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COVID-19, the brain and aging are now interconnected, scientists say.

Researchers are constantly gathering important information about the effects of COVID-19 on the body and brain. Two years after the pandemic, these findings raise concerns about the long-term effects of the coronavirus on biological processes such as aging.

As a cognitive neurologisti focused on my past research on understanding how normal brain changes associated with aging affect people’s ability to think and move – especially in middle age and beyond.

But there is evidence that COVID-19 can affect the body and brain for several months after infection, my research team has shifted some of its focus to a better understanding of how disease can affect the natural aging process. This was largely motivated by new new work from the United Kingdom investigating the effects of COVID-19 on the human brain.

Looking at the brain’s response to COVID-19

In a large study published in the journal Nature on March 7, 2022, a team of researchers from the UK investigated brain changes in people aged 51 to 81 years who underwent COVID-19. This work provides new important insights into the effects of COVID-19 on the human brain.

In the study, the researchers relied on a database called Biobank of Great Britaincontaining brain imaging data from more than 45,000 people in the UK going back to 2014. This means that there were source data and brain images of all these people before the pandemic.

The study group compared people who had COVID-19 with those who did not, carefully selecting groups based on age, gender, baseline test date and study location, and common disease risk factors such as health and socioeconomic variables. status. .

The team found noticeable differences in gray matter – or neurons that process information in the brain – between those who were infected with COVID-19 and those who were not. In particular, the thickness of the gray matter tissue in areas of the brain known as the frontal and temporal lobes was reduced in the COVID-19 group, which differs from the typical patterns observed in people who did not have COVID-19 infection.

In the general population it is normal to observe some changes in the volume or thickness of gray matter over time as people age. But the changes were broader than usual in those infected with COVID-19.

Interestingly, when the researchers separated individuals who were ill severely enough to require hospitalization, the results were the same as for those who underwent milder COVID-19. That is, people who were infected with COVID-19 showed loss of brain volume, even if the disease was not severe enough to require hospitalization.

Finally, the researchers also investigated changes in the performance of cognitive tasks and found that those infected with COVID-19 processed information more slowly than those who did not. This processing ability correlated with volume in an area of ​​the brain known as the cerebellum, indicating an association between brain tissue volume and cognitive ability in patients with COVID-19.

This study is particularly valuable and insightful because of the large sample size both before and after the disease in the same people, as well as its careful selection with people who did not have COVID-19.

What do these changes in brain volume mean?

At the beginning of the pandemic, one of the most common reports from those infected with COVID-19 was loss of sense of taste and smell.

Surprisingly, areas of the brain that researchers from the UK have found to be affected by COVID-19 are all related to the olfactory bulb, a structure near the front of the brain that transmits odor signals from the nose to other areas of the brain. The olfactory bulb has connections to areas of the temporal lobe. Researchers often talk about the temporal lobe in the context of aging and Alzheimer’s disease because it where the hippocampus is located. The hippocampus probably plays a key role in the aging process, given its involvement in memory and cognitive processes.

Smell is also important for the study of Alzheimer’s disease, as some evidence suggests that people at risk for the disease have a reduced sense of smell. Although it is too early to draw conclusions about the long-term effects of COVID on the sense of smell, research into possible links between brain changes associated with COVID-19 and memory is of great interest – especially given regions and their importance in memory and Alzheimer’s disease.

The study also highlights the potentially important role of the cerebellum, an area of ​​the brain involved in cognitive and motor processes; what is important it also affects aging. There is also a line of work involvement of the cerebellum in Alzheimer’s disease.

Looking ahead

These new findings raise important yet unanswered questions: what do these post-COVID-19 brain changes mean for the aging process and rate? Also, does the brain recover after a viral infection over time and to what extent?

These are active and open areas of research that we are beginning to pursue in my lab combined with our ongoing work on the study of brain aging.

The work of our lab shows that as people age, the brain thinks and processes information differently. In addition, we observed changes over time in how people’s bodies are moving and how people learn new motor skills. Several decades of work have shown that older people find it more difficult to process and manipulate information – for example, to update the mental list of products – but they usually retain their knowledge of facts and vocabulary. As for motor skills, we know it older people are still learningbut they do it more slowly, then young adults.

When it comes to brain structure, we usually observe a decrease in brain size in adults over 65 years of age. This reduction is not only localized in one area. Differences can be seen in many regions of the brain. There is also usually an increase in cerebrospinal fluid that fills the space due to loss of brain tissue. In addition, white matter, insulation on axons – long cables that carry electrical impulses between nerve cells – also less intact in the elderly.

Life expectancy has increased in recent decades. The goal is for everyone to live a long and healthy life, but even at best, when a person ages without illness or disability, older life makes a difference in the way we think and move.

Exploring how all these puzzle pieces come together will help us unravel the mysteries of aging so we can help improve the quality of life and function of aging people. And now, in the context of COVID-19, it will help us understand the extent to which the brain can recover from disease.

Jessica Bernard is an Associate Professor of Psychology and Brain Science at the University of Texas A&M.

This comment was originally posted Conversation and reprinted here under Creative Commons.

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