Annette M. Boyle
BETHESDA, MD — Despite concerns about unhealthy lifestyles and rising obesity among recruits, the U.S. military might be in better shape than ever, as measured by cardiovascular disease markers.
That’s according to a new study published in the Journal of the American Medical Association, which found that, among combat casualties from 2001 to 2011, 8.5% showed signs of coronary atherosclerosis, down 82% from the 45% rate seen during the Vietnam War and 77% detected among those killed in the Korean War. A total of 12.1% had coronary or aortic atherosclerosis.1
“We believe the drop in atherosclerosis is mostly due to the fact that the current military population has a healthier cardiovascular risk profile than earlier generations. It’s worth noting that the poor physical condition of Korean draftees motivated Eisenhower’s President’s Physical Fitness Program,” said lead researcher Maj. Bryant Webber, MD, of the Uniformed Services University of the Health Sciences in Bethesda, MD.
While many studies have shown an increase in average weight and rising rates of obesity and diabetes in the general and military population, Webber told U.S. Medicine that “at the same time, the rate of ischemic heart disease is down more than 70% since the 1970s. Other risk factors, such as hypertension, dyslipidemia and smoking have improved significantly and may be offsetting those risk factors that are going up.”
Webber urged care in direct comparison of the three studies used for the research. The current study included all U.S. servicemembers who died of combat or unintentional injuries while deployed during Operations Enduring Freedom and Iraqi Freedom/New Dawn between October 2001 and August 2011 whose autopsy results were available in January 2012. More than 98% of those analyzed were male, and the average age was 26.
Researchers established disease classifications to create consistency with the previous studies. In this context, minimal disease was defined as fatty streaking only; moderate disease indicated 10% to 49% luminal narrowing of one or more vessels; and severe disease was assigned to those with 50% or more narrowing. The autopsies of 3,832 servicemembers were included in the analysis or more than 60% of all casualties during the period studied.
In contrast, the Vietnam and Korea studies looked at less than 1% of combat fatalities and they “were looking for atherosclerosis, so there is the possibility of expectation bias,” noted Webber. Also, “our understanding of atherosclerosis has changed; some of what researchers called early coronary atherosclerosis in the Korean War timeframe now is considered normal.”
Few Diagnosed Before Autopsy
Looking only at the level of severe disease, however, still shows significant improvement over time. During the Korean War, 15% of autopsies showed 50% or greater blockage, compared with 5% in Vietnam and 2.3% in the current study.
Despite the improvement, Webber said the study showed that “even young, healthy, military who are fit enough to be deployed are susceptible to coronary atherosclerosis. The disease process is clinically silent and may progress undiagnosed for years. We saw 464 servicemembers with atherosclerosis at autopsy, but only two of them had been diagnosed with the disease.”
As a result, the researchers concluded that “military and civilian healthcare systems should continue to help patients reduce their cardiovascular risk factors, beginning in childhood and continuing throughout adult life. Despite remarkable progress in prevention and treatment, cardiovascular disease remains the leading cause of death in the United States and other developed nations, and even small improvements in the prevalence of smoking and other risk factors may reduce death rates further and prolong healthy lives.”
In drilling down through the data, researchers found that age was the single most significant risk factor for atherosclerosis. The average age of those with atherosclerosis was five years older (30) than those without (25). “If you compare other age groups to a reference group of those under age 25, atherosclerosis was 1.7 times more prevalent among those 25-29 years old, 3.4 times more prevalent in those in their 30s and 7.0 times more prevalent in those over 40,” Webber said.
While age, genetics and family history have a role in development of atherosclerosis, Webber noted that many other factors contributing to disease progression, such as weight, diet and smoking, can actually be modified.
A higher body mass index (BMI) on military entrance was associated with higher prevalence of atherosclerosis, after adjusting for age. Those who entered with BMIs in the overweight (25.0 to 29.9) range had a prevalence rate of 1.39 and those in the obese (above 30) range had a prevalence rate of 1.87 compared to those with BMIs of 18.5 to 24.9.
In their commentary, the researchers attributed much of the decline in atherosclerosis to reduction in risk factors, particularly to a 40% drop in smoking prevalence among military personnel, which declined from 51% in 1980 to 30% in 1998. The abstract, however, noted that “smoking was not significantly associated with a higher prevalence of atherosclerosis” in this study.
“We know from a huge body of evidence that smoking is associated with heart disease and atherosclerosis, so it is reasonable to conclude that reduced rates of smoking are associated with the drop” in atherosclerosis seen in the study, said Webber. Researchers relied on electronic health records for servicemembers to determine who smoked, he pointed out, explaining, “We think smoking is under-captured in defense medical surveillance. The records showed just 3% had a smoking diagnosis, but we know from a recent survey that 30% of military personnel smoke.”
All education levels beyond high school were associated with lower age-adjusted prevalence of disease than those with high school diplomas or less.
“We found that some college decreased prevalence of disease, compared with high school or lower educational attainment at a statistically significant level. Those with college degrees or more advanced education also had lower prevalence but did not reach statistical significance, in part because study had small numbers of individuals in those categories,” Webber pointed out.
- Webber BJ, Seguin PG, Burnett DG, Clark LL, Otto JL. Prevalence of and Risk Factors for Autopsy-Determined Atherosclerosis Among US Service Members, 2001-2011. JAMA. 2012;308(24):2577-2583.