ABSTRACT
Objective
This study examined racial and ethnic differences in the association between mild traumatic brain injury (mTBI) and work duty limitations in active-duty service members (ADSMs).
Methods
This study used retrospective and cross-sectional data from the 2019–2021 Military Health System Data Repository on 910,700 ADSMs who were 18–64 years old and were grouped into racial and ethnic categories of White, non-Hispanic; Black, non-Hispanic; Hispanic/Latino; and Asian or Pacific Islander, non-Hispanic.
Results
Descriptive statistics showed that Black, Hispanic/Latino, and Asian or Pacific Islander patients had a lower proportion of having a diagnosis of mTBI compared to White patients (ps < 0.001). Further, the proportion of history of deployment varied by racial and ethnic group and deployment location. Multivariate logistic regression results showed odds of 1.52 (p < 0.001) for White patients with mTBI, odds of 1.61 (p < 0.001) for Black patients with mTBI, odds of 1.57 (p < 0.001) for Hispanic/Latino patients with mTBI, and odds of 1.99 (p < 0.001) for Asian or Pacific Islander patients with mTBI for being placed on work duty limitations.
Discussion
These results advance our understanding of the work duty limitations for racial/ethnic minority patients with mTBI in the Military Health System.
Introduction
Racial and ethnic minorities represent a significant and increasing proportion of the US military (Citation1). While the military may present greater opportunities for minorities to further their education and acquire new skills and experience, minority soldiers, similar to others, face the possibility of injuries during deployment. About 20% of the soldiers who participated in Operation Enduring Freedom and Operation Iraqi Freedom (OEF/OIF) wars have been diagnosed with traumatic brain injury (TBI), the majority of which are mild (mTBI) (Citation2). Although minority active-duty service members (ADSMs) are overrepresented in military combats, a recent study that used data from 46,488 ADSMs found that Hispanic and Asian ADSMs have lower odds of being diagnosed with TBI despite the fact that they screen positive for TBI post-deployment at the same rate as their White counterparts (Citation3,Citation4). Black ADSMs are less likely to screen positive for TBI and have lower odds of being diagnosed with TBI post-deployment compared to their White counterparts (Citation3,Citation4).
Similar to our study, a paper by Sherer et al. (2003) used data from 1083 adults diagnosed with TBI in the civilian population to examine the association between race and productivity 1-year post injury (Citation5). The authors considered those who were ‘employed at least part-time, in school at least part-time, or a full-time homemaker’ as being productive. The authors found that African Americans and racial and ethnic minorities were more likely to be ‘nonproductive’ than Whites and concluded that factors such as pre-injury productivity, education, and cause of injury were significant predictors of ‘productivity.’
The concept of ‘work duty limitation’ used in this study is equivalent to the concept of ‘productivity lost’ or work performance as the ADSM is gainfully employed but cannot perform certain duties, tasks, or activities that are typically associated with his/her rank, occupation, and pay because of the injury. More importantly, these ADSMs cannot be deployed as they are not militarily ready. Being placed on ‘work duty limitations’ does not result in any financial loss to the individual but represents a loss of productivity or opportunity costs as the military must find someone else to either complete the tasks or be deployed in the stead of the individual being placed on ‘work duty limitation’. Hence, this represents a strong ‘proxy’ measure for medical readiness in the military. To our knowledge, the current study is the first to examine racial and ethnic differences in the association between mTBI and work duty limitations in an active-duty population. Further, this study accounts for an array of symptoms that are commonly associated with mTBI, which would have important implications for military readiness and treatment of mTBI in military and civilian populations.
Using the Traumatic Brain Injury Center of Excellence symptoms classification system (Citation6), this study hypothesized that racial and ethnic differences in work duty limitations are driven by common symptoms of mTBI such as cognitive/linguistic, hearing, neurologic, emotional/behavioral, sleep, vision, and other categories of disturbances experienced by service members who participated in the OEF/OIF and Operation New Dawn (OND) wars (Citation7). Findings from the current study are important because many studies have found that racial and ethnic minority veterans who participated in the OEF/OIF and OND wars and were diagnosed with TBI were less likely to receive appropriate medical care, had longer wait times to see physicians, received fewer therapy services (physical, occupational, speech, and psychotherapy) during inpatient rehabilitation, had worse functional outcomes such as related to employment, and had higher all-cause mortality rates compared to their non-Hispanic White counterparts, even after controlling for a host of covariates including comorbid conditions (Citation5,Citation8–18).
