(Bloomberg) -- The healthy young adults deliberately infected with the coronavirus didn’t notice any cognitive effect, but their test scores showed otherwise.
A unique study from the UK exploring the virus’s impact found a small but persistent reduction in memory and executive function among experimentally-infected people. The finding — published Saturday in the journal eClinicalMedicine — adds to evidence that Covid-19 may have led to measurable cognitive changes in the broader community.
“Future research should examine the biological mechanisms that mediate this relationship, determine how they differ to those observed for other respiratory infections, and explore whether targeted interventions can normalize these memory and executive processes,” Adam Hampshire and Gregory Scott of the Department of Brain Sciences at Imperial College London and colleagues wrote.
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The average effect size across cognitive tasks at the follow-up time points were -0.42 standard deviations — comparable to what the researchers observed from earlier “citizen science” research involving more than 81,000 participants during the UK’s first pandemic wave in 2020.
The fact that memory precision was reduced is of interest, the authors said, as this process has been closely associated with brain function in the organ’s medial temporal lobe, where signs of accelerated shrinkage were observed after mostly mild Covid illness in a study in the journal Nature in 2022.
Small Reductions
For the latest research, 34 volunteers ages 18 to 30 completed 11 computerized tasks during two consecutive days before they were nasally inoculated with the original, or wild-type, SARS-CoV-2 strain in early 2021.
“This was the first, and likely will be the only, Human Challenge study in which unvaccinated virus-naive volunteers were inoculated with wild-type SARS-CoV-2,” the authors said.
Roughly half the group developed a mild Covid infection; the others remained uninfected.
None of the participants reported any cognitive deficits after their initial exposure to the coronavirus. However, six further rounds of testing found the infected group had small, but measurable reductions in cognitive scores compared with those who weren’t infected. The differences were still evident a year after their inoculation.
The study participants were mostly white males, which might limit how generalizable the findings are to other groups. The researchers also cautioned against generalizing the results to more recent variants, which have been linked to smaller cognitive deficits. Vaccination against Covid is also associated with a reduced risk of lingering cognitive problems following infection.
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