New study: COVID-19 may cause or accelerate neurological diseases
Danish researchers published a study suggesting that COVID-19 increases the risk of neurodegenerative diseases such as Alzheimer’s and Parkinson’s disease.
They presented the research at the European Academy of Neurology (EAN) Congress in Vienna, and the results were published in Frontiers in Neurology.
Specifically, after analyzing data from health records in Denmark, they found that people who tested positive for COVID-19 were more likely to suffer from Alzheimer’s disease, Parkinson’s disease and ischemic stroke.
“COVID-19 has had a disproportionate impact on people with dementia, their carers and their families,” Sara Imarisio, Ph.D., head of research at Alzheimer’s Research UK, said of the study. “The risk of developing Alzheimer’s disease, the leading cause of dementia, is caused by a complex mix of age, genetics and other environmental factors. This research suggests that having COVID-19 is linked to an increased risk of being diagnosed with Alzheimer’s disease, however, this was no stronger than the link to other respiratory diseases like the flu.”
She noted that diseases such as Alzheimer’s develop in the brain over many years, but COVID-19 has only been present outside China since early 2020. “It may be that people in the very early stages of Alzheimer’s are more susceptible to catching diseases like COVID-19,” Imarisio added.
The study analyzed 919,731 people who tested positive for COVID-19. Of them, 43,375 had a 3.5 times increased risk of being diagnosed with Alzheimer’s disease, 2.6 times higher risk of Parkinson’s disease, 2.7 times higher risk of ischemic stroke and 4.8 times higher risk of intracerebral hemorrhage. It’s possible that neuroinflammation increased the development of neurodegenerative disorders. The patients evaluated were in- and outpatients in Denmark between February 2020 and November 2021. It also included influenza patients from the corresponding pre-pandemic period.
“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,” Dr. Pardis Zarifkar, M.D., lead author, department of neurology, Rigshospitalet, Copenhagen, Denmark, explained. “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 risk of most neurological diseases was no higher in COVID-19 patients than in people diagnosed with the flu or other respiratory diseases, although COVID-19 patients over 80 had 1.7 times higher risk of ischemic stroke compared to influenza and bacterial pneumonia. The researchers found no increase in other neurodegenerative diseases like multiple sclerosis, myasthenia gravis, Guillain-Barre syndrome and narcolepsy for any of the viral diseases.
Zarifkar added, “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. Reassuringly, apart from ischemic stroke, most neurological disorders do not appear to be more frequent after COVID-19 than after influenza or community-acquired bacterial pneumonia.”
A 2021 study described a potential link between COVID-19 and the onset of Parkinson’s disease. The study out of the University of Twente in The Netherlands showed in laboratory assays that the SARS-CoV-2 N-protein interacts with alpha-synuclein, a protein in the brain, and increases the speed of the formation of amyloid fibrils, which is a defining feature of Parkinson’s disease. Interestingly, one of the predominant features of both early Parkinson’s disease and COVID-19 infection is the loss of sense of smell.
It has been clear for some time that COVID-19 is more than a respiratory disease, with a broad range of symptoms including “brain fog,” blood clots and strokes, possible gastrointestinal and other issues. In addition to links to neurological diseases, an increase in new-onset diabetes has been tied to COVID-19 infections.
Recent research from Osaka University in Japan suggests the association has to do with the insulin/IGF signaling pathway, a key pathway in energy metabolism regulation and cell survival. COVID-19 infection appears to impair insulin/IGF signaling by increasing IRF1 expression, which disrupts blood sugar metabolism.
In light of these discoveries, researchers will likely dig deeper to discover how and why COVID-19 is associated with a higher risk of other seemingly unrelated diseases.