According to a study, COVID-19-positive outpatients are at much increased risk of neurodegenerative disease compared to those who tested negative for the SARS-CoV-2 virus. The researchers found that those who tested positive for COVID-19 had a much higher risk of Alzheimer’s disease, Parkinson’s disease and ischemic stroke.
The study, presented Sunday at the 8th Congress of the European Academy of Neurology (EAN) in Vienna, Austria, analyzed the health records of more than half of the Danish population. Of the 919,731 individuals tested for COVID-19 in the study, researchers found that the 43,375 people who tested positive had a 3.5 times greater risk of developing Alzheimer’s disease. They also had a 2.6-fold increased risk of being diagnosed with Parkinson’s disease, 2.7-fold with ischemic stroke, and 4.8-fold with intracerebral haemorrhage (bleeding in the brain). While neuroinflammation may contribute to accelerated development of neurodegenerative diseases, the researchers also emphasized the implications of the scientific focus on long-term COVID.
The study analyzed inpatient and outpatient patients in Denmark between February 2020 and November 2021, as well as flu patients from the corresponding pre-pandemic period. Researchers used statistical techniques to calculate relative risk, and the results were stratified by hospitalization status, age, gender and co-morbidities. 19 on neurological disorders remained uncharacterized,” explains Pardis Zarifkar, lead author of the Department of Neurology, Rigshospitalet, Denmark.
“Previous studies have shown an association with neurological syndromes, but so far it is not known whether COVID-19 also affects the incidence of specific neurological diseases and whether it differs from other respiratory infections,” Zarifkar said. However, the increased risk of most neurological diseases was not higher in COVID-19-positive patients than in people diagnosed with the flu or other respiratory illnesses. COVID-19 patients had a 1.7 times higher risk of ischemic stroke compared to flu and bacterial pneumonia in patients older than 80 years.
The frequency of other neurodegenerative diseases such as multiple sclerosis, Guillain-Barre syndrome, myasthenia gravis and narcolepsy did not increase after COVID-19, flu or pneumonia. “We found support for an increased risk of neurodegenerative and cerebrovascular disease diagnosis in COVID-19 positive compared to COVID negative patients, which needs to be confirmed or disproved by large registry studies in the near future,” added Zarifkar.
“Reassuringly, aside from ischemic stroke, most neurological disorders do not appear to be more common after COVID-19 than after flu or community-acquired bacterial pneumonia,” he said. The findings will help provide us with insight into the long-term effect of COVID-19 on the body and the role infections play in neurodegenerative diseases and stroke, the researchers added.