What Are the New Findings?

As in previous years, among service members deployed during 2020, injury/poisoning, musculoskeletal diseases and signs/symptoms accounted for more than half of the total health care burden during deployment. The percentage of encounters attributable to mental health disorders increased slightly over that observed in 2019 but remained below levels seen in the period 2008-2014. Compared to garrison disease burden, deployed service members had relatively higher proportions of encounters for respiratory infections, skin diseases, and infectious and parasitic diseases.

What Is the Impact on Readiness and Force Health Protection?

Injuries and musculoskeletal diseases account for the greatest burden of deployed medical care and continued focus on surveillance and preventive measures for these health threats is warranted. While deployed, readiness may be impacted by conditions associated with austere environmental and sanitary conditions.

Background

Every year, the MSMR estimates illness- and injury-related morbidity and health care burdens on the U.S. Armed Forces and the Military Health System (MHS) using electronic records of medical encounters from the Defense Medical Surveillance System (DMSS). These records document health care delivered in the fixed medical facilities of the MHS and in civilian medical facilities when care is paid for by the MHS. Health care encounters of deployed service members are documented in records that are maintained in the Theater Medical Data Store (TMDS), which is incorporated into the DMSS. This report updates previous analyses examining the distributions of illnesses and injuries that accounted for medical encounters ("morbidity burdens") of active component members in deployed settings in the U.S. Central Command (CENTCOM) and the U.S. Africa Command (AFRICOM) areas of operations during the 2020 calendar year.¹

Methods

The surveillance population included all individuals who served in the active or reserve components of the U.S. Army, Navy, Air Force, or Marine Corps and who had records of health care encounters captured in the TMDS during the surveillance period. The 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 (e.g., SAMS, SAMS8, SAMS9) or where the military treatment facility descriptor indicated that care was provided aboard a ship (e.g., USS George H.W. Bush or USS Dwight D. Eisenhower) were excluded from this analysis. Encounters from aeromedical staging facilities outside of CENTCOM or AFRICOM (e.g., the 779th Medical Group Aeromedical Staging Facility or the 86th Contingency Aeromedical Staging Facility) were also excluded. Inpatient and outpatient medical encounters were summarized according to the primary (firs listed) diagnoses (if reported with an International Classification of Diseases, 9th Revision [ICD-9] code between 001 and 999 or beginning with V27 or with an International Classification of Diseases, 10th Revision [ICD-10] code between A00 and T88 or beginning with Z37). Primary diagnoses that did not correspond to an ICD-9 or ICD-10 code (e.g., 1XXXX, 4XXXX) were not reported in this burden analysis.

In tandem with the methodology described on pages 2–3 of this issue of the MSMR, all illness- and injury-specific diagnoses were grouped into 153 burden of disease-related conditions and 25 major categories based on a modified version of the classification system developed for the Global Burden of Disease (GBD) study.² The morbidity burdens attributable to various conditions were estimated on the basis of the total number of medical encounters attributable to each condition (i.e., total hospitalizations and ambulatory visits for the condition with a limit of 1 encounter per individual per condition per day) and the numbers of service members affected by the conditions. In general, the GBD system groups diagnoses with common pathophysiologic or etiologic bases and/or significant international health policymaking importance. For this analysis, some diagnoses that are grouped into single categories in the GBD system (e.g., mental health disorders) were disaggregated. Also, injuries were categorized by the affected anatomic sites rather than by causes because external causes of injuries are not completely reported in TMDS records. It is important to note that because the TMDS has not fully transitioned to ICD-10 codes, some ICD-9 codes appear in this analysis. 

Results

In 2020, a total of 154,203 medical encounters occurred among 58,440 individuals while deployed to Southwest Asia/Middle East and Africa. Of the total medical encounters, 205 (0.13%) were indicated to be hospitalizations (data not shown). A majority of the medical encounters (75.8%), individuals affected (80.4%), and hospitalizations (79.5%) occurred among males (Figures 1a, 1b).

Medical encounters/individuals affected by burden of disease categories

During 2020, the percentages of total medical encounters by burden of disease categories in both deployed men and women were generally similar; in both sexes, more encounters were attributable to injury/poisoning, musculoskeletal diseases, and signs/symptoms (including ill-defined conditions) than any other categories (Figures 1a, 1b, 2a, 2b). Of note, females had a greater proportion of medical encounters for genitourinary diseases (6.3%) compared to males (1.3%).

Among both males and females, 5 burden conditions (other back problems, arm and shoulder injuries, knee injuries, all other signs and symptoms, and upper respiratory infections) were among the top 6 burden conditions that accounted for the most medical encounters in 2020 (Figures 3a, 3b). The remaining burden conditions among the top 6 were organic sleep disorders (specifically, circadian rhythm disorders) among males and foot and ankle injuries among females.

