- Rebecca Nightshade
- Scientific Correspondent, BBC
Being infected with covid-19 can lead to changes in the brain, according to a study published in the journal Nature.
The researchers found significant differences in MRI scans performed before and after infection.
Even after a mild infection, the images showed that the overall size of the brain had decreased slightly, with less gray matter in regions related to smell and memory.
It’s unclear whether these changes are permanent, say the researchers, who point out that the brain has the ability to recover.
“We looked at a mostly mild infection, and the surprise was that there really were differences in the brain and that it had changed a lot compared to people who hadn’t been infected,” said Gwenaelle Douaud, lead author of the study and a professor at the Wellcome Institute Center for Integrative Neuroimaging. from the University of Oxford.
The UK Biobank project has tracked the health of 500,000 people for about 15 years and has a database of exams recorded before the pandemic. This provided a unique opportunity to study the long-term health impact of the virus.
The researchers performed a new scan:
- 401 participants, 4.5 months on average after infection. 96% with mild covid
- 384 participants who did not have covid
- The overall brain size of infected participants was reduced by 0.2-2%
- There were gray matter losses in olfactory areas, related to smell, and in areas related to memory.
- People who recently recovered from Covid had a little more difficulty performing complex mental tasks
Researchers still don’t know whether these changes are reversible or really important for health and well-being.
“You have to keep in mind that the brain is really plastic – meaning it can heal itself – and so there’s a good chance that over time the adverse effects of infections will wear off,” Douaud said.
The greatest loss of gray matter is in the olfactory areas, but it is unclear whether the virus directly attacks this region or if the cells simply die from lack of use, after people with covid have lost their sense of smell.
It is also unclear whether all variants of the virus cause this damage.
Scans were performed when the parent virus and alpha variant were prevalent and loss of smell and taste was a primary symptom.
However, now that the omicron variant is prevalent, both symptoms have been greatly reduced.
“Your mind is what you exercise”
Paula Totaro lost her taste and smell when she contracted covid in March 2020.
“When I lost them, it was like living in a bubble or in a vacuum, I found it made me feel really isolated,” she told BBC News.
But after contacting the nonprofit AbScent, which supports people who have lost their sense of smell and taste, she tried to practice.
“What smell training does, especially if you do it twice a day, regularly and religiously, is force you to come into contact with the smell, let it come back to your nose, and then think about how it feels.”
“And that connection between what’s in the outside world and what’s going into your brain and your mind is what’s being exercised.”
Totaro has now regained most of his sense of smell, although he still struggles to identify the different smells.
“It’s a mixture of joy that the sense of smell has returned, but I still feel a little anxious about the lack.”
In the opinion of Naomi Allen, Scientific Director of Biobank UK, the study “raises all sorts of questions that other researchers can investigate further about the effect of coronavirus infection on cognitive function, brain fog and other areas of the brain, to really focus research on how best to mitigate this.”
David Werring, a professor at the Institute of Neurology at University College London, said that other health-related behaviors may have contributed to the observed changes.
“Changes in cognitive function were also subtle and of unclear relevance to daily function,” he said.
“And these changes are not necessarily seen in all infected people and may not be relevant to newer strains.”