Even mild Covid-19 can affect the brain

Since the start of the Covid-19 pandemic 18 months ago, several studies have been devoted to the effects of the disease on the body and the brain. There is ample evidence that a SARS-CoV-2 infection can impact the body and brain for months after infection.

Currently, scientists fear that the long-term effects of the disease may also impact certain biological processes such as aging. Jessica Bernard, associate professor at Texas A&M University, and her team are among those interested in this troubling topic. They decided to explore this area in order to better understand the process.

Among the work that caught the attention of Bernard and his colleagues was a preliminary, but large-scale, study conducted in August 2021. This study looked at changes in the brain in people who have been infected with the SARS-CoV-2. The results showed that the infection took its toll on the brain systems of those who contracted Covid-19. This results in the reduction of the thickness of the gray matter tissue in the frontal and temporal lobes.

Brain changes seen in people already infected with SARS-CoV-2

During their research, the scientists behind the study used the UK Biobank database which contains brain imaging data from over 45,000 people in the UK, collected since 2014, that is – say several years before the pandemic. Among these people, those who were infected with SARS-CoV-2 were called back for additional brain tests. The results of their analyzes were then compared with those of other participants who never caught Covid-19.

Between the two groups, differences were observed in the level of gray matter which is made up of the cell bodies of neurons processing information in the brain. The researchers noticed a reduction in the thickness of the gray matter of people who contracted Covid-19 in the regions of the brain which are the frontal lobes and temporal lobes, compared to the group who never had to deal with the Covid -19.

According to the explanations, a change in the volume or thickness of gray matter is generally normal as one gets older. However, scientists reported that the changes seen in people who were infected with SARS-CoV-2 were larger than normal.

It also turns out that the loss of brain volume is the same for people who have had severe symptoms requiring hospitalization as it is for those who have only mild symptoms. When it comes to cognitive tasks, those who contracted Covid-19 were slower to process information, compared to those who were never infected.

The importance of the study results

Loss of taste and smell are the most common symptoms in patients with Covid-19 around the onset of the pandemic. According to researchers from the United Kingdom, all regions of the brain affected by Covid-19, such as the temporal lobe, are linked to the olfactory bulb, responsible for the transmission of olfactory signals from the nose to the brain.

The changes observed in the temporal lobe in people who have been infected with Covid-19 are particularly interesting since this part of the brain is known to be involved in the processes of aging and the onset of Alzheimer’s disease. The temporal lobe indeed contains the hippocampus which is involved in memorization and cognitive processes, thus playing a key role in aging. On the other hand, research on Alzheimer’s disease has shown that people at risk have a reduced sense of smell.

According to scientists, studying the possible links between changes in the brain due to Covid-19 and memory is of great interest, given that the regions involved play an important role in memorization and the appearance of Alzheimer’s disease.

Bernard explained that as a person ages, even without disabilities or illnesses, old age always brings about changes in the way they think and move. In the context of Covid-19, studies of brain aging will help to understand how well the brain can recover from disease.