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.
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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 than the normal changes that
01:00showed up in people who never caught the virus. In particular, damage appeared in brain areas
01:05involved in smell processing and memory encoding. The orbitofrontal cortex and perihippocampal gyrus
01:13showed the most pronounced shrinkage in people who caught COVID-19, and those individuals also
01:18showed a greater reduction in overall brain size than those who didn't catch the virus. Tissue damage
01:24also appeared in brain areas connected to the primary olfactory cortex, which receives sensory
01:30information from scent-detecting neurons in the nose. Plus, people who caught COVID-19 showed greater decline
01:37on various cognitive tests, which were designed to assess attention and executive function compared
01:42with the control group. The new study doesn't address exactly how this damage occurs, although
01:48scientists have several theories on this front. The virus may directly infect brain cells, some think,
01:54others suspect that inflammation in the brain may be to blame for the changes, or potentially a loss of
02:00sensory information from the nose caused by smell loss may cause various brain areas to atrophy over time.
02:07A study published in Cell last month hinted that the virus likely doesn't invade the brain directly,
02:13but the study author still mentioned this as a possibility. It's also possible that the way in
02:18which the coronavirus wreaks havoc in the brain differs slightly between different coronavirus variants.
02:24Future studies should address this question directly, as well as the question of how long the
02:29observed cognitive deficits might last. The new study also doesn't address whether the COVID-related
02:35damage could accelerate normal structural brain changes that typically occur in line with aging.
02:42Future research can look into these potential downstream effects, while other studies can focus on how
02:47these findings might apply to people with long COVID, who often report symptoms like memory issues and brain fog.
02:53Future research can look into this