What Are the New Findings?

The numbers of medical evacuations of service members in 2019 were roughly similar to the numbers for the previous 4 years. The proportions of evacuations that were due to battle injuries (5%) and to disease/non-battle injuries (95%) remained steady during this period. Evacuations for mental health disorders were the most common among the ICD-10 major diagnostic categories. Most service members who were evacuated were soon returned to duty.

What Is the Impact on Readiness and Force Health Protection?

Only 1,142 service members were evacuated during 2019, but the process of medical evacuation of service members to Europe and CONUS is logistically demanding. The effort expended to evacuate service members to sources of definitive, modern health care is a reassuring investment in the health, welfare, and importance of the men and women serving overseas.

Abstract

In 2019, there were 1,142 medical evacuations of service members from the U.S. Central Command area of responsibility that were followed by at least 1 medical encounter in a fixed medical facility outside the operational theater. There were more medical evacuations for mental health disorders than for any other single category of illnesses or injuries. The number of medical evacuations attributable to battle injuries increased steadily from 2015 through 2017 then decreased in 2018 and remained relatively stable through 2019, for an overall increase of 65.7%.

The number of medical evacuations attributable to non-battle injuries and illnesses remained relatively stable through 2017, rose slightly in 2018, and decreased in 2019. Compared to their respective counterparts, non-Hispanic white service members, those aged 20–24 years, Army members, junior and senior enlisted personnel, and those in repair/engineering occupations accounted for the largest proportions of medical evacuations. Most service members who were evacuated were returned to normal duty status following their post-evacuation hospitalizations or outpatient encounters.

Background

Although there have been substantial reductions in combat operations taking place in the U.S. Central Command (CENTCOM) area of responsibility (AOR) in Southwest Asia,¹ he number of service members deployed to the CENTCOM AOR is still significant. Recent reports and budget documents indicate that there may be as many as 15,000 service members in Afghanistan for Operation Freedom's Sentinel and another 7,200 in Iraq and Syria for Operation Inherent Resolve.^2–5 In theaters of operations such as Afghanistan, most medical care is provided by deployed military medical personnel; however, some injuries and illnesses require medical management outside the operational theater. In these cases, the affected individuals are usually transported by air to a fixed military medical facility in Europe or the U.S. where the service members receive the specialized, technically advanced, and/or prolonged diagnostic, therapeutic, and rehabilitative care required.

Medical air transports, or medical evacuations, are costly and generally indicative of serious medical conditions. Some serious conditions are directly related to participation in or support of combat operations (e.g., battle wounds); however, many others are unrelated to combat and may be preventable. This report summarizes the natures, numbers, and trends of conditions for which male and female military members were medically evacuated from CENTCOM AOR operations during 2019 and compares them to the previous 4 years.

Methods

The surveillance period was 1 Jan. 2015 through 31 Dec. 2019. The surveillance population included all members of the active and reserve components of the U.S. Army, Navy, Air Force, and Marine Corps who were deployed to the CENTCOM AOR during the period. The outcome of interest in this analysis was medical evacuations during the surveillance period from the CENTCOM AOR (e.g., Afghanistan or Iraq) to a medical treatment facility outside the CENTCOM AOR. Records of all medical evacuations conducted by the U.S. Transportation Command (TRANSCOM) maintained in the TRANSCOM Regulating and Command & Control Evacuation System (TRAC2ES) were utilized. Evacuations were included in the analyses if the affected service member had at least 1 inpatient or outpatient medical encounter in a permanent military medical facility in the U.S. or Europe during a time interval extending from 5 days before to 10 days after the reported evacuation date.

Medical evacuations included in the analyses were classified by the causes and natures of the precipitating medical conditions (based on information reported in relevant evacuation and medical encounter records). First, all medical conditions that resulted in evacuations were classified as either "battle injuries" or "non-battle injuries and illnesses" (based on entries in an indicator field of the TRAC2ES evacuation record). Evacuations due to non-battle injuries and illnesses were subclassified into 17 illness/injury categories based on International Classification of Diseases, 9th and 10th Revisions (ICD-9 and ICD-10, respectively) diagnostic codes reported on the records of medical encounters after evacuation. For the purposes of this report, all records of hospitalizations and ambulatory visits from 5 days before to 10 days after the reported date of each medical evacuation were identified. In most cases, the primary (first-listed) diagnosis for either a hospitalization (if any occurred) or the earliest ambulatory visit after evacuation was considered indicative of the condition responsible for the evacuation. However, if the first-listed diagnostic code specified the external cause (rather than the nature) of an injury (ICD-9 E-code; ICD-10 V-, W-, X-, or Y-code) or an encounter for something other than a current illness or injury (e.g., observation, medical examination, or vaccination [ICD-9 V-codes; ICD-10 Z-codes, other than those related to pregnancy]), then secondary diagnoses that specified illnesses and injuries (ICD-9: 001–999; ICD-10: A00–T88) were considered the likely reasons for the subject evacuations. If there was no secondary diagnosis or if the secondary diagnosis also was an external cause code, the first-listed diagnostic code of a subsequent encounter was used.

