Cognitive impairment caused by severe Covid-19 can be compared to the decline that occurs between the ages of 50 and 70, according to a recent study by the University of Cambridge and Imperial College London.
The researchers said the decline was equivalent to losing 10 IQ points. The findings, published earlier this month, were the latest in a series of studies suggesting that Covid-19 has an effect on the brain.
The lasting impact of Covid-19 on the millions who contracted it is still being assessed more than two years into the pandemic, with few areas of uncertainty as urgent and worrisome as the possible lasting effects on the brain.
Scientists are examining the exact mechanisms that cause neurological effects and whether symptoms will prove temporary, or the heaviest health burdens may still lie in the future.
What are the most surprising findings about the effect of Covid-19 on the brain?
Amid a growing body of anecdotal evidence, Alzheimer’s Disease International, a federation of dementia societies, suggested in September that the degenerative effect of the coronavirus could be fueling a “dementia pandemic”. The World Health Organization estimates that the number of people with dementia, which currently stands at about 55 million, will rise to about 80 million by 2030 as the aging population grows.
A study by Oxford University researchers and published in March found tissue damage and shrinkage of parts of the brain linked to smell in people who had mild episodes of Covid-19. The researchers, who analyzed nearly 800 brain scans from the UK Biobank – one of the world’s largest biomedical databases – found a reduction in whole brain volume compared to unaffected people and, on average, greater cognitive decline.
The loss of smell, which people began noticing in the early days of the epidemic, may be caused by damage to the olfactory nerve that runs to the brain and transmits this function, according to a study published in Gamma Neurology Last month.
How concerned are the experts?
Andrew Josephson, MD, Department of Neurology at the University of California, San Francisco, and Editor-in-Chief Gamma NeurologyPeople with mild COVID-19 described symptoms, such as mental fatigue, that may be brain related, he said. “We’re seeing more and more studies showing changes in the brain that may be related to it,” he said.
Difficulties with memory, language, and concentration are among the wide range of symptoms that fall under the long term “Covid-19.” Medical experts define it as having symptoms for 12 weeks or more after being diagnosed with Covid-19, and experts have estimated that it affects more than 100 million people.
But other experts point out that the apparently worrisome findings may not be as worrisome as they first appeared.
“The majority of patients we see clinically have . . . a disturbance in concentration and the ability to direct your thinking,” said Alan Carson, a consultant neuropsychiatrist at the University of Edinburgh. “It is very disturbing, but it is not a permanent neurodegenerative condition – it is treatable.”
It’s not clear the extent of the Covid-specific brain changes, nor their significance, said Serena Spodich, a professor of neuroscience at Yale University School of Medicine. “People might lose some gray matter and it might have a bit of real meaning,” she said.
What is the ongoing research to find out more?
Research into the relationship between Covid-19 and dementia is in its early stages. The scientists said it was theoretically possible for the disease to affect the brain in a similar way to some other viruses.
A 2020 US study found that people with HIV had a 50 percent higher risk of developing dementia. If SARS-Covid-2 “travels along brain pathways in a similar way to HIV, Covid infection potentially increases the risk of Alzheimer’s disease,” explained Dennis Chan, who is leading a study on cognitive impairment in long Covid funded by the National Institutes of Health. British Health and Welfare Research.
Other scientists said that the belief that the virus could be transmitted to the broader central nervous system via the olfactory nerve now appears to be wrong. “It has proven to be very difficult to infect the brain with coronavirus,” Carson said.
Josephson said the researchers were analyzing spinal fluid samples from living patients for “unusual antibodies or inflammatory cells” that could shed new light on the long-term Covid disease.
Experts suggested that the disappointing precedents of history have not yet been repeated.
Doctors fear that the epidemic “may be associated with Parkinson’s disease encephalitis that was described after the Spanish flu,” said Anna Cervantes-Arslanian, a neurologist at Boston University School of Medicine.
But the study she led found only 0.5 percent of people with severe Covid-19 had meningitis or encephalitis. About 10 percent change the functions or structure of the brain, according to research published in April in the journal Critical Care Explorations.
Are new treatments being developed?
Researchers led by Chan are using MRI scans to understand the causes of Covid’s effects on memory, thinking speed, and decision-making. He said his team will also test cognitive rehabilitation techniques used to treat memory problems after stroke, such as setting tasks to increase mental focus.
Other scientists are investigating the possibility of new drug treatments. Studies are underway to examine changes in tissues and organs that cause or are caused by Covid-19 in order to try treatments.
It is not yet clear whether the effects on the brain are due to an overactive immune system, or the other way around, Josephson said. However, he said, if this cannot be demonstrated quickly, it may be best to proceed with a trial of drugs that modulate the immune system, either by decreasing or strengthening it, to help those whose symptoms suggest cognitive impairment.
But separating the impact of Covid from other elements that are indirectly related to the virus remains a mystery in progress for researchers.
“The effects of Covid on the brain are real — some people have very specific and distinct conditions and others have things that we don’t understand very well,” Spuditch said. “The problem is that there are many other social factors, stresses, stresses associated with these pandemic times that are definitely muddying the waters.”