Sudden Death in Young Adults: A 25-Year Review of Autopsies in Military Recruits

Context Sudden nontraumatic death in military recruits may offer insight into the causes and prevention of sudden death in young adults. Contribution Among 6.3 million military recruits age 18 to 35 years, sudden nontraumatic death occurred at a rate of 13.0 per 100000 recruit-years. Over half of the 126 autopsied decedents had an identifiable cardiac abnormality; one third had an anomalous coronary artery. More than one third of deaths had no explanation. Cautions This study had no control recruits who did not die suddenly. Implications Sudden nontraumatic death among military recruits occurs rarely. Whether more intensive screening would effectively prevent sudden death is unknown. The Editors Sudden death in healthy persons is uncommon and is usually due to previously undetected cardiovascular disease (1, 2). Most sudden deaths among apparently healthy young athletes occur during exertion and are most often caused by cardiac abnormalities (3-5). Gardner and colleagues (6) reported that 60% to 78% of exercise-related deaths in U.S. military personnel during 19961999 were attributable to a cardiac cause. Among young adults (persons 17 to 34 years of age), 50% of exercise-related deaths were attributable to preexisting heart disease (6). Maron and colleagues (7, 8) identified 158 sudden deaths in U.S. athletes younger than 35 years of age from 1985 through 1995 and found that 85% had a cardiovascular cause. In this and other studies of young athletes, hypertrophic cardiomyopathy, coronary artery anomalies, and cystic medial necrosis with a subsequent ruptured aorta were commonly associated with sudden death (3, 7, 9, 10). Uncommon causes of cardiac death in persons who exercise include myocarditis, floppy mitral valve, aortic stenosis, aortic dissection, and sarcoidosis (3, 11). Phillips and colleagues (12) identified 19 sudden cardiac deaths from 1965 through 1985 during Air Force basic military training at Lackland Air Force Base, Texas, the only training site for Air Force basic military training. The most frequent underlying cause of these deaths was myocarditis (42%), followed by coronary anomalies (16%). The frequency of sudden death in athletes younger than35 years of age is not clearly defined (13). Regardless of frequency, sudden death in young adults garners disproportionate attention from the media and raises important issues of legal liability (5). Deaths occurring during basic military training are of particular concern because they occur despite a preenlistment health screening program and have a substantial effect on the structure of basic training. The medical screening, conducted at a Military Entrance Processing Station, consists of a personal (but not family) medical history questionnaire and physical examination. The physical examination includes a clinical evaluation; blood and urine testing; and measurements of blood pressure, pulse, height, and weight. Cardiovascular screening is limited to heart auscultation. Electrocardiography is performed only if any abnormalities are identified. Cardiovascular diagnoses that prompt rejection for enlistment include valvular heart diseases, coronary artery disease, symptomatic arrhythmia, persistent resting sinus tachycardia, documented ventricular arrhythmias, left bundle-branch block, Mobitz type II second-degree and third-degree atrioventricular block, the WolffParkinsonWhite syndrome, hypertrophy or dilatation of the heart, cardiomyopathy (including myocarditis or pericarditis), history of heart failure, all congenital anomalies except for corrected patent ductus arteriosus, and hypertension. Disqualification for cardiac or vascular system abnormalities is very rare. In 2000, approximately 55 of almost 365000 enlisted applicants (0.15%) to military service were found to be unfit for military service because of cardiac or vascular disqualification. The duration of basic military training and the graduation requirements vary among the military services. In general, however, basic training may include basic rifle marksmanship; hand grenade, bayonet, and hand-to-hand combat training; unarmed combat training; physical fitness tests (that is, pushups, sit-ups, and a timed run); obstacle courses; live-fire exercises; foot marches (3, 5, 8, 10, and 15 kilometers); and field training exercises. Efforts to understand and prevent the rare, but tragic, occurrence of sudden death among these young adults depend on active surveillance of the population and accurate determination of mortality rates. However, published information on cause-specific mortality in this population is limited to isolated case reports (14-18), and population-based studies focused on a single military service (19) or specific cause of death (12, 20). To provide surveillance data specifically for recruit deaths, the Armed Forces Institute of Pathology implemented the Department of Defense Recruit Mortality Registry (DoD-RMR) in the Medical