Researchers from the University of Sydney have found that the risk of having a heart attack increases by 17 times following a respiratory infection.
This is the first of its kind study to link heart attack with respiratory infections such as pneumonia, influenza and bronchitis.
“Our findings confirm what has been suggested in prior studies that a respiratory infection can act as a trigger for a heart attack,” says senior author Professor Geoffrey Tofler, cardiologist from University of Sydney, Royal North Shore Hospital and Heart Research Australia.
“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.”
Every 7 minutes someone in the UK will have a heart attack. Every year 160,000 people die from heart and circulatory disease in the UK.
The Australian research team set out to investigate the connection between respiratory infections and the risk of heart attack.
The researchers examined 578 patients who had a heart attack due to a coronary artery blockage.
The patients provided information on recent and usual occurrence of symptoms of respiratory infection, including bronchitis and pneumonia.
Patients were asked about symptoms including cough, fever, sore throat, sinus pain, and other flu-like symptoms.
The subjects were admitted to the Royal North Shore Hospital in New South Wales, Australia. The researchers used coronary angiography – a special X-ray test used to detect blockages in coronary arteries – to confirm diagnosis of a heart attack.
Respiratory infection linked to heart attack
Among the patients, 17% reported symptoms of respiratory infection within 7 days of the heart attack, and 21% within 31 days.
The team interviewed the patients about their activities before the onset of their heart attack. They were asked questions like, if they experienced a recent “flu-like illness with fever and sore throat.”
A second analysis was conducted among those who reported symptoms of upper respiratory tract infections, including colds, sinusitis, pharyngitis, and rhinitis.
“For those participants who reported milder upper respiratory tract infection symptoms the risk increase was less, but was still elevated by 13 fold,” said lead author Dr. Lorcan Ruane
“Although upper respiratory infections are less severe, they are far more common than lower respiratory tract symptoms. Therefore it is important to understand their relationship to the risk of heart attacks, particularly as we are coming into winter in Australia,” he said.
As for the reasons why respiratory infection may trigger a heart attack, researchers pointed to various scenarios such as an increased tendency towards blood clotting, inflammation and toxins damaging blood vessels, and changes in blood flow.
Associate Professor Thomas Buckley, study investigator from Sydney Nursing School said:
“The incidence of heart attacks is highest during winter in Australia. This winter peak in 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. People should take measures to reduce exposure to infection, including flu and pneumonia vaccines where appropriate.”
The study was published in Internal Medicine Journal.