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 all medical encounters in 2023 among service members deployed to the U.S. Central Command and Africa Command. Three common injury conditions occurred among male and female service members deployed to U.S. CENTCOM and U.S. AFRICOM: other back problems, arm and shoulder injuries, and knee injuries.

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 (TRAC2ES).¹

The health encounters of service members deployed to 2 specific theaters of operation, US Central Command and US 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 fixed 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 2023 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 burden analysis.

Results

A total of 182,943 medical encounters occurred among 53,215 individuals deployed to Southwest Asia, the Middle East, and Africa in 2023. Of those 182,943 total medical encounters documented in 2023 among deployed service members, 84 (0.05%) were recorded as hospitalizations. The majority of medical encounters (n=137,447; 75.1%), individuals affected (n=43,001; 80.8%), and hospitalizations (n=70; 83.3%) occurred among male service members.

In 2023 the largest percentages of medical encounters attributed to a major ICD-10 diagnostic category were coded as musculoskeletal system/connective tissue disorders, followed by administrative and other health services (Z codes; includes factors influencing health status and health service contact) (Figure 1).

The most common diagnosis within the musculoskeletal system/connective tissue disorders group was for lower back pain (ICD-10 code beginning with M545) (Table). 

The percentage of total medical encounters attributed to other health services decreased from 43.5% in 2021 to 25.7% in 2023. COVID-19 accounted for only 0.7% of deployed service members’ total medical encounters in 2023 (Table). The percentages of in-theater medical encounters attributed to musculoskeletal system disorders (29.6% to 27.9%) and injuries (7.9% to 7.4%) decreased only slightly from 2019 to 2023 (Figure 1). Lower back pain (M545) 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 by male service members was pain in the right shoulder (M25511), while for female service members it was pain in the left knee (M25562) (Table).

The percentages of in-theater medical encounters attributed to mental health disorders increased from 4.7% to 6.5% during the surveillance period (Figure). Adjustment disorder with mixed anxiety and depressed mood (F4323) accounted for the most frequent mental health disorder diagnoses, with a higher percentage of in-theater encounters for this disorder among women (1.4%) than men (0.8%) (Table). 

Discussion

As in prior annual reports of illness- and injury-related morbidity and health 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 mental health disorders, consistent with the 2019-2023 increased rate of in-garrison ambulatory encounters for mental health disorders. The percentage of total ambulatory encounters attributed to mental health disorders in garrison (14.6%) was substantially higher, however, than the percentage observed in theater (6.5%).⁴ No absolute rate comparisons can be made due to the lack of in-theater denominator (person-time) data.

Encounters for certain conditions are generally rare in deployment settings. 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 forward 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 underestimate 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 evacuations from CENTCOM and AFRICOM, it does not describe any medical evacuations 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

1. Defense Health Agency, U.S. Department of Defense. Joint Operational Medicine Information Systems Theater Medical Data Store. Fact Sheet. Jul. 2019. Accessed Jun. 11, 2024. https://www.health.mil/Reference-Center/Fact-Sheets/2019/07/30/TMDS-Fact-Sheet
2. The White House. Letter to the Speaker of the House and President pro tempore of the Senate Regarding the War Powers Report. Jun. 8, 2023. Accessed Jun. 11, 2024. https://www.whitehouse.gov/briefing-room/statements-releases/2023/06/08/letter-to-the-speaker-of-the-house-and-president-pro-tempore-of-the-senate-on-war-powers-report 
3. Armed Forces Health Surveillance Division. Update: morbidity burdens attributable to various illnesses and injuries among deployed active and reserve component service members, U.S. Armed Forces, 2022. MSMR. 2023;30(7):2-5. 
4. Armed Forces Health Surveillance Division. Ambulatory visits among active component members, U.S. Armed Forces, 2023. MSMR. 2024;31(6):20-26.