The 4-digit ICD-10 code with the most medical encounters in the other back problems category during 2020 was for low back pain (data not shown). For all other musculoskeletal diseases, the most common 4-digit ICD code for both males and females was for cervicalgia. The most common 4-digit ICD10 codes for arm and shoulder injuries and knee injuries were for pain in the specified body part (e.g., pain in right or left shoulder or pain in right or left knee) (data not shown). The 4-digit ICD-10 code with the third most medical encounters was for acute nasopharyngitis (i.e., common cold) (data not shown).

Of note, among males, less than 0.3% of all medical encounters during deployment were associated with any of the following major morbidity categories: other neoplasms, metabolic/immunity disorders, endocrine disorders, diabetes mellitus, congenital anomalies, nutritional disorders, and malignant neoplasms (Figure 1a). Among females, less than 0.3% of all medical encounters during deployment were associated with maternal conditions, other neoplasms, nutritional disorders, blood disorders, congenital anomalies, metabolic/ immunity disorders, malignant neoplasms, perinatal conditions, and diabetes mellitus (Figure 1b).

Among both sexes in 2020, injury/poisoning, musculoskeletal diseases, and signs/ symptoms were the top 3 categories that affected the most individuals. (Figures 1a, 1b).

Editorial Comment

This report documents the morbidity and health care burden among U.S. military members while deployed to Southwest Asia/Middle East and Africa during 2020. Similar to results from earlier surveillance periods,^1,3 3 burden categories—injury/poisoning, musculoskeletal diseases, and signs/symptoms— together accounted for more than 50% of the total health care burden in theater among both male and female deployers.

Compared to the distribution of major burden of disease categories documented in garrison, this report also demonstrates a relatively greater proportion of in-theater medical encounters due to respiratory infections, skin diseases, and infectious and parasitic diseases. The lack of certain amenities and greater exposure to austere environmental conditions may have compromised hygienic practices and contributed to this finding. In contrast, compared to the distribution of burden of disease in garrison, a relatively lower proportion of in-theater medical encounters due to mental health disorders was observed.⁴ This finding may be due to a number of factors including predeployment screening and the continued emphasis on promoting psychological health and resilience in deployed service members.

However, 4 of the top 5 major burden of disease categories in-theater—injury/poisoning, musculoskeletal diseases, signs/symptoms, and mental health disorders—were the same as those reported in non-deployed settings.⁴ Injury and musculoskeletal diseases ranked first and second in both settings. The similarity in these top conditions is likely attributable to the fact that both deployed and non-deployed populations generally comprise young and healthy individuals undergoing strenuous physical and mental tasks.

Encounters for certain conditions are not expected to occur often in deployment settings. For example, the presence of some conditions (e.g., diabetes, pregnancy, or congenital anomalies) makes the affected service members ineligible for deployment. As a result of this selection process, deployed service members are generally healthier than their non-deployed counterparts and, specifically, less likely to require medical care for conditions that preclude deployment. The overall result of such predeployment medical screening is diminished health care burdens (as documented in the TMDS) related to certain disease categories.

Interpretation of the data in this report should be done with consideration of some limitations. Not all medical encounters in theaters of operation are captured in the TMDS. Some care is rendered by medical personnel at small, remote, or austere forward locations where electronic documentation of diagnoses and treatment is not feasible. As a result, the data described in this report likely underestimate the total burden of health care actually provided in the areas of operation examined. In particular, some emergency medical care provided to stabilize combat-injured service members before evacuation may not be routinely captured in the TMDS. Another limitation derives from the potential for misclassification of diagnoses due to errors in the coding of diagnoses entered into the electronic health record. Although the aggregated distributions of illnesses and injuries found in this study are compatible with expectations derived from other examinations of morbidity in military populations (both deployed and non-deployed), instances of incorrect diagnostic codes (e.g., coding a spinal cord injury using a code that denotes the injury was suffered as a birth trauma rather than using a code indicating injury in an adult) warrant care in the interpretation of some findings. Although such coding errors are not common, their presence serves as a reminder of the extent to which this study depends on the capture of accurate information in the sometimes austere deployment environment in which health care encounters occur.

References

1. Armed Forces Health Surveillance Branch. Morbidity burdens attributable to various illnesses and injuries, deployed active and reserve component service members, U.S. Armed Forces, 2019. MSMR. 2020; 27(5): 33–38. 
2. Murray CJ and Lopez AD, eds. In: Global Burden of Disease: A Comprehensive Assessment of Mortality and Disability from Diseases, Injuries, and Risk Factors in 1990 and Projected to 2020. Cambridge, MA: Harvard University Press; 1996:120–122. 
3. Armed Forces Health Surveillance Branch. Morbidity burdens attributable to various illnesses and injuries in deployed (per Theater Medical Data Store [TMDS]) active and reserve component service members, U.S. Armed Forces, 2008–2014. MSMR. 2015;22(8):17–22. 
4. Armed Forces Health Surveillance Branch. Absolute and relative morbidity burdens attributable to various illnesses and injuries, active component, U.S. Armed Forces, 2020. MSMR. 2021;28(5): 2–9.