Prevalence of Polytrauma Clinical Triad Among Active Duty Service Members

Introduction: The polytrauma clinical triad (PCT), encompassing traumatic brain injury, PTSD, and chronic pain, has been identified as a significant concern in the Military Health System (MHS). Conditions in this triad mutually reinforce one another and can pose a significant challenge to treatment for patients and providers. Polytrauma clinical triad has previously been studied in deployed veterans but remains understudied in the active duty military population. Therefore, this novel study seeks to determine the prevalence of PCT among active duty service members and to identify the subpopulations most at risk for PCT. Materials and Methods: This cross-section study used the MHS Data Repository in order to retrospectively review all administrative claim data for active duty service members within the Army, Navy, Air Force, and Marine Corps from fiscal years 2010 to 2015. Specific ICD-9 codes were extracted that correlated with traumatic brain injury, PTSD, and chronic pain to determine the risk of PCT. We used logistic regression to compare individuals presenting with the PCT conditions to those service members without any of the PCT diagnoses codes. Results: The study identified 2,441,698 active duty service members eligible for inclusion. The prevalence of all three conditions of PCT was 5.99 per 1,000 patients. Patients with PCT were most likely to be 20–29years old (52.15%), male (89.83%), White (59.07%), married (64.18%), Junior Enlisted (55.27%), and serving in the Army (74.71%). Conclusion: This study is the first to identify the risk of PCT in the active duty military population. Awareness of the risk and subsequent prompt identification of the triad will enable treatment through an integrated, team approach, which should alleviate potential patient suffering and improve the efficiency of care and readiness of service members.


INTRODUCTION
The polytrauma clinical triad (PCT), collectively encompassing traumatic brain injury (TBI), chronic pain, and PTSD, 1 poses a unique challenge for both patients and providers, as conditions within the triad are interconnected and often mutually reinforcing, and thus prove difficult to treat effectively. 1,2 Polytrauma clinical triad consistently leads to chronic issues, 3 especially if not addressed and monitored comprehensively, and is linked to significantly increased risk of sleep disorders, cognitive defects, or even suicide. 4 Chronic pain and PTSD in particular significantly increase the risk of separation from the military. 5 Therefore, identification of PCT and the population at risk for its conditions might help to alleviate patient suffering and improve military readiness through more efficient medical care.
Research regarding the prevalence of PCT among military service members has been focused on small populations of deployed veterans. For example, a 2009 study identified prevalence of PCT, defined in this case as persistent postconcussive symptoms including pain, with PTSD, at 42.1% of 340 veterans of Operation Enduring Freedom (OEF) and Operation Iraqi Freedom (OIF), 18.5% of individuals having a single condition in isolation, and the remaining 39.4% presenting with two of the three conditions. 6 Other research focused on veterans acknowledges the need for integrated care and the burden placed on patients to be their own health care managers across multiple specialties, clinics, and schedules. 7,8 In the Military Health System (MHS), programs like the National Intrepid Center of Excellence (NICoE) and its related Intrepid Spirit Centers aim to address the fragmentation of care, particularly for those patients with TBI, PTSD, and associated comorbidities, through an intensive outpatient program in which all providers associated with a patient's care are co-located at one facility. 9,10 However, the prevalence of the full triad and its associated risk factors among active duty service members is understudied, which limits the ability of the MHS to address PCT comprehensively at system-wide and local levels. This study aims to address this gap through analysis of data in the MHS Data Repository (MDR), identifying active duty service members at risk of one, two, or all three conditions of the PCT. Although each segment of this triad may occur in isolation, there is value in knowing whether diagnosis of a single condition presents a heightened risk for the full triad, and whether there is a need to screen for the remaining segments of PCT when one is identified.

