ABSTRACT
BACKGROUND: Cognitive symptoms are often reported by those with a history of COVID-19 infection. No comprehensive meta-analysis of neurocognitive outcomes related to COVID-19 exists despite the influx of studies after the COVID-19 pandemic. This study meta-analysed observational research comparing cross-sectional neurocognitive outcomes in adults with COVID-19 (without severe medical/psychiatric comorbidity) to healthy controls (HCs) or norm-referenced data. METHODS: Data were extracted from 54 studies published between January 2020 and June 2023. Hedges' g was used to index effect sizes, which were pooled using random-effects modelling. Moderating variables were investigated using meta-regression and subgroup analyses. RESULTS: Omnibus meta-analysis of 696 effect sizes extracted across 54 studies (COVID-19 n=6676, HC/norm-reference n=12 986; average time since infection=~6 months) yielded a small but significant effect indicating patients with COVID-19 performed slightly worse than HCs on cognitive measures (g=-0.36; 95% CI=-0.45 to -0.28), with high heterogeneity (Q=242.30, p<0.001, τ=0.26). Significant within-domain effects was yielded by cognitive screener (g=-0.55; 95% CI=-0.75 to -0.36), processing speed (g=-0.44; 95% CI=-0.57 to -0.32), global cognition (g=-0.40; 95% CI=-0.71 to -0.09), simple/complex attention (g=-0.38; 95% CI=-0.46 to -0.29), learning/memory (g=-0.34; 95% CI=-0.46 to -0.22), language (g=-0.34; 95% CI=-0.45 to -0.24) and executive function (g=-0.32; 95% CI=-0.43 to -0.21); but not motor (g=-0.40; 95% CI=-0.89 to 0.10), visuospatial/construction (g=-0.09; 95% CI=-0.23 to 0.05) and orientation (g=-0.02; 95% CI=-0.17 to 0.14). COVID-19 samples with elevated depression, anxiety, fatigue and disease severity yielded larger effects. CONCLUSION: Mild cognitive deficits are associated with COVID-19 infection, especially as detected by cognitive screeners and processing speed tasks. We failed to observe clinically meaningful cognitive impairments (as measured by standard neuropsychological instruments) in people with COVID-19 without severe medical or psychiatric comorbidities.
