The findings represent striking evidence of the effect of the virus on the central nervous system.
Even a mild case of COVID-19 can cause damage to the brain and extra thinking, scientists have found in a study that highlights the disease’s alarming effect on mental function.
Researchers identified brain damage associated with COVID months after infection, including areas associated with smell and shrinking in size equivalent to a decade of normal aging. The changes were linked to cognitive decline in the study, which was published Monday in the journal Nature.
The findings represent striking evidence of the effect of the virus on the central nervous system. More research will be needed to understand whether evidence from the Wellcome Center for Integrative Neuroimaging at the University of Oxford means that COVID-19 will increase the global burden of dementia – which cost an estimated $1.3 trillion the year the pandemic began. – and other neurodegenerative conditions.
“This is a very novel study with conclusive data,” said Avindra Nath, clinical director of the US National Institute of Neurological Disorders and Stroke, who was not involved in the research. “The findings are very interesting with important implications for the population at large.”
The SARS-CoV-2 virus is widely considered to be a respiratory pathogen that attacks the lungs. Taking a narrow view of it, however, misses the myriad neurological complications – including confusion, stroke and neuromuscular disorders – that appear during the acute phase of the disease. Other effects such as impaired concentration, headache, sensory disturbances, depression, and even psychosis can persist for months, as a group of symptoms known as long covids.
To examine the changes in the brain, neuroscientist Gwynelle Doud and her colleagues took advantage of the world’s largest magnetic resonance imaging database. Preliminary MRI scans of the brains of 785 volunteers were taken before the pandemic began as part of UK Biobank research, which marries massive genomic and detailed clinical data for half a million people.
A subsequent scan was taken an average of 38 months later. Till then, 401 participants had tested positive for COVID. The uninfected remainder served as a control group that was similar to the survivors in several risk factors, including age, sex and blood pressure, obesity, smoking, socioeconomic status and diabetes. The study participants, aged 51 to 81, were mostly Caucasian.
‘Quite surprised’
“We were quite surprised to see how the brain had changed in the participants who were infected,” Doud said in an interview. Whether the effect persists, or may be partially reversed as the neuronal network is repaired, requires further investigation, she said. “The brain is ‘plastic’ and can heal itself.”
In those infected an average of 4.5 months before their second scan, the researchers found a greater reduction in gray matter thickness in areas of the brain associated with smell, known as the orbitofrontal cortex, and the parahippocampal gyrus. This finding may help explain the impaired olfaction experienced by many COVID patients, either as a result of direct viral damage or inflammation resulting from the body’s immune response to the virus.
The loss of gray matter, which makes up the outermost layer of the brain, represents degeneration, said Leah Beauchamp, a neuropharmacologist at the Florey Institute of Neuroscience and Mental Health in Melbourne. “It’s really worrying,” she said.
The infected group displayed a 0.2% to 2% greater reduction in brain size than those who had not been infected and showed greater cognitive decline depending on the complex tasks they performed. It was associated with atrophy, or shrinkage, in a specific part of the cerebellum—the area at the back and bottom of the brain—linked to cognition. The difference between infected and non-infected participants was more pronounced in older people.
‘Identify the system’
“What is going to be appropriate now is to identify the mechanisms that are leading to this degeneration in the acute phase of the disease so that we can try to intervene,” Beauchamp said.
of neurology at the Yale School of Medicine in New Haven, Connecticut, Gilbert H. Glaser Professor Serena Spudich, said studies of blood and central nervous system samples from patients are needed to determine the extent to which these brain changes result.
Recent research has revealed the plasticity of the brain’s connectivity and structure, he said. He said the findings suggest that there may be renewal of damaged neuronal pathways that may eventually lead to a full recovery for affected patients.
“We are fortunate to have an extremely flexible mind that can work with many potential insults without harm,” she said in an email. “Hopefully, these neuroimaging findings are similar to some clinical outcomes in most people who are infected with SARS-CoV-2.”
The study participants were not selected because they were experiencing symptoms of COVID for a long time. It is possible that some of the findings were accidental and had no effect. Still, both Nath and Beauchamp said it would be important to identify whether long-term covid symptoms are related to brain abnormalities or results of some other pathology test.
subtle changes
Doud said the size of the change in individual scans was “subtle” and not visible to the naked eye. A 0.2% reduction in gray matter represents about one year of normal aging in an older person’s brain. A decrease of 2% represents a mean age of approximately 10 years.
Almost all infected participants recovered at home, which suggests that the findings may be relevant to most COVID survivors worldwide. Doud said that among the 15 people who were hospitalized for Covid, there were signs of an even stronger and more widely distributed effect in the brain.
Research supports growing evidence that brain-based changes can occur after SARS-CoV-2 infection, even in people who did not require hospitalization, says Joanna Helmuth, a neurologist and assistant professor in Memory of the University of California, San Francisco. Aging Center. “Future research efforts may help us understand whether these brain changes are clinically relevant, and if they are associated with specific neurological issues after COVID,” she said.
(Except for the title, this story has not been edited by NDTV staff and is published from a syndicated feed.)