Winter viruses can trigger heart attack or stroke, study reveals

Melbourne: Winter is here, along with cold days and the inevitable seasonal surge in respiratory viruses.

But it’s not only the sniffles we need to worry about. Heart attacks and strokes also tend to rise during the winter months.

In new research out this week we show one reason why.

Our study shows catching common respiratory viruses raises your short-term risk of a heart attack or stroke. In other words, common viruses, such as those that cause flu and COVID, can trigger them.

Wait, viruses can trigger heart attacks?

Traditional risk factors such as smoking, high cholesterol, high blood pressure, diabetes, obesity and lack of exercise are the main reasons for heart attacks and strokes.

And rates of heart attacks and strokes can rise in winter for a number of reasons. Factors such as low temperature, less physical activity, more time spent indoors – perhaps with indoor air pollutants – can affect blood clotting and worsen the effects of traditional risk factors. But our new findings build on those from other researchers to show how respiratory viruses can also be a trigger. The theory is respiratory virus infections set off a heart attack or stroke, rather than directly cause them. If traditional risk factors are like dousing a house in petrol, the viral infection is like the matchstick that ignites the flame. For healthy, young people, a newer, well-kept house is unlikely to spontaneously combust. But an older or even abandoned house with faulty electric wiring needs just a spark to lead to a blaze.

People who are particularly vulnerable to a heart attack or stroke triggered by a respiratory virus are those with more than one of those traditional risk factors, especially older people.

Our team conducted a meta-analysis (a study of existing studies) to see which respiratory viruses play a role in triggering heart attacks and strokes, and the strength of the link. This meant studying more than 11,000 scientific papers, spanning 40 years of research.

Overall, the influenza virus and SARS-CoV-2 (the virus that causes COVID) were the main triggers. If you catch the flu, we found the risk of a heart attack goes up almost 5.4 times and a stroke by 4.7 times compared with not being infected. The danger zone is short – within the first few days or weeks – and tapers off with time after being infected.

Catching COVID can also trigger heart attacks and strokes, but there haven’t been enough studies to say exactly what the increased risk is.

We also found an increased risk of heart attacks or strokes with other viruses, including respiratory syncytial virus (RSV), enterovirus and cytomegalovirus.