Mental fog, fatigue, shortness of breath… it is now estimated that 5 to 15% of people who have contracted the coronavirus are likely to see certain symptoms persist over time. If what is now called “Covid long” is still poorly understood, more and more research is being carried out to understand the mechanisms behind this evolution of symptoms. New Scientist reports on one of these studies published on April 28 on the cognitive damage caused by certain severe infections.
Between March and July 2020, and about six months after the initial infection, a research team from the University of Cambridge subjected forty-six patients hospitalized with Covid-19 to cognitive tests. The results were then compared with those of nearly 66,000 people from the general British population.
Scientists found hospitalized patients fared much worse “verbal analogical reasoning tests, which assess an individual’s ability to recognize relationships between ideas and to think methodically”. Their study also shed light on slower information processing in these patients.
According to their findings, people hospitalized with Covid-19 “can lose ten IQ points, the equivalent of the natural cognitive decline that occurs between the ages of 50 and 70.”
Cognitive damage with multiple causes
How to explain such significant cognitive damage? According to the research team, the reasons are multiple. A severe infection due to Covid-19 would first reduce the blood supply to the brain. “A blockage of blood vessels and microscopic bleeding caused by the SARS-CoV-2 virus, as well as damage triggered by an overactive immune system” could also be the cause of this cognitive decline.
Added to this are the findings of previous studies on long Covid which suggest that after a severe infection, glucose is used less effectively. “in the part of the brain responsible for attention, complex problem solving and memory”develops New Scientist.
“In England alone, nearly 40,000 people have been in intensive care with Covid-19 and many more have been seriously ill but have not been admitted to hospital”explains in a press release Adam Hampshire, professor of neuroscience at Imperial College London, at the origin of this new study. “That means there are a large number of people who still have cognitive problems several months later.”
The scientists point out, however, that gradual improvements have been observed in some hospitalized patients who have been subject to this kind of cognitive impairment.