Health Conditions Among Navy Submariners at the End of Active Duty; A Retrospective Cohort Study

Abstract

Introduction: Maintaining healthy, well-trained, and highly qualified armed forces is critical for ensuring military readiness. The purpose of this article is to contribute to the body of research focused on the health of U.S. Navy submariners and to identify the health conditions of U.S. Navy submariners during their final year of active duty service.

Materials and methods: In this retrospective cohort study, we examined medical records and personnel files of separating U.S. Navy sailors who were: (1) active duty between 2009 and 2018; (2) separated before 2019; and (3) were assigned to a submarine for at least 30 days. Both officers and enlisted service members were included. We linked, described, and analyzed data from the Defense Health Agency, Military Health System Data Repository (MDR), and the Bureau of Naval Personnel (BUPERS). International Classification of Diseases (ICD) diagnoses codes were obtained from MDR. Data collected from BUPERS include age, sex, and rank. We determined the number of individuals who had at least one diagnosed condition (identified as a three-digit ICD code). We report the number of diagnoses and calculate prevalence rates and confidence intervals per condition, as well as prevalence rates per year, using standard formulas. The study was approved by the Naval Submarine Medical Research Laboratory Institutional Review Board.

Results: During the study period, 26,014 submariners separated from the Navy. The average number of separations per year was 2,601. About a third of the separating submariners were in the 25 to 29 age group and over 50% were under 30 years of age. Of the three-digit individual ICD codes, some of the highest operationally relevant rates over the 10-year study period (2009-2018) were for joint disorders (prevalence rate [PR] = 180 per 1,000 submariners), back disorders (PR = 128), and sleep disorders (PR = 134). Three mental-health-related conditions were also among the 20 conditions with the highest rates.

Conclusions: High rates of specific diagnoses such as joint disorders indicate the need for additional study to examine causal relationships, to determine which conditions may contribute to lost work time, early separations, or low rates of reenlistment and which conditions might be a result of specific military occupations or duties. Study strengths are the large number of subjects and the long period of observations. A study weakness was the inability to identify submariners who separated because of health conditions. The overall impact of the study is that it identifies urgent health risks and establishes a way to prioritize future research. Future research should include a focus on medically separated personnel; compare rates for submariners to other military groups including all-Navy and all-Department of Defense; and determine specific and relative risks as a necessary precursor to developing, implementing, and testing risk reduction and health improvement interventions.