TORONTO -- A new study has found that 82 per cent of people who were hospitalized due to COVID-19 experienced neurological symptoms.

The study, conducted by the Global Consortium Study of Neurologic Dysfunction in COVID-19 and the European Academy of Neurology Neuro-COVID Registry, involved over 3,700 patients across 13 countries who were assessed between March and October 2020 for neurological complications related to COVID-19.

Researchers report that neurological complications are widespread, and affected 82 per cent of patients who were hospitalized due to the disease.

The average age of patients in the study who were hospitalized with COVID-19 was around 60 years old, with cohorts of patients from the U.S., Europe, Asia, and Africa. 

In the study, neurological complications are categorized by symptoms reported by the patient, such as headaches and the loss of smell, or neurological signs that are observed and diagnosed by a doctor, such as a stroke or a seizure.

Dr. Charles Kassardjian, a neurologist at St. Michael’s Hospital in Toronto, said it’s not fully understood how COVID-19 leads to neurological symptoms, but that many viral illnesses cause similar symptoms. Patients who have contracted COVID-19 have also had lower oxygen levels, which could be why they’re experiencing neurological complications, he said. 

“With COVID-19, many patients are severely hypoxic [very low oxygen levels], and the brain needs oxygen. The reduced oxygen levels in many COVID-19 patients likely contributes to brain dysfunction, such as confusion,” Dr. Kassardijan, who wasn’t part of the study, told

“There are other possible mechanisms such as the overwhelming inflammation that can occur in some patients with COVID-19, as well as data – though far from confirmed – that the COVID-19 virus can invade the nervous system directly.”

The most common self-reported symptom in the study was headaches, which were reported by 37 per cent of patients. The second most common symptom was the loss of smell or taste, which affected 26 per cent of patients.

As for neurological signs and syndromes that were clinically identified by doctors, 49 per cent of patients were diagnosed with acute encephalopathy. This occurs when an individual’s mental state has changed or they suddenly start to show confusion.

Kassardijan said that another term for this neurological sign is delirium.

“There are many risk factors for delirium, including being in the intensive care unit itself. The acute encephalopathy might then be a reflection of the patient’s overall status. In addition, strokes can occur in patients with COVID-19, which would be an additional reason that a patient may be confused.”

The study states that certain demographic groups may also have a greater possibility in being diagnosed with serious neurological complications over others.

“In a model that mutually adjusted for these characteristics, older age, male sex, white race, and preexisting neurological disorders were associated with the risk of developing neurological signs or syndromes with COVID-19,” the study states.

Researchers also found that patients who were clinically diagnosed with neurological signs due to COVID-19 were associated with a higher mortality rate than patients who weren’t diagnosed with neurological signs. Patients who had self-reported symptoms had a lower risk of death.

“The presence of neurological signs or syndromes with COVID-19 significantly increased the risk of dying during acute hospitalization after adjusting for variations by study site and baseline characteristics,” the study states.

“Taken together, these observations highlight the importance of neurological manifestations in COVID-19 and their potential impact on disease outcome.”