Role of Department of Defense Policies in Identifying Traumatic Brain Injuries Among Deployed US Service Members, 2001–2016

Abstract

Objectives. To examine the role of Department of Defense policies in identifying theater-sustained traumatic brain injuries (TBIs).

Methods. We conducted a retrospective study of 48 172 US military service members who sustained their first lifetime TBIs between 2001 and 2016 while deployed to Afghanistan or Iraq. We used multivariable negative binomial models to examine the changes in TBI incidence rates following the introduction of Department of Defense policies.

Results. Two Army policies encouraging TBI reporting were associated with an increase of 251% and 97% in TBIs identified following their implementation, respectively. Among airmen, the introduction of TBI-specific screening questions to the Post-Deployment Health Assessment was associated with a 78% increase in reported TBIs. The 2010 Department of Defense Directive Type Memorandum 09-033 was associated with another increase of 80% in the likelihood of being identified with a TBI among soldiers, a 51% increase among sailors, and a 124% increase among Marines.

Conclusions. Department of Defense and service-specific policies introduced between 2006 and 2013 significantly increased the number of battlefield TBIs identified, successfully improving the longstanding problem of underreporting of TBIs.

In the United States, traumatic brain injury (TBI) has long been considered a significant public health issue.¹ Defined as “a bump, blow or jolt to the head or a penetrating head injury that disrupts the normal function of the brain,”^1(p2) TBI contributes to death, long-term disability,² and adverse outcomes.^3,4 It is also linked to degenerative brain diseases such as chronic traumatic encephalopathy,⁵ Parkinson’s disease,⁶ and dementia.⁷ In 2013, approximately 2.8 million TBIs occurred among civilians, leading to the death of more than 56 000 people.⁸ In addition, TBI is a major concern among US military service members both at home and during combat deployments. Since 2001, an estimated 369 000 service members have been diagnosed with at least 1 TBI.⁹ About 2.5 million service members deployed to Operation Enduring Freedom (OEF), Operation Iraqi Freedom (OIF), and Operation New Dawn.¹⁰ An estimated 48 900 of them sustained TBIs, often because of blast-related exposure,^11,12 with postconcussive sequelae¹³ and risk of medical retirement.^14,15

The complex nature of warfare poses significant challenges to determining the true extent of TBIs in the deployed environment. At the onset of OEF/OIF, the few TBIs identified relative to overall casualties⁹ surprised observers because blast injury, especially from improvised explosive devices, was widely recognized as the signature injury mechanism of OEF/OIF. Whereas visible injuries sustained to the head, such as moderate, severe, or penetrating brain injuries, are more likely to be reported and diagnosed, nonvisible injuries to the head, especially mild TBI, are thought to have been underreported.¹⁶ A number of reasons could account for underreporting, including a misunderstanding of what classifies as a mild TBI or concussion, and a “tough it out” military culture that discourages self-reporting as a sign of weakness.¹⁷

To address possible underreporting of theater-sustained TBIs and ensure screening for TBIs sustained by deployed service members, the Department of Defense (DoD) and military services introduced a number of policies. These policies directed concussion screening of service members on the battlefield, in-theater neurologic testing, TBI reporting, tracking, TBI screening before and after deployment, and event-based reporting of exposures to potentially concussive events. The first policy was introduced in 2006 and the most recent in 2013. With the hypothesis that these policies would increase the identification of deployment-related TBIs, we examined the relationship between the policies and TBI incidence rate among deployed service members from 2001 to 2016.

METHODS

We conducted a retrospective cross-sectional study by using monthly counts of deployment-related active-duty first TBI diagnoses among US military service members from October 1, 2001, to December 31, 2016, according to the official TBI case definition.¹⁸

Data

We obtained data from the Armed Forces Health Surveillance Branch, using the International Classification of Diseases, Ninth Revision and Tenth Revision, Clinical Modification codes for TBI.¹⁸ Because DoD medical record data cannot distinguish repeat service member TBIs from routine TBI-related encounters, an incident case was limited to 1 per lifetime to avoid double-counting.¹⁹ To date, no method exists to capture service members with multiple TBIs using administrative data.

