Cognitive tests show that COVID lowers IQ

People with long COVID performed six points lower on IQ tests.

People with long COVID performed six points lower on IQ tests. Photo: Getty

Did you have a dose of COVID-19? Mild case, sick for a few days – up and at it with half the tissues still in the box?

That’s lovely. And yet, a large and sobering study from Imperial College London suggests your cognitive and memory abilities lost their shine.

Overall, the study revealed “small deficits in the performance of cognitive and memory tasks in people who had recovered from COVID-19 compared with those who had not had COVID-19”.

For most people, this would have made little to no difference when doing their jobs. For some, such as engineers or surgeons, their genius for exactness might have been compromised.

Unsurprisingly, the study showed that “the cognitive deficits were larger for people who were hospitalised, who had ongoing long duration symptoms, or who were infected with earlier variants of the virus”.

Large population study

The researchers enrolled more than 140,000 participants in the study. Each of these “undertook at least one cognitive task, with many having experienced COVID-19 at various levels of severity and persistence”.

Participants in the study performed an online cognitive assessment on the Cognitron platform.

This is an artificial intelligence (AI) test “designed to model human mental skills” developed by a team of psychologists, neuroscientists and engineers at Imperial College.

The assessment comprised “tasks that can detect subtle changes in different aspects of their brain function, such as memory, reasoning, executive function, attention and impulsivity”.

The researchers say that the large scale of the study, and the sensitivity of the computerised tests, allowed post-COVID deficits “to be examined in very fine detail while controlling for population variables such as age, demographics and pre-existing medical conditions”.

Cognitive findings

The study revealed small deficits “that were still detectable a year or more after infection, even in people who had short duration illness”.

The deficits were larger for people who had symptoms lasting 12 weeks or more (what we call long COVID).

They were larger in those who had been to hospital for their illness. And those who were infected with one of the early variants of the SARS-CoV-2 virus. Early variants were more virulent.

These deficits were in multiple areas of cognition, “most notably in memory, such as the ability to remember pictures of objects that were viewed a few minutes earlier”.

The researchers believe “this may be due to problems forming new memories rather than accelerated forgetting”.

People also showed small deficits “in some tasks testing executive and reasoning abilities, such as those that require spatial planning or verbal reasoning”.

The good news

Professor Paul Elliott, senior author and director of the REACT program, from the School of Public Health at Imperial College London, said:

“It is reassuring that people with persistent symptoms after COVID-19, that had resolved, may expect to experience some improvement in their cognitive functions to similar levels as those who experienced short illness.”

He said the cognitive impact of COVID-19 “appears to have reduced since the early stages of the pandemic, with fewer people having persistent illness, and cognition being less affected amongst those that were infected during the time when Omicron was the dominant strain”.

Measured in IQ points

According to a report in The New York Times, the AI assessment represented the deficits in terms of IQ points.

The testing found that “those with persistent post-COVID symptoms scored the equivalent of six IQ points lower than people who had never been infected with the coronavirus”.

People who had been infected and no longer had symptoms “also scored slightly lower than people who had never been infected, by the equivalent of three IQ points, even if they were ill for only a short time”.

The NYT author noted that “the differences in cognitive scores were relatively small, and neurological experts cautioned that the results did not imply that being infected with the coronavirus or developing long COVID caused profound deficits in thinking and function”.

However, “the findings are important because they provide numerical evidence for the brain fog, focus and memory problems that afflict many people with long COVID”.

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