Mortality Surveillance Division at the Office of the Armed Forces Medical Examiner. This registry contains reports of every recruit death and autopsy. Recruit deaths described in the publications mentioned previously were included in the DoD-RMR. Descriptive analyses of nontraumatic and traumatic causes of recruit mortality derived from the DoD-RMR have been published elsewhere (21, 22). In the current study, we used data from the DoD-RMR to determine the cause of nontraumatic sudden death among military recruits over a 25-year period (1977 through 2001). Methods The Institutional Review Board of Brooke Army Medical Center approved this study. Nontraumatic recruit deaths were identified through the DoD-RMR. The registry reflects a review of military personnel records and investigative reports, death certificates and autopsies, and Armed Forces Institute of Pathology consultations and toxicology studies. The DoD-RMR considers a death to be a recruit death if the fatal incident occurred at a military training site before completion of initial training while the recruit was in an enlisted status in the Air Force, Army, Marine Corps, or Navy (22, 23). Of the nontraumatic recruit deaths that occurred from 1977 through 2001, cases were eligible for this study if they were categorized in the DoD-RMR as idiopathic deaths or deaths due to the following causes: cardiac, exertional heat illness, vascular, asthma, and all exercise-related deaths not elsewhere classified. We obtained demographic data and details about the circumstances of the fatal incident from the DoD-RMR because clinical histories were not consistently available from pathology reports from the military treatment facilities or civilian hospitals where these deaths were initially evaluated. The inclusion criteria for this study were a nontraumatic death with an available autopsy report for pathologic confirmation of the cause of death. We used the DoD-RMR to obtain and manually review records from each case that met the inclusion criteria. Cases were classified as sudden (cardiac, noncardiac, or idiopathic) and nonsudden. Sudden death was defined as an event resulting in death or terminal life support within 1 hour of the inciting event. Deaths were defined as cardiac in origin if the decedent had pathologically confirmed heart disease with clinical circumstances defined as potentially cardiac in origin. Idiopathic sudden death was defined as any sudden death unexplained by preexisting disease and without identifiable cause on postmortem examination. Crude mortality rates are presented as deaths per 100000 recruit-years (calculated by multiplying numeric death rates [number of deaths/number of recruits] by average training period expressed in years). The average training period was 8 weeks for the Army and the Navy, 6 weeks for the Air Force, and 11 weeks for the Marine Corps. We obtained population data from the Defense Manpower Data Center. Of the cases that made up this series, 5 have been discussed in detail in previous case reports (14-18), and 26 have had their sickle-cell status reported (without detailed discussion of causes of death) (12, 20, 22). We calculated CIs for mortality rates by using the Rothman binomial method (24), and we calculated P values for comparisons by using the MantelHaenszel method (25). We considered P values less than 0.05 to be significant. Statistical analysis was performed by using JMP Professional 5.0.1 (SAS Institute, Inc., Cary, North Carolina). Results The DoD-RMR contains 277 deaths identified from among 6.3 million recruits from 1977 through 2001. No recruit was noted to have preentry cardiovascular disease, and postmortem toxicology reports showed no evidence of illicit drug use. A family history of premature death or cardiovascular disease is not routinely gathered on initial-entry service members. Autopsy reports were available for 148 (97%) eligible nontraumatic deaths. The 126 sudden nontraumatic cases form the basis of the current study. The median age of the recruits was 19 years (range, 17 to 35 years), and 111 (88%) were male. The rate of nontraumatic sudden death was 13.0 per 100000 recruit-years, a figure that did not vary significantly over the 25-year study period (Table 1). Approximately half (64 of 126 recruits) of the nontraumatic sudden deaths were due to an identifiable cardiac abnormality, and slightly more than one third (44 of 126 recruits) were idiopathic (Table 2). A temporal relationship to exertion was noted in 86% (108 of 126 recruits) of events. There were 18 noncardiac sudden deaths: 6 from coagulopathy and hemorheologic causes (3 sickle-cell crises, 2 episodes of pulmonary embolism, and 1 internal hemorrhage), 5 from intracranial hemorrhage, 4 from pulmonary causes (respiratory distress due to asthma [n= 2], sarcoidosis [n= 1], and alveolar hemorrhage [n= 1]), and 3 from exertional rhabdomyolysis or heat stroke. Table 1. All-Service Nontraumatic Sudden Death Rates for Recruits by 5-Year Categories, 19772001 Table 2. Demographi