Background Knowledge on the nature of post-COVID neurological sequelae often manifesting as cognitive dysfunction and fatigue is still unsatisfactory. Objectives We assumed that cognitive dysfunction and fatigue in post-COVID syndrome are critically linked via hypoarousal of the brain. Thus, we assessed whether tonic alertness as a neurocognitive index of arousal is reduced in these patients and how this relates to the level of central nervous activation and subjective mental fatigue as further indices of arousal. Methods 40 post-COVID patients with subjective cognitive dysfunction and 40 matched healthy controls underwent a whole-report paradigm of briefly presented letter arrays. Based on report performance and computational modelling according to the theory of visual attention, the parameter visual processing speed (VPS) was quantified as a proxy of tonic alertness. Pupillary unrest was assessed as a measure of central nervous activation. The Fatigue Assessment Scale was applied to assess subjective mental fatigue using the corresponding subscale. Results VPS was reduced in post-COVID patients compared to controls (p = 0.005). In these patients, pupillary unrest (p = 0.029) and mental fatigue (p = 0.001) predicted VPS, explaining 34% of the variance and yielding a large effect with f2 = 0.51. Conclusion In post-COVID patients with subjective cognitive dysfunction, hypoarousal of the brain is reflected in decreased processing speed which is explained by a reduced level of central nervous activation and a higher level of mental fatigue. In turn, reduced processing speed objectifies mental fatigue as a core subjective clinical complaint in post-COVID patients.
Background and objectives. Cognitive symptoms persisting beyond 3 months following COVID-19 present a considerable disease burden. We aimed to establish a domain-specific cognitive profile of post-COVID syndrome, and relationships with clinical variables, to provide relevant information for outcome prediction and treatment decision-making. Methods. We compared cognitive performance on the Oxford Cognitive Screen-Plus between a large post-COVID cohort (n = 282) and a socio-demographically matched healthy control group (n = 52). We assessed task- and domain-level dysfunction and relationships between clinical and patient-reported outcomes. Results. Patients scored significantly lower on delayed verbal memory, attention, and executive functioning than healthy controls and in each of these domains, 10-20% of patients scored below cutoff. Delayed Memory was particularly affected and a rather small proportion of its variace was explained by hospitalization (β = -.67, p < .01) and age (β = -.03, p < .01; R2adj. = .06). Hospitalization further predicted attention performance (β = -.83, p < .001; R2adj. = .04). Interpretation. Post-COVID syndrome is associated with long-term cognitive dysfunction, particularly in delayed verbal memory, attention, and executive functioning, relatively independent of original disease severity. Next, longitudinal investigation of the domain-dysfunctions in this cohort is needed to examine their trajectory.
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