The Decibel - What COVID does to the brain

Episode Date: November 2, 2022

Neuroscientists are trying to figure out how the COVID virus, SARS-COV-2, is affecting the brain. Many people who have gotten COVID end up having lingering cognitive impairments of some kind, whether that’s brain fog, forgetting vocabulary, difficulty remembering or general sluggishness in trying to think.Dr. Adrian Owen, who has a PhD in cognitive assessments in brain disorders, is a professor of neuroscience and imaging at Western University. His recent study looked at what kinds of cognitive issues people face and how it’s impacting them.Questions? Comments? Ideas? Email us at [e-mail]

Hi, I'm Maina Karaman-Wilms, and you're listening to The Decibel, from The Globe and Mail. Scientists are trying to understand exactly how SARS-CoV-2, the virus that causes COVID, affects the brain. Dr. Adrian Owen, who has a PhD in cognitive assessments and brain disorders, is a professor of neuroscience and imaging at Western University. His recent study looks at the way COVID impacts how people process information and what effect that has on them. This is The Decibel. Adrian, thank you so much for joining me today. Thanks for having me on. So when we talk about cognitive problems after COVID-19, what kind of symptoms do people tell you about? Well, people usually come to us and they use expressions like brain fog, which obviously means very little to a neuroscientist like me.

And when we probe them a little bit further, they say, well, you know, I'm just not as sharp as I used to be. Again, we often push them and they'll generally resort to reporting memory difficulties. They'll say, well, I just, I'm very forgetful now. Also, maybe they can't concentrate on things they used to. I had somebody tell me, for example, that they tried to read a book and they find themselves mind-wandering, being unable to concentrate on the page to sort of keep going. So those are the sort of symptoms that people are reporting.

And just how bad are people saying that these are? Like, how much are these symptoms kind of affecting people's day to day lives? I think it's very variable, actually. I think some people don't really notice much at all. We've had people whose partners have said, well, you know, he thinks he's fine, but actually, he's become very forgetful. And then other people come and, you know, really, they say it's having a quite profound effect on their ability to function, their ability to, you know, make decisions and get through everyday activities. Adrian, how unique is all of this to COVID? Are there other diseases out there that cause these kind of cognitive issues?

There are. I mean, this is actually why we and others started looking at this early on. I mean, we launched our study in June of 2020. And this was really before people were talking about brain fog, certainly long before anybody talked about long COVID. And that was simply because this looked like a virus that was going to cause brain problems. And part of that is because, I mean, the first thing most of us heard is that, you know, it was a problem that affected people's smell. And then we were seeing reports of headaches and dizziness. You know, some people were even reported to be having more severe neurological symptoms like delirium and seizures

and these sorts of things. So very early on, it was looking like a brain issue. But, you know, we can look at the SARS-1 virus, for example. And when you look back, obviously that infected far fewer people. When you look back, it's very clear that that also had effects on the brain. It also led to neurological and cognitive symptoms in some individuals. And, you know, that was an early indicator for us that this was likely to do the same thing. I'm wondering about how widespread this is. Like what proportion of people who actually get COVID end up having some kind of cognitive issue? Yeah, and that's a really

difficult question. In our sample, you know, as a group, they were statistically impaired at tests of reasoning and decision making and speed of thinking and these sorts of things. One way we did look at the data to directly answer your question was to say, well, how many people are outside of the sort of normal distribution? Now, statistically speaking, the way this is done is people often look at people who are, say, less than 1.5 standard deviations from the norm. And in what we call a normal distribution, a normal sort of healthy population, you'd expect about 6% of people to be below 1.5 standard deviations from the norm. In our sample, it was about 16% of individuals. I don't think that's an unreasonable

estimate. There were many things that we did to try to make our study as representative as we possibly could. So I think it was reasonably representative. And from the people I've spoken to and the people I know, I would say that 16% is not an unreasonable estimate. And of course, the important thing is that 600 million people around the world have been exposed to this virus, have had COVID-19, and 16% of 600 million is still an awfully large number. Yeah. One of the symptoms people often report after having COVID is losing their sense of smell. Can you just connect the dots for us here, Adrian? Like what is actually going on here when people are reporting losing their sense of smell? What's actually causing that?