Study Design and Data Source
We conducted a retrospective cross-sectional study on existing administrative and health care claims data from the MDR from fiscal years (FY) 2010 to 2015 (October 1, 2009 to September 30, 2015). The MDR stores encounter and claims data from MHS beneficiaries who receive care at military treatment facilities (direct care) and at civilian fee-for-service treatment facilities (purchased care) through TRICARE. TRI-CARE is the DoD insurance product that provides universal health care coverage to 9.6 million beneficiaries, to include active duty military personnel, retirees, and their dependents. The database does not capture care delivered in combat zones or through the Veterans Health Administration. The MDR has been utilized and proven to be a useful research tool in multiple previous studies investigating health and service utilization in active duty service members. [11][12][13] Population Utilizing the Defense Enrollment Eligibility Reporting System, this study identified U.S. active duty service members in the Army, Air Force, Navy, and Marine Corps aged 18 years and older from FY 2010 to 2015. Utilizing ICD-9, diagnostic codes, we subsequently identified all active duty service members with health care claims for one or more of the components of PCT, to include chronic pain, PTSD, and TBI. The complete list of ICD-9 codes can be found in Supplementary Materials, Table S1, and was compiled with references from previous studies. 14 Codes were chosen for TBI when trauma occurred without permanent damage or disability. Return to baseline symptoms after concussion or TBI was not examined in our study because of that information not being available in the dataset. Only one code was used for PTSD. Chronic pain codes were chosen when it was not in conjunction with another illness and focused on chronic pain because of trauma or an undefined condition. Chronic pain codes were excluded if they were secondary to another condition such as autoimmune, inflammatory, post-operative, neoplastic, infectious, or other diseases.

Analysis
Analyses included descriptive statistics for patient demographics (age category, gender, race, marital status) and military characteristics (rank, service, and occupational specialty), and prevalence of PCT as well as each component of PCT. Prevalence rates were calculated and expressed as per 1,000 active duty service members. Among the population of active duty service members with one or more components of PCT, a multivariable logistic regression analysis with 95% CIs was performed to assess the risk for PCT in active duty service members, with all patient demographics and military characteristics included as predictor variables. Logistic regression is the epidemiologic standard when examining the relationship between an independent categorical variable and a dependent dichotomous variable. 15 Service members with missing, incomplete, or plausibly inaccurate records were removed from the logistic regression analysis, resulting in 6.2% excluded. All analyses were conducted using SAS software version 9.4 (SAS Institute Inc., Cary, North Carolina). This study was considered exempt by the Institutional Review Board of the Uniformed Services University of the Health Sciences.

RESULTS
We identified 2,441,698 active duty service members between 2010 and 2015, of which 458,718 had one or more components of PCT, and 14,616 had all three components consistent with PCT, a prevalence rate of 5.99 per 1,000 active duty service members. Figure 1 shows the individual prevalence of TBI, chronic pain, and PTSD. Within this sample, 41,029 active duty service members presented with only TBI, 56,351 with only PTSD, and 279,086 with only chronic pain. Additionally, Figure 1 highlights the number of individuals presenting with two of the three conditions, which emphasizes the multiple possible combinations of these conditions. Table I shows the demographics and military characteristics of active duty service members who present with all three components of PCT. The majority of individuals   A total of 430,270 active duty service members were included in the multivariable logistic regression analysis for risk of PCT, and the results can be found in Table II. Compared to service members aged 20-29 years, those aged 30-39 years had a 6% greater risk for PCT (1.06-1.11 95% CI; P = .0079), while all other age categories had a protective effect, excluding the results for those 60 years and older which were statistically insignificant. Female (0.67 OR, 0.63-0.71 95% CI; P < .0001) and single (0.69 OR, 0.66-0.72 95% CI; P < .0001) active duty service members had a lower risk of PCT when compared to their male and married colleagues. Compared to White active duty service members, all minority (non-White) races had a lower risk for PCT, excluding other, which had a 34% greater risk. Native American/Alaskan Native service members had a lower risk; however, this was not found to be a significant result. Compared to Army service members, Marines had an 11% greater risk for PCT (1.06-1.17 95% CI; P < .0001), while service members in the Air Force (0.23 OR, 0.22-0.25 95% CI; P < .0001) and Navy (0.35 OR, 0.32-0.38 95% CI; P < .0001) had a significantly lower risk. Excluding Senior Enlisted active duty service members, all other ranks had a lower risk of PCT when compared to Junior Enlisted service members. Senior Enlisted service members had a 20% greater risk for PCT (1.14-1.26 95% CI; P < .0001) compared to Junior Enlisted service members. Finally, when examining occupational specialties and using "other" as the comparison group, all occupations had a higher risk for PCT, excluding Aviation and Naval Transport/Operations which had statistically insignificant results. Warfighter/Combat specialists (3.62 OR, 3.44-3.81 95% CI; P < .0001) and health care personnel (2.53 OR, 2.35-2.73 95% CI; P < .0001) presented with the greatest risks for PCT.

