Researchers have steadily gathered important insights into the effects of COVID-19 on the body and brain.
Two years after the pandemic, these findings raise concerns about the long-term effects the coronavirus may have on biological processes such as aging.
As a cognitive neuroscientist, my previous research has focused on understanding how normal brain changes associated with aging affect people’s ability to think and move, especially in middle age and beyond.
But when evidence came in showing that COVID-19 could affect the body and brain months after infection, my research team shifted some of its focus to a better understanding of how the disease might affect the natural aging process. This was largely motivated by exciting new work from the UK examining the impact of COVID-19 on the human brain.
Watching the brain’s response to COVID-19
In a large study published in the journal Nature on March 7, 2022, a team of researchers in the UK examined brain changes in people aged 51 to 81 who had experienced COVID-19.
This work provides important new insights into the impact of COVID-19 on the human brain.
In the study, researchers relied on a database called the UK Biobank, which contains brain imaging data from more than 45,000 people in the UK dating back to 2014.
This means there was basic data and brain imaging from all those people from before the pandemic.
The research team compared people who had experienced COVID-19 with participants who had not, carefully matching the groups for age, gender, baseline test date and study location, as well as general risk factors for disease, such as health variables and socioeconomic status.
The team found marked differences in gray matter — or the neurons that process information in the brain — between those infected with COVID-19 and those who didn’t.
Notably, gray matter thickness in brain regions known as the frontal and temporal lobes was reduced in the COVID-19 group, in contrast to the typical patterns seen in the people who did not have COVID-19 infection. had had.
In the general population, it is normal to see some change in the volume or thickness of gray matter over time as people age. But the changes were more extensive than usual in those infected with COVID-19.
Interestingly, when the researchers separated the individuals who were seriously ill enough to require hospitalization, the results were the same as for those who had experienced milder COVID-19. That is, people infected with COVID-19 showed a loss of brain volume even when the disease was not severe enough to require hospitalization.
Finally, researchers also examined changes in performance on cognitive tasks and found that those who contracted COVID-19 were slower at processing information than those who did not. This processing ability was correlated with volume in an area of the brain known as the cerebellum, suggesting a link between brain tissue volume and cognitive performance in people with COVID-19.
This study is particularly valuable and insightful because of the large sample size, both before and after illness in the same people, and because of the careful matching with people who had not had COVID-19.
What do these changes in brain volume mean?
Early in the pandemic, one of the most common reports of people infected with COVID-19 was the loss of: sense of taste and smell†
Notably, the brain regions the UK researchers found to be affected by COVID-19 are all linked to the olfactory bulb, a structure at the front of the brain that relays signals about odors from the nose to other brain regions.
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 that’s where the hippocampus is located.
The hippocampus probably plays a key role in aging, given its involvement in memory and cognitive processes.
The sense of smell is also important for Alzheimer’s research, as some data has suggested that those at risk for the disease have a decreased sense of smell. While it is too early to draw conclusions about the long-term effects of COVID-19-related effects on the sense of smell, it is of great interest to explore possible links between COVID-19-related brain changes and memory, especially given the regions involved and their importance in memory and Alzheimer’s disease.
The study also highlights a potentially important role for the cerebellum, an area of the brain involved in cognitive and motor processes; Importantly, it is also affected by aging. There is also an emerging line of work involving the cerebellum in Alzheimer’s disease.
These new findings raise important but unanswered questions: What do these post-COVID-19 brain changes mean for the process and pace of aging? Does the brain also recover from a viral infection over time, and to what extent?
These are active and open areas of research that we are starting to address in my lab in conjunction with our ongoing research on brain aging.
Our lab’s work shows that as people age, the brain thinks and processes information differently. In addition, we observed changes over time in how people’s bodies move and how people learn new motor skills. Several decades of work have shown that older adults have a harder time processing and manipulating information — such as updating a mental shopping list — but typically retain their knowledge of facts and vocabulary.
With regard to motor skills, we know that older people still learn, but at a slower rate than younger people.
When it comes to brain structure, we usually see a decrease in brain size in adults over the age of 65. This decrease is not only localized in one area.
Differences can be seen in many brain regions. There is also typically an increase in cerebrospinal fluid filling the space due to the loss of brain tissue. In addition, white matter, the insulation on axons — long cables that carry electrical impulses between nerve cells — is also less intact in older adults.
Life expectancy has increased in recent decades.
The goal is for everyone to live a long and healthy life, but even in the most favorable scenario where someone is aging without illness or disability, older adulthood brings about changes in how we think and move.
By learning how all these puzzle pieces fit together, we can unravel the mysteries of aging so that we can help improve the quality of life and functioning of aging individuals. And now, in the context of COVID-19, it will help us understand to what extent the brain can also recover after illness.
This article is republished from The Conversation under a Creative Commons license. Read the original article.