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Q&A
Researchers are trying to explain COVID’s profound effects on the brain
When COVID-19 first reared its head back in 2019, it brought with it a slew of strange symptoms beyond just respiratory problems. One of the most puzzling symptoms in those early days was something called “brain fog” — cognitive issues like confusion, forgetfulness, and trouble focusing.
And while other symptoms have changed as the virus mutated, brain fog is still a common complaint of COVID sufferers not only during the initial illness, but extending for months or even years afterwards. Several recent studies have been trying to understand exactly what this virus is doing to our brains — and how to stop it.
Dr. Ziyad Al-Aly, the chief of research and development at the VA St. Louis Health Care System, spoke with
Quirks & Quarks host Bob McDonald about what he’s seeing in his research on COVID and the brain. Here is part of their conversation.
Take me through some of these effects that COVID has had on the brain. What have you seen?
One of
the key manifestations that people experience after SARS-CoV-2 infection is what we call colloquially as brain fog. That’s the mental haziness, the inability to remember things, to connect the dots, to really think clearly.
In addition to brain fog,
we see people coming back to the clinics with mini strokes. We see a lot of people with headache disorders, sleep disturbances, sleep problems. A lot of people come back to the clinic with tingling of the extremities, tingling in the legs or sometimes in the arms. In rare cases, seizure disorders. So really a variety of health problems in the brain.
Is COVID actually affecting the way the brain functions?
There are
studies that have been done comparing people who had COVID-19, versus people who didn’t, and then gave them cognitive testing to measure their ability to cognitively process information and test their IQ. And there’s very clear differences in the IQ of people who had been infected with COVID-19 versus people who did not. Even mild COVID can give people about a three-point loss of IQ.
The key caveat to those studies is that most of these were done from the original phase of the pandemic when we didn’t have vaccination, when the virus was very different and we didn’t have antivirals. And we also don’t really know whether those cognitive losses that I just described, that three-point IQ loss, we don’t really know how permanent that is.
What about brain aging?
It’s very, very clear that in some individuals they do experience structural abnormalities and some other abnormalities of imaging that are commensurate with what normal people experience with about
seven years of brain aging.
Now the hope is that those effects are not are not long lasting and then the brain with neuroplasticity and other other sort of mechanisms will be able to restore itself back to normal health. But I think that really remains to be characterized and seen in studies.
How is the virus that comes in through the lungs affecting the brain so much?
It
induces inflammation of the brain. One of the clear signals from the studies that we’ve done and a lot of other people have done over the past several years is that clearly in some people it can provoke inflammatory reactions in the brain or neuroinflammation and that may explain some of the symptoms that are experienced by some individuals.
It can affect multiple substances on which the brain really depends to function normally. One of them is cortisol. So
people have studied this out of Yale University and have shown that people with long COVID or people after SARS-CoV-2 infection can experience inappropriately low level of cortisol and that’s actually an important hormone for a lot of certain normal physiologic processes, including cognitive performance, and a lower cortisol level than where it should be can explain some of the cognitive dysfunction that is seen in some people after SARS-CoV-2 infection. There are some studies also done on
showing low serotonin levels and that can also explain some of the symptoms.
But doesn’t the brain have a protective mechanism, the so-called blood brain barrier?
By inducing that inflammation of the brain, that actually
makes that barrier leaky, so it starts leaking things into the brain that shouldn’t be there. And things from the brain to outside the brain that also should not exit outside the brain. So a leaky blood brain barrier can also explain, you know, some of the manifestations that we see after COVID-19 infection.
How is this changing over time as the virus mutates?
We’re in a different phase of the pandemic now than what we all experienced in March 2020. We have a different virus. We have availability of vaccines now. We have antivirals. So all of these drivers have now sort of reduced overall the burden of long COVID.
That doesn’t mean that SARS-CoV-2 infection is benign, is inconsequential. We still see people in the hospital with SARS-CoV-2 infection, we still see people with strokes and heart attacks and, you know, brain fog and all other manifestations. But overall, I think the risk has sort of declined over the course of the pandemic.
How unique are these other effects on the body and the brain and the heart to COVID?
The big revelation or the big aha moment in this pandemic was the realization that SARS-CoV-2 infection can produce this really large basket of long-term adverse health effects. When we went back and started thinking about what happened to people after the Spanish flu, we found historical accounts that sort of resemble, to a large degree, what we described now after SARS-CoV-2 infection, people having increased risk of Parkinson’s disease, headaches, brain fog etcetera.
I think one of the major lessons that I learned from this pandemic is that there are long tails to pandemics. And yes, we can focus all we want on the acute phase, or the tip of the iceberg, but the reality is that there is a really much larger chunk of disability and disease beneath that tip of the iceberg.
Q&A edited for length and clarity.
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