Mild symptoms not to be taken lightly
A positive COVID-19 test result often triggers tension – whether we ourselves get tested or some one we care for does. However, people usually feel relieved if they experience mild symptoms, since it does not seem as scary as getting a severe infection or getting hospitalised.
However, brain scans now show that even a mild case of COVID-19 can shrink part of the brain, causing physical changes equivalent to a decade of ageing. Exactly why is still a mystery.
Drastic impact of COVID-19 on brain
Some of the most compelling evidence of neurological damage after mild COVID-19 comes from U.K. researchers who investigated brain changes in people before and after they got the disease.
The 785 participants, between 51 and 81 years old, were scanned before the start of the pandemic, and then were scanned on average three years apart, as part of the U.K. Biobank project. Medical records showed that 401 of these volunteers got infected with SARS-CoV-2. Most of them had mild infections, only only 15 of the 401 were hospitalised.
The results showed that four and a half months after a mild COVID infection, patients had lost (on average) between 0.2 and 2 percent of brain volume and had thinner grey matter than healthy people.
Decline in cognitive abilities
The infected participants took 8 and 12 percent longer on the two tests that measured attention, visual screening ability, and processing speed. The patients were not significantly slower on memory recall, reaction time, or reasoning tests.
Overall, studies consistently show that COVID-19 patients score significantly lower in tests of attention, memory, and executive function compared to healthy people. Jacques Hugon, a neurologist at University of Paris Lariboisiere Hospital, says it isn’t clear if the brain will mend itself or whether patients will ever recover, even with cognitive rehabilitation. The damage COVID-19 causes in the brain can also evolve into various neurodegenerative disorders.
What exactly is COVID-19 brain fog?
While this isn’t a formal medical term, says Edward Shorter, a professor of psychiatry at University of Toronto, it has become an umbrella term for describing an array of symptoms such as confusion, word-finding difficulties, short-term memory loss, dizziness, or inability to concentrate. As per reports, many people have recovered from the acute, life-threatening effects of COVID-19, but still don’t feel that their thinking and memory are back to normal.
Brain fog is one common and especially troublesome issue with long COVID. Experts believe cognitive slowing and mood problems after a person is infected with COVID-19 seem to be much more prevalent than with most other viral infections. Brain fog can affect people's work, with some struggling to stay productive and others leaving their jobs because they find it impossible to function.
What causes brain fog and cognitive decline?
COVID-19 can elicit a severe immune response that triggers a storm of proteins called cytokines, which amplify inflammation throughout the body. Long-term inflammation can promote cognitive decline and neurodegenerative diseases.
Because COVID-19 affects respiration, it can starve the brain of oxygen, as seen in autopsy data from Finland. COVID-19 also increases the risk for blood clots for up to six months, which can cause strokes that deprive the brain tissue of oxygen.
Some scientists even fear that COVID-19 survivors could be at higher risk for Alzheimer’s disease, based on evidence for a protein called beta-amyloid in the brains of younger patients who died of COVID-19.
Several studies also show evidence of the SARS-CoV-2 virus invading the brain. A study by the U.S. National Institutes of Health illustrates how SARS-CoV-2 can spread well beyond the lungs and the respiratory tract. This suggests that the inability of the immune system to clear the virus from the body could be a potential contributor to long COVID symptoms, including brain fog.
Read more: Hypnosis for Weight Loss. Does It Work?
Don't let your guards down
Experts worry that due to the wide availability of vaccines and relatively milder Omicron variants, people are letting their guard down too soon. They are not concerned about the possible cognitive damage from getting sick. Although COVID-19 vaccines are highly effective in protecting against serious illness, they do not protect against long COVID in people who become infected despite vaccination.
“We need to move away from quantifying the impact of the disease only in terms of deaths and severe cases,” says the University of Oxford’s Douaud, “as evidence from studies on long COVID, and our study, show that even mild infection can be damaging.”