Differences in Disease Non-battle Injury Between Combatant Commands

Andrew Hall, Anwar E Ahmed, Christopher Cieurzo, Chelsea Payne, Ramey L Wilson, Differences in Disease Non-battle Injury Between Combatant Commands, Military Medicine, Volume 188, Issue 7-8, July/August 2023, Pages e2414–e2418, https://doi.org/10.1093/milmed/usac413

ABSTRACT

Disease and non-battle injury (DNBI) have historically been a major or primary medical burden in expeditionary military populations. The United States has multiple deployed populations conducting operations across the world. This study aims to determine if DNBI rates are different between military populations by comparing the United States Africa Command (USAFRICOM) and United States Central Command (USCENTCOM) areas of responsibility.

The study period was from January 1, 2017 to December 31, 2021. Individual evacuation data including date, necessary specialty care, and combatant command (CCMD) were acquired via United States Transportation Command Regulating and Command & Control Evacuation System. Total population data was acquired from USAFRICOM and USCENTCOM headquarters. Total inpatient and outpatient encounters at each CCMD were acquired via Theater Medical Data Store. The proportions and evacuation rates of DNBI types within USAFRICOM and USCENTCOM were compared.

USCENTCOM had significantly higher proportions of outpatient and inpatient services for mental disorders, musculoskeletal diseases, and neurologic conditions compared to USAFRICOM. USCENTCOM had a significantly lower evacuation rate compared to USAFRICOM for every year analyzed: 2017 (P-value < .0001; relative risk [RR] = 0.834; 95% CI = 0.80-0.87), 2018 (P-value < .0001; RR = 0.818; 95% CI = 0.78-0.85), 2019 (P-value < .0001; RR = 0.785; 95% CI = 0.75-0.82), 2020 (P-value < .0001; RR = 0.889; 95% CI = 0.84-0.94), and 2021 (P-value < .0001; RR = 0.868; 95% CI = 0.83-0.91).

The evacuation rates of different categories of DNBI vary between CCMDs. There will be CCMD-specific factors that impact the effectiveness of initiatives to reduce the DNBI burden.

INTRODUCTION

Disease and non-battle injury (DNBI) are defined as all illnesses and injuries are not resulting from enemy or terrorist action or caused by conflict. 1 Historically, DNBI have made up a significant proportion, if not the majority, of military casualties. 2, 3 The military medical system is charged with delivering combat casualty care; however, it is also responsible for providing care to service members stricken by endemic diseases or non-battle illnesses that accompany any military deployment of forces. From pregnancy and myocardial infarctions to unintentional injuries and new diagnoses of cancer, any deployment of service members to austere locations creates a “baseline” medical care requirement in the expeditionary care system. The military patient movement system, as the key resource connecting expeditionary care to U.S.-based care, supports the evacuation of all patients, combat-related or not.

The primary purpose of this study is to compare the DNBI burden within two combatant commands (CCMDs) over a prolonged identical period and determine whether differences exist. We examine the evacuation rates and proportions of disease types within two CCMDs. The academic literature to date contains studies describing the impact of DNBI on specific operations or discrete events. 4, 5 These reports often demonstrate how DNBIs deplete available combat power, increase the requirements of non-trauma care, and call for improved preventive measures to be enacted and resourced. As these studies tend to be focused on specific operations or unit rotations, they tended to be limited by their scope or study period. A question of universal applicability across CCMD areas of responsibility (AORs) of historical or current norms exists.

METHODS

United States Transportation Command (USTRANSCOM) evacuation records for DNBI occurring within the United States Africa Command (USAFRICOM) and United States Central Command (USCENTCOM) AORs during the study period between January 1, 2017 and December 31, 2021. The population examined was all patients that utilized the health care facilities within the CCMD AORs. The evacuation database used was the TRANSCOM Regulating and Command & Control Evacuation System (TRAC2ES) which records all regulated, validated movements conducted by the DoD Transportation System. When applicable, the date individuals were declared ready for evacuation was used for comparisons. USAFRICOM and USCENTCOM were used given their large, persistently deployed forces in austere conditions. During this period, COVID-19 was a very limited problem for several months and was artificially elevated because of an evacuation requirement regardless of severity. 6 COVID-19 evacuations were therefore eliminated for purposes of evacuation comparisons. A total of 10 USAFRICOM and 246 USCENTCOM COVID-19 evacuations were excluded.

Monthly evacuation rates were calculated using CCMD provided population numbers. USAFRICOM provided an identical monthly population from January 1, 2017 to December 31, 2018, a second mean monthly population from January 1, 2019 to December 31, 2020, and a third from January 1, 0201 to December 31, 2021. A corresponding monthly population for those periods was calculated from population data provided by USCENTCOM. The monthly population was used to determine evacuation rates per 1,000 individuals per month in each CCMD. DNBI conditions necessitating evacuation were organized by the clinical provider required for management at the next level of care as determined at the time of evacuation. If the evacuation record listed minor variations such as psychiatry, psychiatry (general care), or psychiatry (intensive care), these categories were combined. The top three required specialties for evacuated personnel for each CCMD were identified.

