Rapid vigilance and episodic memory decrements in COVID-19 survivors

Abstract

Recent studies indicate that COVID-19 infection can lead to serious neurological consequences in a small percentage of individuals. However, in the months following acute illness, many more suffer from fatigue, low motivation, disturbed mood, poor sleep and cognitive symptoms, colloquially referred to as ‘brain fog’. But what about individuals who had asymptomatic to moderate COVID-19 and reported no concerns after recovering from COVID-19? Here, we examined a wide range of cognitive functions critical for daily life (including sustained attention, memory, motor control, planning, semantic reasoning, mental rotation and spatial–visual attention) in people who had previously suffered from COVID-19 but were not significantly different from a control group on self-reported fatigue, forgetfulness, sleep abnormality, motivation, depression, anxiety and personality profile. Reassuringly, COVID-19 survivors performed well in most abilities tested, including working memory, executive function, planning and mental rotation. However, they displayed significantly worse episodic memory (up to 6 months post-infection) and greater decline in vigilance with time on task (for up to 9 months). Overall, the results show that specific chronic cognitive changes following COVID-19 are evident on objective testing even amongst those who do not report a greater symptom burden. Importantly, in the sample tested here, these were not significantly different from normal after 6–9 months, demonstrating evidence of recovery over time.

SciScore for 10.1101/2021.07.06.21260040: (What is this?)

Please note, not all rigor criteria are appropriate for all manuscripts.

Table 1: Rigor

Ethics	Consent: All participants provided written informed consent and the study was approved by the University of Oxford ethics committee. IRB: All participants provided written informed consent and the study was approved by the University of Oxford ethics committee. Field Sample Permit: The study was approved by the local ethics committee and carried out in accordance with the relevant guidelines and regulations.
Sex as a biological variable	Participants: 135 participants (49 females, mean age 26.2 years (SD 8.0)) were recruited from the Prolific online recruitment platform (www.prolific.co, see Table 1 for demographics).
Randomization	Participants were instructed to press the spacebar on their keyboard as soon as they saw “0” (the target, presented randomly with a probability of 25%); no response was required for other digits.
Blinding	not detected.
Power Analysis	not detected.

Table 2: Resources

Software and Algorithms
Sentences	Resources
The experiment was implemented using PsychoPy v2021.1.2.25 To minimise the variance in latency caused by different browsers, all participants were required to use the Chrome browser on a desktop computer, although the operating system was not restricted.	PsychoPy suggested: (PsychoPy, RRID:SCR_006571)
To investigate the effect of group and time on minute-wise performance and the three ratings, all the values were z-scored across participants and mixed-effects generalised linear models (GLM) were conducted using the MATLAB function fitglme with Laplace approximation as the method for estimating model parameters.	MATLAB suggested: (MATLAB, RRID:SCR_001622)

Results from OddPub: We did not detect open data. We also did not detect open code. Researchers are encouraged to share open data when possible (see Nature blog).

Results from LimitationRecognizer: We detected the following sentences addressing limitations in the study:

There are some limitations to our study. Although the majority of participants from our COVID group reported a PCR-confirmed COVID-19 positive result with none reporting the need for post-COVID treatment, our study was limited by our reliance on self-reports of positive/negative COVID-19 tests and timing of diagnosis, which might increase or decrease our estimate of the prevalence and duration of COVID-associated cognitive deficits. Our study is also constrained by a relatively small sample size (n=135) with under-representation of the over 70s, thus any generalization should be taken carefully. Overall, the findings here show that COVID-19 survivors are significantly impaired in their ability to sustain attention and motivation on a demanding task up to nine months after COVID-19 infection, along with mild, but significantly worse, episodic memory for up to six months. Just as the acute illness of COVID-19 demonstrates a wide severity spectrum from asymptomatic to fatal forms43, our findings show that post-COVID cognitive deficits too can also manifest a wide severity spectrum. They highlight a pressing need to measure cognitive performance objectively in order to better understand how the brain is affected by COVID-19.

Results from TrialIdentifier: No clinical trial numbers were referenced.

Results from Barzooka: We did not find any issues relating to the usage of bar graphs.

Results from JetFighter: We did not find any issues relating to colormaps.

Results from rtransparent:

Thank you for including a conflict of interest statement. Authors are encouraged to include this statement when submitting to a journal.
Thank you for including a funding statement. Authors are encouraged to include this statement when submitting to a journal.
No protocol registration statement was detected.

Results from scite Reference Check: We found no unreliable references.

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Rapid vigilance and episodic memory decrements in COVID-19 survivors

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