Diagnoses and factors associated with medical evacuation and return to duty for service members participating in Operation Iraqi Freedom or Operation Enduring Freedom: a prospective cohort study

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.