Large-scale study offers new insights into the brain effects of severe COVID-19

In the largest UK study to date, researchers have gained insight into the immediate and long-term impacts of COVID-19 on the brain.

Published in Natural medicineThe study, led by researchers led by the University of Liverpool in collaboration with King’s College London and the University of Cambridge as part of the COVID-CNS Consortium, shows that 12 to 18 months after hospitalization with COVID-19, patients have poorer cognitive function than matched control participants.

Importantly, these findings correlate with reduced brain volume in key areas on MRI scans as well as evidence of abnormally high levels of brain damage proteins in the blood.

It is striking that the post-COVID cognitive deficits observed in this study were equivalent to 20 years of normal aging. It is important to emphasize that these were patients who had suffered from COVID, requiring hospitalization, and that these findings should not be overly generalized to all people who have had a COVID experience.

However, the magnitude of the deficit in all cognitive skills tested and the links to brain damage in brain scans and blood tests provide the clearest evidence yet that COVID can have significant impacts on brain and mind health long after respiratory problems have healed.

This work is part of the University of Liverpool COVID-19 Clinical Neuroscience Study (COVID-CNS), which addresses the critical need to understand the biological causes and long-term outcomes of neurological and neuropsychiatric complications in hospitalised patients with COVID-19.

Study author Dr Greta Wood from the University of Liverpool said: “Following hospitalisation with COVID-19, many people report persistent cognitive symptoms often referred to as ‘brain fog’.

“However, it was unclear whether there was objective evidence of cognitive impairment and, if so, whether there was biological evidence of brain damage; and especially whether patients recovered over time.

“In this latest study, we studied 351 COVID-19 patients who required hospitalization with or without new neurological complications. We found that people with and without acute neurological complications of COVID-19 had more severe cognitive impairment than would be expected given their age, sex, and education level, based on 3,000 control subjects.”

Professor Benedict Michael, corresponding author and Professor of Neuroscience at the University of Liverpool, said: “COVID-19 is not just a lung disease. Often the patients most severely affected are those with brain complications.

“These results indicate that hospitalization for COVID-19 may result in global, objectively measurable cognitive deficits that can be identified even 12 to 18 months after hospitalization.

“These persistent cognitive deficits were present in people hospitalized with and without clinical neurological complications, indicating that COVID-19 alone can cause cognitive impairment without a neurological diagnosis having been made.

“The association with biomarkers of brain cell damage in the blood and reduced volume of brain regions on MRI indicates that there may be measurable biological mechanisms underlying this.

“Our group is now working to understand whether the mechanisms we have identified in COVID-19 may also be responsible for similar outcomes in other serious infections, such as influenza.”

Professor Gerome Breen of King’s College London said: “Long-term research is now essential to determine how these patients recover or who might get worse and to establish whether this is specific to COVID-19 or a common brain injury with other infections.

“Importantly, our work may help guide the development of similar studies in people with long COVID who often have much milder respiratory symptoms and also report cognitive symptoms such as ‘brain fog’, and also to develop therapeutic strategies.”