To obtain a measure of exposure, we collected data from the Defense Manpower Data Center Contingency Tracking System on monthly US Military service members deployed on contingency operations.²⁰ We calculated incidence rates as the total number of cases divided by the total number of service members deployed. We considered TBIs identified during deployment or within 30 days upon return from deployment “deployment-associated TBI.”²¹ We obtained deployment-related data on wounded in action (WIA) and killed in action as part of overseas contingency operations from the Defense Casualty Analysis System of Defense Manpower Data Center.²² We obtained data on combat-related upper- and lower-extremity amputations from the Extremity Trauma and Amputation Center of Excellence.²³ We obtained data on theater-sustained lower-extremity fractures from the Theater Medical Data Store. We identified data on administrative policies, specifically those with a direct mechanism to have an impact on the identification of TBIs, from military service Web sites, the DoD Web site, the Defense Health Agency Web site, and consultations with experts at the Defense and Veterans Brain Injury Center and service TBI program chiefs.^24,25 Table A, available as a supplement to the online version of this article at http://www.ajph.org, presents key policies relevant to this study, including policies and control variables parametrized in this study.

Statistical Analyses

We used a negative binomial regression model, stratified by service, to model the effect of policies on theater TBI. We chose negative binomial because Poisson models lacked fit.²⁶ We used both the Akaike information criterion and the log likelihood test for best model fit. Specified full models, with composite variables, were superior to both a null model and those with noncomposite variables. We determined final model fit by using the fit metric (Pearson statistic/degrees-of-freedom). To adjust for any possible violation of the assumption of homoscedasticity across our data, we estimated the incidence rate ratios (IRRs) by using the Huber–White sandwich estimate for heteroscedasticity-consistent standard errors.²⁷ We used the monthly natural log of the number of service members deployed at time of injury as an exposure variable. We exponentiated coefficients to report IRR. Missing values on model covariates, notably lower-extremity fractures, a proxy for theater medical health informatics infrastructure, led to exclusion of observations before October 2003. We examined estimated model robustness with sensitivity analyses by using 3 methods: negative binomial regression to impute missing values for lower extremity rates, multiple imputation using the fully conditional method with main model reported variables as predictors, and simplifying main model by removing all nonsignificant predictors. We performed all analyses with SAS version 9.4 (SAS Institute Inc, Cary, NC).

RESULTS

Between October 2001 and December 2016, 48 738 service members were diagnosed with a TBI in theater or within 30 days upon return from deployment. The majority were identified among soldiers (83.8%), followed by Marines (10.8%), airmen (3.5%), and sailors (1.9%). Table 1 shows case distribution according to policies in place at time of diagnosis.

TABLE 1—

Distribution of Traumatic Brain Injury Cases Before and After the Introduction of Traumatic Brain Injury Policies: United States, 2001–2016

		Traumatic Brain Injury Cases, No.
Policy	Date Enacted	Army Before	Army After	Navy Before	Navy After	Air Force Before	Air Force After	Marine Corps Before	Marine Corps After
ALARACT 143/2006	Jul 2006	2 771	37 832	. . .	. . .	. . .	. . .	. . .	. . .
ALARACT 160/2007	Jul 2007	6 383	34 220	. . .	. . .	. . .	. . .	. . .	. . .
ALARACT 173/2008	Jul 2008	13 921	26 682	. . .	. . .	. . .	. . .	. . .	. . .
EXORD 242/11	Jul 2011	28 479	12 124	. . .	. . .	. . .	. . .	. . .	. . .
NAVMED 07/021	Dec 2007	. . .	. . .	336	690	. . .	. . .	1 483	3 851
NAVMED 11/004	Sep 2011	. . .	. . .	731	295	. . .	. . .	4 282	1 052
BUMED 6310.12	Jul 2011	. . .	. . .	712	314	. . .	. . .	4 081	1 253
MARADMIN 294/2012	May 2012	. . .	. . .	. . .	. . .	. . .	. . .	4 776	558
PDHA	Jan 2008	9 809	30 794	342	684	408	1 367	1 502	3 832
Definition standardized	Oct 2007	15 142	25 461	401	625	516	1 256	1 703	3 631
DTM 09-033/DoDI 6490.11	Mar 2010	23 316	17 287	600	426	982	793	2 577	2 757

Note. ALARACT = All Army Activities Message; BUMED = US Navy Bureau of Medicine and Surgery; DoDI = Department of Defense Instruction; DTM = Directive Type Memorandum; EXORD = Execution Order; MARADMIN = Marine Administrative Message; NAVMED = Navy Medicine; PDHA = Post-Deployment Health Assessment.

