Even mild cases of Covid-19 can cause brain changes, study finds

Even mild cases of Covid-19 could lead to brain tissue damage and cognitive decline, says a study Posted in Nature Monday. But experts say larger, more specific studies are needed to confirm the findings.

Study details

For the study, researchers looked at brain changes in 785 patients aged 51 to 81 who received two brain scans as part of the UK Biobank study. Of the participants, 401 developed Covid-19 between their two brain scans.

The researchers analyzed data from brain scans, the second of which was usually around five months after infection, and compared the results to 384 similar people who had not fallen ill, as well as a ‘handful’ of people with pneumonia and flu, CBS News reports.

The researchers found that patients’ brains, on average, saw a reduction in gray matter thickness in the orbitofrontal cortex, the area of ​​the brain associated with decision-making, and the parahippocampal gyrus, the area associated with responses. emotional and behavioral.

More extensive damage was seen in brain tissue in the primary olfactory cortex, the area of ​​the brain that receives information from smells, according to the study. This makes sense since many people infected with Covid-19 have lost their sense of smell, according to Gwenaëlle Douaud, lead author of the study and associate professor at the University. Nuffield Department of Clinical Neurosciences to University of Oxford.

The 15 study participants who required hospitalization for Covid-19 showed the most brain changes, but even those with much milder disease showed differences, USA today reports.

In general, patients in the study who developed Covid-19 were found to have experienced a greater reduction in overall brain size and greater cognitive decline on average than those who did not develop the disease. Those who tested positive for Covid-19 took longer to complete a cognitive test, on average, suggesting a decline in executive function.

Douaud noted that patients in the study suffered “brain damage, but it’s possible that it’s reversible. But it’s still relatively scary because it was in mildly infected people.”

The study noted that its results were representative of averages and were not indicative of what would happen in every Covid-19 patient.

“Whether these abnormal changes are a mark of the spread of pathogenic effects, or of the virus itself in the brain, and whether these may foreshadow a future vulnerability of the limbic system in particular, the memory of which, for these participants, remains to be determined. studied,” the researchers wrote in the study.

Reaction

Some experts said the study results are concerning but require further investigation to establish cause and effect.

“To me, this is pretty compelling evidence that something is changing in the brains of this global group of people with Covid,” said Serena Spudich, head of neurological infections and global neurology at Yale School of Medicine.

However, Spudich added: “To conclude that it has long-term clinical implications for patients, I think that’s a stretch. We don’t want to scare the public into thinking, ‘Oh, that’s the evidence. that everyone is going to have brain damage and not be able to function.’”

“None of [the study participants] took enough cognitive tests to know if they had significant deficits in these many regions where they found these volume changes,” said Benedict Michael, associate professor of neurological infections at University of Liverpool. “We don’t know if this actually means anything for the patient’s quality of life or function.”

Michael warned that the study results also could not be extrapolated to younger people with brain fog or other cognitive problems after recovering from Covid-19. And because study participants only had their gray matter and tissue damage measured once after infection, “we don’t know if this is just a transient change that gets better. with recovery,” he added.

Avindra Nath, head of the nervous system infections section at the National Institute of Neurological Disorders and Strokecalled the study “exceptional” and said it could “have major implications as it is unlikely [the brain damage] will reverse on [its] own after so many months. The crucial question is whether this can lead to an acceleration of the neurodegenerative process, since the researchers also noted global atrophy.”

Nath recommended researchers observe more patients with other coronaviruses or influenza “to see if these findings are distinct for Covid-19 or more generalizable.”

“It’s an important study, they did a good job,” Michael said. “[N]Now we need to do studies to look at cognitive and psychiatric symptoms, behavioral and neurological elements and find out what this means for patients,” he added. (choi, The hill, 3/7; george, MedPage today, 3/7; Beluk, New York Times, 3/7; Tin, CBS News, 3/7; Weintraub, USA today3/7)

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