Summary: Preliminary findings suggest even mild COVID-19 infection may have lasting effects on brain health and cognitive function.
Source: The Conversation
After more than 18 months of the pandemic, researchers are collecting consistent, important evidence about how COVID-19 affects the body and the brain. Emerging results are prompting concern about possible long-term consequences of the coronavirus for biological processes linked to aging and cognition.
As a cognitive neuroscientist, my prior work has examined how normal, age-related brain changes influence thinking and movement, especially in middle age and later life. As reports accumulated that COVID-19 can affect the body and brain for months after infection, my team turned attention to whether the virus might alter the typical course of brain aging.
Peering into the brain’s response to COVID-19
In August 2021 a large preliminary study gained attention in the neuroscience community for examining brain changes in people who had contracted COVID-19. That work drew on a substantial resource of pre-pandemic brain scans gathered in the U.K., which provided baseline imaging of individuals from before they were infected.
Researchers re-scanned participants who had gone on to contract COVID-19 and compared them to matched individuals who had not been infected. The groups were carefully matched on age, sex, timing of the original scan, study site and common risk factors such as health status and socioeconomic measures, enabling a rigorous before-and-after comparison.
The study reported notable differences in gray matter—the nerve cell bodies that process information—between people who had had COVID-19 and those who had not. Specifically, thickness in regions of the frontal and temporal lobes was reduced in the COVID-19 group, with changes larger than expected from normal aging alone.
Importantly, these differences appeared regardless of illness severity: participants who had been hospitalized and those who experienced milder symptoms showed similar patterns of brain tissue loss. The researchers also measured cognitive performance and found that individuals who had contracted COVID-19 took longer to process information compared with those who were not infected.
While these results were reported prior to full peer review and must be interpreted cautiously, the study’s use of large samples and pre- and post-infection imaging in the same individuals adds strength to the observations and motivates further investigation.
What do these changes in brain volume mean?
Early in the pandemic, many people with COVID-19 reported losing their sense of smell and taste. Remarkably, the brain regions that showed volume reductions in the study are connected to the olfactory system—the olfactory bulb and its links to temporal lobe structures.
The temporal lobe includes the hippocampus, a critical region for memory and a focal point in aging and Alzheimer’s research. Because smell-related pathways and temporal regions are involved in memory processes, researchers are interested in whether COVID-19–related changes could have implications for memory and longer-term risk pathways associated with neurodegenerative conditions.
It is far too early to draw definitive conclusions about lasting consequences, but the overlap between affected regions and areas important for memory highlights a research priority: tracking how COVID-19-related brain changes relate to cognitive outcomes over time.
Looking ahead
Several pressing questions remain. How do COVID-19-related brain changes affect the pace of aging? To what extent does the brain recover following infection? Ongoing research in multiple labs, including my own, is beginning to address these issues while we continue long-term studies of brain aging.
Decades of aging research have established that cognitive processing and motor learning change with age. Older adults tend to be slower at manipulating and updating information, although they often retain factual knowledge and vocabulary. Motor learning continues throughout life but typically proceeds more slowly than in younger adults. Structurally, aging is associated with gradual brain tissue loss across many regions, increased cerebrospinal fluid filling, and declines in white matter integrity, which affect communication between brain areas.
As populations live longer, understanding how infections like COVID-19 interact with normal aging processes is critical. Clarifying whether and how the brain recovers from viral insult will inform strategies to protect cognitive health and quality of life as people age.
Funding: Jessica Bernard receives funding from the National Institute on Aging and the National Institute of Mental Health.
About this COVID-19 and neuroscience research news
Author: Jessica Bernard
Source: The Conversation
Contact: Jessica Bernard – The Conversation
Image: The image is in the public domain