People who had severe covid-19 show cognitive decline years later

The cognitive abilities of people who were hospitalised with covid-19 during the first wave of the pandemic remain lower than expected, even years later, and there is some evidence that this is forcing them to change jobs.

“What we found is that the average cognitive deficit was equivalent to 10 IQ points, based on what would be expected for their age, et cetera,” says Maxime Taquet at the University of Oxford.

His team looked at 475 people in the UK who had been hospitalised with covid-19 and discharged before 31 March 2021. All had completed psychiatric and cognitive assessments six months after their discharge from hospital as part of another study. Taquet’s team asked them to repeat the assessments two to three years later and found that, on average, peoples’ symptoms of depression, anxiety and fatigue had worsened. “More people are getting worse than getting better,” says Taquet.

Overall, 47 per cent had moderate to severe depression at the second assessment compared with 34 per cent at six months, while 40 per cent had moderate to severe fatigue compared with 26 per cent in the first tests. The proportion of people with moderate to severe anxiety saw a smaller change, rising from 23 per cent to 27 per cent.

Why so many people’s symptoms grew worse isn’t clear, but the team did find that those with more severe symptoms in the initial tests were more likely to see them intensify over time. Taquet says one participant said it was hard to be short of breath for three years and not experience depression.

The team also found that more than a quarter of participants had changed their occupation since being hospitalised, with half of those who changed occupation saying they did so due to poor health. The researchers found a strong association between changing occupation and cognitive decline, but not with depression, anxiety or fatigue. This suggests that many people are making the change because they can no longer cope with the cognitive demands of their previous role, rather than because of a lack of energy or interest, says Taquet.

He acknowledges that the study has some major limitations. Only a fifth of those invited to take part did so, so it isn’t clear how representative the study is. As the participants weren’t tested before being hospitalised, there is also no baseline to compare to, says team member Paul Harrison, also at the University of Oxford. Instead, the conclusion that people lost 10 IQ points on average instead relies on what would be expected for people of the same age, sex and education level, based on a survey called the Great British Intelligence Test.