Neurology
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Long COVID
— Reaction time to visual stimuli shows promise as a cognitive marker
by
Judy George, Deputy Managing Editor, MedPage Today
February 1, 2024
Pronounced cognitive slowing distinguished people with long COVID from others, a cross-sectional study showed.
On a 30-second task measuring simple reaction time, moderate-to-severe cognitive slowing was evident among long COVID patients compared with age-matched healthy individuals who had previous symptomatic SARS-CoV-2 infection and recovered, reported Sijia Zhao, PhD, at the University of Oxford in England, and co-authors in eClinicalMedicine.
Long COVID patients responded to visual stimuli at about 3 standard deviations slower than healthy controls, Zhao and colleagues said. More than half (53.5%) of long COVID patients had a response speed slower than 2 standard deviations from the control mean, suggesting that slow reaction time was a common cognitive deficit.
The study represents the first robust demonstration of slowing as a cognitive signature of post-COVID conditions, the researchers said.
It’s also the first objective cognitive marker found for long COVID, Zhao told MedPage Today. “Importantly, this marker can be reliably and easily measured using a 30-second web-based task, so it has potential to be a marker to track the progress of rehabilitation of long COVID,” she said.
Zhao and colleagues studied 270 patients diagnosed with post-COVID condition (also called long COVID) at two different clinics and compared them with two control groups: those who had SARS-CoV-2 infection but did not experience long COVID after recovery, and those who were never infected.
All long COVID patients completed the study from May 2021 through July 2023 at Jena University Hospital in Germany or the long COVID clinic at Oxford and met the National Institute for Health and Care Excellence (NICE) requirements for long COVID. Mean time from COVID-19 diagnosis was 326 days, and 20% were hospitalized when they had acute SARS-CoV-2 infection.
Participants completed two short web-based cognitive tasks, the Simple Reaction Time (SRT) task and the Number Vigilance Test (NVT).
The SRT task required participants to press the space bar when a large red circle appeared in the center of the screen. After they pressed the space bar, the red circle disappeared and would reappear after randomized intervals that ranged from 0.5 to 2 seconds. The total number of trials was 16 (the first two trials were not included in the analysis).
This task was performed by 119 long COVID patients (mean age about 47 and 67.2% were female), 63 COVID patients who had recovered, and 75 people who never had COVID. The average reaction time for healthy controls (both recovered COVID and no COVID groups) was 0.34 seconds. Long COVID patients responded significantly more slowly at an average of 0.49 seconds. Depression and other mental health symptoms did not predict cognitive slowing.
A total of 194 participants completed the NVT,