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July 29, 2020

Stroke risk among COVID-19 patients may be lower than previously thought

Penn study suggests risk is linked to pre-existing conditions

Illness COVID-19
Stroke risk in COVID-19 patients low Thom Carroll/PhillyVoice

Most COVID-19 patients who experienced a stroke in three Philadelphia hospitals had pre-existing risk factors, such as high blood pressure or diabetes, according to a study conducted by Penn Medicine.

Reports published early in the coronavirus pandemic indicated COVID-19 patients have an increased risk of stroke. But new findings suggest otherwise. 

Penn Medicine researchers found that most COVID-19 patients who experienced a stroke in three Philly hospitals had pre-existing risk factors, such as high blood pressure or diabetes. The overall risk of stroke among COVID-19 patients was low. 

Their study was published in Stroke, an American Heart Association publication.

In April, medical papers suggested that the coronavirus not only attacks the lungs, but also the brain, causing strokes and other neurological damage. The prevailing thought has been that SARS-CoV-2 causes inflammation and increased blood clotting, which leads to a stroke.

The precise mechanism causing stroke in COVID-19 patients remains unknown. It's unclear whether the virus breaches the blood-brain barrier directly or whether the infection leads to side effects, like spikes in blood pressure, that triggers a stroke.

But the latest findings suggest the virus isn't the only agent at play.

"There is a relationship between COVID-19 and stroke, but it is a combination of multiple factors causing the strokes, not COVID-19 alone," senior author Dr. Brett Cucchiara, an associate professor of neurology at the Perelman School of Medicine, told PhillyVoice.

Why the disparity between the earlier research and theirs? 

"Earlier studies were anecdotal case reports," Cucchiara said. "The question is, how often does it happen? And those studies couldn't answer that. Our study is more systematic and found that stroke in a COVID-19 setting is relatively uncommon."

Cucchiara and his team evaluated the risk and incidence of stroke in 844 COVID-19 patients admitted to the Hospital of the University of Pennsylvania, Penn Presbyterian Medical Center and Pennsylvania Hospital between March and May. They also analyzed data on cases of intracranial hemorrhage – bleeding in the brain.

They found that 2.4% of the patients had an ischemic stroke, which is typically caused by a blood clot in the brain. Among the stroke victims, 95% had high blood pressure. Sixty percent had a history of diabetes and more than one-third previously had suffered a stroke. Some of these patients also had heart failure. 

On average, strokes occurred about 21 days after the onset of COVID-19 symptoms, suggesting that blood clotting increases during the first few weeks of the disease. This finding has been observed in other studies too.

The researchers also found that 0.9% of hospitalized COVID-19 patients had intracranial hemorrhage, a higher rate than reported in earlier studies. The increased use of blood thinners in COVID-19 patients may explain that disparity, researchers said.

Also, the COVID-19 patients who suffered strokes tended to be older – unlike the earlier reports, which indicated younger people may be prone. The average age of ischemic stroke patients was 64 years. Only one patient was younger than 50.

The researchers noted that their study population was more diverse than previous studies. Sixty-eight percent of the patients were Black. So were 80% of the stroke victims. Similar racial disparities are being seen across the country, an issue they said that needs to be better understood and addressed. 

Cucchiara acknowledged that there are still many unknowns about the relationship between stroke and COVID-19. 

"We still have a lot to learn," Cucchiara said. "Can we predict who has stroke in a setting of COVID-19 and prevent it? What is the mechanism that links stroke to COVID-19 and why does it happen?"

He added that doctors who see stroke in a hospitalized COVID-19 patient should perform normal diagnostic testing. 

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