We all know that COVID-19 can lead to constant fatigue and brain fog. But one of the most rigorous tests to date of the long-term cognitive effects of severe infection has just yielded some very worrying results.
In a study comparing 46 severe COVID-19 patients with 460 matched controls, researchers found that the mental effects of severe COVID-19 after six months could be equivalent to aging 20 years — from 50 to 70 — or losing 10 IQ points.
Specific mental changes were also distinct from those seen in early dementia or general aging.
says neuroscientist David Menon of the University of Cambridge in the UK, who was lead author of the study.
The new paper didn’t set out to alarm many of us who already had COVID, but instead looked closely at how serious the cognitive changes in the wake of severe cases of infection are, so we can begin to understand how to mitigate them.
“Tens of thousands of people have been in intensive care with COVID-19 in England alone, and many will be very ill, but have not been admitted to hospital,” says lead researcher and cognitive scientist Adam Hampshire of Imperial College London.
“This means that a significant number of people still have cognitive problems after several months. We urgently need to look at what can be done to help these people.”
The trial involved 46 people who went to Addenbrooke’s Hospital in Cambridge as a result of COVID-19 between March and July 2020. 16 of them were placed on mechanical ventilation during their stay.
After an average of six months after injury, researchers supervised them with a test instrument called the Cognitron to see how well they performed in areas such as memory, attention, and thinking, as well as anxiety, depression and PTSD.
The researchers did not have test results from those individuals who had COVID disease for comparison. Instead, they did the next best thing, comparing their results to a matching control group of 460 people.
These results were then mapped to see how much they deviated from the expected scores for their age and demographic, based on 66,008 members of the general population.
The results showed that those who survived severe COVID had lower accuracy and slower response times than the general population.
The magnitude of cognitive loss was similar to the effects of aging between 50 and 70 years old – equivalent to a loss of 10 IQ points.
Accuracy was affected in verbal measurement tasks – where subjects are asked to find similarities between words. This reflects anecdotal reports that after infection people struggle to find the right word, and feel their brain is in slow motion.
The team found that although patients reported varying levels of fatigue and depression, the severity of the initial infection, rather than the survivor’s current mental health, could better predict cognitive outcomes.
“These findings suggest that although fatigue and mental health are both prominent chronic illnesses [consequences] of COVID-19, its severity is likely to be somewhat independent of the cognitive deficits observed,” the researchers wrote in their paper.
The rather good news is that upon follow-up, there were some signs of recovery – but it was gradual at best.
“We’ve followed up with some patients as late as ten months after the acute injury, so we’ve been able to see very slow improvement,” Menon says.
“While this was not statistically significant, at least it goes in the right direction, but it is very likely that some of these individuals will not fully recover.”
This study only looked at the more serious end of hospital patients, but there are plenty of other studies that show that even “mild” cases can cause similar cognitive effects.
What is still not fully understood is why and how SARS-CoV-2 causes this cognitive decline.
Previous research has shown that during severe COVID infection, the brain reduces glucose consumption in the frontal parietal network, which is involved in attention, problem-solving and working memory. It is also known that the virus can directly affect the brain.
But the researchers suggest that the possible culprit is not a direct infection, but rather a combination of factors: including a lack of oxygen or the brain’s blood supply. Vascular thrombosis and microscopic bleeding.
There is also growing evidence that the body’s immune and inflammatory response may have a significant impact on the brain.
“Future work will focus on mapping these cognitive defects for underlying neurological disease and inflammatory biomarkers, and tracking recovery longitudinally in the chronic phase,” the researchers wrote.
Until then, take comfort in the fact that if you’re still feeling sluggish and foggy after months of recovering from COVID-19, you’re definitely not alone.
The search was published in Clinical Medicine.