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WASHINGTON — COVID-19 could be a powerful risk factor for heart attacks and strokes for as long as three years after an infection, a large new study suggests.
The study was published Wednesday in the medical journal Atherosclerosis, Thrombosis, and Vascular Biology. It relied on medical records from roughly a quarter of a million people who were enrolled in a large database called the UK Biobank.
Within this dataset, researchers identified more than 11,000 people who had a positive lab test for COVID-19 documented in their medical records in 2020; nearly 3,000 of them had been hospitalized for their infections. They compared these groups with more than 222,000 others in the same database who didn't have a history of COVID-19 over the same time frame.
People who caught COVID in 2020, before there were vaccines to blunt the infection, had twice the risk of a major cardiac event like a heart attack, stroke, or death for almost three years after their illness, compared with the people who didn't test positive, the study found.
If a person had been hospitalized for their infection, pointing to a more severe case, the risk of a major heart event was even greater — more than three times higher — than for people without COVID in their medical records.
What's more, for people who needed to be hospitalized, COVID appeared to be as potent a risk factor for future heart attacks and strokes as diabetes or peripheral artery disease..
One study estimated that more than 3.5 million Americans were hospitalized for COVID between May 2020 and April 2021.
A finding unique to COVID-19
The elevated heart risks from infection did not appear to diminish over time, the study found.
"There's no sign of attenuation of that risk," said study author Dr. Stanley Hazen, who chairs the Department of Cardiovascular & Metabolic Sciences at the Cleveland Clinic. "That's actually one of the more interesting, I think, surprising findings."
That finding is striking and seems to be unique to COVID-19, said Dr. Patricia Best, a cardiologist at the Mayo Clinic in Rochester, Minnesota, who was not involved in the research.
"We have known for some time that infections raise your risk of having a heart attack, so that if you have influenza, if you get any kind of infection … whether it's bacterial or viral, that increases your risk of having a heart attack," Best said. "But it generally goes away pretty quickly after your infection.
"This is just such a large effect, and I think it's just because of how different COVID is than some of the other infections," she said.
The researchers involved in the study say they don't know exactly why COVID has such apparently long-lasting effects on the cardiovascular system.
Earlier studies have shown that the coronavirus can infect the cells that line the walls of blood vessels. The virus has also been found in sticky plaques that form in arteries that can rupture and cause heart attacks and strokes.
"There might just be something that COVID does to the artery walls and the vascular system that is sustained damage and just continues to manifest over time," said study author Dr. Hooman Allayee, a professor of biochemistry and molecular genetics at the Keck School of Medicine at the University of Southern California.
Their working theory, Allayee said, is that COVID may be destabilizing plaques that are building within the walls of arteries and may make them more prone to rupturing and causing a clot.
Some protective factors
Allayee and his graduate student James Hilser took a closer look to see how COVID might be causing this long-term trouble in the body.
They looked to see whether people with known genetic risk factors for heart disease, or gene changes linked to being susceptible to COVID infection, were more likely than others to have a heart attack or stroke or to die after being hospitalized for COVID. But they weren't.
What did show up, the researchers say, was a distinction by blood type.
Researchers have known that people with certain non-O blood types — A, B or AB — are at higher risk of cardiovascular diseases.
Blood type also appears to play a role in how likely a person is to get COVID. People with O-type blood seem to be a bit protected there, too.
In the new study, people with O-type blood who were hospitalized for COVID didn't have quite as high of a risk of heart attack or stroke as those with A, B or AB blood types. But that doesn't mean they were in the clear, Hazen said: They were still at higher risk of heart attacks and strokes, but their blood type was just another variable to consider.
The researchers believe that the gene that codes for blood type may be playing a role in the increased risk in heart attacks and strokes after COVID, but they aren't sure exactly how.
There was some hopeful news in the study, too. People who were hospitalized for COVID but who were also taking low-dose aspirin had no increase in the likelihood of a subsequent heart attack or stroke. That means the risk can be mitigated, Hazen said.
"Cardiac disease and cardiovascular events are still the No. 1 killer around the world," he said.
When he sees patients, Hazen said, he now makes sure to ask about their COVID history.
"If you've had COVID, we have to be especially attentive to making sure that we're doing everything possible to lower your cardiovascular risk," Hazen said.
That includes controlling blood pressure and cholesterol and perhaps taking a daily aspirin.
