This question demands to be top of mind: What can COVID do to our brains?
Add to a growing stack of relevant research a controversial report published last week by Nature Medicine.
It suggests that seven out of 100 COVID cases could lead to serious brain problems that may last a lifetime.
The authors, led by Dr. Ziyad Al-Aly, a clinical epidemiologist at the Washington School of Medicine in St. Louis, used U.S. Department of Veterans Affairs medical records to track the brain health of 154,000 people who had tested positive for COVID.
Their conclusion, as summed up in a press release: “Those who have been infected with the virus are at increased risk of developing a range of neurological conditions in the first year after the infection.”
The conditions are not trivial. They include strokes. Cognitive and memory problems. Migraine headaches. Epileptic seizures. Involuntary muscle contractions. Hearing and vision abnormalities. Balance and co-ordination difficulties. Depression and anxiety. And symptoms similar to Parkinson’s disease.
“We’re seeing brain problems in previously healthy individuals and those who have had mild infections,” said lead researcher Al-Aly.
“It doesn’t matter if you are young or old, female or male, or what your race is. It doesn’t matter if you smoked or not, or if you had other unhealthy habits or conditions.”
Dr. Wes Ely, an ICU doctor and expert in long COVID at the Vanderbilt University Medical Center, called the results “shattering” and “insane” in a TikTok video.
The study’s findings are “absolutely meeting with what I am seeing on the frontlines with our long COVID patients,” added Ely.
If so, the problem is immense. According to the American Academy of Neurology, long COVID is now the third leading neurological disorder in the United States.
Questions about who was included
However, a few critics caution against drawing firm conclusions from the findings. They say the study largely represents a snapshot of how the virus hammered a population of unvaccinated, older and frailer men at the beginning of the pandemic before vaccination and boosters. (Thirty per cent of the study group were not old.)
They also argue that generalizing from electronic health records of mostly veterans to the general population or a vaccinated population is of questionable validity.
“To optimally assess the epidemiological burden of long-term sequelae of COVID-19, we must not rely on self-report or observational data, but on gold-standard prospective, double-blinded cohort studies,” noted one critic in the British Medical Journal.
But the peer reviewed study adds to already extensive and worrisome scientific literature on how the virus can affect brain function.
Ely noted: “This VA Study is very large and even though it is 70 per cent white males who were unvaccinated, we already have data showing that vaccinated patients are still at risk for neurological and cardiological complications months after acute and mild COVID.”
A growing stack of studies
Other research shows, for example, that even mild COVID infections can result in significant shrinkage of grey matter as well as lasting damage to neurons essential for sensory and motor function.
The virus can also penetrate the blood-brain barrier and ignite central nervous system inflammation. The blood-brain barrier is a sort of immunological roadblock that prevents infections in the blood from entering the brain.
A Danish study also found that risk of ischemic stroke, which blocks blood flow to the brain, was more frequent in COVID-positive patients than in those with respiratory infections.
“There have been several studies by other researchers that have shown, in mice and humans, that SARS-CoV-2 can attack the lining of the blood vessels and then trigger a stroke or seizure,” Al-Aly said in the news release. “It helps explain how someone with no risk factors could suddenly have a stroke.”
So how was Al-Aly’s study conducted and what are its claims?
Tracking a range of 44 different brain disorders, the researchers charted the difference in brain health between 154,000 patients (largely white males) who tested positive between March 2020 and January 2021 and two large control groups representing more than 10 million people. (One control group did not have COVID during the same period and another group predated the pandemic.)
Compared to the uninfected control groups, seven per cent of the patients who survived a COVID infection reported a diverse array of neurological conditions, including strokes, memory loss and Alzheimer’s disease.
That means more than six million Americans currently may suffer from some form of brain impairment from COVID, Al-Aly estimated.
Among the risks asserted in the study:
People infected with COVID have a 77-per-cent increased risk of developing memory losses, which may or may not resolve after a year.
They also have a 50-per-cent increased risk of suffering from an ischemic stroke that blocks blood flow to the brain and could result in paralysis and death.
The list of potential problems goes on. Those infected have an 80-per-cent greater change of suffering from seizures; a 30-per-cent greater chance of enduring vision problems and 42-per-cent greater likelihood of developing Parkinson’s-like involuntary muscle contractions and tremors.
The risks of mental health disorders and muscular skeletal disorders were higher in older adults ages 60 to 80, while the risks of memory and cognitive disorders, sensory problems, encephalopathy and Guillain-Barré syndrome (when the immune system attacks the nervous system) was stronger in younger adults.
“The effects of these disorders on younger lives are profound and cannot be overstated; urgent attention is needed to better understand these long-term effects and the means to mitigate them,” warned the study.
The study also found an increased risk of developing Alzheimer’s disease among older adults. Another recent study found that the risk for developing Alzheimer's disease increases by 50 to 80 per cent in older adults infected by COVID.
Al-Aly is one of North America’s leading researchers on the long-term effects of COVID infections. His research previously highlighted the risk to heart and kidneys.
He has shared a preliminary finding that repeated COVID infections can raise the risk for heart, kidney and brain disorders.
And he has repeatedly warned that most long COVID cases in the world are the product of so-called “mild” infections and that people can still get long COVID after being vaccinated and boosted. Vaccinations lessen the risk but do not eliminate it.
"We've never, ever in the history of the pandemic, in all our studies from the beginning until now, found that COVID-19 is equally risky to the flu," Al-Aly told NPR radio this month. "It's always carried a higher risk."
The study comes with some important caveats. Most of the people in the study were not vaccinated, and given its timeline (the first year of the pandemic), does not include data about Omicron and other variants.
But in a previous study Al-Aly found that vaccinations reduced the risk of long-term brain injuries by about 15 per cent and decreased the risk of blood clotting problems and lung damage by 50 per cent.
A more recent U.K. study found that two vaccinations reduced the odds of coming down with long COVID by 41 per cent compared to unvaccinated people.
Some 40 million new neurological cases globally
Long COVID remains a growing disabling event around the world. A 2022 U.K. study found that 4.5 per cent of Omicron cases (in contrast to nearly 11 per cent of Delta cases) go on to suffer from long COVID. But given the enhanced infectiousness of Omicron, the researchers predicted “future numbers with long COVID will inevitably rise.”
That finding underscores the importance of avoiding infection with effective public health measures such as masking and air filtration combined with up-to-date vaccinations.
Al-Aly estimates that the pandemic has created more than 40 million new cases of neurological disorders worldwide.
“Given the colossal scale of the pandemic, and even though the absolute numbers reported in this work are small, these may translate into a large number of affected individuals around the world — and this will likely contribute to a rise in the burden of neurologic diseases,” concluded the paper.
Which is why, as research on how COVID affects our brains keeps advancing, discoveries bear close attention. The implications look to be socially and personally momentous.
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