The disposition after each medical evacuation was determined by using the disposition code associated with the medical encounter that was used for documenting the category of the medical evacuation. Inpatient disposition categories were returned to duty (code 01), transferred/discharged to other facility (codes 02–04, 09, 21–28, 43, or 61–66), died (codes 20, 30, 40–42, 50, or 51), separated from service (codes 10–15), and other/unknown. Outpatient disposition categories were released without limitation (code 1), released with work/duty limitation (code 2), immediate referral (code 4), sick at home/quarters (codes 3 or S), admitted/transferred to civilian hospital (codes 7, 9, A–D, or U), died (codes 8 or G), discharged home (code F), and other/unknown.

Results

In 2019, a total of 1,142 medical evacuations of service members from the CENTCOM AOR were followed by at least 1 medical encounter in a fixed medical facility outside the operational theater (Table 1). Overall, there were more medical evacuations for mental health disorders (n=309; 27.1%) than for any other single category of illnesses or injuries. In addition, the numbers of evacuations for non-battle injuries and poisonings (n=275; 24.1%); signs, symptoms, and ill-defined conditions (n=111; 9.7%); disorders of the digestive system (n=106; 9.3%); and musculoskeletal system/connective tissue disorders (n=89; 7.8%) were all higher than the number of evacuations for battle injuries (n=58; 5.1%). The top 3 categories—mental health disorders (most frequently adjustment and depressive disorders); non-battle injuries (primarily fractures of extremities, strains, and sprains); and signs, symptoms, and ill-defined conditions (primarily pain and swelling)—accounted for more than half (60.9%) of all evacuations (Table 1).

During 2015–2019, the annual number of medical evacuations attributable to battle injuries increased steadily from 2015 (n=35) through 2017 (n=71), decreased in 2018 (n=56), and remained relatively stable through 2019 (n=58) (Figure). Over the 5-year period, the annual number of battle injury-related evacuations increased 65.7% from the nadir in 2015. The annual number of medical evacuations attributable to non-battle injuries and diseases remained relatively stable at low levels in 2015 (n=1,050), 2016 (n=1,010), and 2017 (n=1,024), increased in 2018 (n=1,209), and decreased in 2019 (n=1,084). In general, the annual numbers of medical evacuations over the course of the 5-year period varied in relation to the numbers of deployed service members, with the highest yearly counts of medical evacuations occurring in 2017 and 2018. The monthly numbers of medical evacuations decreased or remained stable in 2019 (Figure).

Demographic and military characteristics

The number of medical evacuations in 2019 was higher among males (n=962) than females (n=180) (Tables 1, 2). The most frequent causes of medical evacuations among male service members were non-battle injury and poisoning (n=250; 26.0%); mental health disorders (n=236; 24.5%); signs, symptoms, and ill-defined conditions (n=93; 9.7%); and digestive system disorders (n=92; 9.6%) (Table 1). Among female service members, the most frequent causes of medical evacuations were mental health disorders (n=73; 40.6%); non-battle injury and poisoning (n=25; 13.9%); signs, symptoms, and ill-defined conditions (n=18; 10.0%); and digestive system disorders (n=14; 7.8%).

Compared to males, female service members had notably higher percentages of medical evacuations for mental health disorders and genitourinary system disorders (Table 1). In contrast, male service members had higher percentages of evacuation for injuries (both battle and non-battle related). There was just 1 medical evacuation of a female service member during 2019 for a battle injury.

Within the various demographic and military characteristics of those service members who were evacuated, the largest numbers and proportions of evacuees were among non-Hispanic white service members, those aged 20–24 years, members of the Army, junior and senior enlisted personnel, and those in repair/engineering occupations (Table 2). In 2019, most medical evacuations (85.2%) were characterized as having routine precedence. The remainder had priority (10.9%) or urgent (3.9%) precedence. All but 27 (2.4%) of the medical evacuations were accomplished through military transport (Table 2).

