Covid-19 patients showed a decrease in cognitive abilities

Covid-19 patients showed a decrease in cognitive abilities
Covid-19 patients showed a decrease in cognitive abilities

Scientists have confirmed the link between coronavirus infection and cognitive decline based on the analysis of data from more than 81 thousand people.

Patient with coronavirus in the red zone

A study by scientists from Imperial College London and the University of Cambridge (UK) confirmed what has been talked about recently: people who have undergone coronavirus disease have a decrease in the level of cognitive abilities. As it turned out, this fact does not depend on whether they were ill in a mild form or severe. Results published in EClinicalMedicine by The Lancet.

The authors of the study took a large-scale approach and compared data from 12,689 people who recovered from Covid-19 with control groups, taking into account socio-demographic factors and population variability in cognitive functions. The size of the final sample was 81,337 people (average age - 46, 75 years, 93% - residents of the UK, mostly white Europeans), and the analysis was based on the detailed results of their tests and the Great British Intelligence Test from January to December 2020. The researchers also determined whether the degree / or nature of the decline in intelligence was related to the severity of respiratory symptoms, the course of the disease, or the time elapsed since the onset of infection.

“Our tests should not be viewed as testing for IQ in the classical sense, as they were intended to more accurately differentiate aspects of cognitive ability. They were optimized for the elderly and people with mild cognitive and motor impairments. After nine cognitive tests, participants filled out a detailed questionnaire covering a wide range of socio-demographic, economic, occupational and life variables,”the scientists write. Respondents under 16 and those who did not complete the extended questionnaire were excluded from the analysis.


The results showed that those who survived the coronavirus tended to perform worse on testing compared to those who did not get sick. The most difficult tasks were those that required planning and reasoning. Scientists suggest that this is due to the so-called brain fog, when it becomes difficult for a person to think and concentrate - these are the symptoms that correlate with the "long-term" Covid-19.

The greatest decrease in the level of intelligence was found in those who, during the illness, were hospitalized in intensive care and connected to a ventilator: their tests were worse by 0.47 composite points (or seven points on the IQ test). Then there were patients who simply ended up in the hospital with Covid-19: their result was worse by 0.26 points. In those who had a coronavirus infection at home, this indicator decreased by 0.23 points. Scientists emphasize that the decline in cognitive abilities was even stronger than in stroke survivors (minus 0, 24 points).

Although a small group of 275 participants performed the IQ test both before and after exposure, the study largely used a crossover methodology, making it difficult to draw conclusions about cause and effect. However, an expanded and socio-economically diverse sample of 269,264 people allowed us to analyze many factors. Analysis of markers of premorbid intelligence did not confirm that there were any differences prior to infection.

Regarding the relationship between cognitive deficits and the time elapsed since the onset of SARS-CoV-2 symptoms (average 1.96 months), the analysis of this subgroup did not show a significant correlation.

“Previous studies in hospitalized patients with respiratory disease suggest that cognitive decline persists in some cases for up to five years. Therefore, our findings for participants requiring mechanical ventilation were not entirely unexpected. But they turned out to be so for patients treated at home. One possible explanation is that the decline in intelligence may reflect the effects of hypoxia. The observed correlation with the severity of respiratory symptoms is fully consistent with this view. However, there have been cases of other forms of neurological damage after Covid-19, with some patients being the first symptom to be detected. We believe that brain imaging will help confirm and differentiate the psychological and neuropathological consequences of the coronavirus,”the authors of the article concluded.

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