A new study returns to address the long Covid and the consequences of an infection that has also given rise to a disease with moderate symptoms. The survey, published on Nature and among the largest on the subject, he found that the brains of those who have had Covid-19 have suffered one more pronounced loss of gray matter and more performance issues than those who have never developed Sars-CoV-2 syndrome. Unsurprisingly, many of these changes have been spotted in the related area of ​​the brain sense of smell.
“We were quite surprised to see clear differences in the brain even with a mild infection,” she explained Cnn the main author Gwenaëlle Douaud, associate professor of neuroscience in the Nuffield Department of the University of Oxford. She and her team evaluated the brain images of 401 people who had Covid between March 2020 and April 2021, so over a much longer period than other investigations that stopped at the first wave of the pandemic. The comparison was made before the infection and approx four and a half months later. They then compared the results with brain imaging of 384 uninfected people similar in age, socioeconomic status, and risk factors such as blood pressure and obesity. Of the 401 infected people, 15 had been hospitalized. The 785 participants were aged between 51 and 81 and their data were registered on the British Biobank, the research database launched in 2012 by the British government and containing information from 500,000 people.
The author explained that it is normal for people to lose 0.2% to 0.3% gray matter each year in areas of the brain related to memory precisely because of aging. However in the study assessment people who had been infected with the coronavirus they lost a further percentage ranging from 0.2% to 2% of the tissue compared to those who had not been infected.
In addition to imaging the participants were tested in theirs executive and cognitive skills leveraging the Trail Making Test, a tool used to help detect cognitive impairments associated with dementia and analyze a person’s brain processing speed and function. The researchers found that those who had the greatest loss of brain tissue, again unsurprisingly, also scored worst on this test. This is despite the fact that the most affected areas of the brain seem to be related to the olfactory system and this connection has yet to be proved.
“Since the abnormal changes we see in the brains of infected participants could be partly related to their loss of smell, it is possible that recovery could lead to a balance over time,” Douaud added. the harmful effects of the virus, direct or indirect via inflammatory or immune reactions, diminish over time after infection. The best way to find out would be to scan these participants again in a year or two. ‘
The underlying problem remains: if it is true that the investigation has uncovered some association between infection and brain function, the reason or the causal link is not yet clear. Previous studies have shown that people with significant and repeated loss of smell also have an associated loss of gray matter. However, the study in question did not assess whether people actually experienced a loss of smell among the symptoms of Covid-19. In conclusion, the researchers cautioned that the findings crystallize brain state at a given time but also noted that ‘they raise the possibility that the long-term consequences of Sars-CoV-2 infection may contribute to developing the disease over time. Alzheimer’s or other forms of dementia ».
The skeptics
The findings are significant but not enough to cause alarm, he commented Cnn Richard Isaacson, neurologist and director of the Florida Atlantic University Center for Brain Health. Isaacson was not involved in the study. In his opinion, the overall impact on individuals is difficult to determine and could be contained. “It is really difficult to know the long-term clinical impact and impact on quality of life in a situation like this.” While second Alan Carsonprofessor of neuropsychiatry at the Center for Clinical Brain Sciences at the University of Edinburgh, also not involved in the study, “the brain can be influenced by other mechanisms such as immune, inflammatory, vascular, or psychological / behavioral change, but not from direct infection. What this study almost certainly shows is that the impact in terms of neural changes exists. But I don’t think it helps us to understand the mechanisms underlying the mutations in cognitive performance after Covid infection “.
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Source: Vanity Fair

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