A new study confirms that people with fibromyalgia (FM) can experience objective impairments in cognitive and executive function independent of depression.
FM patients “often complain about the so-called ‘Fibro-fog’, a cluster of cognitive disorders not always reflected in poor test-based performance, but which strongly interferes with work and daily life,” lead author Valentina Tesio, PhD, and colleagues write in an article published July 21 in Arthritis Care and Research.
In fact, the American College of Rheumatology has added cognitive dysfunction to its list of diagnostic criteria for FM. However, the authors point out, this has proven difficult to study, in part because ” ‘executive functions’ (EF) represent a multifaceted construct, composed of separable factors…. Considering EF as a whole would therefore not allow identification of subtle differences in cognitive complaints.”
Therefore, the authors used standard tests of memory and EF to compare neuropsychological function in patients with FM and function in healthy control subjects. They then examined the relationship between the test scores for patients with FM and their subjective perceptions of their cognitive problems.
Dr. Tesio, from the Department of Clinical and Oncological Psychology, Città della Salute e della Scienza Hospital of Turin, and the Department of Neuroscience, University of Turin, Italy, and colleagues studied 4 interrelated components of executive function: shifting, or the ability to shift attention between tasks; inhibition, the ability to suppress automatic or routine responses; updating, which involves replacing old, outdated information with newer, more relevant information; and access, which reflects the ability to access long-term memories and is needed for verbal fluency.
They enrolled 30 consecutive female FM patients attending a hospital clinic affiliated with the University of Turin, Italy. All patients were between the ages of 18 and 70 years (mean age, 52.8 years; standard deviation [SD], 9.6 years) and had at least 5 years of formal education. The control group consisted of 30 women matched for age (mean age, 53.8 years; SD, 12.4 years) and educational level, with no history of rheumatologic conditions or chronic pain.
All of the participants underwent 90 minutes of testing that included measurements of pain, anxiety, and depression, as well as EF, memory, working memory, shifting, inhibition, updating, and access. Self-evaluation of cognitive impairment was evaluated using the Functional Assessment of Cancer Therapy-Cognition Scale (FACT-Cog 2), which can be used with populations other than patients with cancer because it does not contain specific references to cancer or cancer treatment.
The patients with FM reported a mean pain intensity level of 6.68 (SD, 2.59) on a visual analog scale, suggestive of moderate pain. On the Hospital Anxiety and Depression Scale, patients with FM had a mean total score of 18.2 (SD, 5.8), indicating severe anxiety and depression, compared with a mean of 11.2 (SD, 5.7), or moderate anxiety and depression, among the control participants (P less than .0001). Scores of 8 or more suggest clinically relevant levels of anxiety or depression.
On the Digit Scan-Backward test, a measure of updating and working memory, the patients with FM had a mean score of 3.8 (SD, 1.1) compared with a mean of 4.4 (SD, 0.9) for the control group (P = .031). Patients with FM also scored lower on the delayed recall portion of the Rey Auditory Verbal Learning Test, with a mean score of 9.9 (SD, 3.6) compared with a mean of 11.7 (SD, 2.4; P = .033), suggesting impairments in episodic memory.
Attentional shifting was measured using the A and B portions of the Trail Making Test (TMT). There was no significant difference between groups on scores for the TMT-A, in which participants connect numbers ascending from 1 to 25. However, on the TMT-B, which requires the test takers to alternate between numbers and letters, FM patients recorded a mean score of 97.3 (SD, 39.9) compared with a mean of 75.7 for the HC group (SD, 28.6; P = .020).
Working memory was measured with the 1-Back test, in which subjects look at colored blocks on a screen for a given period of time and must then press a keyboard to indicate what they have seen. Reaction time is measured in milliseconds, along with accuracy. There was no difference in accuracy between the groups, but the patients with FM had significantly longer reaction times (mean, 891.2 msec; SD, 185.0) compared with the HC group (mean, 722.4 msec; SD, 131.9; P less than .0001).
Patients with FM also showed significantly poorer judgment on all measures of self-perception of cognitive dysfunction, including mental acuity (P = .002 compared with HC participants), deficits noticed by other people (P = .001), verbal and nonverbal memory, verbal fluency, functional interference, and effect on quality of life (P less than .0001 for each).
In general, the more severe a patient’s FM, as measured by the Fibromyalgia Impact Scale, the greater the self-perception of impairments of cognitive domains such as attention and concentration, as well as of negative effect on quality of life.
The small sample size was one limitation of this study. In addition, the authors did not control for pharmacological treatment when enrolling the participants, and they point out that certain medications can have a significant effect on cognitive function. However, they write, “this limitation does not invalidate the main result of the study, which concerns the degree of accordance between subjective and objective reports.”
“[O]ur data indicate that the long-term and working memory, shifting of attention and updating executive functions of FM patients are impaired compared to [HC]s,” the authors conclude. “These impairments are reflected in subjective complaints independently of depressive symptoms.” They recommend inclusion of a self-report questionnaire to assess cognitive impairment in the initial clinical evaluation of patients with fibromyalgia.