Psychological burden, subjective complaints and their impact on the progression of verbal fluency in COVID-19 survivors and healthy controls: a longitudinal analysis

Background This study aimed to investigate the longitudinal change of verbal fluency after COVID-19 and potential influencing factors in a community-based sample. Within the COVIMMUNE-Clin study at the University of Bonn Medical Center, participants with a mild course of COVID-19 ( n = 52), a severe course ( n = 52), and healthy controls ( n = 55) were compared. This focused secondary analysis examined verbal fluency as a distinct cognitive outcome within the broader study. Methods Semantic and lexical verbal fluency, assessed using the Vienna Verbal Fluency Test (WIWO), as well as psychological burden measured by the ICD-10 Symptom Rating Scale (ISR) and subjective complaints assessed with the Everyday Cognition-12 (ECog-12) questionnaire, were administered at the first visit and again after 12 months. A linear mixed model was employed, incorporating Group (mild, severe and healthy controls) and Visit as fixed effects, with Subject and the Intercept as random effects. ISR and ECog-12 were each incorporated into separate models as fixed effects. Results Group and psychological burden had an impact on semantic fluency, in a way that more severe disease and higher psychological burden were associated with lower performance. Contrary to the hypothesis, verbal fluency did not significantly change over 12 months. Across models, verbal fluency types showed distinctive patterns, which is reflected by the fact that psychological burden and subjective complaints only showed an association with semantic fluency performance. Lexical fluency showed no significant effects of these constructs and was primarily positively influenced by education. Conclusion COVID-19 disease severity, psychological burden, and subjective complaints were associated with semantic fluency. These findings support further research on whether verbal fluency measures, in combination with self-reported symptoms, may contribute to practical assessment approaches following COVID-19. Trial registration Specific details of the study design are included at the German Clinical Trials Registry (primary registry trial identifier: DRKS00023806; registration date: March 16, 2021, cross-referenced at World Health Organization’s International Clinical Trials Registry Platform [ICTRP]).