Problems with memory and verbal skills in fibromyalgia patients are associated with lower daytime levels of salivary cortisol, a hormone involved in stress response, a study suggests.
Its researchers recommend further work into stress management as a way of addressing these cognitive difficulties.
The study “Salivary cortisol is associated with cognitive changes in patients with fibromyalgia” was published in the journal Scientific Reports.
Fibromyalgia is characterized by widespread muscle pain along with fatigue, cognitive and sleep disturbances, and depression.
Patients have reported that stress acts as a trigger for their chronic pain, and lower cortisol levels have been found in people with stress-related disorders including post-traumatic stress syndrome.
These findings support views of fibromyalgia as a stress disorder, the researchers wrote.
The hypothalamic-pituitary-adrenal axis in the brain is responsible for the stress reaction and for the production of cortisol, which, as noted, is usually low in people with stress disorders. Some studies also report lower levels in fibromyalgia patients, but findings have been inconsistent.
Cognitive problems, mainly involving memory, executive function and language skills, are known to affect most fibromyalgia patients — more than 76% of cases, the researchers wrote. Executive function refers to thinking processes that control behavior such as planning, organizing, and paying attention.
Researchers in Taiwan evaluated how cortisol levels might correlate with cognitive performance in people with fibromyalgia.
They measured cortisol levels in the saliva of fibromyalgia patients and healthy controls on the day before they took cognitive tests. In total, 44 patients (mean age of 50.7, 91% women) and 48 controls (mean age of 50.8, 79% women) took part in the analysis.
As expected, compared to healthy individuals, fibromyalgia patients more often reported experiencing fatigue, cognitive difficulties, sleep that failed to refresh, headaches, and feeling depressed.
Participants were asked to collect a saliva sample at four times during the day: upon awakening, 30 minutes after awakening, at 3 p.m., and at bedtime.
Cognitive function was evaluated with objective tests given by trained psychologists and research assistants. These included a global assessment using the mini-mental state examination, as well as tests of memory, visuospatial function (needed for movement, depth, and distance perception), language, and executive functioning.
They also answered a “complaint” questionnaire addressing cognitive difficulties with various daily activities within the past two years.
Questionnaire results showed that patients had significantly more difficulty with executive functioning, as well as in memory and language, than controls. A total of 90% patients reported at least one symptom related to executive function, 60% had problems with memory, 33% in language, and 16% in visuospatial domains.
Fibromyalgia patients scored significantly worse (higher scores) overall in the subjective cognitive complaint questionnaire than did controls (mean scores 4.1 vs. 1.3). This difference was independent of education levels.
Daytime cortisol levels tended to be significantly lower in fibromyalgia patients, particularly at 30 minutes after awakening, analysis showed — 0.209 picograms per milliliter (pg/mL) in the fibromyalgia group and 0.386 pg/mL in controls. At bedtime, these levels continued to be lower in the patient group (0.002 pg/mL) than among controls (0.024 pg/mL).
Researchers found a moderate but positive link between cortisol levels at 30 minutes after awakening and verbal learning and memory test scores among the patient group.
A similar connection between higher cortisol levels and better test scores was found for language skills, determined using the Boston Naming Test.
These results support a link between cognitive changes and cortisol, suggesting that “stress maladaptation may play some role in the cognitive dysfunction associated with FM [fibromyalgia],” the researchers wrote.
“Additional studies must elucidate whether stress management improves cognitive performance in patients with FM,” they added.
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