People who get flu have a higher risk of heart attack for a week after they have been diagnosed with the virus, a new study suggests.
Experts said that the risk can be as much as six times higher in the seven days after a person tests positive for the virus compared with the year before or afterwards.
They said the results underline the importance of the flu vaccination programme, as well as awareness of heart attack symptoms among doctors treating patients with flu.
A team of Dutch researchers analysed lab test results from 16 laboratories across the Netherlands and compared them with death and hospital records.
Some 26,221 cases of influenza were confirmed by the laboratories between 2008 and 2019.
Of the 419 heart attacks, 25 were in the first seven days after flu diagnosis, 217 within the year before diagnosis and 177 in the year after flu diagnosis – not including the first seven days.
Just over a third (35%) of patients who had a heart attack – or 139 people – died, of any cause, within a year of being diagnosed with flu, according to the study which is being presented to the European Congress of Clinical Microbiology and Infectious Diseases in Copenhagen in April.
The researchers calculated that people were 6.16 times more likely to have a heart attack in the seven days following a flu diagnosis than in the year before or after.
But when they excluded data from death records, the increase in heart attack risk in the first week was 2.42 times greater compared with the year before or after flu.
Experts suggest that the combination of the body’s response to the flu virus and the virus’s ability to make the blood more “sticky” could be behind the link.
Lead author Dr Annemarijn de Boer, from the University Medical Centre Utrecht in The Netherlands, said: “With the potential public health implications of an association between influenza virus infection and acute heart attacks, showing robustness of results in a different study population is important.
“Our results endorse strategies to prevent influenza infection, including vaccination.
“They also advocate for a raised awareness among physicians and hospitalised flu patients for symptoms of heart attacks.
“While it isn’t clear from our results if those with less severe flu are also at risk, it is prudent for them to be aware of the link.”
Commenting on the study, Dr Sonya Babu-Narayan, associate medical director at the British Heart Foundation, said: “These recent preliminary data from the Netherlands are in keeping with what we know, which is that heart attacks can happen more often during or shortly after an episode of the flu.
“It supports the need to raise public awareness of heart attack symptoms, and reinforces the importance of preventing flu in the first place, particularly among older people.”