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.

00:05A new study shows that COVID-19 infection is linked to shrinkage and damage in specific brain areas.

00:16This 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.

00:35After they recovered, researchers re-scanned their brains 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 COVID-19.

00:55The damage was more extensive and occurred in different regions than 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 parahippocampal gyrus showed the most pronounced shrinkage in people who caught COVID-19,

01:16and those individuals also showed a greater reduction in overall brain size than those who didn't catch the virus.

01:23Tissue damage also appeared in brain areas connected to the primary olfactory cortex,

01:29which receives sensory information from scent-detecting neurons in the nose.

01:34Plus, people who caught COVID-19 showed greater decline on various cognitive tests,

01:39which were designed to assess attention and executive function compared with the control group.

01:44The new study doesn't address exactly how this damage occurs, although scientists have several theories on this front.

01:51The virus may directly infect brain cells, some think.

01:55Others suspect that inflammation in the brain may be to blame for the changes.

01:59Or potentially, a loss of sensory information from the nose, caused by smell loss, may cause various brain areas to atrophy over time.

02:08A study published in Cell last month hinted that the virus likely doesn't invade the brain directly,

02:13but the study authors still mention this as a possibility.

02:17It's also possible that the way in which the coronavirus wreaks havoc in the brain

02:21differs slightly between different coronavirus variants.

02:24Future studies should address this question directly,

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

02:32The new study also doesn't address whether the COVID-related damage

02:36could accelerate normal structural brain changes that typically occur in line with aging.

02:42Future research can look into these potential downstream effects,

02:46while other studies can focus on how these findings might apply to people with long COVID,

02:50who often report symptoms like memory issues and brain fog.