With people already facing an uphill battle recovering from the after-effects of Covid, now a new study has shed light on its potentially deleterious impact on the brain.
A team of scientists from the University of Oxford, UK, has identified some distinct changes in the human brain, especially in the region associated with smell and memory, in people who recovered from Covid in the last two years.
The cognitive changes were noticeable in the brain scans done roughly 11 months after they were first diagnosed.
The findings come at a crucial time with scientists the world over examining the damaging effects of the pandemic and trying to understand how the disease spreads through the central nervous system. But, whether these effects could persist in the long term, or can be partially reversed, is yet to be investigated.
The study published in the journal Nature investigated the brain scans and cognitive test results of as many as 785 participants (aged 51–81 years) from the United Kingdom (UK) Biobank. People were scanned twice in a period of 3.2 years. Out of the total 785 participants, as many as 401 had tested positive for SARS-CoV-2 between their two scans, and 15 of them were hospitalised, while 384 had a mild illness. It is also one of the first large-scale observational studies that have analysed the changes in the brain, both before and after Covid-19 engulfed the world.
Scientists noticed that the grey matter thickness in the front area of the brain (orbitofrontal cortex), involved with the cognitive process of decision-making, had greatly reduced in people who suffered from Covid. They also found changes in the cortical region (parahippocampal gyrus) – which is associated with smell and memory of events.
Additionally, people who recovered from Covid-19 showed evidence of tissue damage in regions associated with the “smell-centre” of the brain (olfactory cortex) and found that the brain size had also shrunk during this period. “On average, the participants who were infected with SARS-CoV-2 also showed greater cognitive decline between their two scans, associated with shrinking of a brain region known as the cerebellum, which is linked to cognition,” found the team. Loss of smell is already a well-recognised symptom of Covid-19.
In order to be certain that the changes were indeed linked to Covid, and not any other respiratory illness, the team also analysed scans of people who recovered from pneumonia, that was not related to Covid.
Ever since the first Covid wave swept the world, there has been increased focus by the scientific and medical community on the effects of mild-to-moderate Covid-19 in the longer term. However, most such studies have been linked to hospitalised patients or those who suffered from severe illness. In this particular study, though, the scientists chose patients who were not hospitalised, recovered after a mild illness, and were relatively more common.
“The findings may indicate the degenerative spread of Covid-19, either via smelling pathways, inflammation of the nervous system, or a lack of sensory input owing to a loss of smell. Whether this deleterious impact can be partially reversed, or whether these effects will persist in the long term, will require further investigation,” said the team.
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