Cognitive dysfunction is a frequent and severely debilitating symptom in post-COVID syndrome (PCS). Previously, we found that visual processing speed is reduced in PCS patients and relates to their level of mental fatigue. Without targeted intervention, cognitive dysfunctions may become chronic. This intention-to-treat study evaluates the efficacy of a self-administered app-based cognitive training for PCS patients with post-infectious mild cognitive impairment.

A randomized controlled trial assigning PCS patients 2:1 to the intervention group ("NeuroNation-MED" training three times weekly for 12 weeks alongside standard care) or a wait-list control group (standard care) was conducted. The primary outcome was the global score in the Neuropsychological Assessment Battery (NAB). Visual processing speed was assessed through a whole-report-task using briefly presented letter arrays and computational modeling based on Bundesen's theory of visual attention. Additionally, processing speed was measured in a simple-response-task of the Test of Attentional Performance (TAP). Other NAB subdomains, additional TAP tasks, and patient-related outcomes, including subjective cognitive failures, fatigue, and neuropsychiatric symptoms, were also examined.

Results indicate significant effects of the training for the main outcome, the processing speed indicators and for several other cognitive outcomes. Among patient-related outcomes, a significant effect was found for cognitive failures in daily life.

App-based neurocognitive training enhances neurocognitive functions in PCS patients with post-infectious mild cognitive impairment. Particularly the slowing of processing speed can be addressed. A specific training gain was found for the cognitive domain, as among the patient-related outcomes only cognitive failure ratings, but not fatigue, psychological burden or sleep were improved.