Relevance
This study is the first to examine the risk of PCT according to diagnosis with one or more component comorbidities in the active duty service member population. The sample size of 2,441,698 individuals far exceeds those of previous studies, which used small sample sizes of deployed veteran populations seeking treatment for trauma or pain, rather than all service members. 6 Moreover, the wide range of demographic variables in this study increases the external validity in comparison to preceding studies, which did not assess variables such as marital status and occupation. Analyzing the specific demographics associated with all three components in this large sample size will aid in future diagnosis and treatment within the MHS by identifying subpopulations with increased risk of developing PCT. Notably, previous studies reviewing persistent sequelae from TBI alone reported an increase in behavioral and motor difficulties with higher rates of psychiatric and neurological conditions, with patients showing greater chronic needs and increased use of health services. 16 The addition of complicating and mutually driving factors such as PTSD and chronic pain poses a significant challenge to patients and providers, as well as to the MHS in terms of ongoing care, lost readiness, and potential disability benefits. Therefore, this study is highly relevant to individual service members and to the MHS as a whole.

Major Findings
This study demonstrated notable differences from the published rates of PCT and its components in previously deployed veterans. Our finding of 5.99 per 1,000 active duty service members, or ∼0.6% of 2,441,698 active duty service members demonstrating the full triad of symptoms associated with PCT, is in stark contrast to the previously reported prevalence of post-concussive symptoms with chronic pain and PTSD at 42.1% in veterans of OIF and OEF, 6 though somewhat comparable to the 9% found by Pugh et al., in 2014. 14 Similarly, the rate of single conditions in our study was 376,466 service members or 15.42% of all eligible active duty service members, while 67,636 service members or 2.8% of all eligible active duty service members were diagnosed with two of the components of PCT. This value is compared to Lew's previously reported rates of 18.5% of individuals having a single condition in isolation and 39.4% presenting with two of the three conditions, when defining PCT according to postconcussive symptoms. 6 This may account in part for the lower rate of all three components seen in our study. This lower rate may also be because of inclusion of all active duty service members with a relevant diagnosis, regardless of deployment status.
As described in the results, those presenting with all three components of PCT were most commonly White, male, enlisted personnel, ages 20-29 years, of Army service and "other" or Combat Warfighter specialties. This aligns to the overall composition of the Armed Forces as majority White, male, and enlisted, that Army has the largest number of members, 17 and that combat exposure increases the risk of PTSD. 18 The finding that greater rates and risk of PCT in married versus unmarried personnel is noteworthy, as marriage has long been considered a protective factor against mental health disorders. 19 However, the protective benefits of marriage are demonstrated to depend on a positive relationship between spouses, while marital discord is associated with a higher risk of PTSD. [20][21][22] Although not necessarily applicable to TBI and chronic pain, the effects of marital discord may be sufficient to enable PTSD to develop in service members already experiencing another component of PCT. Alternately, the increased rate of PCT in married individuals may actually reflect a greater degree of care-seeking at the prompting of a spouse, as similar data exist for social support in cases of PTSD. 23 Age, race, rank, and occupation all highlight specific factors associated with an increased prevalence and risk of PCT. Of the overall military population, ∼25% were between 30 and 39 years old in 2018, 17 while this same age group comprised 34% of the PCT sample and was the only age group with a greater risk for PCT according to logistic regression. Although not the largest proportion of those experiencing PCT, this 34% constitutes an over-representation and may reflect a longer term of service or multiple deployments with the potential to increase the risk of PCT. In contrast, ∼54% of those with all three components of PCT were aged 29 years and under, which is an under-representation of this age group, given that those aged 30 years and under comprised ∼67% of the active duty forces in 2018. 17 However, the fact that this group accounted for the largest percentage of those with PCT indicates an opportunity for targeted screening. When assessed by race, 36.23% of those with PCT were of a minority race (Black, Asian, Native American/Alaska Native, and other), while comprising 31% of active duty forces in 2018, 17 also indicating a slight over-representation for PCT among racial minorities in this population. One study found that non-White race had an 18% greater risk for combat-related PTSD; 16 however, no other study has specifically looked at race as a predictor for PCT. We found that some minority races (Black and Asian/Pacific Islander) had a protective effect for PCT, while minorities identifying as other displayed the greatest risk.
Occupational category may also play a contributory role in the development of PCT among service members. From the sample studied, individuals working in uncategorized (other) jobs accounted for 32.85% of those with PCT, and more detailed analysis of this subsection would be informative. Warfighters and combat specialists accounted for the secondlargest group (19.83%) and with the greatest risk for PCT. This could be because of a higher incidence of TBI, a greater risk of musculoskeletal injury, or a greater exposure to trauma which could serve as the index event for developing PTSD.
Another consideration is the service branch of individuals presenting with PCT. In 2018, 36.18% of active duty DoD members served in the Army and 14.2% served in the Marine Corps, 17 while 74.71% of individuals presenting with the three components of PCT are Army personnel and 15.62% are Marines. Several possibilities for this over-representation may include a higher percentage serving as warfighters, or higher percentage of enlisted personnel, who had the greatest risk of PCT by rank. When comparing among the individual services, although the Marine Corps did not constitute the highest proportion of PCT individuals, they had an 11% greater risk for PCT than individuals in the Army. These results contradict what was found in combat-related PTSD in military personnel, which demonstrated Army personnel had a 2.3 times greater risk. 16

