so, if one or more genes are associated with this increased risk. “This is the first study examining sex-related genetic factors associated with fibromyalgia,” Bradley said.

Earlier studies suggest women with fibromyalgia may have a genetically influenced impaired ability to inhibit pain. There also is evidence that the disorder occurs more frequently among sisters, compared with brothers, of patients with fibromyalgia. “If true, this points to a sex-related, genetic predisposition to the development of the disorder,” Bradley said.

The study is enrolling women with fibromyalgia, women without fibromyalgia, and the male and female siblings of both groups of women. “We want to determine if siblings, especially sisters, also experience a greater sensitivity to pain,” Bradley said. “With partners, we want to see if there any effects on pain sensitivity associated with sharing the same environment with someone who has fibromyalgia.”

The study involves a series of brief tests to assess pain sensitivity and a blood sample to measure levels of serotonin, a substance produced by the central nervous system involved in reducing pain. “In people with fibromyalgia, there is evidence of an abnormality in a particular gene that regulates the production of serotonin,” Bradley said. “If this is confirmed, it might help explain why people with fibromyalgia have unusually low levels of serotonin.”

Findings will provide researchers with a greater understanding of fibromyalgia and may help identify individuals at greater risk for unusually high pain sensitivity associated with the disorder. “It also may provide valuable information about genetic factors involved in the development of fibromyalgia,” Bradley said.

For more information about these or other chronic pain studies under way at UAB, call (205) 934-9614.