I mean, a lot of people, when they tend to think about loss of smell, I guess they think about their nose. And of course, you know, the smell is just another sense, and that sense is decoded by the brain. And loss of smell is actually a neurological symptom. It is something that suggests that the areas of the brain that decode smells and let us know what smells are and these sorts of things, recognize smells, is at fault. So this is some indication that an area of the brain is being affected directly and possibly an indication of how the virus is getting into the brain because it's coming in possibly via the olfactory bulbs and along the olfactory pathway. This is really interesting because I think when people lose their sense of smell with COVID,

because it's a respiratory virus, they assume there's something going on with their nose, but you're saying it's actually in the brain here. Right. I mean, it's the same as, you know, people often think that a respiratory illness wouldn't necessarily lead to any kind of brain damage. But think, I mean, outside of pandemic times, most of the patients that I see who have brain damage have actually incurred that damage because they've had a cardiac arrest. And, you know, most people will say to me, but that's a heart thing, that's not a brain thing. But, you know, in the same way as we're talking about respiratory illnesses, you're leading to potential brain effects, so do heart problems, because it's an

interruption of the oxygen supply to the brain. So it's a sort of a knock-on effect that involves the brain. Okay. And to go back to those symptoms that we were talking about earlier, the symptoms that people tell you about, the brain fog, the memory loss, what do we know about what's going on neurologically when they're experiencing those things? You know, I don't think we really know the answer to that. I mean, all we've been able to do at this stage is to map exactly what those problems are. So we took a group of almost 500 people who'd recovered from COVID-19 infection, and we asked them a lot of information about themselves, about the experiences they'd had, about how severe their reaction to COVID had been.

And then we had them complete a battery of 12 online cognitive tests. And these look at things like memory and concentration and what we call executive function. These are the sort of, you know, the really sort of complicated functions of the brain, the things that allow us to make complicated decisions and to solve complicated problems and these sorts of things. And we looked at both how accurate people were and how quickly they could do all of these things. One of the really surprising findings, given what I've told you about people's subjective feelings of what

was wrong with them, is that there are actually no memory impairments. This was not something that seemed to affect people's memory. However, there were significant problems in those who had recovered from COVID-19 relative to a group of participants who hadn't had COVID-19. There were problems with the ability to reason and to problem solve. So to think about solving everyday sort of problems, and I'm not talking about really big difficult problems that you may only solve, you know, once every few weeks. It was sort of everyday decision making. People were both slow to do that, and they were relatively inaccurate. So decisions kind of like, you know, do I have enough time to go to the grocery store

and then pick my kid up for school, that kind of decision making stuff? Yeah, that's a really good example. I mean, I think people don't realize just how many decisions they make every day, but it's actually hundreds, maybe even thousands of decisions sometimes from small things like that. Do I have time to do this before I do that? How am I going to get to my meeting on time? People are making judgment calls, I suppose, is another way of thinking about it. It's really the everyday decision-making that concerns me, because that's something that really could interfere with people's everyday lives. So just to make sure I understand you then, Adrian, so people are saying, you know, my memory is not as good, but you're saying when you actually looked at the brain, it's not necessarily that the memory part of their brain

was hindered in any way, but it's, I guess, the stuff around it. Can you just kind of like finish that thought for me there? Yeah, I can. So, I mean, probably the simplest way to describe this is if you think about something like memory, it's actually quite a complicated system. I mean, you have your memories, you know, the things that you know about, the stuff that you know about the world, and that's all stored somewhere in your brain. But actually, a far more, in some ways, sophisticated mechanism is how we lay down those memories and organize them and retrieve them. When we're trying to record something, we don't just dip into this huge bank of memories

that we've got in our brain for our entire lives. We generally go about it in a systematic and an organized way. And that's more the type of impairment that we're seeing here. It's a sort of an organizational level impairment rather than a problem with memory per se. Okay, interesting. And I mean, I hear people talking about losing vocabulary when they experience this kind of, you know, so-called brain fog. Is that kind of the same thing then? Like trouble accessing the word as opposed to like actually forgetting the word? That's exactly the problem, right? So the person hasn't completely forgotten the word. Most of us at some point in our lives have word finding difficulty.