Model Results

Table 2 contains the results of the multivariable model examining the relationship between TBI-related deployment laws and the incidence of TBI in the deployed setting. Among soldiers, the July 2006 All Army Activities Message, known as ALARACT 143/2006, which alerted Army commanders to concussions and to medically evaluate soldiers if they show “red flags,” was associated with a higher incidence of TBI following its introduction (IRR = 3.51; 95% confidence interval [CI] = 2.63, 4.67). Similarly, after we adjusted for other administrative policies already in place, the introduction of ALARACT 160/2007 in July 2007 was associated with a 97% increase in the likelihood of identifying a TBI, compared with the period before its introduction (IRR = 1.97; 95% CI = 1.35, 2.90). The 2010 introduction of the DoD-wide Directive Type Memorandum (DTM) 09-033 was associated with an increase of 80% in the likelihood of being identified with a TBI compared with the period before its introduction (IRR = 1.80; 95% CI = 1.46, 2.23). Department of the Army Execution Order (EXORD) 242/11 did not show an independent association with the incidence of TBI. Similarly, the composite measure containing ALARACT 173/2008, Post-Deployment Health Assessment (PDHA), and the Armed Forces Health Surveillance Center case definition lacked association with TBI rates (Figure A, available as a supplement to the online version of this article at http://www.ajph.org).

TABLE 2—

Negative Binomial Regression Models of Deployed Traumatic Brain Injury Incidence Rate According to Service: United States, 2001–2016

Service	Policies	IRR (95% CI)a
Army	ALARACT 143/2006	3.51 (2.63, 4.67)
	ALARACT 160/2007	1.97 (1.35, 2.90)
	EXORD 242/11	1.08 (0.79, 1.47)
	ALARACT 173/2008 and PDHA and definition	0.92 (0.66, 1.30)
	DTM 09-033	1.80 (1.46, 2.23)
Navy	NAVMED 07/021 and PDHA and TBI definition	1.57 (0.86, 2.86)
	BUMED 631012 and NAVMED 11/004	0.69 (0.40, 1.18)
	DTM 09-033	1.51 (1.13, 2.00)
Air Force	PDHA and TBI definition	1.78 (1.20, 2.64)
	DTM 09-033	1.11 (0.78, 1.59)
Marine Corps	NAVMED 07/021 and PDHA and TBI definition	0.82 (0.40, 1.71)
	BUMED 631012 and NAVMED 11/004	0.67 (0.39, 1.17)
	MARADMIN 294/2012	0.39 (0.12, 1.24)
	DTM 09-033	2.24 (1.22, 4.12)

Note. ALARACT = All Army Activities Message; BUMED = US Navy Bureau of Medicine and Surgery; CI = confidence interval; DoDI = Department of Defense Instruction; DTM = Directive Type Memorandum; EXORD = Execution Order; IRR = incidence rate ratio; MARADMIN = Marine Administrative Message; NAVMED = Navy Medicine; PDHA = Post-Deployment Health Assessment; TBI = traumatic brain injury.

^aAdjusted for the natural log of deployed service members in the given service, theater lower-extremity fracture rate, theater amputation rate, theater wounded rate, nondeployed TBI rate, and injury month. Models were estimated by using negative binomial regression. The dependent variable is the count of theater TBIs in the given service. The CI was constructed by using Huber–White adjusted SEs.

In the Navy, only the DTM 09-033 was associated with a significant change in the TBI rate among deployed sailors. It was associated with a 51% increase in new TBI cases, compared with the period before (IRR = 1.51; 95% CI = 1.13, 2.00) when we adjusted for other model covariates (Figure B, available as a supplement to the online version of this article at http://www.ajph.org). Among airmen, the introduction of the TBI screening questions on the PDHA and the standardization of the TBI definition together were associated with an 83% increase in reported TBIs compared with the period before their introduction (IRR = 1.78; 95% CI = 1.20, 2.64; Figure C, available as a supplement to the online version of this article at http://www.ajph.org). Finally, among Marines, only the DTM 09-033 showed independent association with the TBI rate, and was associated with a 124% increase in the TBI rate when we adjusted for combat intensity and other covariates (IRR = 2.24; 95% CI = 1.22, 4.12; Table 2, Figure D, available as a supplement to the online version of this article at http://www.ajph.org).

