Scientists have revealed some of the strongest evidence yet that Covid-19 can harm our brains – particularly in areas linked to smell and memory.
But they caution that more investigation is needed to understand whether the clear pattern they found among the hundreds of UK people they studied did indeed mean long-term damage.
In one of the largest studies of its kind to date, and published today in prestigious scientific journal Nature, a team of researchers led by Oxford University's Professor Gwenaëlle Douaud analysed changes in the brains of 785 participants in the UK Biobank.People in the study had two brain scans around 38 months apart, and also underwent cognitive tests.
A total 401 participants tested positive with mostly-mild Covid-19 infection between their two scans, while the remaining 384 non-infected people were used as age and sex-matched controls for the study.
When the researchers compared those two groups over time, they found "significant, deleterious" long-term effects among those people infected with the virus: notably a reduction in grey matter thickness in regions associated with smell and memory of events.
They also observed tissue damage in regions linked to smell, while post-infected people showed larger cognitive decline than controls between scans.
"On average, the participants who were infected with Sars-CoV-2 also showed greater cognitive decline between their two scans, associated with the atrophy of a brain region known as the cerebellum, which is linked to cognition," the researchers said in a press statement.
"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."
Importantly, the documented effects were still seen after excluding the 15 people who had been hospitalised with Covid-19 – implying even mild illness may have consequences for the brain.
University of Auckland neuroscientist Professor Maurice Curtis said the shrinkage or loss of brain volume shown in the study was "significant" – exceeding a six per cent difference on average.
"Furthermore, those who demonstrated this shrinkage, performed significantly worse on executive function, visual searching and mental flexibility tests," he said.
"We know that loss of the sense of smell very early on in Covid-19 is a key sign of infection and some people never get their sense of smell back.The smell pathway and the memory pathway in the brain are connected and these are the same pathways affected in some dementias, including Alzheimer's disease."
He also pointed out the study authors' conclusion that Covid-19 caused the shrinkage - whereas being infected with the seasonal flu didn't result in such an effect.
"This study demonstrates that there is a long-term consequence to getting Covid-19 and it highlights the importance of taking all measures possible to reduce Covid-19's impact on the body and especially the brain."
Another Kiwi brain expert, Dr Indranil Basak of Otago University's Neurodegenerative and Lysosomal Diseases Laboratory, said the study findings were "very interesting, but worrying as well".
His own research team was exploring what happened to our brains - at a molecular and cellular level – when it was exposed to the virus.
"The results from our experiments will help us understand what is happening inside the cells, which could be leading to the changes in the brain that are highlighted in this study," he said.
"Our preliminary data shows some infection in brain cells, including neurons. However, we still don't know if the virus can enter these cells after crossing the blood-brain barrier, or if the symptoms we're seeing inside the cells are because of some other reason."
"We still don't know how to treat this, because no one has looked at it yet. But we do know that the virus directly, or indirectly, can affect the human brain."
Preliminary findings published recently in prestigious journal Nature, present a cautionary tale of the effects of COVID-19 on brain health. Several areas of concern that were addressed overlap with the researched beneficial effects of Ārepa products and active ingredients.
The research conducted on hundreds of subjects in the UK who contracted the virus, showed a reduction in grey matter thickness in areas of the brain including the hippocampus, affecting memory. Additionally, an increase in brain markers related to tissue damage was found, strongly suggesting an increase in neuroinflammation. Cognitive decline was also identified in those infected when compared healthy controls.
Blackcurrant anthocyanins and L-theanine in Ārepa products induce neurogenesis and have been shown to have neuroprotective effects, with the hippocampus identified as a beneficial target. Effectively this could help cell growth to compensate for those lost, or could help reduce the number of cells lost in the first place.
The brains of the infected subjects showed signs of inflammation, another mechanism potentially responsible for the damage seen and the signs of cognitive impairment. Inflammation is implicated in many disease states such as Alzheimer’s, with these researchers drawing comparisons between the brain of those affected by COVID-19 and early stage Alzheimer’s. Studies have found anthocyanins and Enzogenol can significantly reduce the induction of pro-inflammatory proteins, preventing the cell death and therefore brain shrinkage that they cause.
Cognitive decline was an area of concern identified in this recent publication. L-theanine, a constituent of Ārepa, has strong links to cognitive improvement. This in combination with the neuroprotective effects of the other active ingredients is encouraging as a proactive measure to help offset the negative effects of the COVID-19 virus.