Alzheimer's & Dementia

COVID-19 increases risk of Alzheimer’s, Parkinson’s & stroke, study finds

COVID-19 increases risk of Alzheimer’s, Parkinson’s & stroke, study finds
Looking at millions of health records in Denmark across 2020 and 2021, researchers saw higher rates of several neurodegenerative diseases in patients following COVID-19 infections
Looking at millions of health records in Denmark across 2020 and 2021, researchers saw higher rates of several neurodegenerative diseases in patients following COVID-19 infections
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Looking at millions of health records in Denmark across 2020 and 2021, researchers saw higher rates of several neurodegenerative diseases in patients following COVID-19 infections
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Looking at millions of health records in Denmark across 2020 and 2021, researchers saw higher rates of several neurodegenerative diseases in patients following COVID-19 infections

New research presented recently at the European Academy of Neurology Congress in Vienna has found an increased risk of several neurological disorders in patients following a bout of COVID-19. The study found the risk of Alzheimer’s, Parkinson’s and stroke all increased in COVID-positive subjects compared to those uninfected.

“More than two years after the onset of the COVID-19 pandemic, the precise nature and evolution of the effects of COVID-19 on neurological disorders remained uncharacterized,” said lead author on the new study, Pardis Zarifkar, from the Copenhagen University Hospital. “Previous studies have established an association with neurological syndromes, but until now it is unknown whether COVID-19 also influences the incidence of specific neurological diseases and whether it differs from other respiratory infections.”

The researchers analyzed electronic health records from almost half of Denmark’s total population, spanning 2020 and 2021. Across the study period those who tested positive for COVID-19 were found to be 3.5 times more likely to be diagnosed with Alzheimer’s disease; 2.6 times more likely to be diagnosed with Parkinson’s; 4.8 times more likely to experience bleeding in the brain; and 2.7 times more likely to develop ischemic stroke.

Zarifkar does note the increased risk of these neurological conditions following COVID-19 does mirror what has previously been reported following cases of influenza or bacterial pneumonia. However, due to the sheer prevalence of COVID-19 infections, it is likely baseline rates of these neurodegenerative diseases will rise around the world over the coming years.

“We found support for an increased risk of being diagnosed with neurodegenerative and cerebrovascular disorders in COVID-19 positive compared to COVID-negative patients, which must be confirmed or refuted by large registry studies in the near future,” added Zarifkar. “Reassuringly, apart for ischemic stroke, most neurological disorders do not appear to be more frequent after COVID-19 than after influenza or community-acquired bacterial pneumonia.”

For decades researchers have seen a correlation between certain viral infections and neurodegenerative disease. Perhaps most well-known was the increase in rates of Parkinson’s disease following the Spanish Flu pandemic in the early 20th century.

Since the beginning of the pandemic in 2020 researchers have warned of potential spikes in conditions such as Parkinson’s, and this new data offers early signals these predictions may be coming true. Other more recent studies have started digging into exactly what mechanisms could be contributing to this increased risk of neurodegenerative disease following COVID-19.

For years the most prominent hypothesis to explain the link between viral infections and neurodegeneration has been that inflammation triggered by an infection may either initiate, or accelerate, the development of neurological disease. A review article published back in 2012 suggested repeated viral infections may increase this risk of neurological disease by activating a “cascade of events” corresponding with what is seen in the earliest stages of neurodegeneration.

“We suggest that neurodegeneration can be triggered and then propagated by repeated inflammatory reactions (such as local production of cytokines) over time,” the 2012 review indicated. “Indeed, there is evidence for both microglial and astrocytic (star-shaped glial cells in the brain) activation and reactions that track existing neuronal circuits in the CNS [central nervous system] and PNS [peripheral nervous system]. These inflammatory sequences combined with regional and cell type–dependent neuronal vulnerability could cause the specific structural and functional neurodegenerative patterns that define individual neurodegenerative diseases.”

A number of recent studies have found brain inflammation to be a characteristic of some COVID-19 infections. But it still isn't clear how the virus may be causing this neuroinflammation or whether this autoimmune response will cause long-term problems.

Commenting on the new COVID-19 findings, Sara Imarsio from Alzheimer’s Research UK said it is important to remember that dementia-causing neurological diseases are caused by a constellation of factors, from genetic susceptibility to age and environment. So COVID-19 is potentially only playing a small role in a person’s total risk of developing these diseases.

Imarsio also pointed out a number of other factors could explain why rates of neurodegenerative disease are higher in those infected with COVID-19. And, it certainly is too soon to know the long-term impact of COVID-19 on certain brain diseases that can take decades to develop.

“Diseases like Alzheimer’s develop in the brain over many years and COVID-19 has only been present in Europe since early 2020,” added Imarsio. “It may be that people in the very early stages of Alzheimer’s are more susceptible to catching diseases like COVID-19. While the announcement of these findings is potentially concerning, we will need to see results of this study in a peer-reviewed publication before we can draw any real conclusions from this research.”

The new study was published in the journal Frontiers in Neurology.

Source: European Academy of Neurology

6 comments
6 comments
Vilkas
And, it certainly is too soon to know the long-term impact of COVID-19 shot on certain brain diseases that can take decades to develop.
guzmanchinky
Why vaccinations were never made 100% mandatory I will never understand...
bwana4swahili
Having had COVID-19 I certainly believe the disease can have an impact on the brain and nervous system. I feel like it aged me a decade!
Baker Steve
From the study: 'Given the nature of aggregated data, several caveats need to be considered. First, we could not adjust for potential confounders such as socioeconomic, lifestyle, pre-existing comorbidities, and length of hospitalization.'

This study needs to be clarified for its correlation against the severity of Covd-19. For example, it the risk only raised in those severely affected enough to be hospitalized?
Anechidna
Vilkas, some don't take decades, virologists expect the rate of Parkinson's diagnosis to increase to 3 times the background rate in 2019 by 2025. The virus doesn't cause the disorder rather a viral infection creates the situation for the disorder to develop. This outcome was first noted after the Spanish Flu epidemic and has arisen after every major viral flu outbreak etc as detailed in the article. I suspect the Alzheimers diagnosis is based on similar observations again the virus doesn't cause the disorder but somehow raises susceptibility in the individual.
rpark
...although a clarification for correlation against the severity of Covid-19, i.e., 'risk raised in those severely affected enough to be hospitalized,' could possibly be useful- the boundary conditions for this study were 'COVID-positive subjects compared to those uninfected' (Covid negative) .. if the study is to be believed in its current form, the results would be similar irrespective of severity as the lowest common factors are infected vs. uninfected and not more severe vs. less severe.