Sensitivity Analyses

Table B (available as a supplement to the online version of this article at http://www.ajph.org) shows the model performance across sensitivity analyses. Across all 3 methods, there is consistency in the association between ALARACT 143/2006, ALARACT 160/2007, and DTM 09-033 and an increase in the incidence of TBI. For sailors, the introduction of Navy Medicine (NAVMED) Policy 07/021, the TBI questions on the PDHA, and TBI definition standardization show a significant association at an α of 0.05 level, but not significant at the α of 0.01 level. For airmen, the association of the introduction of the TBI screening questions to the PDHA and the TBI definition standardization kept its strength and direction. For Marines, in one of the imputed models, Marine Administrative (MARADMIN) Message 294/2012 showed a significant association with a decline in TBI rates at the study significance level of 0.01.

DISCUSSION

This study is the first comprehensive analysis of the role of DoD and service TBI policies on deployment TBI. Across the multivariable models, a few relationships stand out. Two of Army’s earliest policies that directed in-theater TBI screening, awareness, and clinical care showed a similar, statistically significant relationship with an increase in the TBI incidence rate. This finding seems reasonable, as at the onset of OEF/OIF operations, combat casualties, especially WIA, surpassed TBIs 30-fold, yet the injury threshold of TBIs, especially mild TBIs, is lower than injuries typically associated with WIA injuries, such as physical injuries rendering the service members incapable of bearing arms (Figure A, available as a supplement to the online version of this article at http://www.ajph.org). During the first few years of OEF/OIF, a substantial number of service members who sustained a TBI may not have been reported, diagnosed, or both.¹⁶ This was of most concern to the Army because more than 70% of deployed service members were soldiers, leading to the Army’s swift enactment of TBI policies through ALARACT channels, best for time-sensitive changes to regulations that cannot wait for the regular revision of a policy or regulation.^28–31 However, ALARACT 173/2008, which coincided with the introduction of the TBI questions on the PDHA and the DoD-wide TBI definition, lacked a statistical association with increased TBI identification. This is surprising because ALARACT 178/2008 disseminated the Military Acute Concussion Evaluation (MACE) tool aimed at improving the field diagnosis of TBI.^32,33

The DTM 09-033 of 2010, establishing “event-based” screening, seems to have led a second wave of TBI detections across 3 of the 4 services after accounting for combat intensity, casualty rate, and other covariates. During the early years of OEF/OIF, concern increased that blast-related events were causing a substantial number of concussions. The DTM 09-033 required commanders to screen all service members exposed to possible concussive events, particularly blast events.³⁴ This event-based system was considered a major advance in the identification of TBI because it skirted self-reported exposures, thought to have led to underreporting of TBI, and required commanders to ensure compliance with reporting.³⁵

The DTM 09-033 was followed by Fragmentary Order 09-1656, which described reporting procedures and required the use of the Blast Exposure and Concussion Incident Report system, which tied TBI identification to reporting of significant operational events, thus compelling commander reporting of service members exposed to potentially concussive events.³⁶ Though slow in adoption, the Blast Exposure and Concussion Incident Report program alone screened more than 16 000 service members in its 4-year cycle.³⁷ The Joint Mental Health Advisory Teams’ reports on the compliance to in-theater concussion assessment showed a marked increase in postexposure evaluations between 2012 and 2013 suggesting improvements in the implementation of DTM 09-033, and lending some support to the effects we observed.³⁸ Within- and between-service differences in reporting and compliance with DTM 09-033 requirements exist, possibly exacerbated by operational, cultural, and Command differences. The Joint Mental Health Advisory Teams reports also note that fewer than a third of those within 50 meters of blast, the most prevalent exposure type, were evaluated for a concussion, likely weakening DTM 09-033’s potential in identifying theater TBI, and affecting estimates of true theater TBI.

