Covid can cause brain shrinkage, study finds

Scientists say damage primarily affects brain tissue linked to memory and smell

Covid-19 can cause brain shrinkage and tissue damage, with some patients experiencing three times the brain degeneration of those who didn’t catch the virus, according to a University of Oxford study published on Monday. 

The study involved 785 UK participants aged between 51 and 81, all of whom had two brain scans roughly three years apart. 401 of these participants were infected with the ‘Alpha’ variant of Covid-19, and received their second brain scan around four months after their diagnosis.

These Covid patients experienced an average loss of 0.7% of brain volume in areas related to smell compared to those who didn’t catch the virus. On average, these areas shrink by 0.2% to 0.3% per year in middle aged and elderly people respectively, meaning those with Covid-19 may have experienced three times the normal rate of brain degeneration.

Those who had Covid-19 also took longer to complete cognitive tests, while the small number of patients in the study who were hospitalized experienced a greater reduction in gray matter and more pronounced cognitive decline.

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Damage was noted in the orbitofrontal cortex and parahippocampal gyrus - two regions of the brain that play key roles in memory coding and retrieval - of Covid patients, and a global reduction in brain volume was also recorded.

These findings could corroborate anecdotal evidence of lingering ‘brain fog’ after infection, but they do not suggest that this damage is permanent. Likewise scientists have cautioned that it is still unclear whether damage to these memory-encoding regions of the brain actually resulted in a real-world loss of memory.

“None of them got thorough enough cognitive testing to know if they had significant deficits in these many regions where they found these changes in volume,” Dr. Benedict Michael, an associate professor of neurological infections at the University of Liverpool, told the New York Times. “We don’t know that it actually means anything for the patient’s quality of life or function.”

“It’s an important study, they’ve done good work,” Dr. Michael continued, adding: “now we need to do the studies to look at cognition and psychiatric symptoms and behavioral stuff and neurological stuff and find out what does this mean for patients.”