Most frequent specific diagnoses

Among both males and females in 2019, a mental health disorder ("reaction to severe stress, and adjustment disorders") was the most frequent specific diagnosis (3-digit ICD-10 diagnosis code: F43) during initial medical encounters after evacuations (Table 3). Of the remaining 5 most common 3-digit diagnoses associated with evacuations of males, 1 was related to digestive system diseases ("inguinal hernia"); 3 were injuries ("fracture at wrist and hand level," "intracranial injury," and "injury of muscle, fascia and tendon at shoulder and upper arm level"); and 1 was related to musculoskeletal disorders ("dorsalgia") (Table 3).

Of the remaining top 5 diagnoses most frequently associated with evacuations of female service members, 1 was a condition that primarily affects women ("unspecified lump in breast") 1 was an injury ("fracture of lower leg, including ankle"); 2 were mental health disorders ("other anxiety disorders" and "major depressive disorder, single episode"); and 1 was related to musculoskeletal disorders ("dorsalgia") (Table 3).

Disposition

Of the 1,142 medical evacuations reported in 2019, a total of 486 (42.6%) resulted in inpatient encounters. About three-quarters (75.7%) of all service members who were hospitalized after medical evacuations were discharged back to duty. Slightly less than one-fifth (18.7%) of service members who were hospitalized after medical evacuations were transferred or discharged to other facilities (Table 4).

Return to duty dispositions were much more likely after hospitalizations for non-battle injuries (72.3%) than for battle injuries (30.0%). The majority (70.0%) of battle injury-related hospitalizations and a little more than one-sixth (17.0%) of non-battle injury-related hospitalizations resulted in transfers/discharges to other facilities (Table 4).

Nearly three-fifths (n=656; 57.4%) of all medical evacuations resulted in outpatient encounters only. Of the service members who were treated exclusively in outpatient settings after evacuations, the majority (80.9%) were discharged back to duty without work/duty limitations; 13.9% were released with work/duty limitations; and less than 1% each were admitted/transferred to a civilian hospital, immediately referred, or discharged to "home sick" for recuperation. Service members treated as outpatients after battle injury-related evacuations were more likely to be released without limitations (n=14; 77.8%) than medical evacuees treated as outpatients for non-battle injuries (n=125; 69.1%) (Table 4).

Editorial Comment

This report documented that only 5.1% of all medical evacuations during 2019 were associated with battle injuries. Counts of evacuations for battle injuries peaked in 2017, likely reflecting an increase in the number of service members deployed to the CENTCOM AOR. More evacuations in 2019 were attributed to mental health disorders than to any other category of illness or injury; the next most common categories, in descending order of frequency, were non-battle injuries and poisonings; signs, symptoms, and ill-defined conditions; digestive system disorders; and musculoskeletal disorders. Evacuations during the entire 5-year surveillance period followed a similar but slightly different pattern, with mental health disorders being the most frequent followed by non-battle injuries; musculoskeletal disorders; signs, symptoms and ill-defined conditions; and digestive system disorders. Of the major diagnostic categories for which there was more than 1 medical evacuation for both men and women, only percentages of evacuations for injuries (battle and non-battle) were noticeably higher among males compared to females. As in previous years, the majority of service members who were evacuated were returned to normal duty status following their post-evacuation hospitalizations or outpatient encounters. However, about one-half of those evacuated for battle injuries were returned to duty immediately after their initial health care encounters.

Overall, the changes in numbers of medical evacuations over the course of the surveillance period reflect the end of Operation Enduring Freedom in 2014, the beginning of Operation Freedom's Sentinel, and the deployment of troops to Afghanistan, Iraq, and Syria.^5,6 The relatively low percentage of medical evacuations in 2019 suggests that most deployers were sufficiently healthy and ready for their deployments and received the medical care in theater necessary to complete their assignments without having to be evacuated. Moreover, the fact that very few medical evacuations were conducted for chronic conditions such as hematologic disorders and congenital anomalies supports the idea that most deployers were sufficiently healthy for deployment. However, it is not surprising that such conditions are occasionally diagnosed among deployed service members. For example, there was 1 medical evacuation for congenital anomalies in 2019 that was due to an instance of "other congenital malformations of nervous system" (data not shown). Because congenital anomalies may not be identified and diagnosed until later in life,⁷ the infrequent detection of such diagnoses during deployment is not unexpected.

