a large brain scanning study finds that some parts of the brains of older adults shrink after infection & mild symptoms of covid. these are small & specific changes in the brain, but every percentage counts. avoid covid.  

original article: Douaud et al., 2022 (Nature), reported in: The Guardian by Linda Geddes on 7th March 2022

this story was in episode 26 #COVID #brain #smell #taste #size #shrinkage

the error bar says

in a study echoed across lots of news media this week, the Guardian reports that brain scientists from Oxford found that even mild cases of COVID shrinks the brain & damages its tissue.

[before i continue, an editorial note: the error bar has not cover COVID stories so far, to avoid the inevitable trolling, but this one was too prominent to ignore.]

the study relied on the UK's BioBank - a long term research study that has scanned the brains & tested the minds & bodies of thousands of people. in this specific study, 785 typically-healthy older adults' brains were scanned twice. the first scan was done before COVID arrived, the second was done an average of 38 months later, which was, coincidentally, four & a half months after infection with COVID in about half of the people.

the scans revealed that the overall brain size decreased more in those who had COVID & that some brain areas linked to smell & taste showed larger & specific decreases in brain size.

perhaps most significant is that these decreases in brain volume were observable even though the volunteers had mostly had mild symptoms, & the differences remained when 15 more severe cases were excluded.

does covid shrink the brain?

yes, it seems so.

but don't believe all the headlines - it's not as bad as it might sound.

first, the study covered a very wide age-range of participants - from 51 to 80 years - but there was much less 'brain shrinkage' in the youngest participants. because of the way the data are presented, it looks like there is a continuous & larger decrease in brain size as age increases from 56 to 76, but this depends partly on the authors using a 10-year 'sliding window' to average the data. that means the 56-year-old data includes 51 to 61 year-olds. so it might be that only those over 65 show brain shrinkage - it's not quite clear.

second, it's not the whole brain that is shrinking, but rather several important parts of the brain related, arguably, to smell & taste. & some brain areas or signals seemed to *increase* in size too. so it's not a simple story, but overall there seem to be clear differences between the groups.

third, although every bit of brain is important & COVID-related brain loss seems to accelerate with age, these are still relatively small changes, occurring in people with only mild illness. the changes may largely reflect what happens when you lose your sense of smell & taste.


this important study shows that, on average, the oldest participants' brains were more affected by covid than the youngest. some brain areas & signals got bigger, some smaller. overall, there was a small decrease in brain size after covid.


The Guardian: fair - scientific story mostly intact