The IQs of people worst affected by Covid-19 plummeted by 8.5 points and their mental decline was equivalent to the brain ageing by 10 years, a research study indicates.
Researchers said their findings backed up evidence that the virus has consequences for cognitive function that persist into the recovery phase. Those who were admitted to hospital with Covid-19 were hit particularly hard.
The team analysed results from 84,285 people who took part in a study called the Great British Intelligence Test. The research has not yet been peer-reviewed.
“At a finer grain, the deficits were broad, affecting multiple cognitive domains,” the researchers wrote.
“They also were more pronounced for tests that assessed semantic problem solving and visual selective attention while sparing tests of simpler functions such as emotional processing and working-memory span.”
Neuroscientist Dr Adam Hampshire from Imperial College London said an important aspect to understand in the future was the duration of symptoms.
“What we can see in the results is that people who suspected they had Covid-19 performed less well than we would expect,” he told the BBC.
"This underperformance is greater for people who were more ill, particularly those who went to hospital, ended up in critical care or on a ventilator. It’s also greater for people who actually had a biological test, so who we know were definitely unwell with Covid-19,” said Dr Hampshire, lead author of the study.
Cognitive tests measure how well the brain performs tasks – such as remembering words or joining dots on a puzzle. Such tests are widely used to assess brain performance in diseases such as Alzheimer’s and can also help doctors assess temporary brain impairment.
The research was carried out by a team from Imperial College London, the University of Cambridge, King’s College London and the University of Chicago.
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But shortcomings of the study were the failure to compare “before and after” scores and the inclusion of those who suspected they had the virus, but had not officially tested positive. One expert not involved in the study said its findings should be interpreted with caution.
“The cognitive function of the participants was not known pre-Covid, and the results also do not reflect long-term recovery – so any effects on cognition may be short term,” said Joanna Wardlaw, a professor of applied neuroimaging at Edinburgh University.
Researchers previously warned that “long Covid” may not be one syndrome but as many as four, causing a roller coaster of symptoms affecting all parts of the body and mind.
At Oxford University, one study found that many patients discharged from hospital still experience symptoms of breathlessness, fatigue, anxiety and depression two to three months after contracting the virus.
The scientists also detected abnormalities in multiple organs and believe persistent inflammation may be a factor for Covid-19 survivors.
