What Are the New Findings?

Three categories of morbidity burdens (injury/poisoning, musculoskeletal diseases, and signs/symptoms and ill-defined conditions) accounted for more than half of the total burden in theater. In 2019, the percentages of encounters due to mental health disorders decreased to levels much lower than during earlier periods of combat engagements. Compared to garrison disease burden, deployed service members had higher proportions of encounters for respiratory infections, skin diseases, and infectious and parasitic diseases.

What Is the Impact on Readiness and Force Health Protection?

The similarities between the burden of disease and injury among deployed and non-deployed service members emphasize the continuing need for surveillance, research, and preventive measures for those ever-present health threats. The dissimilarities highlight those special health threats associated with the more austere environments of deployment areas and the needed area-specific preventive measures of importance.

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 2019 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 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 theater 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 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 (first-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 page 2 of this issue of the MSMR, all illness- and injury-specific diagnoses were grouped into 151 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. In addition to the examination of the distribution of diagnoses by the 151 conditions and the 25 major categories of disease burden, a third analysis depicts the distribution of diagnoses according to the 17 traditional categories of the ICD system.

Results

In 2019, a total of 191,887 medical encounters occurred among 69,405 individuals while deployed to Southwest Asia/Middle East and Africa. A majority of the medical encounters (77.4%) and individuals affected (81.8%) occurred among males (Figures 1a, 1b).

Medical encounters/individuals affected, by burden of disease categories

During 2019, 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 (5.6%) compared to males (1.2%). Females also had a higher proportion of medical encounters for mental health disorders (9.1%) compared to males (5.2%).

Among both males and females, 5 burden conditions (other back problems, arm and shoulder injuries, knee injuries, foot and ankle injuries, and upper respiratory infections) were among the top 6 burden conditions that accounted for the most medical encounters in 2019 (Figures 3a, 3b). The remaining burden conditions among the top 6 were organic sleep disorders (specifically, circadian rhythm disorders) among males and all other signs and symptoms among females.

The 4-digit ICD-10 code with the most medical encounters in the other back problems category during 2019 was for lumbago/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 ICD-10 code for arm and shoulder injuries among males and for knee injuries among males and females was 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).

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, congenital anomalies, blood disorders, malignant neoplasms, nutritional disorders, diabetes, and perinatal conditions (Figure 1a). Among females, less than 0.3% of all medical encounters during deployment were associated with endocrine disorders, other neoplasms, blood disorders, nutritional disorders, maternal conditions, congenital anomalies, malignant neoplasms, metabolic/immunity disorders, perinatal conditions, and diabetes mellitus (Figure 1b).

Among both sexes in 2019, injury/poisoning, musculoskeletal diseases, and signs/symptoms were the top 3 categories that affected the most individuals; musculoskeletal diseases ranked second among males and third among females (Figures 1a, 1b).

Medical encounters, by major ICD-9/ICD-10 diagnostic category

In 2019, among the 17 major ICD-9/ICD-10 diagnostic categories, the largest percentages of medical encounters were attributable to musculoskeletal system and "other" (includes factors influencing health status and contact with health services as well as external causes of morbidity) (Figure 4). The percentage of medical encounters attributable to musculoskeletal system conditions increased from 2015 through 2019, and the percentage attributable to "other" decreased during the same period. Of note, the percentages of medical encounters attributable to mental health disorders decreased slightly from 6.4% in 2015 to 4.7% in 2019. However, the percentage of medical encounters attributable to disorders of the nervous system and sense organs more than doubled from 3.5% in 2015 to 7.8% in 2019. The percentages of medical encounters attributable to other major ICD-9/ICD-10 diagnostic categories were relatively similar during the years 2015, 2017, and 2019.

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 2019. 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. However, the 2019 percentages of encounters due to mental health disorders among males and females (5.2% and 9.1%, respectively) were much smaller than the corresponding percentages during 2008–2014 (13.1% and 13.8%, respectively).³

Compared to the distribution of major burden of disease categories documented in garrison, this report demonstrates relatively greater proportions 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 reduced combat and operational stress in deployed settings 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. In garrison settings, mental health disorders, signs/symptoms, and neurologic conditions ranked third through fifth.⁴ In contrast, sign/symptoms, respiratory infections, and mental health disorders ranked third through fifth in deployed 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. Some of the similarity in the top conditions could also be attributed to service members receiving follow-up care once out of theater. For example, a service member medically evacuated out of theater for an injury could have encounters for injury recorded in both deployed and non-deployed (hospital or ambulatory care) settings.

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, 2018. MSMR. 2019;26(5):34–39.
2. Murray CJL and Lopez AD, eds. 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, 2019. MSMR. 2020;27(5): 2–9.