What are the new findings?
Musculoskeletal disorders, in combination with administrative and other health services (ICD-10 ‘Z’ codes), accounted for more than half of the total medical encounters in 2024 among service members deployed to the U.S. Central Command or Africa Command. Lower back pain accounted for the most frequent musculoskeletal condition among male and female service members deployed to CENTCOM and AFRICOM.
What is the impact on readiness and force health protection?
Thorough examination of the most common causes of injury and illness during deployment can assist senior leaders in the development and implementation of strategies to reduce preventable medical issues, enhance force readiness, and ensure fighting strength.
Background
Each year, MSMR estimates illness and injury-related morbidity and health care burdens on the U.S. Armed Forces and the Military Health System, and this report updates previous analyses of these burden distributions among active and reserve component service members in deployed settings. While deployed service members are primarily selected from a subset of the active component, the reserve component contributes a substantial portion of U.S. deployed forces.
This report utilizes data from the Theater Medical Data Store, which documents service members’ inpatient and outpatient encounters while treated in an operational environment. TMDS receives medical data from Theater Medical Information Program-Joint applications, including AHLTA-Theater, TMIP-Composite Health Care System Cache, Mobile Computing Capability, Maritime Medical Modules, and the U.S. Transportation Command Regulating and Command and Control Evacuation System.1
The health encounters of service members deployed to 2 specific theaters of operation, U.S. Central Command and U.S. Africa Command, are the subject of this report. While U.S. service members are deployed to all the geographic combatant commands, the largest concentrations without access to permanent medical facilities are in the CENTCOM and AFRICOM areas of operation.2 While this report focuses on medical encounters of service members treated in CENTCOM and AFRICOM operational environments during the 2024 calendar year, future reports may incorporate other combatant commands as circumstances dictate and data become available.
Methods
The surveillance population included all individuals who served in the active or reserve components of the U.S. Army, Navy, Air Force, Marine Corps, or Space Force with health care encounters captured in the TMDS during the surveillance period. Analysis was restricted to encounters where the theater of care specified was CENTCOM or AFRICOM, or where the name of the theater of operation was missing or null; by default, this excluded encounters in the U.S. Northern Command, U.S. European Command, U.S. Indo-Pacific Command, or U.S. Southern Command theaters of operations. In addition, TMDS-recorded medical encounters where the data source was identified as Shipboard Automated Medical System, or where the military treatment facility descriptor indicated that care was provided aboard ship, were excluded from this analysis. Encounters from aeromedical staging facilities outside of CENTCOM or AFRICOM were also excluded.
Morbidity burdens attributable to various conditions were estimated by diagnosis distribution according to the 17 traditional categories of the International Classification of Diseases system, with an 18th category for COVID-19. Extended ICD-10 (10th Revision) code groupings were also reviewed for the most common diagnoses. The TMDS has not fully transitioned to ICD-10 codes, so some ICD-9 (9th Revision) codes were included. Primary diagnoses that did not correspond to an ICD-9 or ICD-10 code are not reported in this health care burden analysis.
Results
A total of 191,579 medical encounters occurred among 52,066 individuals deployed to Southwest Asia, the Middle East, and Africa in 2024. Of those 191,579 total medical encounters documented in 2024 among deployed service members, 227 (0.1%) were recorded as hospitalizations. Most medical encounters (n=146,384, 76.4%), individuals affected (n=42,344, 81.3%), and hospitalizations (n=181, 79.7%) occurred among male service members.
In 2024, the largest percentages of medical encounters among deployed service members were coded as musculoskeletal system/connective tissue disorders, followed by administrative and other health services (i.e., ‘Z’ codes, including factors influencing health status and health service contact) (Figure). The most common diagnosis within the musculoskeletal system/connective tissue disorders group was for unspecified lower back pain (ICD-10 codes beginning with M545) (Table). The percentage of total medical encounters attributed to other health services decreased from 32.1% in 2020 to 22.8% in 2024. COVID-19 accounted for only 0.3% of deployed service members’ total medical encounters in 2024 (Figure).
