A study found that COVID-19 infection raises the risk of neurodegenerative disorders among patients--including Alzheimer's, Parkinson's, and stroke--when compared to individuals who tested negative for the deadly virus.

The research study presented at the 8th European Academy of Neurology (EAN) Congress analyzed the health records of more than half of the Danish population. It found that people who tested positive for COVID-19 were at a far greater risk of developing Alzheimer's disease, Parkinson's disease, and ischemic stroke.

COVID-19 Link to Neurodegenerative Disorders

The study analyzed 919,731 individuals who were tested for the deadly virus. It found that the 43,375 who got positive results had a 3.5 times increased risk of being diagnosed with Alzheimer's, 2.6 times with Parkinson's, 2.7 times with ischemic stroke, and 4.8 times with intracerebral hemorrhage, which is bleeding in the brain.

The authors highlighted the implications of the scientific focus on long-term sequelae after COVID-19, which is commonly referred to as long-COVID. The researchers analyzed in- and outpatients in Denmark between February 2020 and November 2021 and also studied influenza patients from the corresponding pre-pandemic period, as per SciTechDaily.

Researchers used statistical techniques to calculate a patient's relative risk, and results were stratified for hospitalization status, age, sex, and comorbidities. The lead author from the Department of Neurology, Rigshospitalet, Copenhagen, Denmark, Dr. Pardis Zarifkar, explained that the precise nature and evolution of the effects of the COVID-19 virus on neurological disorders remains uncharacterized.

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There have been previous studies that established an association with neurological syndromes, but until now, it is unknown whether or not the coronavirus also influences the incidence of specific neurological diseases and whether or not it differs from other respiratory infections.

According to NewAtlas, Zarifkar noted that the increased risk of the neurological conditions following COVID-19 infection mirrors what was previously reported with influenza or bacterial pneumonia. However, due to the sheer prevalence of COVID-19 infections, it is most likely that baseline rates for these neurodegenerative disorders will increase worldwide in the future.

Lasting Effects of COVID-19

The lead author added that they found support for an increased risk of being diagnosed with neurodegenerative and cerebrovascular disorders in COVID-19 positive patients compared to those who tested negative. However, this is something that must be confirmed or refuted by large registry studies in the near future.

"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," said Zarifkar.

Researchers have, for decades, observed a correlation between certain viral infections and neurodegenerative diseases. One of the most well-known was the increase in rates of Parkinson's disease following the Spanish Flu pandemic in the early 20th century.

On the other hand, the senior vice president of medical communications at the Michael J. Fox Foundation for Parkinson's Research, Dr. Rachel Dolhun, said that this kind of study could understandably grab attention and raise concerns among populations.

"We know that COVID, like any infection, can temporarily worsen symptoms in people who live with Parkinson's. We don't yet know whether COVID can bring on Parkinson's," said Dolhun, per Healthline.

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