Brain Shrinkage Linked To COVID-19

COVID-19 may shrink the brain's gray matter, primarily in areas of the brain involved in smell and memory processing, a large study suggests.

Transcript

00:00Even relatively mild COVID-19 infections can leave a distinct mark on the brain.

00:09A new study shows that COVID-19 infection is linked to shrinkage and damage in specific brain

00:15areas. This study was based on data from more than 700 people who had, prior to the pandemic,

00:22contributed brain scans to a large repository based in the UK.

00:26Between March 2020 and April 2021, about 400 of these individuals caught COVID-19.

00:32Most were not hospitalized for their infections. After they recovered, researchers re-scanned their

00:37brains to see whether the organ structure had changed at all following the infection.

00:42The team compared these before and after snapshots to those from 384 people who hadn't caught the virus.

00:49These brain scans revealed distinct patterns of shrinkage in the brains of people who caught

00:54COVID-19. The damage was more extensive and occurred in different regions

00:59than the normal changes that showed up in people who never caught the virus.

01:03In particular, damage appeared in brain areas involved in smell processing and memory encoding.

01:09The orbitofrontal cortex and perihippocampal gyrus showed the most pronounced shrinkage in people

01:15who caught COVID-19. And those individuals also showed a greater reduction in overall brain size than

01:21those who didn't catch the virus. Tissue damage also appeared in brain areas connected to the primary

01:27olfactory cortex, which receives sensory information from scent-detecting neurons in the nose. Plus,

01:34people who caught COVID-19 showed greater decline on various cognitive tests, which were designed to

01:40assess attention and executive function compared with the control group. The new study doesn't address

01:46exactly how this damage occurs, although scientists have several theories on this front. The virus may

01:52directly infect brain cells, some think. Others suspect that inflammation in the brain may be to blame for

01:57the changes. Or, potentially, a loss of sensory information from the nose, caused by smell loss,

02:03may cause various brain areas to atrophy over time. A study published in Cell last month hinted that the

02:10virus likely doesn't invade the brain directly, but the study author still mentioned this as a possibility.

02:16It's also possible that the way in which the coronavirus wreaks havoc in the brain differs slightly

02:21between different coronavirus variants. Future studies should address this question directly,

02:27as well as the question of how long the observed cognitive deficits might last.

02:31The new study also doesn't address whether the COVID-related damage could accelerate normal

02:37structural brain changes that typically occur in line with aging. Future research can look into

02:43these potential downstream effects, while other studies can focus on how these findings might apply to

02:48people with long COVID, who often report symptoms like memory issues and brain fog.