“I was very surprised that even a mild infection made a clear difference in the brain,” Gwenaëlle Douaud, an associate professor of neuroscience at Oxford University, told CNN in an email.
Douaud and her colleagues evaluated brain images of 401 people infected with Covid-19 between March 2020 and April 2021 both before and on average 4.5 months after infection. They compared the results with brain images of 384 uninfected individuals with similar risk factors such as age, socioeconomics, blood pressure and obesity. Of the 401 infected, 15 were hospitalized.
The 785 participants were 51 to 81 years old, all part of UK Biobank. This is an ongoing government health database of 500,000 UK participants launched in 2012.
Douaud explained that it is normal for people to lose 0.2% to 0.3% of gray matter each year in memory-related areas of the brain with age, but research evaluations show that patients infected with the coronavirus are more infected. 0.2% to 2% of the organization compared to those who do not.
In addition to imaging, participants use the trail making test, a tool that helps detect dementia-related cognitive impairment and test the speed and function of the human brain, for executive function and cognitive function. Was also tested. The authors found that those with the highest loss of brain tissue also performed the worst in this trial.
The most affected areas of the brain appear to be related to the sensory system, but Douaud said it is not clear why that is the case.
“The abnormal changes seen in the infected participants’ brains may be partly related to their loss of odor, so upon recovery, these brain abnormalities became noticeable over time. Similarly, the proportion of the virus (directly or indirectly via an inflammatory or immune response) has a detrimental effect that decreases over time after infection, which is best to investigate. The way is to scan these participants again after a year or two, “she said.
Douaud added that researchers expect participants to be reimaged and tested in a year or two.
Greater effects of brain changes
This study finds some link between infection and brain function, but the reason is not yet clear. Previous studies have shown that people with marked loss of odor and repeated odors are also associated with loss of gray matter. However, this study does not assess whether patients actually experienced odor loss.
The authors warned that the findings were only momentary, but said that “the long-term consequences of SARS-CoV-2 infection will eventually increase the likelihood of contributing to Alzheimer’s disease or other forms of dementia.” ..
Dr. Richard Isaacson, a neurologist and director of the Florida Atlantic University Brain Health Center, said the finding was remarkable, but not enough to arouse alertness. Isaacson was not involved in the study.
Isaacson said the findings were noteworthy for clinicians, but added that it was difficult to determine the overall impact on an individual and could be small. “It’s really hard to know the long-term clinical and quality of life effects of this situation,” he said.
“The brain can be affected by other mechanisms such as immunity, inflammation, blood vessels, and psychological / behavioral changes, but direct infections are unaffected,” said the University of Edinburgh Center for Clinical Brain Science. Dr. Alan Carson, a professor of psychiatry, said. Those who were not involved in the study.
“This study almost certainly shows the impact in terms of neural changes,” he said. “But I don’t think it helps to understand the mechanisms that underpin the changes in cognitive function after Covid infection.”