The study, “Lower regulatory frequency for postural control in patients with fibromyalgia and chronic fatigue syndrome,” appeared in the journal PLOS ONE.
Patients with fibromyalgia and CFS exhibit a 50 to 70 percent overlap in symptoms, such as pain, and several diagnostic criteria are common between the two conditions. Deficits in balance and postural control have also been reported in patients with these disorders.
In this study, researchers set out to investigate similarities and differences in postural sway and the underlying control strategies between fibromyalgia and CFS, compared with healthy subjects in a control group, with the goal of deepening knowledge about fibromyalgia and CFS to better understand the symptoms that appear when pain and fatigue become chronic.
They analyzed 75 women — 25 each in fibromyalgia, CFS, and control groups — ages 19 to 49. Investigators chose this age range based on the observation that most patients diagnosed with either condition are young to middle-age women.
Participants were required to stand quietly for 60 seconds on a force platform in each of three conditions: firm surface with vision, firm surface without vision, and compliant surface with vision. In conditions with vision, a red cross was placed 4 meters away at eye level to serve as a visual reference point. Participants had to stand without shoes, feet parallel, arms folded across the chest, and were asked not to move their head or extremities.
Results showed that both fibromyalgia and CFS patients had a different pattern of postural control, leading to greater postural sway from front to back and side to side in all three experimental conditions than those in the control group. Postural sway is defined as the horizontal movement of the body around the center of gravity and is possibly reflective of postural control in the brain.
Data also indicated that without vision, patients showed increased ankle torque in order to control location and movement, which indicates impaired somatosensory information processing, compared with the control group. Somatosensory refers to touch, pain, temperature, and position and movement of the body. This finding is in line with prior results showing deterioration of upper limb control in patients with fibromyalgia, the researchers said.
Subsequent analyses did not reveal significant differences between fibromyalgia and CFS patient groups.
“These findings support our hypothesis that patients with [fibromyalgia] and CFS would show different results from [controls], but would display similar patterns of postural control to each other. Thus, this adds another feature to the list of similarities between [fibromyalgia] and CFS,” the scientists wrote.
However, they added that these similarities do not automatically mean that these disorders are one and the same, but may rather be common expressions of different conditions.