Battle Scars: Combat Injury Linked With Cardiovascular Risk

A study reviewing the experiences of US military personnel has found links between combat injuries and chronic diseases, including coronary artery disease. The more severe the battlefield injury, the more likely it was that military men and women later developed cardiovascular disease, researchers say.

“In the last 13 years of war, 6,683 [US] service members have died and 52,087 have been wounded in combat operations in Iraq and Afghanistan. The men and women who served in these conflicts will continue to suffer for years to come,” write Major Ian J. Stewart, MD, of David Grant Medical Center (Travis Air Force Base, CA), and colleagues, citing the “hidden costs” of war.

Published online November 2, 2015, ahead of print in Circulation, the retrospective cohort study analyzed long-term health risks of 3,846 service members who were admitted to the ICU after being wounded in Iraq or Afghanistan between February 2002 and February 2011. None of the included patients had been diagnosed with the diseases of interest—CAD, hypertension, diabetes, and CKD—prior to being injured. ICD-9 codes were used to ascertain diagnoses.

Median follow-up duration from injury until diagnosis, death, or loss to follow-up ranged from 1.1 years to 2.28 years for those with chronic diseases and was 4.3 years for those that did not develop disease.

More Severe Injury Equals Higher Risk

Patients who developed 1 of the 4 chronic diseases tended to be older, have higher injury severity score, and to be more likely to have acute kidney injury (AKI). Those who died or became chronically ill tended to have injuries that affected the head/neck and chest as opposed to extremity injuries.

Higher injury severity score was independently associated with greater risk for each of the 4 diseases even when considering baseline differences in age, race, mean arterial blood pressure, heart rate, burn injury, and AKI. Each 5-point rise in injury severity score correlated with a 6% increase in hypertension, a 13% increase in CAD, a 13% increase in diabetes, and a 15% increase in CKD.

Rates of hypertension, CAD, and diabetes were 2 to 4 times higher among the most severely injured patients compared with published data for the overall military population.  

“The association between ISS and long-term outcomes is biologically plausible by several mechanisms,” Stewart and colleagues write. Possible culprits are inflammation, PTSD (either by upping the inflammatory response or leading to weight gain and substance abuse), and functional limitations stemming from injury.

These findings set the stage “for additional research to better understand the causal pathways and the longer-term effects of combat-related injury on the risk of chronic disease,” they conclude.

Potential Confounding

In an accompanying editorial Allen J. Taylor, MD, of MedStar Heart and Vascular Institute (Washington, DC), stresses: “Caution is warranted in interpreting the study’s limited and imprecise associations due to a high risk of confounding. Quite simply, the ability to characterize competing cardiovascular risk variables, both medical and social, both prior to and after the traumatic injury, is limited.”

In particular, the “heightened incidence for CAD observed over a short period of follow-up (< 2.8 years) in such a young cohort is surprising and leads one to question whether inaccuracies in coding could be at play,” he writes.

Despite the limitations of the study itself, “the matter is consequential to our military and its people, and thus filling in the puzzle pieces to create a more full understanding is a matter of some urgency,” Taylor comments. If battlefield trauma does in fact have long-term cardiovascular consequences, that knowledge could influence how disability status is conceived and how resources are provided to military and veterans’ health organizations, he suggests.

Disclosures:

• Stewart reports no relevant conflicts of interest.
• Taylor reports being a retired officer from the United States Army Medical Corps. He also has received consulting or speaking relationships with Amgen, Lilly, and Sanofi.