Abstract Text: Introduction: Mild traumatic brain injury (mTBI) is highly prevalent among United States military service members (SMs) and is known to increase risk for post-concussive symptoms (e.g., headaches, irritability) and other health concerns (e.g., pain), which may in turn may impede their ability to perform their military duties. Inability to perform military duties for reasons such as disability, poor performance, misconduct, or other medical reasons may result in an early or unplanned military separation. Not only can these non-routine discharges impact military readiness and retention, they also increase a SM’s risk for unemployment, homelessness, and suicide when attempting to reintegrate back into civilian life. Additionally, as more women have been joining the military and engaging in combat roles in recent years, there has been awareness that more studies are needed to investigate differences in health-related outcomes among female and male service members with mTBI. As such, this analysis investigates whether there are gender differences in the risk of early/unplanned separation among a cohort of active duty SMs with mTBI.
MATERIALS AND Methods: This study was a retrospective analysis of de-identified data collected under IRB protocol #21-13051 for active-duty SMs diagnosed with an index mTBI between 2011 and 2018. SMs were excluded if they experienced a more severe diagnosis of TBI (e.g., Moderate, Penetrating, Severe) following their initial mTBI diagnosis. Patient demographics and separation data were obtained from the Defense Enrollment Eligibility Reporting System and the Defense Manpower Data Center. The primary outcome for this analysis is E/U separation within two years following mTBI, which is defined as a military separation attributed to: disability, misconduct, poor performance, death, or other medical circumstances during this 2-year timeframe. Frequency tables, broken down by separation type and gender, were used to summarize the number of SMs who experienced post-mTBI E/U separation. Unadjusted odds ratios for the effect of gender on the odds of receiving any E/U separation, disability separation, and misconduct separation were calculated and compared. Logistic regression was used to estimate the odds of receiving disability separation for female and male SMs while adjusting for additional SM demographics (including age at injury diagnosis, ethnicity, service branch, and military rank). All statistical analyses were conducted in R (version 4.1.2).
Results: The study sample consisted of 89,057 active duty SMs with a history of mTBI. SMs were 84% male, 58% White (non-Hispanic), 59% Army, 50% junior enlisted, and 27.9 years old, on average, at the time of injury. 11,762 SMs (13.2%) experienced an E/U separation within two years following their initial mTBI. Incidence of E/U separation was lower among female SMs (10.4%) than among male SMs (13.7%). Out of the overall mTBI population, 4,729 SMs (5.3%) were separated due to disability within two years following their initial injury, with disability representing 40.2% of all E/U separations. Similarly, 4,579 SMs (5.1%) experienced separations due to misconduct, which represented 38.9% of the total number of E/U separations. Poor performance, other medical circumstances, and death were the least prevalent separations among the overall mTBI population, at 1.6%, 1.0%, and 0.2%, respectively. Women had significantly lower unadjusted odds of experiencing E/U separation compared to men (OR: 0.73, 95% CI: [0.69, 0.77]) as well as significantly lower unadjusted odds of experiencing disability separation (OR: 0.84, 95% CI: [0.77, 0.91]) and misconduct separation (OR: 0.46, 95% CI: [0.41, 0.51]) compared to their male counterparts. However, the difference in odds of disability separation between women and men was no longer significant after adjusting for additional SM demographics (OR: 1.04, 95% CI: [0.95, 1.13]).
Conclusions: Among active-duty SMs with a mTBI, 13.2% had an E/U separation within two years following an initial diagnosis of mTBI. Disability and misconduct were the most common reasons for E/U separation. Female SMs had lower unadjusted odds of overall E/U separation, disability separation, and misconduct separation. However, additional SM characteristics may account for some of these observed differences.
