REUTERS

Even mild cases of COVID-19 may lead to loss of brain tissue, according to findings from a long-term study involving 782 volunteers. As part of the ongoing UK Biobank study, participants underwent brain scans before the pandemic.

For a before-and-after comparison, researchers invited 394 COVID-19 survivors to come back for follow-up scans as well as 388 healthy volunteers. Most of the COVID-19 survivors had had only mild-to-moderate symptoms, or no symptoms at all, while 15 had been hospitalized. Among the COVID-19 survivors, researchers saw "significant" loss of gray matter in regions of the brain related to smell and taste - the left parahippocampal gyrus, left orbitofrontal cortex and left insula.

Some of the affected brain regions are also involved in the memory of experiences that evoke emotional reactions, the researchers noted in a report posted on medRxiv on Tuesday ahead of peer review. The changes were not seen in the group that had not been infected.

The authors said more research is needed to determine whether COVID-19 survivors will have issues in the longer term with their ability to remember emotion-evoking events. They also do not yet know whether the loss of gray matter is a result of the virus spreading into the brain, or some other effect of the illness. (https://bit.ly/2TDYDMZ)