Epidemiology of Hospitalizations and Deaths from Heat Illness in Soldiers

PURPOSE: Serious heat illness has received considerable recent attention due to catastrophic heat waves in the United States and Europe, the deaths of high-profile athletes, and military deployments. METHODS: This study documents heat illness hospitalizations and deaths for the U.S. Army from 1980 through 2002. Hospitalization data were obtained from the Total Army Injury Health Outcomes Database (TAIHOD) coded according to the International Classification of Diseases, Ninth Revision, Clinical Modification (ICD-9-CM). North Atlantic Treaty Organization Standardization Agreement codes were searched for heat injuries in an effort to detect cases that were not found during the ICD-9-CM search. RESULTS: Five-thousand two-hundred forty-six soldiers were hospitalized, and 37 died due to heat illness. Our results indicate: 1) approximately 60% reduction in hospitalization rates (fewer heat exhaustion cases) over the 22-yr period; 2) fivefold increase in heat stroke hospitalization rates (1.8 per 100,000 in 1980 to 14.5 per 100,000 in 2001); 3) heat stroke cases were associated with dehydration (17%), rhabdomyolysis (25%), and acute renal failure (13%); 4) lower hospitalizations rates among African and Hispanic Americans compared with Caucasians (incidence density ratio, 0.76 [95% confidence interval, 0.71-0.82]; 5) greater rates of hospitalizations and heat strokes among recruits from northern than southern states (incidence density ratio, 1.69 [95% confidence interval, 1.42-1.90]; and 6) greater rates of hospitalizations and heat strokes among women than men (incidence density ratio, 1.18 [95% confidence interval, 1.09-1.27]). CONCLUSIONS: Exertional heat illness continues to be a military problem during training and operations. Whereas the hospitalization rate of heat illness is declining, heat stroke has markedly increased.