Doctors throughout America are reporting that patients in their 30s and 40s with Covid-19 are experiencing strokes at a higher rate than patients in their age group who don't have the disease.

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US doctors report strokes among young Covid-19 patients—including some who were mildly ill

According to the Washington Post, up until the past few weeks, there was limited evidence on the association between Covid-19, the disease caused by the new coronavirus, and strokes. One report from Wuhan, China—where the global Covid-19 pandemic first began—showed that some seriously ill and elderly hospitalized Covid-19 patients were experiencing strokes, but there wasn't similar data regarding patients in the United States, the Post reports.

However, doctors in recent weeks have begun reporting that the new coronavirus in some cases causes damage to organs beyond lungs. And now, three large U.S. medical centers are preparing to publish data on a link between Covid-19 and strokes—with some striking figures on strokes occurring among patients in their 30s and 40s, including some who weren't even aware they had contracted the new coronavirus.

For example, the Post reports that a paper currently under review details reports from doctors at Thomas Jefferson University Hospitals, which operates 14 medical centers in Philadelphia, and New York City-based NYU Langone Health regarding strokes among Covid-19 patients. The doctors said that, over the course of three weeks, they identified 12 patients who were treated for blood blockages in their brains who also tested positive for the new coronavirus. Of those patients, 40% had very few or no risk factors for stroke and were under 50 years old, according to the Post.

Pascal Jabbour, a neurosurgeon at Thomas Jefferson University Hospitals and a co-author of the paper, said the strokes also had unusual characteristics. For instance, the patients mostly experienced large vessel occlusions (LVOs), which are considered the deadliest type of stroke. LVOs also have the ability to destroy the areas of the brain responsible for decision-making, movement, and speech, the Post reports.

Jabbour also noted that some patients are developing more than one clot in their brains. "We'll be treating a blood vessel [in one part of the brain] and it will go fine, but then the patient will have a major stroke," Jabbour said.

Eytan Raz, an assistant professor of neuroradiology at NYU Langone and a co-author of the paper, said the findings are leading providers to question how the new coronavirus can affect younger patients. "We are used to thinking of 60 as a young patient when it comes to [LVOs]," Raz said. "We have never seen so many in their 50s, 40s, and late 30s."

Meanwhile, at Mount Sinai, the largest health system in New York City, physician-researcher J Mocco has reported that the number of patients with large blood blockages in their brains doubled to more than 32 patients over a three-week span. According to Mocco, more than half of those patients tested positive for the novel coronavirus, and those patients on average were 15 years younger than the average age of stroke patients without Covid-19—a finding that is "very, very atypical," Mocco said. "These are people among the least likely statistically to have a stroke," Mocco explained.

According to the Post, Thomas Oxley, a neurosurgeon at Mount Sinai, and colleagues in a letter scheduled to be published next week in the New England Journal of Medicine outlined case studies of five patients in their 30s and 40s who suddenly began experiencing stroke symptoms—including confusion, drooping on one side of the face, numbness in one arm, and slurred speech—while at home. The Post reports that the patient's outcomes overall were grim: one died, two remain hospitalized, one is in a rehabilitation facility, and one was released home in his brother's care—and only one of those patients is able to talk.

But Oxley and colleagues noted that most of the patients had only mild—and in some instances asymptomatic—cases of Covid-19. "Most of these patients have no past medical history and were at home with either mild symptoms (or in two cases, no symptoms) of [Covid-19]," they said.

Oxley and colleagues also noted that at least one of the patients, a 33-year-old woman who was not aware she had Covid-19, had two clots in her brain.

Mocco said the correlations between Covid-19 and strokes is "one of the clearest and most profound" he's ever seen. "This is much too powerful of a signal to be chance or happenstance," he said. Mocco added, "It's very striking how much this disease causes clots to form."

Why are younger Covid-19 patients experiencing severe strokes?

Robert Stevens, a critical care doctor at Johns Hopkins Hospital in Baltimore, said strokes are "one of the most dramatic manifestations" of blood-clotting issues that have been reported among Covid-19 patients. "We've also taken care of patients in their 30s with stroke and [Covid-19], and this was extremely surprising," Stevens said.

According to the researchers, blood clots that form above the heart are the most likely to travel to the brain and cause a stroke. However, researchers still aren't sure why Covid-19 appears to be causing blood clots. Harlan Krumholz, a cardiac specialist at Yale-New Haven Hospital Center, said, "One of the theories is that once the body is so engaged in a fight against an invader, the body starts consuming the clotting factors, which can result in either blood clots or bleeding."

As to why providers are seeing a higher rate of younger Covid-19 patients experiencing strokes, Raz said it's possible that such patients are more likely to live through the respiratory distress caused by Covid-19 than older patients, and the younger patients then develop other complications associated with the disease. "So they survive the lung side, and in time develop other issues," Raz said.

Oxley also noted that younger patients could be experiencing more severe strokes because they delay seeking care. For instance, Oxley and his colleagues noted that the 33-year old patient who had two clots in her brain and who was unaware she had Covid-19 had delayed seeking treatment for about 28 hours out of fear that she would be exposed to the new coronavirus.

Oxley said people of all ages should immediately seek emergency care if they experience any signs of a stroke, noting that even severe strokes usually are treatable if caught early. "The most effective treatment for large vessel stroke is clot retrieval, but this must be performed within six hours, and sometimes within 24 hours," Oxley and colleagues wrote.

"The message we are trying to get out is if you have symptoms of stroke, you need to call the ambulance urgently," he said (Cha, Washington Post, 4/25; Wagner et al., CNN, 4/22; Woodward, Business Insider, 4/24; Rummler, Axios, 4/25).