Long Covid victim discusses daily impact of virus
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The effects were seen even in people who had suffered only mild illness that did not require hospital treatment. Lead author Prof Gwenaelle Douaud, from the Wellcome Centre for Integrative Neuroimaging, at the University of Oxford, said: “We were looking at essentially mild infection, so to see that we could really see some differences in their brain and how much their brain had changed compared with those who had not been infected was quite a surprise.”
The study, published in the journal Nature, involved 785 people enrolled in the UK Biobank who had two brain scans an average of three years apart and underwent cognitive tests.
Between the two scans, 401 participants tested positive for Covid and 15 were hospitalised. The rest were used for comparison.
Researchers found that in those who had been infected, overall brain size shrunk by between 0.2 and 2 percent.
There was evidence of a reduction in grey matter thickness in the orbitofrontal cortex and parahippocampal gyrus – regions associated with smell and memory of events.
Those who had been infected also showed more signs of cognitive decline in the mental tests.
The team also performed an analysis on people who developed pneumonia that was not related to Covid-19 and found that the changes were specific to infection with coronavirus, rather than generic effects linked to respiratory illness.
Experts said further investigation was needed to determine whether the effects may be long-lasting or whether they can be reversed.
Prof Douaud said: “We need to bear in mind that the brain is really plastic – by that we mean it can heal itself – so there is a really good chance that, over time, the harmful effects of infection will ease.”
Meanwhile, a separate study involving more than 57,000 people has identified differences in DNA that may explain why some people become more severely ill if they catch coronavirus.
It identified 16 new genetic variants – differences in DNA – associated with severe Covid-19, including some related to blood clotting, immune response and inflammation.
Professor Kenneth Baillie, chief investigator and a consultant in critical care medicine at University of Edinburgh, said: “Our latest findings point to specific molecular targets in critical Covid-19.
“These results explain why some people develop life-threatening Covid-19, while others get no symptoms at all.
“But more importantly, this gives us a deep understanding of the process of disease and is a big step forward in finding more effective treatments.
“It is now true to say that we understand the mechanisms of Covid better than the other syndromes we treat in intensive care in normal times – sepsis, flu, and other forms of critical illness. Covid-19 is showing us the way to tackle those problems in the future.”
Professor Sir Mark Caulfield from Queen Mary University of London, formerly chief scientist at Genomics England and co-author on the study, said: “We’ve discovered novel gene variants that predispose people to severe illness – which now offer a route to new tests and treatments, to help protect the public and the NHS from this virus.”
The findings were also published in the Nature journal.
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