Association of Musculoskeletal Injury, Subsequent Mild Traumatic Brain Injury, and Sex Differences Among U.S. Service Members

Introduction: Mild traumatic brain injury (mTBI) and musculoskeletal injury (MSKI) negatively impact the health and readiness of U.S. service members. Women generally have higher rates of both injuries. While mTBI may increase the risk of subsequent MSKI, it is unclear if MSKI increases the risk of subsequent mTBI. We investigated whether MSKI is associated with increased risk of subsequent mTBI and if this relationship differs by sex among U.S. service members. Methods: This retrospective cohort study included 776,822 US service members who enlisted from 2016 to 2020 and were followed through 2023. Multivariable logistic regression models were used to estimate the association of MSKI with subsequent mTBI, adjusted for age, race, ethnicity, rank, occupation, and service branch. We assessed sex differences by testing an MSKI-by-sex interaction and conducting sex-stratified analyses. Results: Participants were 20.5 ± 3.4 years of age, and 19% were female. In the multivariable model, female service members had higher odds of mTBI compared with male service members (odds ratio [OR]=1.51, 95% confidence interval [CI] 1.46–1.56), though mTBI was rare in the overall population (2.46%). MSKI was associated with higher odds of a subsequent mTBI (OR = 1.06, 95% CI 1.02–1.09), with male service members having higher odds of an mTBI after MSKI compared with their female counterparts (OR males only =1.06, 95% CI 1.02–1.10; OR females only =1.01, 95% CI 0.94–1.10; p -interaction