Methods
Data source
Retrospective, repeated cross-sectional data from the 2019–2021 Military Health System Data Repository (MDR) was used to complete this analysis. The data was pooled over several years to increase the size of the sample; this is not a time-series analysis. The MDR is a rich data set that contains demographic (including deployment status) and clinical information on all direct and purchased care encounters by service members, retirees, and their families. We used data on Military Treatment Facilities from the MDR Comprehensive Ambulatory/Provider Encounter Record (CAPER) database. This analysis focused on ‘direct care’ data from the CAPER database because data on ‘work duty limitations’ are only captured for ADSMs through this database.
Study subjects
The study protocol was approved by the Uniformed Services University Institutional Review Board and was carried out in accordance with relevant guidelines and regulations. The approved study protocol did not require participants to provide informed consent. However, a waiver of informed consent was approved by the Institutional Review Board as this is the standard in the case of large data sets.
The study used MDR data from 2019 to 2021 on 910,700 ADSMs who were 18–64 years old at the time of the encounter. Participants were grouped into racial and ethnic categories of White, non-Hispanic (n = 545,761), Black, non-Hispanic (n = 204,966), Hispanic/Latino (n = 113,581), and Asian or Pacific Islander, non-Hispanic (n = 46,392). The sample started with 629,111 ADSMs with a history of deployment in the OEF and OIF wars and a history of deployment other than OEF/OIF. Those who were of other race (n = 49,321) and those with missing observations for race (n = 42,982) were excluded.
Measures
Dependent variables and key independent variable
The outcome of interest is a binary variable that measures whether ADSMs were placed on ‘work duty limitations’ as a result of a clinical encounter (yes = 1; 0 otherwise). The key independent variable was a diagnosis of mTBI. mTBI was measured based on the Traumatic Brain Injury Center of Excellence guideline that recommends the use of a specific Department of Defense (DOD) code, reflective of the Glasgow Coma Scale (GCS) scores of 13–15. The GCS is a neurological scale that measures the level of consciousness and consists of three components: eye opening, verbal response, and motor response in the patient (Citation19–21). The DOD used a unique code (DOD0102) equivalent to the GCS scores of 13 to 15 to measure the incidence of mTBI in the MDR.
Covariates
This study controlled for a set of covariates, including age, sex, marital status, military pay grade or rank, branch of service, insurance type, care received, region the patient lives, and time trend effects, based on the literature on this topic. Age is a continuous variable. A square term for age was included to capture any non-linear relationships between this variable and work duty limitations. Marital status included being married, single or never married, and divorced or separated or widowed at the time of the encounter. A dummy variable for ‘unknown marital’ status and ‘missing marital’ status was also included in the analysis. Dummy variables for military ranks of Jr. Enlisted (E-1 through E-4), Sr. Enlisted (E-5 through E-9), Junior/Warrant Officer (O-1 through O-5; W-1 through W-5), and Senior Officer (O-6+) were controlled for in the analysis. Service branches of Army, Airforce, Navy, and Marines were included. Insurance type included TRICARE Prime, other TRICARE insurance, direct care only, and direct care and private care. To determine the severity of a patient’s condition, whether the patient received surgical care (inpatient or outpatient), rehabilitative care (inpatient or outpatient), or was hospitalized were included. The region the patient lives, based on his or her zip code, includes Northeast, Midwest, South, and West to account for any geographic variation in clinical decision-making in the MHS. Dummy variables for year of encounter were also added to capture any trends in medical technology and medicine during the time period of the analysis. Further, this study controlled for an extensive set of symptoms such as cognitive/linguistic, hearing, neurologic, emotional/behavioral, sleep, chronic pain, post-traumatic stress disorder (PTSD), vision, and ‘other symptoms’ that are commonly associated with mTBI. The definition and measurement of these common symptoms of mTBI are based on the International Classification of Diseases (ICD) coding guidance from the Traumatic Brain Injury Center of Excellence (Citation6). Grouped into six constructs of cognitive/linguistic, hearing, neurologic, emotional/behavioral, sleep, and ‘other’ symptoms, it is important to note that the Traumatic Brain Injury Center of Excellence framework includes all of the Neurobehavioral Symptom Inventory elements such as depression, anxiety, alcohol or other substance use, and many more (Citation6). Please see a comprehensive list of all the symptoms that were controlled for in the study at https://www.health.mil/Reference-Center/Publications/2020/07/31/ICD10-Coding-Guidance-for-TBI.
