The first major study to compare brain scans of people before and after they catch Covid has revealed shrinkage and tissue damage in regions linked to smell and mental capacities months after subjects tested positive.
It comes as the largest study to date of the genetics of Covid-19 identified 16 new genetic variants associated with severe illness, and named a number of existing drugs that could be repurposed to prevent patients from getting severely ill, some of which are already in clinical trials.
Together, these studies shed new light on the biological mechanisms that underpin the disease.
In the brain study, researchers at the University of Oxford studied 785 people aged between 51 and 81 who had received brain scans before and during the pandemic as part of the UK Biobank study. More than half of them tested positive for Covid between the two scans.
Compared with 384 uninfected control subjects, those who tested positive for Covid had greater overall brain shrinkage and more grey matter shrinkage, particularly in areas linked to smell. For example, those who had Covid lost an additional 1.8% of the parahippocampal gyrus, a key region for smell, and an additional 0.8% of the cerebellum, compared with control subjects.
Disrupted signal processing in such areas may contribute to symptoms such as smell loss. Those who were infected also typically scored lower on a mental skills test than uninfected individuals. Lower scores were associated with a greater loss of brain tissue in the parts of the cerebellum involved in mental ability.
