An Approach to Reduce the Incidence of Submarine Medical Evacuations by Identifying Individual Risk Characteristics: Preliminary Findings.

Introduction: Military medical evacuations (MEDEVACs) are resource intensive and can disrupt operations and decrease readiness. Medical evacuations are a concern for the submarine force because of the limited medical resources onboard, the impact of manpower loss on smaller crews, and the compromise of operational stealth. Although some medical emergencies cannot be avoided, some MEDEVACs may be preventable. However, there is limited knowledge of the underlying causes and risk factors associated with submarine MEDEVACs. This work describes an approach to identify individual characteristics associated with submarine MEDEVACs by presenting preliminary results and next steps. Identifying those most at risk for a MEDEVAC will foster prevention strategies that lead to fewer MEDEVACs, military operation disruptions, missed work and limited duty days, unplanned losses, early separations, and disability compensation claims among navy submariners.

Materials And Methods: This retrospective study examines MEDEVACs from U.S. Navy submarines from January 1, 2012 to December 31, 2020. Medical evacuation causes were classified by 3 major diagnostic categories: Injury, psychiatric, and medical (i.e., all other non-injury medical events, including dental issues). Diagnostic subcategories were grouped by body region (for injuries) and body system (for non-injuries). Identifiable information from MEDEVAC records were linked to personnel files to capture demographic and occupational variables. Trends across the years were examined, and frequencies and percentages of MEDEVAC cases by both major and sub-diagnostic categories were presented. For cases where both the major diagnostic categories and characteristics were both available, we assessed associations between major diagnostic categories and demographic and occupational characteristics, using Pearson's χ2 test for proportions and Fisher Freeman-Halton exact tests. Pairwise z-tests for proportions were used to determine which proportions differed significantly.

Results: A total of 1,283 MEDEVACs were confirmed from 2012 to 2020, with an annual average of 143. Across the years, 24.3% were caused by psychiatric issues (e.g., suicidal ideation), 18.4% were caused by injuries (e.g., blunt trauma), and the remaining 57.3% were caused by other medical emergencies (e.g., gastrointestinal issues). Among the cases linked to personnel files, the major diagnostic category was associated with age, rank, department, and submarine qualification status (group size varied). By age (n = 973), large differences in MEDEVAC causes were seen among submariners 21 to 25 years old who represented 52.4% of psychiatric versus 37.5% of medical MEDEVACs. In contrast, those 35 and older represented 17.0% medical versus 2.7% psychiatric MEDEVACs.

Conclusions: Medical, non-injury cases were the most common cause for a MEDEVAC. There were proportionately more psychiatric than medical cases among younger, less experienced submariners. Conversely, there were proportionately more medical than psychiatric cases among older submariners. A centralized approach to collecting MEDEVAC data is needed. This is the most comprehensive study examining risk factors associated with submarine MEDEVACs. Follow-on work will include adding prior medical waiver requests, health indicators, and confirmed diagnoses to the dataset to conduct a risk analysis. Considering submarines have smaller crews than most surface ships, limited medical assets, and often operate in austere environments, examination of submarine MEDEVACs should be distinct from other navy and military MEDEVACs.