Covid can lead to cognitive problems three years after infection, study finds

Many people hospitalised with Covid-19 continue to have cognitive and psychiatric problems three years after they were infected, according to a new study.

The study, published in Lancet Psychiatry, found that two-to-three years after being infected with Covid, participants scored, on average, significantly lower in cognitive tests (test of attention and memory) than expected. The average deficit was equivalent to 10 IQ points. One in five also reported severe symptoms of depression, while one in eight reported anxiety, one in four reported fatigue and one in four also reported subjective memory problems, with these symptoms worsening over time.

The research, led by the University of Oxford and the University of Leicester, was conducted with 475 participants who were invited to complete a set of cognitive tests via their computer and to report their symptoms of depression, anxiety, fatigue and their subjective perception of memory problems. They were also asked whether they had changed their occupation and why. The research was carried out as part of PHOSP-COVID, a consortium of scientists from across the UK researching long-term health outcomes for patients hospitalised with COVID-19.

They also found that:

• While many of those experiencing symptoms at two-to-three years had been experiencing them since six months post-infection, some people also experienced new symptoms that they had not been experiencing before. This suggests that early symptoms can be predictive of later, more severe issues, underscoring the importance of timely management, the researchers said.
• More than one in four participants reported changing their occupation, with many citing poor health as a reason. Occupation change was strongly associated with cognitive deficits and not with depression or anxiety – in other words, the research suggests they were not changing their career because they were depressed, but because they could no longer meet the cognitive demands of their job.
• The degree of recovery at six months after having Covid is a strong predictor of longer-term psychiatric and cognitive outcomes. Intervening early to manage symptoms could prevent the development of more complex syndromes and improve overall recovery trajectories.

Understanding  the biological mechanisms is essential

Dr Maxime Taquet, NIHR academic clinical lecturer in the department of psychiatry at Oxford and study lead, said: “These findings help us understand the burden of brain symptoms that people experience years after hospitalisation for Covid-19, who is most at risk, and their impact on their ability to work. This is important for policymakers and clinicians, and to help target preventive interventions.”

The researchers said that while this study provides insights into the long-term effects of Covid-19, further research is essential to develop effective interventions. Understanding the biological mechanisms driving these symptoms and identifying therapeutic strategies to promote cognitive recovery or prevent further decline are crucial next steps, they said.

One limitation of the study is that the sample was made up of people who were hospitalised during the first wave of the pandemic (and hence not vaccinated at the time of the infection) and who consented to follow-up assessments (only 20% of those invited), which may mean the findings are not generalisable to others, such as those who did not require hospital admission.

Paul Harrison, professor of ssychiatry at the University of Oxford, said that it was important for both health professionals and patients to understand the long-term cognitive and psychiatric consequences of Covid-19  hospitalisation, adding: “We hope these findings will stimulate more research into the development of effective interventions to help prevent and treat these brain consequences of Covid-19.”