The percentages of in-theater medical encounters attributed to musculoskeletal system disorders increased from 2020 (23.4%) to 2024 (30.9%) (Figure). Unspecified lower back pain (M5450) was the most frequent ICD-10 diagnostic code for musculoskeletal encounters among both men and women (Table). The second-most frequent ICD-10 diagnostic code for musculoskeletal encounters among male service members was pain in the right shoulder (M25511), while for female service members it was pain in the right knee (M25561) (Table).
The percentages of in-theater medical encounters attributed to mental health disorders increased slightly during the surveillance period, from 5.8% in 2020 to 7.7% in 2024 (Figure). Unspecified reaction to severe stress (F439) accounted for the most frequent mental health disorder diagnoses, with a slightly higher percentage of in-theater encounters for this disorder among women (1.5%) than men (1.0%) (Table).
Discussion
As in prior annual reports of illness- and injury-related morbidity and care burdens in deployed settings, musculoskeletal disorders, in combination with administrative and other health services, accounted for more than half of the total medical encounters in theater. In prior reports during the surveillance period, encounters for COVID-19 screening contributed to an increase in encounters for administrative and other health services, as this specific Z code (Z1152) accounted for almost 5% of all in-theater medical encounters in 2022.3
This report documents an increased percentage of in-theater medical encounters for musculoskeletal disorders, consistent with the 2020-2024 increased rate of in-garrison ambulatory encounters for musculoskeletal disorders. The percentage of total ambulatory encounters attributed to musculoskeletal disorders in garrison (28.1%) was similar to the percentage observed in theater (30.9%).4 No absolute rate comparisons can be made due to the lack of in-theater denominator (person-time) data.
Some conditions, including diabetes, pregnancy, or congenital anomalies, often preclude service member deployment. Due to medical pre-screening, service members who are deployed demonstrate a lower rate of medical conditions that could interfere with deployment operations than their non-deployed counterparts. Deployed service members are also less likely to require medical care for pre-screened conditions.
When interpreting these results and analyses, several limitations of these data should be considered. Not all medical encounters in theaters of operations are recorded in the TMDS. Some care by in-theater medical personnel occurs at small, remote, or austere locations where electronic documentation of diagnosis and treatment is infeasible, and some emergency medical care for stabilization of combat-injured service members prior to evacuation may not be routinely captured in the TMDS. Due to the exigencies of deployment settings that can complicate accurate data reporting or transmission, this report may under-estimate the true burden of health care in the areas of operations assessed.
In any review that relies on ICD coding, some diagnosis misclassification should be expected due to coding errors within the electronic health record. Although the aggregated distributions of illnesses and injuries presented in this report are compatible with assessments derived from other examinations of morbidity in military populations (both deployed and nondeployed), instances of highly unlikely diagnostic codes for a deployed population have been observed. This misclassification bias is likely minor and non-differential.
Because this report only includes medical encounters from CENTCOM and AFRICOM, it does not describe any medical encounters from the recent deployment of troops to EUCOM, INDOPACOM, and SOUTHCOM. Each area of operation is unique, with vastly different medical assets, medical evacuation capabilities, and deployed service member populations. Consequently, the results from CENTCOM or AFRICOM may not be generalizable to other combatant commands.
References
- Defense Health Agency, U.S. Department of Defense. Joint Operational Medicine Information Systems Theater Medical Data Store. Fact Sheet. Jul. 2019. Accessed Apr. 18, 2025. https://www.health.mil/reference-center/fact-sheets/2019/07/30/tmds-fact-sheet
- The White House. Letter to the Speaker of the House and President pro tempore of the Senate Regarding the War Powers Report. Dec. 6, 2024. Accessed Apr. 18, 2025. https://bidenwhitehouse.archives.gov/briefing-room/statements-releases/2024/12/06/letter-to-the-speaker-of-the-house-and-president-pro-tempore-of-the-senate-regarding-the-war-powers-report-5
- Armed Forces Health Surveillance Division. Morbidity burdens attributable to various illnesses and injuries among deployed active and reserve component service members of the U.S. Armed Forces, 2022. MSMR. 2023;30(7):2-5. Accessed Aug. 21, 2025. https://www.health.mil/news/articles/2024/07/01/msmr-deployed-morbidity-2023
- Armed Forces Health Surveillance Division. Ambulatory health care visits among active component members of the U.S. Armed Forces, 2024. MSMR. 2025;32(9):21-27.