You have six times the chance of having a heart attack in the first seven days of having influenza, according to a new study. (CBC)

Heart attack more likely right after catching flu, study shows


A person is six times more likely to have a heart attack in the first week after being diagnosed with influenza, say Canadian researchers. Previous studies have suggested an association between the flu and heart attacks, but this research published in the New England Journal of Medicine is the first to provide laboratory confirmation.

Millions of Canadians get the flu annually

Government statistics show that millions of Canadians get seasonal influenza every year. Most people recover within ten days. But an average 12, 200 people are hospitalized and 3,500 die from the flu each year.

For this study, researchers looked at records of nearly 20,000 cases of influenza what were confirmed by lab tests in the province of Ontario between 2009 and 2014.They identified 332 patients who were hospitalized for a heart attack within one year of diagnosis and analysed their time lines.

Flu can increase blood pressure and have other effects that stress the heart. (iStock)

Why flu increases risk for heart attack

The study did not prove why flu is linked to heart attacks, but the lead researcher has some ideas: “With influenza, it’s like with other infections, you can have inflammation,” says Dr. Jeff Kwong, a scientist at Public Health Ontario and the Institute for Clinical Evaluative Sciences.


“Inflammation can lead to damage to the blood vessels—the lining of the blood vessels that serve the heart. And it can lead to increased chance of clots forming in the heart…Infection can also cause stressors on the body. It can lower the amount of oxygen in the blood, it can lower your blood pressure. So, all of these things make the body have to work harder, make your heart have to work harder and so, increases your chances of a heart attack.”

Kwong and his colleagues were also surprised to find that other viral infections besides the flu increased the risk of heart attack but not by as much as the flu.

Older people may be at higher risk, as well as patients with influenza B and those experiencing their first heart attacks.

Getting the yearly vaccine can reduce the risk of getting the flu and along with it, the risk of having a heart attack. (Chanss Lagaden/CBC)

Get vaccinated, wash hands, recommends doctor

Kwong says the results suggest people should reduce their risk of getting the flu by getting the annual vaccine and by washing their hands frequently. He adds that people who experience heart symptoms particularly within the first week of an acute respiratory infection see a doctor without delay.

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