Contrary to our expectation, the introduction of DTM 09-033 was not associated with increases in TBI rates among airmen. This finding could be attributable to differences in theater exposures between the services and the nature of Air Force service in theater. Whereby soldiers, sailors, and Marines may be more likely to be exposed to reportable events, especially blast events, because of their participation in direct tactical ground combat, or providing fire support and operational assistance to combat elements, airmen are more likely to serve in combat service support roles, which provide logistical support to combat units.³⁹ Furthermore, airmen tend to have shorter deployment cycles in comparison with other services, decreasing their exposure to the theater environment.³⁹

Non-Army service-specific policies were not statistically associated with changes in the TBI incidence rate, with NAVMED 07/021 introduced 18 months after the introduction of Army’s ALARACT 143/2006. Differences between Navy, Marine Corps, and Army policies may explain this discrepancy. Whereas Army policies direct those with “red flag” symptoms and those involved in a blast, fall, vehicle crash, or direct impact, to undergo TBI evaluation, it is unclear whether NAVMED 07/021 reporting requirements apply to deployed sailors. Similarly, Navy Bureau of Medicine Instruction 6310.12 lays the foundation for TBI care at Navy medical treatment facilities but lacks a mechanism by which deployed sailors are encouraged to report sustained TBIs, or a mechanism for increasing the awareness for TBI. MARADMIN 294/12, closest in language to ALARACT 143/2006 and ALARACT 160/2007, sets the foundations for the Marine Corps TBI program and reiterates the DTM 09-033 requirement that commanders report all Marines exposed to potentially concussive events and document their injury. In addition, it requires all Marines to complete the PDHA following their return from deployment and mandates TBI training. However, in contrast to the 2 Army policies, which preceded the DTM 09-033, MARADMIN 294/12 came 2 years after the introduction of the DTM 09-033, and 6 years after Army’s first ALARACT, thereby possibly failing to explain any rate changes, with DTM 09-033 already in the model.

Other operational demands hindering the administration of a TBI screen may also explain within- and between-service reporting differences. When we controlled for combat intensity, Marine TBI rates were highly correlated with, but lower than, Marine WIA rates and dropped more sharply after 2012 than did Army’s TBI rate. As expected, Army TBI rates were higher than Army WIA rates and had a prolonged elevated rate, even as WIA Army rates began declining at the end of 2011 (Figures A and D, available as supplements to the online version of this article at http://www.ajph.org). We hypothesize that the Marines’ high WIA–TBI rate correlation may be attributable to reporting of more severe TBI cases, such as those in which loss of consciousness was observed, hence closely trailing the Marines’ wounded rate.

This reporting difference may mirror the service’s Purple Heart award policies. Until mid-2011, Purple Hearts, awarded to those wounded or injured by enemy-caused action, were only awarded to Marines sustaining TBIs if the Marine lost consciousness. In the Army, a soldier seeking treatment of any diagnosed TBI was eligible for a Purple Heart. This assumption is supported by the Joint Mental Health Advisory Teams’ reports on theater-TBI screening revealing that by 2012, up to 92.9% of those injured with reported loss of consciousness were evaluated, in contrast to 29% of those within 50 meters of blast, the most prevalent exposure type.³⁸ However, the intent of DTM 09-033 and MARADMIN 294/12 was to ensure the reporting and evaluation of all those with exposures to potentially concussive events, especially those with nonobservable head injuries, injuries most likely to be missed.

In a national sample of veterans with TBI receiving care at Department of Veterans Affairs medical centers between 2004 and 2010, Dismuke et al. noted a changing composition of those seeking care, with an increased share of combat-sustained mild TBIs and a decline in moderate and severe TBIs.⁴⁰ This provides some support to our findings given that DoD policies targeted concussions or mild TBIs, injuries most likely to go underreported and underdiagnosed.

The modification of the PDHA to contain questions that screen for TBI, coupled with standardization of the TBI definition, was only associated with a significant change in TBI incidence among airmen. For sailors and Marines, it also coincided with the introduction of NAVMED 07/021. However, these specific policies taken together were not associated with changes in reported TBIs. Although the TBI-specific questions in the PDHA have high specificity (96%)⁴¹ it is a voluntary screening tool, often administered immediately upon return from deployment. A positive response to its TBI screening questions may result in medical referral, delaying reunification with family. This may be an incentive for service members to neglect the assessment.