We have a tip of the tongue thing. We can't remember what that word is. But the word is still there in your brain. And we know that because a little while later, you'll be able to retrieve it. So it must have been there all the time. The problem is you are unable to retrieve it. What we call your executive mechanisms of the brain that dip into the huge lexicon of memories was unable to retrieve it at that time. We'll be back in a moment. One of the things that you found in your study as well that you recently did is that COVID seems to be aging people's brains.

I mean, this seems like a pretty significant issue. What exactly did you find, Adrian? Okay, we need to be a little bit clearer about that. So, I mean, that's one way of interpreting the data. So one thing that we did is we looked at the size of the impairment and related it to people's age, because obviously, in general, people experience actually taken our tests over the last few years. So we're able to dip into that database and say, well, you know, let's look at this participant, Adrian Owen. Is he really performing like a 56-year-old? Or is he actually looking like somebody much older? That's the way to think about it. And what we found is that people are typically responding as though they are 12 to 16 years older than they actually are. So in my case, I would be more like a 70-year-old than a 56-year-old on these tests.

How long can these symptoms actually last? Yes, another great question. And to be honest, we don't yet know the answer. In our sample of 500 we had quite a lot of variability in the amount of time that had elapsed since the last positive test so people were from a few days to up to i think 240 days that's the only way we had of looking at how long these symptoms last because we could look at the people that had where more time had elapsed since their last positive test to see whether they were getting any better or any worse relative to those who were coming right out of the acute or the immediate effects of the virus. And actually, there was no difference between those groups. There's no relationship between time and the extent of the cognitive impairments.

Now, you could read that as good news or bad news, really. I mean, on the good side, it does look like people aren't getting any worse over time. But the bad news is they don't be getting any better either. And I mean, we're not the only study that's shown this. There was an Oxford study, Oxford in the UK study recently that had a very similar result that the changes that they observed, both in the brain itself and cognitively, didn't seem to dissipate over time. Okay. Does everyone who gets COVID have an equal chance of experiencing this?

Or I guess, what do we know about who is most likely to experience these cognitive issues? Okay, well, I can only really speak to the data that we collected. And in our study, those people who experienced the worst physical symptoms associated with COVID-19 certainly went on to have the most pronounced long-term cognitive impairments. So the worse your COVID reaction, the more severe your ongoing cognitive challenges would be. Now, that said, it's extremely important to point out that we also saw significant impairments among those people who did not have an extremely severe reaction. So even when we just looked at the group that had stayed out of hospital and had a relatively mild infection,

we still were able to pick up significant cognitive impairments. And in fact, that's exactly what the Oxford study has found too. So I think the only way to interpret that is to say it could be anybody. It doesn't really target any particular demographic in particular. Okay, so let's actually get into what is causing these symptoms. Like what's actually going on in the brain? Well, you know, I think we don't know exactly what's going on in the brain. I think there are a number of possibilities. I generally divide them into what I would call direct brain effects and indirect brain effects. And a direct brain effect would be where the virus has actually entered the brain itself and is attacking brain cells and is having a direct

effect on brain function. And there's certainly some evidence for that. Sorry, the evidence that the virus itself, the SARS-CoV-2 virus is actually in the brain then? Right. I mean, there's certainly been a few academic papers published recently, citing evidence of finding the virus in the brain of some people. It isn't something that seems to be the case in every case. There's also some actually pretty good reports of brain-related changes, changes in people who've had COVID-19 and have measurable changes in the structure and the function of their brain.