The number and type of outpatient and inpatient encounters within USAFRICOM and USCENTCOM were acquired from the Theater Medical Data Store (TMDS) via the Armed Forces Health Surveillance Division (AFHSD). Disease categories of encounters were defined by the AFHSD. Primary diagnoses were pulled from TMDS/TMDS_ICD10 encounters between 2017 and 2021 specific to USAFRICOM or USCENTCOM. Encounters with a primary diagnosis not contained in the burden dictionary were excluded. Encounters with an “MTF_DESC” indicating that the encounter came from an air staging facility in the United States or indicating that the encounter came from a location in other CCMDs were excluded. Shipboard encounters with an unknown location were excluded as these vessels often crossed between CCMDs and their location at the time of the encounter was not available. Individual medical records were not available to analyze as part of this study.

Traumatic injuries caused by hostile action could not be excluded from TMDS data. The total wounded in action for USCENTCOM was acquired from the USCENTCOM J1 to document the number of potentially non-DNBI within these data.

Data analyses were performed using SAS version 9.4 (SAS Institute, Cary, NC, USA). The probit model was used to estimate the probabilities of binary responses that are grouped (for each disease category, e.g., blood disorders), specifically model r/n = x, where r is the number of monthly outpatient and inpatient encounters for a particular disease category, n represents the total number of monthly evacuations, and x represents headquarters (USAFRICOM vs. USCENTCOM). Relative risk (RR) and 95% CI were calculated for USAFRICOM as compared to USCENTCOM ( Table I). Probit models were used to assess the evacuation rates between USAFRICOM and USCENTCOM in each year.

Proportion of Outpatient and Inpatient Encounters per Month Within Each Disease Category Within the USAFRICOM and USCENTCOM AOR Between January 1, 2017 and December 31, 2021

Abbreviations: LCL = lower confidence interval for RR; RR = relative risk; UCL = upper confidence interval for RR; USAFRICOM = United States Africa Command; USCENTCOM = United States Central Command.

Proportion of Outpatient and Inpatient Encounters per Month Within Each Disease Category Within the USAFRICOM and USCENTCOM AOR Between January 1, 2017 and December 31, 2021

Abbreviations: LCL = lower confidence interval for RR; RR = relative risk; UCL = upper confidence interval for RR; USAFRICOM = United States Africa Command; USCENTCOM = United States Central Command.

RESULTS

The total numbers of evacuated populations were 1,133 (USAFRICOM) and 5,873 (USCENTCOM) between January 1, 2017 and December 31, 2021. During the study period, there were a total of 24,307 USAFRICOM and 887,358 USCENTCOM inpatient/outpatient encounters registered in TMDS. USCENTCOM had significantly lower proportions of outpatient and inpatient services for cardiovascular diseases, digestive diseases, genito-urinary diseases, infectious and parasitic diseases, metabolic and immunity disorders, oral conditions, other neoplasms, respiratory infections, signs and symptoms, and skin diseases compared to USAFRICOM. USCENTCOM had significantly higher proportions of outpatient and inpatient services for congenital anomalies, mental disorders, musculoskeletal diseases, neurologic conditions, and sense organ diseases compared to USAFRICOM ( Table I). The total number of U.S. personnel wounded in action in the USCENTCOM AOR was 756.

The mean monthly populations for USAFRICOM were 6,667 (2017-2018), 6,692 (2019-2020), and 6,692 (2021). For USCENTCOM, the mean monthly populations were 65,996 (2017-2018), 66,271 (2019-2020), and 48,140 (2021). The evacuation rate varied between 1.0 and 5.2 per 1,000 population per month for USAFRICOM and 1.1 and 2.8 per 1,000 population per month for USCENTCOM ( Fig. 1). USCENTCOM had a significantly lower evacuation rate compared to USAFRICOM, in 2017 (P-value < .0001; RR = 0.834; 95% CI = 0.80-0.87), 2018 (P-value < .0001; RR = 0.818; 95% CI = 0.78-0.85), 2019 (P-value P-value < .0001; RR = 0.889; 95% CI = 0.84-0.94), and 2021 (P-value < .0001; RR = 0.868; 95% CI = 0.83-0.91).

Evacuation rate per 1,000 population per month in USCENTCOM and USAFRICOM between January 1, 2017 and December 31, 2021.

