Background
COVID-19 survivors may experience a wide range of chronic cognitive symptoms for months or years as part of post-COVID-19 conditions (PCC). To date, there is no definitive objective cognitive marker for post-COVID-19 conditions (PCC). We hypothesize that a key common deficit in people with PCC could be generalized cognitive slowing .
Methods
To examine cognitive slowing , patients with PCC completed two brief web-based cognitive tasks, the simple reaction time (SRT) and the numerical vigilance test (NVT).
270 patients diagnosed with PCC at two different clinics in the United Kingdom and Germany were compared with two control groups: individuals who contracted COVID-19 before but did not experience PCC after recovery (non-PCC group) and uninfected individuals (non-PCC group). without COVID).
All CCP patients completed the study between May 18, 2021 and July 4, 2023 at Jena University Hospital, Jena, Germany, and the Long COVID clinic, Oxford, United Kingdom.
Results
We identified a pronounced cognitive slowing in patients with PCC, which distinguished them from age-matched healthy individuals who previously had symptomatic COVID-19 but did not manifest PCC.
Cognitive slowing was evident even in a 30-s task measuring simple reaction time (SRT), with PCC patients responding to stimuli approximately 3 standard deviations slower than healthy controls.
53.5% of patients with PCC had a response speed less than 2 standard deviations from the control mean, indicating a high prevalence of cognitive slowing in PCC. This finding was replicated in two clinical samples in Germany and the United Kingdom.
Comorbidities such as fatigue, depression, anxiety, sleep disturbances, and post-traumatic stress disorder did not explain the degree of cognitive slowing in patients with PCC . Furthermore, cognitive slowing on the SRT was highly correlated with PCC patients’ poor performance on the NVT measure of sustained attention.
Interpretation Taken together, these results strongly demonstrate a pronounced cognitive slowing in people with PCC, distinguishing them from healthy people of the same age who previously had symptomatic COVID-19 but did not manifest PCC. This could be an important factor contributing to some of the cognitive impairments reported in patients with PCC. |
Discussion
The present study reported significant psychomotor slowing in individuals diagnosed with PCC. Importantly, this cannot be attributed to poor global cognition as measured by a cognitive screening test (MoCA), fatigue, mental health-related symptoms, or a trade-off between speed and accuracy. Furthermore, the data indicate that this deterioration does not improve over time . We also replicated this finding within each individual participant, as well as with a separate cohort of patients with PCC diagnosed by a different clinic located in a different country.
Funding: Wellcome Trust (206330/Z/17/Z), NIHR Oxford Health Biomedical Research Centre, Thüringer Aufbaubank (2021 FGI 0060), German Forschungsgemeinschaft (DFG, FI 1424/2-1) and the EU Horizon 2020 Framework Program European (ITN SmartAge, H2020-MSCA-ITN-2019-859890).
