Brain fog of post-COVID-19 condition and Chronic Fatigue Syndrome, same medical disorder?

Abstract

Background: Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS) is characterized by persistent physical and mental fatigue. The post-COVID-19 condition patients refer physical fatigue and cognitive impairment sequelae. Given the similarity between both conditions, could it be the same pathology with a different precipitating factor?

Objective: To describe the cognitive impairment, neuropsychiatric symptoms, and general symptomatology in both groups, to find out if it is the same pathology. As well as verify if the affectation of smell is related to cognitive deterioration in patients with post-COVID-19 condition.

Methods: The sample included 42 ME/CFS and 73 post-COVID-19 condition patients. Fatigue, sleep quality, anxiety and depressive symptoms, the frequency and severity of different symptoms, olfactory function and a wide range of cognitive domains were evaluated.

Results: Both syndromes are characterized by excessive physical fatigue, sleep problems and myalgia. Sustained attention and processing speed were impaired in 83.3% and 52.4% of ME/CFS patients while in post-COVID-19 condition were impaired in 56.2% and 41.4% of patients, respectively. Statistically significant differences were found in sustained attention and visuospatial ability, being the ME/CFS group who presented the worst performance. Physical problems and mood issues were the main variables correlating with cognitive performance in post-COVID-19 patients, while in ME/CFS it was anxiety symptoms and physical fatigue.

Conclusions: The symptomatology and cognitive patterns were similar in both groups, with greater impairment in ME/CFS. This disease is characterized by greater physical and neuropsychiatric problems compared to post-COVID-19 condition. Likewise, we also propose the relevance of prolonged hyposmia as a possible marker of cognitive deterioration in patients with post-COVID-19.

Keywords: Brain fog; Cognition; Hyposmia; Myalgic Encephalomyelitis/Chronic Fatigue Syndrome; Neuropsychological impairment; Post-COVID-19 condition; SARS-CoV-2.

Fig. 1

Severity and frequency of symptoms (DSQ). *p < 0.05 **p ≤ 0.01; 0: Lack of symptoms; 1: Mild; 2: Moderate; 3: Severe; 4: Very severe; F: Frequency; ME/CFS: Myalgic Encephalomyelitis/Chronic Fatigue Syndrome; S: Severity

Fig. 2

Percentage of patients with SS less than six in the cognitive tests and with deficient TP-R test results. Benton JLO: Benton Judgment Line Orientation test; BVMT-R: Brief Visuospatial Memory Test-Revised; GIAP: Global Index of Attention and Perception; HVLT-R: Hopkins Verbal Learning Test-Revised; ICI: Impulsivity Control Index; MoCA: Montreal Cognitive Assessment; M-WCST: Modified Wisconsin Card Sorting Test; SDMT: Symbol Digit Modality Test; SPCT: Salthouse Perception Comparison Test; TCF: Taylor Complex Figure; TMT: Trail Making Test; TP-R: Toulouse-Piéron-Revised test; WAIS-IV: Wechsler Adult Intelligence Scale IV

Fig. 3

Z scores by cognitive domains and neuropsychiatric assessment. *p < 0.05; **p < 0.01, *** p < 0.001; C-SSRS: Columbia Suicide Severity Rating Scale; GDS: Geriatric Depression Scale; ME/CFS: Myalgic Encephalomyelitis/Chronic Fatigue Syndrome; MFIS: Modified Fatigue Impact Scale; PSQI: Pittsburgh Sleep Quality Index; SF-36: The 36-Item Short Form Health Survey; STAI: State-Trait Anxiety Inventory

Fig. 4

Distribution of cognitive performance according to BSIT results. Benton JLO: Benton Judgement Line Orientation; MoCA: Montreal Cognitive Assessment; SDMT: Symbol Digit Modality Test

Fig. 5

Percentage of variance correlated with cognitive performance. BVMT-R: Brief Visuospatial Memory Test-Revised; DI: discrimination Index; GDS: Geriatric Depression Scale; GIAP: Global Index of Attention and Perception; HVLT-R: Hopkins Verbal Learning Test-Revised; ICI: Impulsivity Control Index; MFIS: Modified Fatigue Impact Scale; MoCA: Montreal Cognitive Assessment; M-WCST: Modified. Wisconsin Card Sorting Test; PSQI: Pittsburgh Sleep Quality Index; SDMT: Symbol Digit Modality Test; SPCT: Salthouse Perceptual Comparison Test; TCF: Taylor Complex Figure; TMT: TP-R: Toulouse-Piéron-Revised Test; WAIS-IV: Weschler Adult Intelligence Scale-IV