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People previously hospitalized due to COVID-19 show significant decreases in cognition

According to a new study, people who were previously infected with SARS-CoV-2 showed a substantial decrease in cognitive function, with those being hospitalized showing a 7-point decrease in IQ, on average.

The need to understand and respond to prolonged symptoms following the SARS-CoV-2 infection is becoming more urgent as the COVID-19 pandemic unfolds. Symptoms including exhaustion, shortness of breath, and depression could potentially impair millions of individuals throughout the world. These signs and symptoms that persist or worsen after acute COVID-19 are frequently referred to as “long COVID.”

In a recently published study, Adam Hampshire and his team at the Imperial College London tested 81,337 individuals’ cognition using the Great British Intelligence Test. The data gathered indicated a significant difference in the cognitive abilities between those who had previously tested positive for COVID-19 and those who never were infected.

Hampshire and his colleagues originally had a different purpose when administering the Great British Intelligence Test to the selected testing population. However, due to rising suspicion of long-term cognitive effects from COVID-19, such as “brain fog,” Hampshire’s team decided to use their data to test the magnitude of these long term effects on cognitive function. 

The results indicated that those who had recovered from COVID-19, showed a significant decrease in cognitive ability. Although there was a notable difference in intelligence scores between those who had previously contracted the virus and those who had not, the intensity of the infection seemed to have a greater effect on cognition. Those who had been hospitalized by the virus tended to demonstrate an equivalent drop of 7 IQ points.  

“By coincidence, the pandemic escalated in the United Kingdom in the middle of when I was collecting cognitive and mental health data at a very large scale as part of the BBC2 Horizon collaboration the Great British Intelligence Test,” Dr. Hampshire, an associate professor in the Computational, Cognitive and Clinical Neuroimaging Laboratory at Imperial College London, said. “The test comprised a set of tasks designed to measure different dimensions of cognitive ability that had been designed for application in both citizen science and clinical research. A number of my colleagues contacted me in parallel to point out that this provided an opportunity to gather important data on how the pandemic and COVID-19 illness were affecting mental health and cognition.”

81,337 people varying in age, sex, and ethnicity participated in the Great British Intelligence Test. The test consists of nine different tests all focused on examining cognitive abilities such as spanning planning/reasoning, working memory, and attention and emotion processing abilities. After testing, the researchers sent out a questionnaire to the participants asking whether they had been infected with COVID-19 and the severity of the infection. The paper states that the study controlled for age, gender, education level, income, racial-ethnic group, pre-existing medical disorders, tiredness, depression and anxiety, 

Hampshire emphasized the sense of urgency he feels “long COVID” needs to be addressed with, stating, “We need to be careful as it looks like the virus could be affecting our cognition. We do not fully understand how, why, or for how long, but we urgently need to find out. In the meantime, don’t take unnecessary risks and do get vaccinated.”


The study was published in The Lancet, on July 22nd, 2021.

Abstract. People who had recovered from COVID-19, including those no longer reporting symptoms, exhibited significant cognitive deficits versus controls when controlling for age, gender, education level, income, racial-ethnic group, pre-existing medical disorders, tiredness, depression and anxiety. The deficits were of substantial effect size for people who had been hospitalised (N = 192), but also for non-hospitalised cases who had biological confirmation of COVID-19 infection (N = 326). Analysing markers of premorbid intelligence did not support these differences being present prior to infection. Finer grained analysis of performance across sub-tests supported the hypothesis that COVID-19 has a multi-domain impact on human cognition.

Hampshire A, Trender W, Chamberlain SR, Jolly AE, Grant JE, Patrick F, Mazibuko N, Williams SC, Barnby JM, Hellyer P, Mehta MA. Cognitive deficits in people who have recovered from COVID-19. EClinicalMedicine. 2021 Jul 23:101044. doi: 10.1016/j.eclinm.2021.101044. Epub ahead of print. PMID: 34316551; PMCID: PMC8298139.

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