Rates of Neuropsychological Dysfunction in Fibromyalgia and Rheumatoid Arthritis

An Automated Clinical Rating Approach

Luis D. Medina, PhD; Linda Hirshberg, PhD; Michael J. Taylor, PhD; Paul E. Gilbert, PhD; Robert K. Heaton, PhD

Disclosures

J Clin Rheumatol. 2019;25(6):252-257. 

In This Article

Abstract and Introduction

Abstract

Background/Objective: Fibromyalgia (FM) is a chronic pain syndrome of unknown etiology that can include subjective cognitive symptoms and variable evidence of cognitive dysfunction. Rates of occurrence and severity of cognitive impairment remain unclear. Additionally, comparison of this group with other pain conditions has been limited. The current cross-sectional study sought to identify rates of clinically significant cognitive impairment in FM and rheumatoid arthritis (RA) using an automated clinical rating approach.

Methods: A total of 61 females (32 with FM, 29 with RA) completed a comprehensive neuropsychological (NP) battery and an assessment of personality and psychological distress. All study measures were completed in one visit and all participants were recruited over the span of 3 years. Demographically corrected NP scores were used to compare participants with normative expectations and a summary score was calculated to compare groups on NP impairment.

Results: Compared to normative expectations using a 1 standard deviation cutoff, moderately increased rates of cognitive deficits were observed in both groups (FM = 23.3%, RA = 34.5%), with most test scores in affected individuals falling in the mild to moderate ranges of impairment. Compared to RA, FM participants endorsed higher and significant levels of psychological symptoms overall. These were not associated with cognitive performance in either patient group.

Conclusions: Increased rates of cognitive dysfunction as well as psychological distress exist in both FM and RA compared to a normative sample. However, psychological distress was unrelated to cognition in both groups. These findings have implications regarding the clinical presentation of individuals with FM and RA.

Introduction

Fibromyalgia syndrome (FM) is a chronic, musculoskeletal pain syndrome that is associated with diffuse achiness, stiffness, fatigue, and multiple symmetrical tender points.[1,2] Although its etiology is uncertain, FM appears to be more common in women than men and its prevalence is higher in people over fifty than in younger individuals.[3] The criteria for diagnosing the syndrome were established in 1990 by the American College of Rheumatology after a multi-center trial.[2] These criteria were revised in 2010[4] and further updated in 2016[5] to include four main requirements for a diagnosis: (1) generalized pain in at least four of five specified regions; (2) presence of symptoms at a similar level for at least 3 months; (3) specific cutoff scores on the widespread pain index (WPI) and the symptom severity scale (SSS); (4) diagnosis is valid irrespective of other diagnoses and a diagnosis does not exclude the presence of other clinically important illnesses.

FM is characterized primarily by achiness concentrated in axial locations, such as the neck and back, as well as in the pelvic girdle, but can be more generalized and include upper and lower limbs. Other symptoms include diffuse stiffness that is usually worse in the morning, chronic pain that varies in severity, tension headaches, paresthesias, pain or cramps in the lower abdomen, fatigue with non-restorative or non-refreshing sleep, and depression.[5] Given the variety of symptoms that can be seen, the syndrome appears to have a large impact on physical functioning as well as on psychological/emotional outcomes, and individuals generally report worse quality of life[6] as well as possible disability.[7] With regard to diagnosis and for appropriate treatment, FM needs to be distinguished from other similar syndromes such as axial arthritis, psychogenic rheumatism, and chronic fatigue syndrome among others.

Patients with FM also have reported cognitive difficulties, a subjective sense of mental "fogginess" often referred to as "fibrofog" in the literature.[8,9] However, this subjective appraisal of cognitive dysfunction in FM has not consistently predicted objective impairment,[10] resulting in many providers considering these subjective cognitive problems as a reflection of depressive symptoms and viewing FM as a psychosomatic condition.[11] However, there is growing evidence that some patients with FM demonstrate poorer cognitive performance across several domains. Despite evidence that perceived deficits are disproportionately greater than objective deficits,[12] cognitive symptoms have included reports of visual and verbal memory deficits, as well as difficulties with speed of information processing, visual and verbal attention or concentration, and reasoning and problem solving abilities.[8,12–16] A recent meta-analysis found poorer performance in FM across multiple cognitive domains compared to healthy controls; these differences were greatest in inhibitory control and memory.[17] While cognitive deficits may not be present globally across all cognitive domains,[14] in terms of disease impact, patients rank problems in cognition highly[9,18] and these problems seem to be related to the severity of their pain symptoms,[10] but do not appear to be explained by medication use[19] or psychological factors such as depression and anxiety.[16] Additionally, these symptoms may be worsened by comorbid conditions, such as chronic fatigue syndrome.[20]

Research characterizing the cognitive symptoms associated with FM has generally focused on directly comparing performance of FM patients with that of healthy controls. However, little is known regarding the rates of clinically relevant impairment, and few studies have compared FM patients with other clinical populations (e.g., whiplash,[21] chronic fatigue syndrome[20,22]). The current study was designed with several objectives. First, we sought to explore if FM patients demonstrate neuropsychological evidence of clinical brain dysfunction. For this purpose, we compared performance on a comprehensive NP test battery by FM patients with demographically corrected normative standards on the cognitive battery. Second, utilizing an automated clinical rating approach, we examined where NP performance of our FM group differed from that of patients with another chronic pain condition, namely, patients with rheumatoid arthritis (RA). The RA group was chosen for comparison because like FM, RA is associated with chronic, debilitating pain that could interfere with neuropsychological test performance. However, unlike FM, RA has a pathophysiology that is better understood and that is not thought to directly affect brain function. Additionally, RA is not generally associated with neurocognitive complaints. Third, we determined whether demographically comparable groups of FM and RA patients show similar results with respect to personality and emotional functioning. Lastly, we investigated whether measures of emotional distress were related to NP functioning in either or both of these patient groups.

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