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.

Risks for Enlisted Navy Divers Compared to Other Enlisted Sailors: An Examination of Illnesses That May Be Associated With Exposure to Contaminated Water Diving.

INTRODUCTION: Illnesses among Navy divers degrade readiness, decrease manpower levels, and increase costs for medical care. Prior research has shown that Navy divers have high rates of the types of illnesses that might be because of diving in contaminated water. The objectives of this study were to examine medical records of U.S. Navy Sailors from 2016 to 2022 and determine if divers have higher incidence rates of health conditions that might be associated with contaminated water diving compared to non-divers. MATERIALS AND METHODS: For this retrospective cohort study, we used data from the Defense Medical Epidemiology Database (DMED). The DMED is operated by the Armed Forces Health Surveillance Division and uses data from the Defense Manpower Data Center to classify occupations. The DMED provides free online access to a de-identified subset of data contained within the Defense Medical Surveillance System.The population was U.S. Navy enlisted males, aged 25 to 29 years. Divers were compared to non-divers using 8 selected diagnoses that may reasonably be associated with diving in contaminated water. RESULTS: During the study period, the database contained a total of 5,474 diver and 827,406 non-diver person-years. Of the 8 diagnoses, the ones with the largest number of cases for divers were upper respiratory infections with 128 and ear disorders with 62. The relative risks (RRs) for divers compared to non-divers were higher for otitis externa (RR = 1.44; confidence interval = 1.03, 2.01) and for ear disorders (RR = 1.15; confidence interval = 0.89, 1.47); for the other 6 diagnoses, the divers had lower rates than the non-divers. CONCLUSIONS: The high RRs found for otitis externa and ear disorders support the need to devote resources to better understand the reasons for these higher risks and to develop, test, and implement targeted risk-reduction strategies. Future studies should attempt to link verified contaminated water exposures with adverse health outcomes and calculate risks based on criteria such as age and dive factors.

The Differential Translation Capabilities of the Human DHFR2 Gene Indicates a Developmental and Tissue-Specific Endogenous Protein of Low Abundance.

A functional role has been ascribed to the human dihydrofolate reductase 2 (DHFR2) gene based on the enzymatic activity of recombinant versions of the predicted translated protein. However, the in vivo function is still unclear. The high amino acid sequence identity (92%) between DHFR2 and its parental homolog, DHFR, makes analysis of the endogenous protein challenging. This paper describes a targeted mass spectrometry proteomics approach in several human cell lines and tissue types to identify DHFR2-specific peptides as evidence of its translation. We show definitive evidence that the DHFR2 activity in the mitochondria is in fact mediated by DHFR, and not DHFR2. Analysis of Ribo-seq data and an experimental assessment of ribosome association using a sucrose cushion showed that the two main Ensembl annotated mRNA isoforms of DHFR2, 201 and 202, are differentially associated with the ribosome. This indicates a functional role at both the RNA and protein level. However, we were unable to detect DHFR2 protein at a detectable level in most cell types examined despite various RNA isoforms of DHFR2 being relatively abundant. We did detect a DHFR2-specific peptide in embryonic heart, indicating that the protein may have a specific role during embryogenesis. We propose that the main functionality of the DHFR2 gene in adult cells is likely to arise at the RNA level.