Does COVID really shrink and rot your Brain?

There have been media stories that report that even mild COVID infections can impact the human brain. I don’t simply mean the tabloids, but also reputable sources such as Reuters have run this. For example …

Permit me to quote the opening of the above …

COVID-19 can cause the brain to shrink, reduce grey matter in the regions that control emotion and memory, and damage areas that control the sense of smell, an Oxford University study has found.

The scientists said that the effects were even seen in people who had not been hospitalised with COVID

Yikes, that sounds really scary stuff. That is especially scary if even a mild infection does that. These days, when we are now pretending that COVID is gone and no longer masking, it becomes more probable that you might get it.

But wait, just how conclusive is all this?

Let’s take a look at the alpha source, the actual study that all of this leans upon.

Nature (Mar 7, 2022) : SARS-CoV-2 is associated with changes in brain structure in UK Biobank

What is going on here, what is this study all about?

There exists in the UK the BioBank project. This is where they track a large number of individuals over many decades and mine a lot of data from them.

For this specific study, they picked 785 of the BioBank participants and conducted two MRI scans of each. Between the scans, 401 people had COVID-19 and 384 people did not.

Doing this enables them to do the following …

  • For those that had COVID compare the before and after MRI scans
  • Then compare those results against the before and after scans of those who did not have COVID.

What exactly did they find?

Those who had COVID had a reduction of the parts of the brain associated with smell.

Is COVID really hitting the brain like that?

This is where a lack of knowledge in the media enables some to jump to the wrong conclusion and declare that COVID rots your brain.

We do know that COVID will impact your sense of smell and taste. That happens because the virus appears to attack support cells at the back of the nose.

The way we sense odors is through a cluster of nerve cells called “olfactory sensory neurons”. These are located high up at the back of the nose in a structure called the olfactory bulb. These neurons have tiny hair-like projections which extend out into the mucus-covered nasal lining and respond to odor molecules that we breathe through our noses.

COVID is hitting the support cells in the nasal lining which interact with these neurons. That stops your sense of smell dead in its tracks. However, since the olfactory sensory neurons are intact and not affected by COVID, then when your nasal lining rebuilds itself, you get your sense of smell back.

OK, so why the brain hit, what is that about?

The key is understanding that we all have Brain plasticity, also known as neuroplasticity. This is the biological, chemical, and physical capacity for the brain to reorganize its structure and function.

Your brain is constantly changing, it is not a static entity.

If you get a cold and that stuffs up your nose and hits your ability to smell, then your brain will adapt and there is a measurable impact to the gray matter within the smell region of your brain for even that. Once you recover, it once again adapts.

Is that true?

Yep, research has shown that stuffy noses can lead to brain changes, too. Some of those changes are similar to those that the researchers found within the recent brain-scanning study.

For almost anything and everything you do, your brain will adjust.

So that’s a conclusive answer?

Well, no.

The infected participants within the study also showed on average larger cognitive decline between the two timepoints. 


They look upon that as follows within the study …

..These mainly limbic brain imaging results may be the in vivo hallmarks of a degenerative spread of the disease via olfactory pathways, of neuroinflammatory events, or of the loss of sensory input due to anosmia. Whether this deleterious impact can be partially reversed, or whether these effects will persist in the long term, remains to be investigated with additional follow up.

Look, let’s be clear about this. Getting COVID is not a good thing, it really is best avoided. You know what you should be doing, so stick with it and be wise about this.

If you do get it, does it directly impact the brain?

The various media reports are claiming “Yep”, and cite this study. The problem is that this study does not actually verify that. There is good evidence to suggest that it is simply an indirect impact due to the sense of smell being shutdown. The brain adjusts to reflect that.

But …

Well yes, there is always a “but” with stuff like this. There is a lot that is just not known … yet.

What now?

They need more data. They will have to follow up the same people and see what has happened to them long term. Once their sense of smell bounces back, do they then see a corresponding response to that within the MRI scans of participant brains?

In summary

It’s complicated.

Your brain is dynamic. Brain areas grow and shrink over the course of days. Such changes can be tethered to hormone levels across the menstrual cycle. 

There are many unknowns in play. They measured brain changes, but what brain changes are normal, reversible or inconsequential, and what is deeply serious and impactful in the long term?

Right now the data to come to a decisive clear conclusion is not there.

Be ware of scary media claims, things are often not as decisive as described.

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