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Another Reason to Get Your Flu Shot, It Can Protect Your Heart

  • A new study found that 1 in 8 people hospitaliSed with the flu experienced serious heart complications.

  • It’s long been understood that there’s a link between the flu and subsequent cardiac events, but this is the largest study of its kind showing just how common this is.

  • Health experts are also worried about the people who develop both COVID-19 and influenza in one season.

With the Northern Hemisphere gearing up for a potential “twindemic” — simultaneous COVID-19 and influenza outbreaks — doctors are reminding us that COVID-19 isn’t the only virus that can trigger cardiac issues this fall and winter.

New research from the University of Washington has further established the link between influenza and the heart.

The study, which was published in the Annals of Internal Medicine in late August, looked at the health data of almost 90,000 flu patients and found that about 12 percent — or 1 in 8 people — experienced serious heart complications soon after being diagnosed with the flu. It’s long been understood that there’s a link between the flu and subsequent cardiac events, but this is the largest study of its kind showing just how common this is.

“This study is key because it truly highlights how common it can be to experience serious heart complications after getting the flu — including in some people that did not have any prior chronic health conditions,” said Dr. Natasha Bhuyan, a practicing family physician in Phoenix, Arizona.

What the research team looked at The research team set out to understand how prevalent cardiovascular events are in people with flu, along with the risk factors for such events.

Looking at the health data of 89,999 flu patients between the 2010 to 2018 influenza seasons, the researchers determined that 11.7 percent of these people experienced an acute cardiovascular event like acute heart failure and acute ischemic heart disease.

The team also identified a number of risk factors:

  • tobacco use

  • older age

  • obesity

  • diabetes

  • heart disease

  • kidney disease

Though flu patients with one of these risk factors had a higher chance of experiencing a cardiac event after contracting the flu, 5 percent had no previous underlying health conditions.

“In our study, we showed that acute cardiovascular events such as heart failure or heart attacks are common complications associated with adults hospitalised with influenza,” lead author Dr. Eric Chow, an infectious diseases fellow at the University of Washington School of Medicine, told Healthline.

How does influenza put stress on the heart? Past evidence suggests that respiratory illnesses like the flu (and as we know now, COVID-19) can cause a widespread, systemic inflammatory response.

This inflammation puts a lot of stress on the body and can trigger all sorts of complications, particularly involving the heart. It could lead to new heart disease or worsen underlying cardiac conditions.

For example, the inflammation caused by influenza can disrupt plaque functioning, setting the stage for acute ischemic heart disease.

Bhuyan said the inflammation could theoretically also cause an arrhythmia.

Though the new report from the University of Washington is the largest of its kind establishing the link between the flu and heart problems, it’s not the first.

Initial evidence pointing to the flu-heart relationship dates back to the 1930s, when researchers first reported that some patients with respiratory infections were experiencing cardiovascular problems, according to Chow.

Over the years, it’s become increasingly clear there’s a real connection between the flu and the heart.

A study from 2018 found that a significant number of people with acute respiratory infections, especially the flu, also experienced acute myocardial infarction — aka heart attacks.

Flu complications also tend to be worse in people with underlying cardiovascular problems. “We knew that people who got the flu that had underlying health issues, including heart disease, were more likely to be hospitalised with the flu,” said Bhuyan.

The flu isn’t just a respiratory illness A key lesson here is that the flu isn’t just a respiratory illness. Researchers are learning more every year about the many complications that occur outside the lungs.

Another study Chow worked on earlier in the year found that up to 46 percent of people hospitalised with the flu had a non-respiratory diagnosis, such as sepsis and acute kidney injury.