The Covid-19 pandemic may have negatively affected the brain health of men and women — even among those who were never diagnosed with the virus, according to new research from the United Kingdom.
While the SARS-CoV-2 virus has long been known to impair cognitive functions and brain health, the precise long-term effects have remained unclear. Now, researchers from the University of Nottingham and Imperial College London have evaluated the so-called "brain age" — a key indicator of biological aging — in adults before and after the pandemic, using data from the extensive UK Biobank.
How the Study Was Conducted
The researchers split participants into two main groups. The first group included 564 individuals, aged 45 to 82 (53% women), who underwent brain MRI scans before March 2020. The second group included 432 participants, aged 47 to 79, who had MRI data from both before and during the pandemic.
This second group was further divided into two subgroups: one of 134 participants who had confirmed Covid-19 infections (58% women), and another of 298 individuals with no recorded infections (60% women). None of the subjects had chronic health conditions.
"The analysis revealed that the average brain age in both pandemic-era subgroups was nearly half a year older than in those scanned before the pandemic," the authors reported.
The researchers examined key neurological markers, including cortical thickness, gray and white matter volume, and the presence of pathological changes.
Only the Infected Showed Cognitive Decline
Perhaps the most intriguing finding: individuals without a Covid-19 diagnosis did not show any measurable decline in cognitive abilities. In contrast, those who had recovered from the virus exhibited reduced mental flexibility and slower information processing in standardized tests.
The scientists suggest that the brain aging seen across all participants — including the uninfected — may be linked to pandemic-related social stress: anxiety over health, forced isolation during lockdowns, job loss, or financial hardship.
"Further international research is needed to confirm whether these effects are driven by psychosocial stressors," the study concluded.
Could Some Uninfected Have Had Covid-19 Without Knowing?
The authors also noted an important caveat: while some participants reported not having been infected, their true Covid-19 status remains uncertain. Many people experienced the illness in mild or asymptomatic form and may have never been diagnosed, especially given the unreliability of rapid tests during the height of the pandemic.
Previous studies found that the number of people with antibodies to the virus's N-protein — indicating natural infection rather than vaccination — may be several times higher than the official number of diagnosed cases.
