Infected persons with Covid-19 may have higher grey matter loss and tissue damage in the brain than those who are not infected with the virus, according to the findings of a big new research published in Neurology.
The research, which was published on Monday in the journal Nature, is thought to be the first to include participants who had brain scans done both before and after contracting Covid, according to the authors. Researchers who were not involved in the study praised it as valuable and innovative, but they cautioned that the implications of the changes were unclear and did not necessarily indicate that people would suffer long-term consequences or that the changes would have a significant impact on thinking, memory, or other functions.
The study, which included 81 participants ranging in age from 51 to 81, discovered shrinkage and tissue damage largely in brain regions associated with the sense of smell; some of these areas are also associated with other brain functions, according to the researchers.
UK Biobank, a collection of medical and other data from around half a million individuals in the United Kingdom, was the setting for the research, which included 785 participants. In addition to standard cognitive tests, the individuals each got two brain scans that were about three years apart. The coronavirus was detected in 401 of the participants in the period between their two scans, who were all infected between March 2020 and April 2021.
The other 384 individuals served as a control group since they had not been exposed to the coronavirus and had many characteristics with the infected patients, such as age, gender, medical history, and socioeconomic position.
Each year, adults lose a little portion of their grey matter as a result of natural ageing. It has been shown that in areas associated with memory, the normal yearly loss is between 0.2 percent and 0.3 percent, according to the researchers.
In this research, the effects may have been especially noticeable since the subjects were largely persons who, like the vast majority of Covid patients in the general community, were only minimally affected by their first Covid infection, and did not get ill enough to need hospitalisation.
Despite the fact that the study’s sample size of 15 hospitalised patients was too small to provide conclusive results, the lead author, Gwenalle Douaud, a professor in the department of clinical neurosciences at the University of Oxford, stated that their brain atrophy appeared to be worse than that of the mildly afflicted patients.
Persons who had Covid also exhibited higher decrease on a cognitive test that measured their ability to pay attention and work efficiently while doing a challenging job than people who were not sick. According to Dr. Douaud and other observers, the cognitive testing in the research was basic, and the findings are restricted in terms of determining if the grey matter loss and tissue damage that the Covid patients experienced impaired their cognitive abilities.
For example, despite the fact that some of the most significant grey matter loss occurred in regions associated with scent, such as the orbitofrontal cortex and parahippocampal gyrus, same areas are also engaged in memory and other cognitive tasks. However, Dr. Douaud said that the Covid patients did not do worse on memory tests than noninfected volunteers, despite the fact that the memory tests they conducted were quick and rudimentary.
The trail-making exam, which is a form of connect-the-dots activity that involves alternating letters and numbers, was the primary cognitive measure in which Covid patients had a deficiency. Patients with Covid took slower to finish the test, which might indicate difficulties with concentration, processing speed, and other abilities.
Dr. Michael emphasised that the results could not be generalised to the large number of younger individuals who are having post-Covid brain fog and other cognitive difficulties as a result of their treatment. Furthermore, since grey matter and tissue damage were only examined at one point in time after infection, “we don’t know whether it’s simply a temporary shift that gets better with recovery,” he said.
According to outside specialists and the study’s authors, the wide variety of brain locations in which Covid patients see more grey matter loss raises fascinating issues about how the disease affects the brain.
The exact cause of the brain alterations is yet unknown. The authors highlighted possibilities such as inflammation, which has been seen in previous research, and “sensory deprivation” caused by a disordered sense of smell, which has also been demonstrated in other investigations.
Doctor Avindra Nath of the National Institute of Neurological Disorders and Stroke, who was not involved in the research, said another “important concern” was whether the brain alterations in Covid patients made them more susceptible to dementia or other problems in the future.
Furthermore, although the researchers did not see the same brain abnormalities in individuals who did not have Covid pneumonia, Dr. Nath urged that researchers look into patients who had other coronaviruses or the flu “to investigate whether these results are specific to Covid-19 or more generalizable.”
As a result, Dr. Spudich believes that the study’s greatest usefulness may be its suggestion that “something has changed in the brains of these individuals,” noting that “many have felt that it is so ambiguous, so difficult to assess.”