Many people that have been sickened by COVID-19 have described symptoms that are related to brain function, such as fatigue, brain fog, and disturbances with their sense of taste or smell. European researchers have now analyzed the health records of about half the entire population of Denmark to learn more about the long-term impact of COVID-19 on neurological disorders in the brain. This study included 919,731 people who were tested for COVID-19; of those, 43,375 people had tested positive. The investigators found that a COVID-19 infection increased an individuals risk of several neurodegenerative disorders; the risk of an Alzheimer's disease diagnosis increased 3.5 times, Parkinson's disease risk increased 2.6 times, ischemic stroke risk increased 2.7 times, and the risk of bleeding in the brain, otherwise known as intracerebral hemorrhage, increased 4.8 times. It's only been a few years since the onset of the pandemic, so these numbers may also change in the future.
Several neurodegenerative diseases, including Alzheimer's and Parkinson's, have been associated with some types of viral infection and neuroinflammation. But this research also included health data for people who had tested positive for influenza and pneumonia. The research showed that the flu and other respiratory illnesses did not cause any higher risk of neurodegenerative disease. The statistical analysis also corrected for other factors like comorbidities, sex, and hospitalization status. The study authors added that this research highlights the importance of investigating the long-term impact of COVID-19.
The study also indicated that COVID-19, flu, or pneumonia do not have any impact on the risk of developing other neurodegenerative diseases including Guillain-Barré syndrome, multiple sclerosis, myasthenia gravis, or narcolepsy. The findings were presented at the 8th European Academy of Neurology (EAN) Congress.
"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," said lead study author Dr. Pardis Zarifkar of the Department of Neurology, Rigshospitalet. "Reassuringly, [other than] ischemic stroke, most neurological disorders do not appear to be more frequent after COVID-19 than after influenza or community-acquired bacterial pneumonia."
Scienitsts still have a lot more to learn about how the virus that causes COVID-19, SARS-CoV-2, can affect the brain. This research will help scientists and clinicians learn more about how COVID-19 may affect people over the long term, and could help create ways to prevent or treat diseases that may be more likely after an infection.