During the study period, psychiatric conditions made up the largest segment of evacuations for USCENTCOM at 27% but were 12% for USAFRICOM. Orthopedic conditions made up the largest segment of evacuations from USAFRICOM at 18% of DNBI evacuations but were 15% at USCENTCOM. Internal medicine was the third within USAFRICOM at 6% of evacuations, and neurology was the third most common within USCENTCOM at 7%. Evacuations of Afghan refugees performed as part of Operation Allies Refuge were not regulated through TRAC2ES and were excluded from this analysis.

DISCUSSION

This study demonstrates that DNBI evacuation rates and proportional burden on military assets are not consistent across CCMDs, and therefore initiatives aimed at decreasing DNBI should consider local and environmental factors. The study also provides baseline evacuation rates to assess DNBI mitigation and treatment programs.

There will always be illness in large populations. For military populations, DNBI can be a greater medical burden than injuries acquired because of combat. 7 Definitive treatment of any injury or illness is often not available in expeditionary settings and requires evacuation through the patient movement system to access care outside the theater of operations. This is true for both combat casualties and non-combat injuries and illnesses. Initiatives and the development of best practices are required to best manage disease in these conditions along with baseline proportions and rates of disease to determine if initiatives are successful.

The variation between USCENTCOM and USAFRICOM can be multifactorial. Chronic disease prevalence within the population deploying to an AOR may result in exacerbation and subsequent evacuation. USAFRICOM and USCENTCOM do have similar, but different standards required for entry into their respective AORs. 8, 9 USAFRICOM theater entry standards for some conditions, such as behavioral health, are stricter than USCENTCOM because of the lack of medical capabilities in the theater and wider geographic distribution of populations and medical assets. The lower USCENTCOM evacuation rate may be attributable to more mature and more extensive medical capabilities. 10 With more facilities, patient holding capacity, ability to manage complications, and medical personnel, conditions may be more amenable to being managed in the theater in USCENTCOM compared to USAFRICOM. 11 In addition, the availability and capability of host and partner countries in AORs vary considerably, and the nature of ongoing military operations may also be a contributing factor. 12 Endemic diseases and environmental factors in these regions are also different. Finally, the yearly population within USAFRICOM was approximately 10% of USCENTCOM, so normal variation in evacuation rates could have a material difference in a calculated rate per 1,000. Given the relatively low levels of encounters within USAFRICOM, a surge in one type of condition could statistically alter the proportion of disease encounters. This is most evidenced by the category of congenital anomalies where both had relatively tiny numbers of cases but were nonetheless statistically different.

Reducing DNBI medical care and evacuation may be possible while maintaining entry standards and infrastructure in the theater. In this study, psychiatric and orthopedic conditions are the largest categories requiring evacuation in both CCMDs. There have been initiatives that have shown signs of reducing evacuations for DNBI. 13 Orthopedic injury, or injury in general, that meets the criteria for DNBI has been historically related to accidents or sports. 14, 15 Some injuries can be prevented by restricting high risk or combat sports and providing appropriate equipment for recreational activities. Psychiatric conditions may develop or become exacerbated during deployment, making prevention more complicated than self-injury. 16, 17 Those with a history of behavioral health treatment may be protected to some degree during deployment, so encouragement of care may prevent evacuation. 18 Medical capabilities can also be expanded through telehealth. The improved virtual connection can offer social support and has been found to be effective in expanding behavioral health support. 19 With limited resources in austere and operationally active locations, preventing those at high risk of unmanageable mental health decline may be the best strategy. In large-scale operations, a much larger population would be required to meet threats, however. A highly restrictive policy would likely not be practicable. Within large, deployed populations, highly reliable, low-burden screening tools that allow targeted therapy of those at risk for developing unmanageable diseases would be ideal. Prospective studies on any generalized programs are required to determine effects and best practices.

This study represents a strategic overview of DNBI in two CCMDs. A finer analysis of individual locations is needed to better understand the differences between and within CCMD AORs. Other limitations include potential gaps in data. For example, evacuations, not using the DoD Transportation System, may not be logged in the TRAC2ES database, and USAFRICOM military facilities are particularly austere and may not log encounters accurately. Commercial services have been used within CCMDs to facilitate patient movement; consequently, true evacuation rates may be higher. The future applicability of this study’s data may also be questionable. USCENTCOM and USAFRICOM have enjoyed a permissive environment for airborne evacuation assets throughout this study period. In a contested environment, the ability to evacuate individuals may be more limited, and a higher threshold for evacuation may be required. Ultimately, this could lead to longer holding times and accentuate the need to prevent DNBI or manage it in place.

CONCLUSIONS

DNBI represent a substantial burden to CCMDs. The evacuation rates and proportions of disease non-battle injury types are variables between CCMDs. The reason for this variability is at least due in part to differences in entry standards, but likely also related to different environments. Initiatives that successfully reduce orthopedic injuries and psychiatric illness in the theater would yield the greatest reduction of DNBI rates and evacuation requirements for deployed populations, but each CCMD will likely need to be looked at individually because of innate differences in risk and resources.