We all know that COVID-19 can cause persistent fatigue and brain fog. But one of the most rigorous examinations to date of the long-term cognitive impacts of a serious infection has just returned some pretty disturbing results.
In a study comparing 46 patients with severe COVID-19 to 460 matched controls, researchers found that the mental impacts of severe COVID-19 six months later may be equivalent to aging 20 years (going from 50 to 70 years) or lose 10 IQ points.
The specific mental changes were also different from those seen in early dementia or general aging.
“Cognitive decline is common to a wide range of neurological disorders, including dementia and even routine aging, but the patterns we saw, the cognitive ‘fingerprint’ of COVID-19, were distinct from all of these,” says neuroscientist David Menon of the University of Cambridge in the UK, who was the study’s lead author.
The new paper is not meant to alarm many of us who have already had COVID, but rather to take a closer look at how serious cognitive changes are after severe cases of the infection, so that we can begin to understand how to mitigate them.
“Tens of thousands of people have been through intensive care with COVID-19 in England alone and many more will have been very ill, but not admitted to hospital,” says lead researcher and cognitive scientist Adam Hampshire of Imperial College London.
“This means that there are a large number of people who are still experiencing cognitive problems many months later. We urgently need to see what can be done to help these people.”
The experiment involved 46 people who had gone to Addenbrooke Hospital in Cambridge as a result of COVID-19 between March and July 2020. Sixteen of them received mechanical ventilation during their stay.
An average of six months after infection, the researchers monitored them using a testing tool called Cognitron to see how they fared in areas such as memory, attention, reasoning, as well as anxiety, depression and stress disorder. post-traumatic
The researchers did not have test results before these people became sick with COVID to compare. Instead, they did the next best thing and compared their results to a control group of 460 people.
These results were then mapped to see how far they deviated from the expected scores for their age and demographics, based on 66,008 members of the general public.
The results showed that those who had survived severe COVID were less accurate and had slower response times than the general public.
The magnitude of cognitive loss was similar to the effects of aging between ages 50 and 70, and equivalent to losing 10 IQ points.
Accuracy on verbal analogy tasks, where people are asked to find similarities between words, was most affected. This reflects anecdotal reports suggesting that post-infection people are struggling to find the right word and feel like their brain is in slow motion.
Interestingly, although patients reported varying levels of fatigue and depression, the severity of the initial infection, rather than the survivor’s current mental health, might better predict cognitive outcome, the team found.
“These results indicate that although both fatigue and mental health are prominent chronic diseases [consequences] of COVID-19, its severity is likely to be somewhat independent of observed cognitive deficits,” the researchers write in their paper.
The good news is that after follow-up, there were some signs of recovery, but it was gradual at best.
“We followed some patients up to ten months after their acute infection, so we could see very slow improvement,” says Menon.
“While this was not statistically significant, it is at least going in the right direction, but it is entirely possible that some of these people may never fully recover.”
This study only looked at the extreme end of hospitalized patients, but there are plenty of other studies showing that even “mild” cases can cause similar cognitive impacts.
What is not yet fully understood is why and how the SARS-CoV-2 virus causes this cognitive decline.
Previous research has shown that during severe COVID, the brain reduces glucose consumption in the frontoparietal 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 likely culprit is not a direct infection, but a combination of factors: including reduced oxygen or blood supply to the brain; coagulation of vessels; and microscopic hemorrhages.
There is also growing evidence that the body’s own immune and inflammatory response can have a significant impact on the brain.
“Future work will focus on mapping these cognitive deficits to underlying neural pathology and inflammatory biomarkers, and longitudinally tracking recovery to the chronic phase,” the researchers write.
Until then, take comfort in the fact that if you’re still feeling sluggish and confused months after recovering from COVID-19, you’re certainly not alone.
The research has been published in Electronic clinical medicine.