A new study led by Stanford University School of Medicine offers new insights into the lingering symptoms of COVID-19, with evidence suggesting that the brain fog experienced by some patients bears striking similarities to the cognitive impairment seen in cancer patients after chemotherapy.
The study found that the excessive inflammation caused by COVID-19 and the cognitive impairment that can occur after chemotherapy, sometimes called “chemo-brain,” damage the same brain cells and processes.
The findings were published Tuesday in the peer-reviewed scientific journal Cell.
The study examined mice with mild SARS-CoV-2 infection, the virus that causes COVID-19, and postmortem human brain tissue collected early in the pandemic.
The researchers found that even mild COVID-19 can cause enough inflammation to cause cognitive impairment.
“I think we’re really still beginning to understand this,” Dr. Michelle Monhe, a neuro-oncologist and professor at Stanford, told CTV’s Your Morning on Wednesday.
“People who were infected with COVID early in the pandemic showed quite shockingly high rates of cognitive impairment. Many studies show that one in four patients have some degree of permanent cognitive impairment, and so we’re trying to understand that.”
Inflammation is a defense mechanism the body uses to respond to injury or infection, such as when a person’s skin swells after a cut.
Inflammation that persists for a long time or occurs in healthy tissue, known as chronic inflammation, can be harmful.
For many patients, COVID-19 can lead to cognitive symptoms such as attention, concentration, memory and executive functioning problems that can potentially last two months or more after a mild infection, researchers say.
Monje and her team have previously studied the effect of chemotherapy on cognitive impairment.
They say chemotherapy can damage the brain’s white matter, areas of isolated nerve fibers that quickly transmit signals using a fatty coating called myelin.
During “brain chemotherapy,” damaged myelin can slow nerve signal transmission.
COVID-19 also triggers an immune response strong enough to create widespread inflammation, which Monge suspects may be causing the cognitive problems seen in prolonged COVID.
Even if the virus causes a mild infection limited to the lungs, Monje says the inflammation can create a cascading effect that affects a person’s brain cells.
The study authors say the effect of newer sub-variants of COVID-19, such as Omicron, as well as breakthrough infections in vaccinated people, remains to be fully determined.
However, they say emerging data suggest that the risk of cognitive impairment may be lower in breakthrough infections in fully vaccinated individuals.
The brain effects of respiratory infection with COVID-19 in children and the elderly also require more research, they said.
But understanding this link between COVID brain fog and chemotherapy could offer “new therapeutic insights and hopefully correct this cognitive impairment,” says Monje.
Her team is currently conducting research on drugs that could alleviate brain fog after chemotherapy, which she says could prove useful after a COVID-19 infection.
“I think what’s really encouraging is that the cognitive impairment that occurs after cancer therapy is now well enough understood that there are the beginnings of clinical trials,” she said.
“In fact, some of this really promising work is being done out of Toronto at SickKids[hospital]and I’m hoping that some of these insights from the cognitive impairment associated with cancer treatment will help us figure out new ways forward to make the cognitive disability that occurs after COVID better for patients.”
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