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COVID-19 patients had a significantly higher risk of ischemic stroke than respiratory flu patients, data from two New York City hospitals suggested.

Stroke occurred in 1.6% of nearly 2,000 COVID-19 patients who visited an emergency department (ED) or who were hospitalized -- a rate more than seven times higher than the stroke rate in a comparable series of influenza patients, reported Babak Navi, MD, MS, of Weill Cornell Medicine in New York City, and co-authors, in .

"Although the overall rate of stroke in patients with COVID-19 was low, the rate was substantially higher than among patients with influenza," said co-author Neal Parikh, MD, MS, also of Weill Cornell Medicine.

"Fundamentally, our results support the notion that COVID-19 infection is more severe than influenza infection," Parikh told 麻豆传媒.

"Initially, our understanding of stroke in COVID-19 was based on case series and other small studies," he pointed out. "We sought to approach the topic with a systematic study to better understand the risk of stroke in COVID-19 infection."

The researchers conducted a direct comparison of the two viral respiratory diseases by looking at data from two sets of patients at NewYork-Presbyterian/Weill Cornell Medical Center and NewYork-Presbyterian Lower Manhattan Hospital.

The first group was a series of 1,916 patients with test-confirmed, active COVID-19 who visited the ED or were hospitalized from March 4 through May 2, 2020. The second group encompassed 1,486 patients who visited the ED or were hospitalized with lab-confirmed influenza from January 2016 through May 2018, spanning moderate and severe flu seasons.

A total of 31 COVID-19 (1.6%, 95% CI 1.1%-2.3%) patients and three influenza (0.2%, 95% CI 0.0%-0.6%) patients presented with or developed acute ischemic stroke while hospitalized. After adjusting for age, sex, and race, stroke likelihood was more than seven times higher in the COVID-19 group than the flu group (OR 7.6, 95% CI 2.3-25.2).

The median age of COVID-19 stroke patients was 69, and 18 of the 31 patients (58%) were men. Stroke was the reason for hospital presentation in eight cases (26%).

Plasma D-dimer levels were higher in COVID-19 versus flu patients. "This confirms previous observations that we are likely dealing with a diffuse microvascular thrombotic state, due to the infection of endothelial cells throughout the body," observed Edwin van Beek, MD, PhD, of the University of Edinburgh, who wasn't involved with the study. "D-dimer has been shown to be a predictor for poor outcomes in patients with COVID-19."

"It is safe to say that we are learning about this disease and how massive the impact is on virtually all organs in the body," van Beek told 麻豆传媒. "The brain, although generally well protected, is far from immune from the effects of this virus."

Several factors might explain why stroke rates were higher in COVID-19 than in flu, Navi and colleagues noted. COVID-19 infection is associated with a vigorous inflammatory response and coagulopathy, which may explain the high prevalence of thromboses seen in patients, they suggested. Patients with COVID-19 also are at heightened risk for complications like atrial arrhythmias, myocardial infarction, heart failure, myocarditis, and venous thromboses, which may add to ischemic stroke risk.

Baseline stroke risk factors like hypertension, diabetes, and coronary artery disease were more common in the COVID-19 group, but "even when adjusting for the number of vascular risk factors, we identified a higher risk of ischemic stroke with COVID-19 vs with influenza," the researchers pointed out.

The study has several limitations, they added. The true rate of ischemic stroke in patients hospitalized with COVID-19 infection may have been underestimated because some patients may have been too unstable to undergo brain imaging. Other patients with undiagnosed COVID-19 and stroke may have died before reaching the hospital. The COVID-19 surge in New York also may have affected decisions to go to the hospital and influenced outcomes.

The study involved only two hospitals and results may not apply to other settings, they noted. Importantly, they could not estimate the population-level incidence of ischemic stroke among COVID-19 patients and compare this to the general population.

The researchers plan to conduct further research and create a stroke risk score algorithm that can identify which COVID-19 patients are most likely to develop strokes.

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