Changes to the human brain following a Covid-19 infection have been described in a new paper.
Researchers investigated the changes in the brains of 785 UK Biobank participants aged 51–81 who had two brain scans, on average 38 months apart, and also underwent cognitive tests.
The UK Biobank is a large database that includes genetic and health information on half-a-million people living in the UK.
The authors identified various long-term effects following infection – with an average of 141 days between participants receiving a Covid diagnosis and the second imaging scan.
The effects included a greater reduction in grey matter thickness in the orbitofrontal cortex and parahippocampal gyrus – regions associated with smell and memory of events.
Participants who had Covid-19 displayed evidence of tissue damage in regions associated with the olfactory cortex, an area linked to smell, and an average reduction in whole brain sizes.
On average, the participants who were infected with SARS-CoV-2 also showed greater cognitive decline between their two scans, associated with the atrophy of a brain region known as the cerebellum, which is linked to cognition.
The research, titled Sars-CoV-2 is associated with changes in brain structure in UK Biobank and carried out by Gwenaelle Douaud from the University of Oxford and others, appeared in the Nature journal.
Dr Max Taquet, NIHR Oxford Health BRC senior research fellow, University of Oxford, said: “This is the first large-scale study to investigate the actual changes in the brain that can occur after a Covid-19 infection.
“It is well established that Covid-19 infection is associated with subsequent risks of neurological and psychiatric problems in some people including brain fog, loss of taste and smell, depression, and psychosis.
“But why this occurs remains largely unknown. This study starts to shed light on this important question by showing that brain regions connected to the ‘smell centre’ of the brain can shrink after Covid-19 in some people.
“These brain changes were not observed in every patients and they were mostly subtle.
“These findings might help explain why some people experience brain symptoms long after the acute infection.
“The causes of these brain changes, whether they can be prevented or even reverted, as well as whether similar changes are observed in hospitalised patients, in children and younger adults, and in minority ethnic groups, remain to be determined.”