The risk of having a heart attack increases 17 times in the seven days after a respiratory infection, including pneumonia, according to recent research from Australia.
The study, “Triggering of acute myocardial infarction by respiratory infection,” was published in the Internal Medicine Journal.
Previous studies have suggested that respiratory infections increase the short-term risk of having a heart attack, but no medical confirmation had been carried out.
To address this question, researchers conducted interviews within four days of hospitalization with 578 patients who had a confirmed heart attack. The goal was to investigate whether these patients had a recent respiratory infection and the annual frequency of infection symptoms.
The analysis indicated that 100 (17 percent) patients reported experiencing symptoms of respiratory infection within seven days and 123 (21 percent) patients experienced symptoms within 35 days before having a heart attack.
Indeed, the relative risk for a heart attack occurring within the first seven days after symptoms of respiratory infection was 17 times higher. This risk decreased with time.
“Our findings confirm what has been suggested in prior studies, that a respiratory infection can act as a trigger for a heart attack,” Prof. Geoffrey Tofler, the study’s senior author, said in a news release. “The data showed that the increased risk of a heart attack isn’t necessarily just at the beginning of respiratory symptoms, it peaks in the first 7 days and gradually reduces but remains elevated for one month.”
The risk of heart attack was lower in patients taking regular heart medications.
In patients reporting symptoms of milder upper respiratory tract infection (including cold, pharyngitis, rhinitis and sinusitis), the risk of having a heart attack in the following seven days increased 13.5 times.
“Although upper respiratory infections are less severe, they are far more common than lower respiratory tract symptoms,” said Lorcan Ruane, the study’s first author. “Therefore it is important to understand their relationship to the risk of heart attacks, particularly as we are coming into winter in Australia.”
According to Thomas Buckley, another author of the study, the incidence of heart attacks rises in Australia during the winter, but not only in that country.
“This winter peak seen not only in Australia but also in other countries around the world is likely due in part to the increased incidence of respiratory infections,” Buckley said. “People should take measures to reduce exposure to infection, including flu and pneumonia vaccines where appropriate.”
Tofler believes that respiratory infections may increase blood clotting, inflammation, blood vessel damage, and changes in circulation, all of which are factors known to increase the risk of a heart attack.
“Our message to people is while the absolute risk that any one episode will trigger a heart attack is low, they need to be aware that a respiratory infection could lead to a coronary event,” Tofler said. “So consider preventative strategies where possible, and don’t ignore symptoms that could indicate a heart attack.”