Problems in thinking and attention linked to COVID-19 infection

UK researchers have found further evidence of the ongoing mental impacts of COVID-19 in people who have recovered from the disease.

In a study involving more than 80,000 people, researchers found that those with more severe COVID-19 symptoms scored lower in an a series of online tests, with performance on reasoning and problem-solving tasks being most affected.

Further analysis showed that those who received mechanical ventilation to help them breathe whilst in hospital had the greatest impairment on cognitive tasks.

According to the team, the findings further highlight how COVID-19 infection can have lasting, and measurable, impacts on people’s brain function.

The study was a collaboration between King’s College London, Imperial College London and Cambridge University.

Dr Adam Hampshire, from Imperial’s Department of Brain Sciences and first author, said the work adds to a growing body of research looking at how COVID-19 might be impacting the brain and brain function.

“This research is all converging to indicate that there are some important effects of COVID-19 on the brain that need further investigation,” he says.

The latest study carries on from a series of online tests developed by Dr Hampshire as part of BBC2 Horizon’s Great British Intelligence test. In early 2020, the study team extended the questionnaires to gather information on SARS-CoV-2 infection, the symptoms experienced and the need for hospitalisation.

From 81,337 people who provided complete data, 12,689 people suspected they had COVID-19. Participants reported a range of severity of illness, with many experiencing respiratory symptoms whilst still being able to stay at home (3,559 participants).

Nearly 200 were hospitalised (192 participants) and about a quarter of these (44 participants) required mechanical ventilation.

The time since illness onset was around one to six months, meaning the study could not draw any definitive conclusions about whether these effects on cognition were long-lasting.

Researchers found a relationship between deficits in overall cognitive performance and the severity of respiratory symptoms people experienced.

They also found that not all areas of thinking ability correlated in the same way with COVID-19 illness and that some abilities were spared, including emotional discrimination (recognition of faces that were expressing the same emotion) and working memory (remembering where a sequence of squares appears on the screen).

In comparison ‘executive’ tasks that required skills in reasoning (such as deciding if relationships between words were similar) and problem solving seemed to show the greatest deficit.

To understand the size of the deficits the authors compared the pattern of scores on the tests to cognitive changes that occur for other reasons.

The effects in those hospitalised with mechanical ventilation were similar to the average cognitive decline seen over a period of ten years of ageing and equivalent to a seven-point difference in IQ.

As part of the study, the team wanted to ensure these cognitive effects were associated with COVID-19, and not linked something else. By separating those who had a confirmed positive test for SARS-CoV-2 they could show the cognitive deficits were greater in those who had a confirmed infection.

Further checks suggested the results were not due to a minority with pre-existing conditions or on-going symptoms of COVID-19. Analysis also indicated that it was unlikely that the results could be explained by the fact that those who contracted more severe COVID-19 disease were less cognitively able before they were ill.

Dr Hampshire adds: “Going forward it would be valuable to bring together brain imaging and cognitive tests with other information on mental health and everyday function, ideally in studies that track peoples’ trajectories for months or even years. To really know what the long-term effects are for people will require people to be followed up over time.”