COVID-19 positive outpatients are at an increased risk of neurodegenerative disorders compared with individuals who tested negative for the virus, a new study presented today at the 8th European Academy of Neurology (EAN) Congress has shown. The study, which analysed the health records of over half of the Danish population, found that those who had tested positive for COVID-19 were at an increased risk of Alzheimer's disease, Parkinson's disease, and ischaemic stroke. Out of the 919,731 individuals that tested for COVID-19 within the study, researchers found that the 43,375 people who tested positive had a 3.5 times increased risk of being diagnosed with Alzheimer's disease, 2.6 times with Parkinson's disease, 2.7 times with ischaemic stroke and a 4.8 times increased with intracerebral haemorrhage. While neuroinflammation may contribute to an accelerated development of neurodegenerative disorders, the authors highlighted implications of the scientific focus on long-term sequelae after COVID-19. The study analysed Danish in- and outpatients between February 2020 and November 2021, as well as influenza patients from the corresponding pre-pandemic period. Researchers used statistical techniques to calculate relative risk, and results were stratified for hospitalisation status, age, sex, and comorbidities. Dr Pardis Zarifkar, lead author from the Department of Neurology, Rigshospitalet, Copenhagen, Denmark, explained, "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 uncharacterised. 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 increased risk of most neurological diseases was, however, no higher in COVID-19 positive patients than in people who had been diagnosed with influenza or other respiratory illnesses. COVID-19 patients did have a 1.7 times increased risk of ischaemic stroke in comparison to influenza and bacterial pneumonia in patients over 80 years of age. The frequency of other neurodegenerative illnesses such as multiple sclerosis, myasthenia gravis, Guillain-Barré syndrome and narcolepsy did not increase after COVID-19, influenza, or pneumonia. Dr Pardis Zarifkar added, "These findings will inform our understanding of the long-term effect of COVID-19 on the body and the role that infections play in neurodegenerative diseases and stroke." SOURCE : EAN Congress 2022