Professor Gwenaëlle Douaud and colleagues from Oxford University assessed changes in the brains of 785 participants from UK Biobank, a large-scale biomedical database and research resource.
Participants aged 51-81 underwent two brain scans, on average 38 months apart, as well as cognitive tests. A total of 401 participants tested positive for Covid between their two scans, of whom 15 were hospitalised.
The remaining 384 individuals, who didn’t get infected, acted as controls. About 4 and a half months following an infection, the researchers noted a greater reduction in grey matter thickness in the regions of the brain associated with smell (the orbitofrontal cortex and parahippocampal gyrus) and a reduction in the size of the whole brain.
On average, the participants who were infected with Covid also showed greater cognitive decline between their two scans, associated with the shrinkage of a specific part of the cerebellum (hindbrain) which is linked to cognition.
Professor Stephen Smith, senior author on the study, commented: “Another strength of this study is that it investigated the same people at two different times. Importantly here, the first scan of UK Biobank participants was obtained before they became infected with SARS-CoV-2, with the second scan after infection.