When I first started investigating dementia over a decade ago, it was a personal mission. My mother’s diagnosis pushed me into deep research. I spent 12 years trying to understand neurodegeneration—what causes it, how it progresses, and what could potentially reverse it.
Then came COVID-19.
Like many, I pivoted. But I didn’t abandon what I had learned—I simply applied the same investigative lens to this new disease. Very early on, I proposed that COVID-19 is a viral mediated autoimmune disease, and that this process could impact not only the body but also the brain. Now, five years later, it feels like the evidence is circling back—bringing my dementia research and COVID work full circle.
A new study published in Nature Communications (June 2025) uses data from the UK Biobank to examine accelerated brain ageing during the COVID-19 pandemic. It’s an impressive study: thousands of participants, detailed neuroimaging, and cognitive tests. But as I read through it, something major stood out:
There was no mention of COVID-19 vaccination status. None.
That’s not a minor oversight. This was a carefully matched study that considered socioeconomic status, physical health, alcohol intake, even education levels. But somehow, in the middle of a global mass vaccination campaign using novel mRNA platforms, they forgot to ask: were these people vaccinated?
Mohammadi-Nejad, Ali-Reza, et al. "Accelerated brain ageing during the COVID-19 pandemic." Nature Communications 16.1 (2025): 6411.
Except they didn’t forget.
UK Biobank did collect vaccination status. In fact, over 95% of the cohort had been vaccinated according to their own data from early 2023. That means this study—whether it mentions it or not—is actually reporting on accelerated brain ageing in a vaccinated population.
Mayer, Craig S. "Informatics assessment of COVID-19 data collection: an analysis of UK Biobank questionnaire data." BMC Medical Informatics and Decision Making 24.1 (2024): 321.
So what exactly did they find?
Is Brain Fog in COVID Like Perpetual Intoxication?
Thursday 31st July at 7PM UK time
Participants showed measurable increases in “brain age gap” (BAG)—meaning their brains looked older on scans than their chronological age. This effect was seen across the population, even in those who never had COVID-19. The ageing signal was strongest in white matter, the brain’s wiring system, and it was correlated with worsened cognitive performance, especially in those who had COVID.
In other words:
The pandemic aged brains.
COVID infection aged them more.
But even without infection, there was an upward trend in brain ageing.
And the vast majority of participants were vaccinated.
This raises uncomfortable questions.
Could repeated exposure to the spike protein—via vaccination and reinfection—be silently accelerating brain ageing?
We know that spike protein persists in circulation longer in vaccinated individuals. We know that immune activation, particularly in the vascular and neurological systems, is different in the vaccinated. Mild COVID infections in the unvaccinated often remain localized to the upper airway. In vaccinated individuals, even mild infection can lead to systemic spike protein spread. That’s a fundamentally different exposure pattern.
The study’s authors didn't discuss any of this. They didn’t analyze vaccination as a variable. But by excluding long COVID sufferers and anyone with chronic illness, they created a cohort that was likely youngish, healthy, and fully vaccinated.
So what we’re seeing is brain ageing in the group we were told would benefit most from vaccination.
That’s not an anti-vaccine statement. It’s a scientific red flag. When a dataset this powerful shows signals like this, we need full transparency, not selective reporting.
I believe the real issue we’re facing is something I call the COVID storm - a two-part process:
Immune priming from vaccination
Repeated re-exposure to the spike protein through reinfection
Together, these create an inflammatory “epoxy” that settles into the body and brain. It may not cause immediate devastation—but over time, the subtle erosion becomes visible. In this case, it’s visible on MRI.
I suspect this is also behind the wave of brain fog that so many people are experiencing—but not talking about. Why don’t they say anything? Because they’re still functioning… just not optimally. And because cognitive decline carries a silent shame. People fear dementia. They fear being seen as unstable or incompetent.
But we need to talk about it. And we need to study it honestly.
If we continue to dismiss vaccination status in studies of brain ageing, cognitive decline, and neurodegeneration, we will miss the bigger picture. We’ll assume the pandemic alone caused these problems, when it may in fact be the combination of spike exposure, immune priming, and reinfection.
That’s the storm I believe we’re caught in. And unless we change course, I fear the neurological fallout has only just begun.
Vejon COVID-19 Review is a reader-supported publication. To receive new posts and support my work, consider becoming a free or paid subscriber.
