The neuropsychological impacts of COVID-19 in non-hospitalized patients with long COVID and brain fog

Background: Coronavirus disease 2019 (COVID-19) causes persistent symptoms, including brain fog. Based on limited research on the long-term consequences of mild COVID-19, which has yielded inconsistent results, we investigated which cognitive functions were most affected by COVID-19 in non-hospitalized Asian patients with long-term COVID and subjective cognitive complaints. Methods: Fifty-five non-hospitalized patients with long COVID and brain fog (24 males and 31 females, mean age: 45.6 ± 14.6 years, mean duration of education: 14.4 ± 3.0 years) were recruited. Neuropsychological assessments included screening tests for overall cognition, and comprehensive tests for memory, executive function, processing speed, and subjective emotional and disease symptoms. Cognitive test scores were converted into Z-scores. Moreover, principal component analysis (PCA) was employed to define cognitive domains across subtest scores. Results: Comprehensive assessments revealed cognitive impairment in 69.1% of patients (<1.5 standard deviation in at least one test). The processing speed (27.3%), memory recall (21.8%), memory learning (20.0%), and inhibitory control (18.2%) were the most affected areas. Self-reported anxiety and depression were observed in 35% and 33% of patients, respectively. Furthermore, the degree of self-anxiety can be used to predict learning performance. Conclusion: Nearly 70% of patients with subjective cognitive complaints and long COVID had objective cognitive impairments. A comprehensive evaluation is essential for patients with long COVID and brain fog, including those with mild symptoms.