Background: Anticipation of the types of injuries that occur in modern warfare is essential to plan operations and maintain a healthy military. We aimed to identify the diagnoses that result in most medical evacuations, and ascertain which demographic and clinical variables were associated with return to duty. Methods: Demographic and clinical data were prospectively obtained for US military personnel who had been medically evacuated from Operation Iraqi Freedom or Operation Enduring Freedom (January, 2004-December, 2007). Diagnoses were categorised post hoc according to the International Classification of Diseases codes that were recorded at the time of transfer. The primary outcome measure was return to duty within 2 weeks. Findings: 34 006 personnel were medically evacuated, of whom 89% were men, 91% were enlisted, 82% were in the army, and 86% sustained an injury in Iraq. The most common reasons for medical evacuation were: musculoskeletal and connective tissue disorders (n=8104 service members, 24%), combat injuries (n=4713, 14%), neurological disorders (n=3502, 10%), psychiatric diagnoses (n=3108, 9%), and spinal pain (n=2445, 7%). The factors most strongly associated with return to duty were being a senior officer (adjusted OR 2·01, 95% CI 1·71-2·35, p<0·0001), having a non-battle-related injury or disease (3·18, 2·77-3·67, p<0·0001), and presenting with chest or abdominal pain (2·48, 1·61-3·81, p<0·0001), a gastrointestinal disorder (non-surgical 2·32, 1·51-3·56, p=0·0001; surgical 2·62, 1·69-4·06, p<0·0001), or a genitourinary disorder (2·19, 1·43-3·36, p=0·0003). Covariates associated with a decreased probability of return to duty were serving in the navy or coast guard (0·59, 0·45-0·78, p=0·0002), or marines (0·86, 0·77-0·96, p=0·0083); and presenting with a combat injury (0·27, 0·17-0·44, p<0·0001), a psychiatric disorder (0·28, 0·18-0·43, p<0·0001), musculoskeletal or connective tissue disorder (0·46, 0·30-0·71, p=0·0004), spinal pain (0·41, 0·26-0·63, p=0·0001), or other wound (0·54, 0·34-0·84, p=0·0069). Interpretation: Implementation of preventive measures for service members who are at highest risk of evacuation, forward-deployed treatment, and therapeutic interventions could reduce the effect of non-battle-related injuries and disease on military readiness. Funding: John P Murtha Neuroscience and Pain Institute, and US Army Regional Anesthesia and Pain Management Initiative.
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