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Getting your flu shot can help protect you from getting sick this fall. Getty Images
  • A new study found that 1 in 8 people hospitalized 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.

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 hospitalized with influenza,” lead author Dr. Eric Chow, an infectious diseases fellow at the University of Washington School of Medicine, told Healthline.

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 hospitalized with the flu,” said Bhuyan.

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 hospitalized with the flu had a non-respiratory diagnosis, such as sepsis and acute kidney injury.

“Influenza is more than ‘just a cold’ and we need to take respiratory virus infections like influenza seriously, as they can result in severe complications, hospitalizations, and sometimes death,” Chow said.

The growing evidence suggests that doctors should expand diagnostic criteria.

Keep in mind that COVID-19 hasn’t been around a full year, so we have yet to fully understand what a “twindemic” could look like.

But health experts are worried about the unlucky people who develop both COVID-19 and influenza in one season.

“I am concerned about the possibility of having both influenza and SARS-CoV-2 circulating in the community as both can result in severe complications, especially in those with underlying medical conditions,” said Chow.

The effects, particularly on the cardiovascular system, could be devastating.

“While we don’t fully know the extent, it is likely they could face a slew of medical complications, including heart damage,” said Bhuyan.

If a person developed both illnesses, it’s possible they could face not only short-term health issues, but long-term complications as well, Bhuyan added.

Bhuyan said the good news is that there are a number of things you can do to protect yourself.

First and foremost is to get the flu shot.

“Getting the flu shot can minimize the chances of getting the flu as well as minimizing the severity of the flu if you do end up getting sick,” Bhuyan said.

Remember: The flu shot protects not only yourself, but friends, family, and at-risk members of your community, too.

As the pandemic rages on, face masks, hand hygiene, and quarantining will continue to be critical.

Taking care of your overall health remains important, too.

Healthy habits like quitting smoking, managing other health conditions, eating a healthy diet, and exercising frequently will improve your health.

“People often don’t realize how deadly and dangerous the flu can be,” said Bhuyan. “It’s important we take it seriously every year and prioritize getting the flu vaccine.”

New research from the University of Washington further establishes the link between the flu and cardiovascular events.

Nearly 12 percent of people with flu go on to experience a heart issue, such as a heart attack or heart disease.

Though people with risk factors like obesity, diabetes, or underlying heart disease are most at risk, 5 percent of flu patients who developed a heart issue didn’t have an underlying health issue.

The findings highlight the importance of getting the flu shot each year.