Flu increases the risk of a heart attack

Fever, aches and pains, and a general feeling of weakness - you may have caught the dreaded flu. Influenza is a serious viral infection spread via fluids and can lead to serious complications like pneumonia and bronchitis. The flu contributes to about 3,000 deaths in Australia each year - particularly among vulnerable groups like the elderly, but can it also cause heart attacks?

In this study, the researchers looked at a sample of almost 150,000 laboratory tests for influenza between 2009 and 2014. Of those, about 19,000 were positive for influenza. They then linked the influenza cases to hospital admissions data for those who went to hospital because of a heart attack. The link meant they could see all those who had a confirmed case of influenza and had had a heart attack. From there, they were able to look at when the heart attack occurred relative to the person coming down with the flu, to determine if there was a relationship between the two things.

The researchers found that people were six times more likely to be admitted to hospital for heart attack in the week after coming down with the flu compared with any other time and it wasn’t just the flu. Other respiratory viruses also elevated the heart attack risk (though not by as much). The data also suggested the risk was higher for those over the age of 65. The elevated risk of heart attack was present even if the person who had come down with the flu had been vaccinated against influenza.

Implications

It’s unclear exactly why having the flu could lead to an increased risk of heart attack, though the researchers suggest the heart needing to work harder to pump oxygen around the body and increased inflammation could play some part. The best thing to do if you want to limit your risk of heart attack is control for the lifestyle factors that can contribute to elevated risk - diet, exercise, smoking and alcohol consumption among them - and when flu season comes around, ensure you’ve got your vaccination, wash your hands regularly and do all you can to avoid coming down with influenza.

References

Kwong, et al. (2018). Acute Myocardial Infarction after Laboratory-Confirmed Influenza Infection. The New England Journal of Medicine doi: 10.1056/NEJMoa1702090.