The proportion of medical evacuations attributed to mental health disorders (27.1%) was similar to the proportion reported in recent MSMR analyses of medical evacuations in 2018 (28.2%) but slightly higher than the proportion reported in 2017 (23.6%) and considerably higher than the proportion (11.6%) reported in an earlier MSMR report examining evacuations from Iraq during a 9-year period between 2003 and 2011.^1,8 However, that article also reported that during the last 4 years (2008–2011) of the surveillance period, as the proportion of evacuations for battle injuries fell sharply, the proportions of evacuations for mental disorders increased dramatically for both males (peak of 20.9% in 2010) and females (peak of 26.6% in 2010). Although some studies have indicated improved access to mental health care in deployed settings, the results from the current analysis indicate that mental health diagnoses still represent the single most common basis for medical evacuations out of the CENTCOM AOR.⁹ This could be due, at least in part, to variations in the availability of mental health care in deployed settings. In these settings, the distribution of providers and clinics that deliver such services is uneven and varies according to factors such as the number of deployed personnel and the assessed needs of the particular unit.⁹ In addition, although the number of mental health care providers in Afghanistan increased from 2005 through 2010, this number decreased after 2013 as part of the overall drawdown of U.S. troops from the region.⁹

Several important limitations should be considered when interpreting the results of this analysis. Direct comparisons of numbers and percentages of medical evacuations by cause, as between males and females, can be misleading; for example, such comparisons do not account for differences between the groups in other characteristics (e.g., age, grade, military occupation, locations, and activities while deployed) that are significant determinants of medical evacuation risk. Also, for this report, most causes of medical evacuations were estimated from primary (first-listed) diagnoses that were recorded during hospitalizations or initial outpatient encounters after evacuation. In some cases, clinical evaluations in fixed medical treatment facilities after medical evacuations may have ruled out serious conditions that were clinically suspected in the theater. For this analysis, the causes of such evacuations reflect diagnoses that were determined after evaluations outside of the theater rather than diagnoses—perhaps of severe disease—that were clinically suspected in the theater. To the extent that this occurred, the causes of some medical evacuations may seem surprisingly minor.

Overall, the results highlight the continued need to tailor force health protection policies, training, supplies, equipment, and practices based on characteristics of the deployed force (e.g., combat vs. support; male vs. female) and the nature of the military operations (e.g., combat vs. humanitarian assistance).

References

1. Armed Forces Health Surveillance Branch. Update: Medical evacuations, active and reserve components, U.S. Armed Forces, 2018. MSMR. 2019;26(7):28–33.
2. Garamone J. Dunford: U.S. Forces busy implementing defense strategy worldwide. DOD News. 28 Aug. 2018. https://dod.defense.gov/News/Article/Article/1614521/dunford-us-forces-busyimplementing-defense-strategy-worldwide/. Accessed 14 April 2020.
3. Lead Inspector General for Overseas Contingency Operations. Operation Freedom’s Sentinel: Report to the United States Congress. https://media.defense.gov/2018/May/21/2001919976/-1/-1/1/FY2018_LIG_OCO_OFS2_MAR2018_3.PDF. Accessed 14 April 2020.
4. North Atlantic Treaty Organization. Resolute Support Mission (RSM): key facts and figures. https://www.nato.int/nato_static_fl2014/assets/pdf/pdf_2018_06/20180608_2018-06-RSM-placemat.pdf. Accessed 14 April 2020.
5. Office of the Under Secretary of Defense (Comptroller)/Chief Financial Officer. Defense Budget Overview. United States Department of Defense Fiscal Year 2020 Budget Request. March 2019.
6. Defense Manpower Data Center. DOD personnel, workforce reports and publications. https://www.dmdc.osd.mil/appj/dwp/dwp_reports.jsp. Accessed 12 March 2019.
7. The Centers for Medicare and Medicaid Services and the National Center for Health Statistics. ICD-10-CM Official Guidelines for Coding and Reporting. FY 2018. https://www.cms.gov/Medicare/Coding/ICD10/Downloads/2018-ICD-10-CM-Coding-Guidelines.pdf. Accessed 17 April 2020.
8. Armed Forces Health Surveillance Center. Medical evacuations from Operation Iraqi Freedom/Operation New Dawn, active and reserve components, U.S. Armed Forces, 2003–2011. MSMR. 2012;19(2):18–21.
9. United States Government Accountability Office. Report to Congressional Committees. Defense health care: DOD is meeting most mental health care access standards, but it needs a standard for follow-up appointments. April 2016. https://www.gao.gov/assets/680/676851.pdf. Accessed 17 April 2020.