A brain imaging study by scientists at Oxford University shows that the SARS-CoV-2 virus can cause changes in the functions as well as size of the brain even in people who suffered only from mild infections.
The UK biobank study only focused on patients between the ages of 51-81. It was also conducted in UK when the alpha variant was the most dominant variant of the virus in the country. The effect of the consequent variants on brain function, the researchers said, needs to be further investigated. The data was taken from the biobank which is an extensive database providing genetic and health information.
This is not the first time that changes in the brain function and structure have been linked to COVID-19. Several infected people have complained about long term COVID effects that speak about being distracted, not being able to concentrate, and continuously feeling lethargic.
Published in the science journal Nature, the study involved 748 participants who had gotten their brains scanned/imaged twice. Of these 745, around 401 participants were infected by the virus between the two scans while close to 348 acted as controls. The study also had 15 patients that were hospitalised in the interim period between the two scans. Interestingly, the results of the hospitalised patients and those who suffered mild infections were really similar.
The study comes at a time when the world is witnessing a reduction in the number of COVID-19 cases.
Which Areas Of The Brain Were Affected?
The results showed that the size of the brain among the participants who were infected witnessed shrinking by at least 0.2 to 2%. It was also seen that the control group had participants who were older than the participants who tested positive.
Along with the brain size shrinking, the researchers also found that the grey matter - that processes different information in the brain- was thinner in the areas controlling smell, memory, and even decision making. The brain images also showed that the people who were infected by SARS-CoV-2 had higher tissue damage in the region that controls smell in the body. This anosmia (complete loss of smell) which is a stark symptom of COVID-19 could have further damaged the olfactory cortex (controlling the sense of smell), and also could have had reactions which could have inflamed the nerves that carry signals of smell.
The researchers also decided to gauge whether the cognitive abilities of the COVID-19 positive group witnessed any changes due to the infection. The brain imaging scans, with a difference of over three years between the two scans, showed that there was cognitive decline among the patients. Patients took longer to solve numeric and alphanumeric trails than their older counterparts who were not infected.
While this data is only till May 2021, the researchers also found that most of the 401 patients had been infected by the alpha variant. Research is required to establish how the Delta and Omicron variants affect brain shape and cognitive functions.
The researchers said they did not have enough information on the vaccination status of the participants.
Are These Changes Reversible?
The researchers added that there needs to be continuous, longitudinal (across time with the same people) research to assess whether these changes are reversible. They also added that follow up is also important to know if these changes leave a long-term impact.
According to neurology, our brain is considered to be plastic, which means that it is continuously changing and forming new connections amongst neurons. This leads to the formation of new signals over time and helps the brain develop as well as recover from any injury.