Sex Differences in Early/Unplanned Separation Among US Service Members With a History of Mild Traumatic Brain Injury.

Objective: To investigate the incidence of early/unplanned (E/U) separations following mild traumatic brain injury (mTBI) and assess whether sex impacts the hazard of separation.

Setting: Military Health System (MHS).

Participants: Active duty service members (N = 75,730) with an initial mTBI diagnosis in military records between January 2011 and January 2018.

Design: Retrospective cohort study of electronic health records in the MHS. Cause-specific Cox proportional hazards models were used with sex at birth as the primary predictor.

Main Measures: Early/unplanned (E/U) separation, defined as military separation attributed to disability, misconduct, poor performance, death, or other medical circumstances, within 2 years following the initial mTBI.

Results: Incidence of E/U separation within 2 years following mTBI was 13.7% (11.0% in women and 14.2% in men). Disability and misconduct separations were most common. Female service members had lower adjusted hazards for any E/U separation (Hazard Ratio [HR] = 0.65; 95% Confidence Interval [CI]: 0.61,0.69), disability separation (HR = 0.71; 95% CI: 0.65, 0.78), misconduct separation (HR = 0.40; 95% CI: 0.36, 0.45), and poor performance separation (HR = 0.84; 95% CI: 0.72, 0.99), compared to males, but had higher adjusted hazards for separations due to other medical circumstances (HR = 1.24; 95% CI: 1.04, 1.48).

Conclusion: Male and female service members had different hazards of E/U separation following mTBI. Separating early may increase the risk of adverse health and socioeconomic outcomes, so additional research is needed on why these separations occur and why they may be impacting men and women differently.