So that's another possible indicator that the virus is having a direct effect on the brain. The second broad sort of cluster of possibilities really are indirect effects on the brain. And this is something that I personally know much more about because we've been studying it for some years. And by an indirect effect, what I mean is any sort of peripheral thing that could have affected brain function. So, you know, imagine a respiratory illness like COVID-19 is going to interrupt the normal oxygen supply to the brain. You're not getting normal levels of oxygen just because of the effect on the lungs and the effect on your breathing. But obviously, in patients who have more severe reaction to COVID-19, that's going

to be even worse than that. They may end up in hospital on a ventilator. Now, a ventilator is certainly going to interrupt your normal levels of oxygen to the brain. And therefore, it affects the brain indirectly. The brain obviously to function normally, it has to have a good, a rich supply of oxygen. And really anything that gets in the way of that can lead to an impairment of brain function. Okay. When we're talking about, I guess, what might be causing

this, do we know about the role of the immune system? Because I think this is something that we're hearing that the immune system and the reaction of your own body might actually be playing a role here. That's absolutely true. And I mean, that's probably something that accounts for some of the variability across individuals. I mean, obviously, this is not a virus that affects everybody equally. And certainly, it does seem that in some particularly severe cases, the immune system almost goes into sort of overdrive. It responds to the virus in a way that, you know, almost has a direct effect on the host. The enormous immune response to the virus itself can actually have a detrimental effect on brain function. I don't think that's likely to be the case for most people,

especially those who experience milder symptoms. Okay. How likely do you actually think it is that people experiencing these cognitive problems will make a full recovery? Well, I don't have a sort of an empirical answer to that problem. I can't point at some data and say this is what I think is going to happen. My hunch is that this is actually going to be a really serious ongoing issue that people are only really going to come to terms with maybe a couple of years from now when we really know exactly how many people is this affecting and how badly. I just don't have any reason to believe these things are going to go away. I suppose that's a fairer way of putting it. We don't see any evidence right now that as long

as you leave it six months, everything goes away. So that's not happening. We now have people who are, you know, coming up to two years out of COVID and still reporting, you know, cognitive and neurological challenges. So yeah, I mean, that's the best answer I can give, I'm afraid. Until we can look back with, you know, the benefit of hindsight, I don't think we'll really know exactly what the answer is. Yeah. Just lastly here, Adrian, if someone is experiencing these issues, is there anything that they can do to help their brain recover a little bit? I think everybody has agreed that rest and relaxation is the right thing to do. sort of tried to take it easy, especially during the acute phase of COVID, rather than just carry on and, you know, work through it, tend to fare better. But I mean, at the moment, we're really at the stage of still trying to understand exactly what these problems are. And it's only when we

fully understand the problems and fully understand exactly, you know, what they are, who they're affecting and how badly that I think we'll be able to develop sort of remediation strategies things that people could do to um assist themselves saying that there's a huge amount of research going on um not necessarily uh in canada but in the us and the uk uh large amounts of money have been put into exploring this phenomenon i i don't see any reason why, you know, down the line, therapies are not going to become available. Once we understand exactly what long COVID is, and we understand the underlying brain mechanisms, then I think people will start to develop, you know, perhaps drugs or other types of interventions that may assist people and help

them to get better more quickly. Adrian, thank you so much for taking the time to speak with me today. Thanks very much for having me on. It was a real pleasure. Before you go, we'd like to hear about your own experiences after having COVID-19. If you've experienced any cognitive issues or any form of long COVID, send us an email and tell us about it. You can reach us at thedecibel at globeandmail.com. That's it for today. I'm Mainika Raman-Wilms. Our producers are Madeline White, Cheryl Sutherland, and Rachel Levy-McLaughlin. David Crosby edits the show. Kasia Mihailovic is our senior producer, and Angela

Pichenza is our executive editor. Thanks so much for listening, and I'll talk to you tomorrow.