Even if you never contracted COVID-19, the pandemic may still have aged your brain.

A major study using UK Biobank data has found that the COVID-19 pandemic significantly accelerated brain ageing in healthy individuals, regardless of whether they were ever infected with the virus.

“Our findings reveal that, even with initially matched brain age gaps (predicted brain age vs. chronological age) and matched for a range of health markers, the pandemic significantly accelerates brain ageing,” the researchers write. The effect, they say, was observable even among participants “classified as healthy, with no history of chronic disorders.”

The study, published in Nature Communications, used a sophisticated brain age prediction model trained on over 15,000 healthy participants’ MRI scans collected before March 2020. The model extracted hundreds of imaging features to predict brain age. Researchers then applied the model to a separate cohort of 996 participants, half of whom had one MRI scan before and one after the pandemic, called the “Pandemic group” and the other half who had both scans before the pandemic began, identified as the Control group.

Crucially, the study’s design ensured that participants in both groups were matched for age, sex, and health status, and that no one had developed a new chronic condition between scans. 

“Only participants with a minimum inter-scan interval of 2 years, who did not develop an interim health condition, were considered,” the authors point out.

The key metric used to assess change was the “brain age gap” (BAG), which measures the difference between a person’s estimated brain age and their actual age. The researchers calculated the rate of change in this gap between scans, termed “RBAG”.

The result: “The Pandemic group displayed significantly higher RBAG compared with the Controls… indicating accelerated brain ageing.” This was seen across both grey matter (GM) and white matter (WM).” 

The average increase in brain age gap at the second time point for those in the Pandemic group was around 5.5 months, compared to the Control group.

This phenomenon was more pronounced in men and people from disadvantaged socio-economic backgrounds. “Accelerated brain ageing is more pronounced in males and those from deprived socio-demographic backgrounds,” the paper states. Importantly, these changes were observed regardless of whether a person had ever been infected with SARS-CoV-2.

However, cognitive decline linked to this brain ageing was observed only among participants who had tested positive for COVID-19. The study notes: “Accelerated brain ageing correlates with reduced cognitive performance only in COVID-infected participants.”

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