Tuesday, August 25, 2020

CDC: Another Study Linking Severe Influenza To Heart Damage



In an average year, seasonal flu kills roughly as many Americans as does gun violence, or car accidents. In a bad year - such as we saw in 2017-2018, influenza can kill as many as both of those combined.


The CDC has an `expected range' of seasonal influenza hospitalizations and deaths (see chart above), but over the past 10 years, we've increasingly seen influenza and other respiratory infections linked to a significant increase in heart attacks, strokes, and even Alzheimer's/Dementia. 

Despite some less-than-stellar influenza Vaccine Efficiency (VE) numbers - particularly among those in the highest risk groups (65+) - we've seen evidence that vaccination does reduce complications like heart attacks and strokes.

Although getting the flu can be a miserable experience, these are the primariy reasons why I get the flu shot each and every year, and recommend it to others.  Particularly now that I'm part of that dreaded `elderly' demographic. 

While the flu vaccine doesn't guarantee you'll avoid infection, most years it provides moderately good protection against circulating influenza viruses. And for those who are vaccinated - but still get the flu - they are less likely to have a severe bout.

This from the CDC:

Flu Vaccine Reduces Serious Flu Outcomes

Flu vaccination has been shown to reduce flu illnesses and more serious flu outcomes that can result in hospitalization or even death in older people. For example, a 2017 study showed that flu vaccination reduced deaths, intensive care unit (ICU) admissions, ICU length of stay, and overall duration of hospitalization among hospitalized flu patients; with the greatest benefits being observed among people 65 years of age and older.

All of which brings us to a CDC press release, and a link to a new study in the Annals of Internal Medicine, which finds that roughly 12% of adults hospitalized with severe influenza incur some degree of cardiac injury. 

CDC Study Finds Sudden, Serious Cardiac Events Common in Adults Hospitalized with Flu

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August 25, 2020 – A CDC study published today that looked at more than 80,000 U.S. adults hospitalized with flu over eight flu seasons (2010-11 through 2017-18) found that sudden, serious heart complications were common and occurred in one out of every eight patients (~12% of patients).

The study looked at a range of sudden heart complications called “acute cardiac events” that resulted in the following:
  • damage to the heart muscle,
  • inflammation of the heart muscle,
  • fluid or inflammation of the sac surrounding the heart, or
  • weakening of the pumping function of the heart.
The most common acute cardiac events reported in the study were acute heart failure and acute ischemic heart disease. Acute heart failure is the sudden inability of the heart to pump enough blood to meet the body’s demands, while acute ischemic heart disease is a term that describes heart problems caused by narrowed or blocked heart arteries.

Previous studies have looked at the relationship between influenza infection and heart attacks or heart failure, but few large, population-based studies have examined the frequency of acute cardiac events associated with laboratory confirmed influenza infection. Therefore, this study contributes new and important findings to the scientific body of evidence on this topic.

The study also assessed risk factors for acute cardiac events. Older age, tobacco use, underlying cardiac disease, diabetes, and kidney disease were significantly associated with higher risk of acute heart failure and acute ischemic heart disease in adults hospitalized with laboratory-confirmed influenza infection.

Although vaccinated people had a lower risk of acute ischemic heart disease and acute heart failure, this study was not designed to assess flu vaccine effectiveness. However, other studies support the importance of influenza vaccines for people with underlying chronic conditions.

The study is subject to several limitations. There was likely under-detection of influenza cases, as flu testing was based on practitioner orders. Also, acute cardiac events were identified by ICD discharge codes and may be subject to misclassification bias.

CDC recommends that everyone 6 months and older get a flu vaccine this and every flu season. Flu vaccination is always considered important for people who are at high risk of developing serious flu complications, including people with heart disease. Flu shots are approved for use in people with heart disease. People with heart disease should not receive the live attenuated influenza vaccine (LAIV, also known as the nasal spray flu vaccine). However, any intramuscular flu shot (i.e., any inactivated or recombinant influenza vaccine) can be given.

This study is available for viewing online via the Annals of Internal Medicine website.

Acute Cardiovascular Events Associated With Influenza in Hospitalized Adults
A Cross-sectional Study

Eric J. Chow, MD, Melissa A. Rolfes, PhD, Alissa O'Halloran, MSPH, …


Next month I'll get my 15th seasonal flu shot in the past 15 years. While I recognize it probably only provides my age group with 30%-40% protection, given the long list of things that can go wrong during or following flu infection, I'll take whatever advantage I can get. 

I view getting a yearly flu shot like always wearing a seat belt in an automobile. It doesn't guarantee a good outcome in a wreck, but it sure increases your odds of walking away.

And that, to me, is an extra bit of insurance worth having.