COVID-19 elevates risk of neurodegenerative disorders

COVID-19-positive outpatients had an increased risk of a broad range of neurodegenerative and cerebrovascular disorders compared with participants who tested negative. However, no excess risk was detected compared with influenza A/B and community-acquired pneumonia, except for ischaemic stroke.

More than 2 years after the onset of the COVID-19 pandemic, the precise nature and evolution of the effects of COVID-19 on neurological disorders are still not characterised. Previous studies have established an association with neurological syndromes, but it is still unknown whether COVID-19 influences the incidence of specific neurological diseases and whether it differs from other respiratory infections [1,2]. Dr Pardis Zarifkar (Rigshospitalet, Denmark) and her group utilised electronic health records of 2,972,192 patients, which is about half of Denmark’s population, to characterise the influence of COVID-19 on neurological diseases [3,4]. Included were patients tested for COVID-19 or diagnosed with community-acquired bacterial pneumonia in hospital-based facilities between February 2020 and November 2021, as well as influenza patients from the corresponding pre-pandemic period a year earlier (February 2018 to November 2019).

Of the study cohort, 919,731 individuals tested for COVID-19, of whom 43,375 tested positive. Compared with COVID-19-negative outpatients, positive outpatients had an increased relative risk (RR) of Alzheimer’s disease (RR=3.5; 95% CI 2.2–5.5), Parkinson’s disease (RR=2.6; 95% CI 1.7–4.0), ischaemic stroke (RR=2.7; 95% CI 2.3–3.2), and intracerebral haemorrhage (RR=4.8; 95% CI 1.8–12.9).

The increased risk of most neurological diseases was, however, not higher in COVID-19-positive patients than in patients diagnosed with influenza or other respiratory illnesses. There were 2 exceptions: the RR for ischemic stroke was increased compared with influenza inpatients (RR=1.7; 95% CI 1.2–2.4) and compared with bacterial pneumonia inpatients ≥80 years (RR=2.7; 95% CI 1.2–6.2). 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.

“We found support for an increased risk of neurodegenerative and cerebrovascular disorders in COVID-19-positive compared with COVID-19-negative patients, which must be confirmed or refuted by large registry studies in the near future,” Dr Zarifkar concluded. “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.”

1. Liotta EM, et al. Ann Clin Transl Neurol. 2020;7(11):2221–2230.
2. Chou S H-Y, et al. JAMA Netw Open. 2021;4(5):e2112131.
3. Zarifkar P, et al. Frequency of neurological diseases after COVID-19, influenza A/B and bacterial pneumonia. OPR-033, EAN 2022, 25–28 April, Vienna, Austria.
4. Zarifkar P, et al. Front Neurol. 23 Jun, 2022. DOI: 10.3389/fneur.2022.904796.

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Posted on 22 August, 2022