Statistical analysis
Chi-square tests for categorical variables and T-tests for continuous variables were used to compare mean and proportion differences between those with mTBI and those without mTBI for each of the groupings: total sample, White, non-Hispanic, Black, non-Hispanic, Hispanic/Latino, and Asian or Pacific Islander, non-Hispanic. The study modeled each grouping separately. Given that the dependent variable, being placed on ‘work duty limitations,’ is a binary outcome, logistic regression models that controlled for the covariates mentioned above were used, and odds ratios (ORs) for each of the groupings were computed and presented for ease of interpretation. Please note, we are comparing the size of the coefficients, not their significance. The region where the patient lives and time trend effects were accounted for. The study also used ICD-10 codes from the MDR to measure mTBI as a robustness check and found the results to be similar.
Results
Descriptive statistics
As depicted in , descriptive statistics showed that about 3% of ADSMs had a diagnosis of mTBI. This varied by race, with Black (2.25%), Hispanic/Latino (3.17%), and Asian or Pacific Islander (2.27%) patients having a significantly lower proportion of a diagnosis of mTBI compared to White patients (3.41%). Further, almost 6% of ADSMs in the total sample were placed on work duty limitations following an outpatient encounter. While there was no statistical difference between White and Black patients being placed on work duty limitations (5.99% and 5.96%, respectively), summary statistics showed significant differences between White and Hispanic/Latino patients (5.99% vs 5.67%, p < 0.001) and White and Asian or Pacific Islander patients being placed on work duty limitations (5.99% vs 5.28%, p < 0.001), with a higher proportion found in Whites. Bivariate models () showed that each patient group with mTBI had higher odds of being released with work duty limitations (White: [OR 1.51, CI: 1.43–1.59, p < 0.001], Black: [OR 1.62, CI: 1.46–1.79, p < 0.001], Hispanic/Latino: [OR 1.57, CI: 1.40–1.78, p < 0.001], Asian or Pacific Islander: [OR 2.05, CI: 1.67–2.52, p < 0.001]).
Table 1. Demographic and military service characteristics of active duty service members by race and ethnicity, Military Health System Data Repository, 2019–2021.
Table 2. Unadjusted odds ratios of being released with work duty limitations with mild traumatic brain injury by race and ethnicity, Military Health System Data Repository, 2019–2021.
Of the total sample, 19% had a history of deployment for OEF, 19.5% had a history of deployment for OIF, and 31.6% had a history of deployment other than OEF/OIF. For a history of deployment for OEF, Black and Asian or Pacific Islander patients had a significantly lower proportion of deployment (17.3% and 16.9%, respectively) compared to White patients (19.7%) (ps < 0.001). Additionally, Hispanic/Latino patients had a significantly higher proportion of deployment (20.7%) compared to White patients (19.4%) (p < 0.001), while Asian or Pacific Islander patients had a significantly lower proportion of deployment (17.8%) compared to White patients (p < 0.001) for a history of deployment for OIF. Lastly, for a history of deployment other than OEF/OIF, all minority groups had significantly different proportions of deployment compared to White patients (ps < 0.001).
