Impaired auditory sensory gating as a neurophysiological correlate of cognitive fatigue in long COVID.

Objective: Fatigue is among the most disabling symptoms across neurological and postinfectious conditions and is a defining feature of long COVID, yet objective neurophysiological markers remain scarce.Auditory sensory gating, indexed by P50 suppression, has been proposed as a correlate of cognitive fatigue in multiple sclerosis, but its relevance in long COVID is unclear.Additionally, we compared the utility of the Beck Depression Inventory-II and Beck Depression Inventory-Fast Screen (BDI-FS) in this fatigued population.Method: Seventy-one individuals with long COVID-related fatigue completed questionnaires assessing fatigue (Modified Fatigue Impact Scale) and depressive symptoms (BDI-FS).Auditory sensory gating was assessed using a paired-click electroencephalography paradigm.Auditory sensory gating was assessed using a paired-click electroencephalography paradigm.Associations between cognitive fatigue, sensory gating, and depressive symptoms were examined using correlational analyses and two hierarchical regression models.Results: Reduced P50 suppression was associated with higher Modified Fatigue Impact Scale cognitive scores (τ = -.173,p = .037).Cognitive fatigue correlated with depressive symptoms measured by the Beck Depression Inventory-II (τ = .239,p = .005),but not by the BDI-FS (τ = .131,p = .135).Neither depression measure correlated with sensory gating.P50 suppression accounted for unique variance in cognitive fatigue beyond demographics and depressive symptoms.Conclusions: Auditory sensory gating shows a small but meaningful association with cognitive fatigue in long COVID and contributes uniquely beyond depressive symptoms.The BDI-FS demonstrated less symptom overlap, supporting its suitability for depression screening in fatigued populations.These findings underscore the importance of distinguishing fatigue related from affective symptoms and suggest sensory gating as a promising transdiagnostic target in fatigue research. Key Points Question:Is auditory sensory gating also associated with cognitive fatigue in long COVID, and how robust is this association when other potentially influencing variables are considered?How well do depression questionnaires differentiate fatigue from depressive symptoms in this population?Findings: Reduced P50 sensory gating was linked to greater cognitive fatigue also in long COVID patients and explained unique variance beyond other variables.The Beck Depression Inventory-Fast Screen showed less overlap with fatigue-related symptoms than the Beck Depression Inventory-II.Importance: These findings highlight sensory gating as a potential transdiagnostic marker of cognitive fatigue and support a fatigue-specific depression screening in long COVID.Next Steps: Future work should assess sensory gating as a transdiagnostic biomarker in other fatigue-related diseases, clarifying whether it reflects a phenotypic vulnerability or infection-related effects and evaluating its sensitivity to disease course and intervention.