Persistent cognitive slowing in post-COVID patients: longitudinal study over 6 months

Area of Science:

• Neuroscience
• Cognitive Psychology
• Clinical Neurology

Background:

• Fatigue is a primary, debilitating symptom in post-COVID syndrome (PCS).
• A proposed cause of PCS fatigue is reduced activity in the brain's arousal network, manifesting as slower cognitive processing.
• The precise nature and temporal course of this cognitive slowing in PCS remain unclear.

Purpose of the Study:

• To determine if PCS patients exhibit specific deficits in tests measuring processing speed.
• To conduct the first longitudinal evaluation of processing speed in PCS patients.

Main Methods:

• Neuropsychological assessment of 88 PCS patients with cognitive complaints and 50 healthy controls.
• Primary outcome: tonic alertness measured by the Test for Attentional Performance.
• Secondary assessment at 6-month follow-up for 77 patients, evaluating attention and cognitive domains via the Neuropsychological Assessment Battery.

Main Results:

• PCS patients demonstrated significantly slower reaction times in simple and complex tasks compared to controls (p < 0.001).
• Reduced alertness correlated with increased fatigue (r = -0.408, p < 0.001).
• Cognitive slowing and alertness deficits showed no significant change at the 6-month follow-up (p = 0.240).

Conclusions:

• Hypoarousal, evidenced by selective processing speed reduction, is a core deficit in PCS.
• This deficit is detectable using standard neuropsychological tests.
• The core deficit of hypoarousal in PCS is persistent, showing no improvement over six months.