Limitations

The current study has limitations. As with any modeling study, adequate model specification is essential in examining the questions at hand, and our specification may not entirely control for unidentified factors. Although the study provides some support that a number of DoD-wide and service-specific initiatives successfully increased TBI reporting and, thus, TBI diagnosis, in-theater TBI incidence may have remained suppressed throughout the duration of the study period. First, although we considered all TBIs diagnosed within 30 days upon return from deployment as theater-sustained TBIs, studies have shown that theater-sustained TBIs continue to be diagnosed long after the end of deployment.⁴² Misclassification bias of this sort may lead to underestimation of the role of theater policies on TBI reporting and diagnosis.

Second, the theater TBI rate is expected to significantly surpass theater casualty rate. Although it does exceed the theater-wounded rate in 2007 for the Army, and 2009 for the Navy and Air Force, it does not exceed the Marine Corps wounded rate. This suggests that TBI reporting may still not be fully documented, similar to a study by Chase and Nevin that estimated that some 21 000 service members may have experienced undocumented incident TBIs while deployed in Afghanistan or Iraq.¹⁶

Public Health Implications

Service members deployed to combat operations are at great risk of morbidity and mortality. The prolonged deployments, increasing combat intensity and the complex nature of warfare, pose significant challenges to identifying and treating those injured, especially those with injuries that are not always visible, such as concussions or mild TBIs. Combat injuries, visible or not, directly affect the immediate and long-term well-being of service members, and with it troop welfare, retention, and readiness.

The DoD has sought to prevent TBIs in theater by supporting helmet research,⁴³ reinforcements to armored vehicles to withstand improvised explosive devices,⁴⁴ and research on the impact of blast waves on the brain.⁴⁵ It has also examined various means of increasing reporting and identification of theater-sustained TBIs. Those efforts include the testing of electronic helmet sensors to measure head acceleration and deceleration,⁴⁶ body armor–mounted blast gauges to determine the risks from overpressure exposure,⁴⁷ and the introduction of postdeployment screenings to identify TBIs among returning service members. Moreover, the Army in 2006, and the entire DoD in 2010, introduced mandatory in-theater screening of those exposed to blast or other potentially concussive events as a means of identifying TBIs.

The findings of this study point toward a combination of theater policies that help identify those with invisible TBIs that otherwise would often have been missed. The Army’s earliest policies, ALARACT 143/2006 and ALARACT 160/2007, were associated with a nearly 3-fold increase in the rate of reported TBIs among deployed soldiers. The DTM 09-033, introduced across the DoD in 2010, was significantly associated with an increase in identified TBI among 3 of the 4 services. These findings also suggest significant underidentification of TBIs in the deployed setting before 2006.

Another key implication of this study is the need for thorough dissemination and implementation of DoD and service policies to adequately identify and report TBIs. Solely establishing policy will not suffice. For example, the 2006 development and introduction of the MACE, a concussion-screening tool for those exposed to potentially concussive events, lacked a simultaneous and widespread dissemination mechanism. It was only in 2008 that the MACE was disseminated within the Army, as part of ALARACT 173/2008. Thus, despite the existence of the carefully crafted MACE, intended as a simple and quick screening tool for TBI, it was the general Army-disseminated message to evaluate for concussion those who show red flags (ALARACT 143/2006) that had the greatest impact, likely attributable to its widespread and rapid dissemination.

This study and its findings also draw attention to the complexity and multitude of efforts in the deployment environment needed to ensure the identification and treatment of service members, often in difficult conditions and with little assurance of success. An understanding of facilitators as well as barriers to the implementation of theater TBI policies is crucial to their continued success. Future studies must identify strengths and weaknesses of theater screening efforts and identify ways to reduce barriers to the implementation of theater screening, including wider dissemination of helmet sensors or blast gauges that take into account operational factors. Improved methods to increase capture of theater exposures through the PDHA are also needed. Furthermore, there is also a need for studies that examine the extent identified service members with TBI truly represent the full burden of TBI in the military.