With more than 18 months of the pandemic in the rearview mirror, researchers have been steadily gathering new and important insights into the effects of COVID-19 on the body and brain. These findings are raising concerns about the long-term impacts that the coronavirus might have on biological processes such as aging.

As a cognitive neuroscientist, my past research has focused on understanding how normal brain changes related to aging affect people’s ability to think and move – particularly in middle age and beyond. But as more evidence came in showing that COVID-19 could affect the body and brain for months or longer following infection, my research team became interested in exploring how it might also impact the natural process of aging.

Peering in at the brain’s response to COVID-19

In August 2021, a preliminary but large-scale study investigating brain changes in people who had experienced COVID-19 drew a great deal of attention within the neuroscience community.

In that study, researchers relied on an existing database called the UK Biobank, which contains brain imaging data from over 45,000 people in the U.K. going back to 2014. This means – crucially – that there was baseline data and brain imaging of all of those people from before the pandemic.

The research team analyzed the brain imaging data and then brought back those who had been diagnosed with COVID-19 for additional brain scans. They compared people who had experienced COVID-19 to participants who had not, carefully matching the groups based on age, sex, baseline test date and study location, as well as common risk factors for disease, such as health variables and socioeconomic status.

The team found marked differences in gray matter – which is made up of the cell bodies of neurons that process information in the brain – between those who had been infected with COVID-19 and those who had not. Specifically, the thickness of the gray matter tissue in brain regions known as the frontal and temporal lobes was reduced in the COVID-19 group, differing from the typical patterns seen in the group that hadn’t experienced COVID-19.

In the general population, it is normal to see some change in gray matter volume or thickness over time as people age, but the changes were larger than normal in those who had been infected with COVID-19.

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

Finally, researchers also investigated changes in performance on cognitive tasks and found that those who had contracted COVID-19 were slower in processing information, relative to those who had not.

While we have to be careful interpreting these findings as they await formal peer review, the large sample, pre- and post-illness data in the same people and careful matching with people who had not had COVID-19 have made this preliminary work particularly valuable….