COVID19 is bad for your brain even if you aren’t hospitalized

We now know that even COVID19 that doesn’t put you in the hospital is bad for your brain.  How do we know this?  Think of how you would design an experiment to find this out using real people.

Only a monster would do something like this.  Take 800 people, study the hell out of them.  MRI their brain, do cognitive tests, know just about everything about the medical and social history.  Then expose them to the pandemic virus.  Some get infected (as judged by their health records and antibody to the virus tests).  I’ll call the infected COVID19 to save time. Wait a few months then test them all over again, MRIs, cognitive tests, medical history etc. etc.

Such an experiment was done and what follows is a description of a paper given in a link a friend sent —  doi: 10.1038/s41586-022-04569-5. Online ahead of print. PMID: 35255491.  To be noted, is that the paper is still being edited by Nature, so some things may change but I’m pretty sure the conclusions will stand.

The work was done by the UK Biobank which which recruited 500,000 volunteers   aged 40 to 60 from 2006 to 2010 and is following them for 30 years.  All donated urine, saliva and blood in addition to filling out questionnaires with consent for access to their electronic health records.  Last year the Biobank released the (anonymized hopefully) complete genome sequences of 200,000 people.

This was long before the pandemic hit.   The paper reports results on 785 participants ages 51 – 81 who had MRIs twice (once before the pandemic hit, and once afterward).  There were 401 who had been infected.  The 384 uninfected controls were selected to be matched for age, sex, ethnicity and time between the two MRIs (which were an average of 38 months apart).   The average time between becoming infected and the second MRI and testing was 20 weeks.

How many of the 785 were hospitalized?  Just 15/401 infected (3.7%) showing that most pandemic infections were pretty benign.  The 15 hospitalized were excluded from further analysis

The paper was submitted to Nature in August of 2021, long before omicron appeared on the scene.

So these are huge numbers of subjects, all of whom had been intensively studied before the pandemic hit, which makes it so valuable.

There is a huge amount of data, but here are a few of the high points. All of what follows compares the infected to uninfected controls.

l. The infected had a greater reduction in gray matter between the MRIs, particularly in that part of the brain close to the nose.2. The infected had greater reductions in brain size (but not that much, the average atrophy was 2%).

3. We all cognitively decline as we get older, but the decline was greater in the infected.

With this many people in the study, they could group people into two year bins.  So there was no atrophy in one area (relative to controls) in people between 55 and 60, but at 76 the same area showed 20% atrophy in patients but only 5% in controls.

It is obvious on looking at the graphs plotting results for the infected vs age and results for the uninfected in the same panel, that the differences between the infected and the controls increased with age.

The cognitive testing reported was rather simple — but it could be quantitated.  It was time to complete the trail A and trail B tests.  In these trials subjects are to connect a set of 25 dots as quickly as possible.  The observer notes mistakes and allows people to correct them until they get everything right.

Part A has the dots numbered and they are to be connected in order.  This is thought to test cognitive processing speed.

Part B has the first 13 integers and letters from A to L.  They are to be connected as follows 1 – A – 2 – B – 3 -C —   This is thought to test executive function.

There are, tons more data of interest to a neurologist — which particular parts of the brain are hardest hit etc. etc. but I’ll leave it to you to follow the link


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  • MStriker  On March 13, 2022 at 1:56 pm

    Covid19’s mild-case nasal focus, plus brain neuron pruning effects per the day’s activations, suggests a why to the reduction in the nasal area grey matter/volume. (My next thought was “might want to provide non-monotonous (educational?) mental stimulation for hospital-bound patients”.)

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