LIMITATIONS
This study has several limitations. As noted above, the MDR does not capture deployment data, and therefore, they could not be included in the study. This study also does not capture care sought outside the MHS or in combat zones as described above. Similarly, social or professional factors associated with the decision to seek or not to seek care, particularly for mental health issues such as PTSD, are not captured in this dataset. As with all large databases, the MDR is subject to inaccuracies in coding, 24 and the codes may not capture the clinical nuances of the patients' conditions, particularly for chronic pain. Published literature introduces further nuance, with some sources citing persistent post-concussive symptoms 6 as a major component of PCT and others interpreting this to mean TBI, 1,14 which requires careful examination when comparing findings between studies. The five-year time frame used for this study may have eliminated some patients who developed elements of the PCT more than five years after their initial TBI diagnosis or whose initial diagnosis was before the study period. Conversely, the 5-year timespan may result in the artificial clustering of symptoms indicating risk of PCT for patients who are not actually at risk. Critically, deployment status is not available in the MDR and therefore not assessed in this study, which represents a significant limitation in determining factors which lead to PCT in active duty service members. Finally, although the goal of this is to inform decision-making with the tools available to physicians, the review of health records cannot be a substitute for in-person examination and diagnosis.

RECOMMENDATIONS AND NEXT STEPS
This assessment of PCT in active duty service members has illustrated several opportunities for further investigation and intervention. First, the percentage of service members experiencing one, two, or all three trauma conditions suggests that these conditions tend to occur in isolation more often that in combination. In turn, this suggests there is no particular need to screen for all three conditions when one is present.
Second, the over-representation of Army personnel and service members aged 30-39 years, and the higher rate of PCT among married personnel, suggest the suitability for targeted screening in these populations. Third, the success of programs such as NICoE suggest an expansion of this approach in the MHS to meet the needs of those with PCT. Further research to support these endeavors should include the differentiation of those experiencing and not experiencing deployment, those in uncategorized occupations, and clinical factors differentiating between those who do and do not develop PCT following the diagnosis of the first triad condition. Additional value would be gained through the investigation of PCT and its component conditions in men versus women.

SUPPLEMENTARY MATERIAL
Supplementary material is available at Military Medicine online.

FUNDING
This study was funded through the Comparative Effectiveness and Provider-Induced Demand Collaboration (EPIC)/Low-Value Care in the National Capital Region Project, by the United States Defense Health Agency, Grant # HU0001-11-1-0023. The funding agency played no role in the design, analysis, or interpretation of findings.

DATA AVAILABILITY
The data that support the findings of this study are available from the U.S. Defense Health Agency. Restrictions apply to the availability of these data, which were used under federal Data User Agreements for the current study, and so are not publicly available.

ETHICS APPROVAL AND CONSENT TO PARTICIPATE
Due the secondary analysis of existing, de-identified data, this study was deemed exempt from human subjects review by the Institutional Review Board of the Uniformed Services University of the Health Sciences. Because of these conditions, written consent to participate, including by parents or guardians for children under 18 years, is not applicable.

CONSENT FOR PUBLICATION
Because of the secondary analysis of de-identified data, consent for publication is not applicable.