The findings, published in the journal JACC: Advances, suggest that annual health screenings may miss heart conditions that put firefighters at risk of sudden cardiac death. National screening recommendations primarily rely on exercise stress testing, which may not detect some heart conditions.

“Our research shows there may be a blind spot when it comes to routine heart screenings for firefighters in the U.S.,” said Alan Kwan, MD, assistant professor of Cardiology in the Smidt Heart Institute at Cedars-Sinai and senior author of the study. “Identifying heart conditions when they can be treated is key to addressing these new findings.”

Investigators found that many on-duty firefighter deaths involved coronary artery disease, also known as narrowing of arteries that feed the heart. But a greater number were tied to something harder to detect: an enlargement of heart muscle mass.

Heart muscle enlargement, which can take various shapes and forms, is not readily detected by standard exercise stress tests that firefighters undergo as part of their yearly physical. As firefighters train, they build heart muscle, which may represent athletic cardiac changes but also may mask heart muscle changes caused by dangerous cardiac conditions.

“It’s possible that national firefighter health guidelines need to be updated to include screening for excess heart muscle mass,” said study author Susan Cheng, MD, MMSc, MPH, chair of the Department of Cardiology in the Smidt Heart Institute. “It’s not clear why firefighters appear to be at risk for this condition, and so we need to learn more through additional research.”

Investigators reviewed U.S. Fire Administration records documenting 3,401 on-duty firefighter deaths from 1990 through 2025 and found that 43% were cardiac in origin.

The team analyzed firefighter deaths during the years from 1990 through 2019, before the COVID-19 pandemic. Over that span, on-duty deaths fell overall, but the odds that any given death was heart-related increased by 2.2% each year. In the U.S. population at large, the trend ran the opposite direction: Cardiac deaths as a proportion of all deaths fell 1.3% per year.

“This trend suggests that prevention of on-duty cardiac death has not kept pace with other domains of firefighter safety,” Kwan said. “This work builds on prior research reporting that cardiac events are a major cause of death for firefighters. We plan to continue our study of firefighter health risks to inform prevention efforts.”

Additional Cedars-Sinai authors include Sandy Y. Joung, MBA, MSHS; Lori Martinez-Rubio, DDS, MS; Michelle Bravo, MSN, RN, PHN; Rahul Gupta, MD; Yeran Lee; Eli M. Friedman, MD; Evan Kransdorf, MD, PhD; and Joseph E. Ebinger, MD, MS.

Other authors include: Brian Claggett, PhD, and Stefanos Kales, MD, MPH.

Funding: The study was partially supported by the Spiegel Family Fund, the Smidt Discovery Fund of the Smidt Heart Institute, the Erika J. Glazer Family Foundation, NIH grant KL2TR001882, and R01AG099094.

Read More From the Cedars-Sinai Newsroom: Cedars-Sinai Reports Heart Attacks, General Illness Spiked After LA Fires

The findings, published in the journal JAMA Network Open, revealed a heightened risk for diabetes after having COVID-19. Investigators also found that those who were vaccinated against COVID-19 had a lower chance of developing diabetes than those who were unvaccinated.  

“The potential effects of a COVID infection are likely different than other viral infections that we’re used to—seasonal colds, even flus,” Kwan told The Globe and Mail. “And so, in the space of uncertainty, really protecting yourself against infection is important.” 

It remains unknown why COVID-19 leads to an increased risk of developing Type 2 diabetes. The culprit could be inflammation, which makes it difficult for the body to process sugar and respond to insulin, Kwan told The Globe and Mail. He explained that inflammation may be caused by a COVID-19 illness or dexamethasone, a steroid medication used to treat COVID-19 patients in hospitals.

Kwan told Saskatoon Morning guest host Theresa Kliem that COVID-19 affects more than just the lungs, and he hopes the research raises awareness of the need for diabetes screenings. Kwan advised that “if you’re experiencing ongoing issues after a COVID infection, be aware of this possibility and really try and take care of your overall health, not just the COVID infections.”

Click here to read the complete article from The Globe and Mail. Click here to listen to the complete episode of Saskatoon Morning with Leisha Grebinski.