Multivariable models
Multivariate logistic regression results () showed odds of 1.52 [CI: 1.44–1.61, p < 0.001] for being placed on work duty limitations for White patients with mTBI, odds of 1.61 [CI: 1.45–1.80, p < 0.001] for being placed on work duty limitations for Black patients with mTBI, odds of 1.57 [CI: 1.38–1.79, p < 0.001] for being placed on work duty limitations for Hispanic/Latino patients with mTBI, and odds of 1.99 [CI: 1.60–2.49, p < 0.001] for being placed on work duty limitations for Asian or Pacific Islander patients with mTBI. History of deployment for OEF and other than OEF/OIF was associated with lower odds of being placed on work duty limitations for White patients [OEF: OR .90, CI: 0.86–0.94, p < 0.001; other than OEF/OIF: OR .86, CI: 0.83–0.88, p < 0.001] and similarly for Black patients [OEF: OR .90, CI: 0.84,0.96, p < 0.01; other than OEF/OIF: OR .85, CI: 0.81–0.89, p < 0.001]. Further, history of deployment to OIF was associated with lower odds of being placed on work duty limitations for all groups (White: [OR .88, CI: 0.84–0.92, p < 0.001]; Black: [OR .83, CI: 0.77–0.89, p < 0.001]; Hispanic/Latino: [OR .89, CI: 0.81–0.98, p < 0.05]; Asian or Pacific Islander [OR .78, CI: 0.66–0.92, p < 0.01]).
Table 3. Odds ratios of being released with work duty limitations by race and ethnicity, Military Health System Data Repository, 2019–2021.
Discussion
This study found a statistically significant association between mTBI and work duty limitations for all minority ADSM patients and White patients. Similar to the study by Sherer et al. (2003) that found that African Americans and racial and ethnic minorities were more likely to be ‘non-productive’ than Whites (Citation5), the current study found a higher association between mTBI and work duty limitations for minority ADSM sub-groups than White patients. Of note, about 63% of patients in the study by Sherer et al. (2003) were diagnosed with severe TBI on admission to the Emergency Department with GCS scores ranging from 3 to 8 (Citation5). It is well documented in the civilian literature that the severity of the injury plays an important role in patients’ ability to return to work (Citation22,Citation23). Although the diagnosis of mTBI itself is very complex, over 82% of ADSMs who have been diagnosed with TBI between 2000 and 2019 have been diagnosed with mTBI (Citation24). As such, the current study focuses on the work performance of ADSM patients with mTBI as they are more likely to return to work than those with moderate/severe TBI.
Further, findings from logistic regression models showed that being a Marine Corps member, regardless of race/ethnicity, was associated with higher odds of being placed on work duty limitations. In addition, chronic/general pain, rehabilitative services, and PTSD were associated with higher odds of being placed on work duty limitations for each subgroup of service members, with Black patients having higher odds for pain and Hispanic/Latino and Asian or Pacific Islander patients having higher odds for PTSD. The finding related to PTSD is consistent with the literature as the association between psychiatric and neuropsychological symptoms and work performance by racial and ethnic status is well documented (Citation17,Citation18,Citation23). With regard to rehabilitative services, there is a propensity to remain in limited duty once in rehabilitative care. Indeed, future research may investigate the extent to which service members who receive rehabilitative services return to work without duty limitations and whether they return to work faster than those who do not receive rehabilitative services.
This study has some limitations that are worth noting. Missing data for race may have introduced a certain level of bias in the analysis. However, any potential bias of the missing data on work duty limitations might be minimal. Further, there could be issues of sample selection and omitted variable bias, so we cannot make any causal inferences. Future studies may use cross validation in a prospective, longitudinal cohort to further investigate the association between mTBI and work limitations in both civilian and military populations.
Nevertheless, this study has many strengths that may help to confirm the credibility of the findings to support the design of rehabilitative services and delivery of care for minority patients with mTBI in the MHS and even the civilian population. A large data set with an extensive set of variables, based on a well-validated framework (Citation6,Citation7), allowed for the ability to conduct the analysis by racial/ethnic groups and to capture issues of sample selection. The rigor in the design of the current study allowed the uncovering of important findings to inform research, policymaking, and the delivery of care for patients with mTBI in the military, Veterans Affairs, and civilian populations.
Conclusions
These results advance our understanding of the role that commonly understood symptoms of TBI, such as PTSD, pain, depression, anxiety, and cognitive and linguistic symptoms, may play in work duty limitations for racial/ethnic minority patients diagnosed with mTBI. Additional research is needed to understand the role that these symptoms may play in the duration of limited duty for minority ADSMs diagnosed with mTBI.
Disclosure statement
The author(s) report there are no competing interests to declare.
Additional information
Funding
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