Brain scans from almost 800 UK Biobank participants reveal damage in ‘smell centre’ – but it’s likely that the brain can heal itself.
Summary
COVID-19 infections – even mild ones – seem to slightly shrink the brain, particularly parts responsible for smell and memory. Researchers looked at brain scans from around 400 UK Biobank participants who had been scanned before and after they contracted COVID-19. They compared them with scans from 400 participants who had not caught the virus. Brain health experts stress that the brain can heal itself, so people don’t necessarily experience lasting changes.
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.
Dr Gwenaëlle Douaud, University of Oxford, UK
COVID-19 infections seem to slightly shrink the brain, particularly the regions linked to smell and memory. A study of almost 800 UK Biobank participants also revealed that those who had COVID-19 scored slightly lower in cognitive tests.
But this doesn’t mean COVID-19 causes lasting brain damage. “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,” the study’s lead researcher Gwenaëlle Douaud explains in BBC News.
The researchers compared the brain scans from UK Biobank participants who had been scanned twice – half had tested positive for COVID-19 a few months before the second scan. Most people had only mild infections with very few requiring a hospital visit.
To disentangle normal changes over time from those related to COVID-19 infections, it was essential that all of UK Biobank’s imaging centres had identical magnetic resonance imaging machines and methods for using them, explains brain health scientist Randy Gollub in a Nature comment about the study.
No memory loss
These sorts of changes are seen after many forms of disease onslaught, and even that of healthy ageing. The key difference shown here is that they appear to be happening faster than with ageing alone.
Dr Rebecca Dewey, University of Nottingham, UK
The brains of people who had COVID-19 lost 0.2% to 2% more volume than the brains of people who had not had not been ill, or who had pneumonia or flu. For context, as we age, our brains’ memory regions naturally shrink by up to 0.3% every year. “To me, this is pretty convincing evidence that something changes in brains of this overall group of people with COVID-19,” brain scientist Serena Spudich tells the New York Times.
Spudich and others note that this doesn’t necessarily mean that people have profound or lasting memory or other problems. “These sorts of changes are seen after many forms of disease onslaught, and even that of healthy ageing. The key difference shown here is that they appear to be happening faster than with ageing alone,” brain imaging specialist Rebecca Dewey tells the Science Media Centre.