Self-Reported Concussion Symptomology during Deployment: Differences as a Function of Injury Mechanism and Low-Level Blast Exposure.

Traumatic brain injury (TBI), which can result from either direct impact to the head or blast exposure, has been the leading cause of morbidity and mortality in recent military conflicts. However, little research has compared mTBIs by mechanism of injury. The present research addressed two research questions: (1) Are blast-related mTBIs (mbTBIs) associated with significantly more symptoms than impact-related mTBIs (miTBIs), and (2) are mTBIs associated with more self-reported symptoms among service members with higher (vs. lower) risk of low-level blast (LLB) exposure. We obtained data from 181,423 active duty enlisted United States Marines deployed between 2003 and 2012, who completed the Post-Deployment Health Assessment. We examined the self-reported symptoms of Marines who completed an mTBI screen and could be classified as at high or low risk for LLB exposure, using their military occupation as a proxy (n = 12,013). Symptoms were compared as a function of blast exposure (blast vs. impact), probable mTBI (yes vs. no), occupational risk of LLB (high vs. low), and symptom type (neurological vs. musculoskeletal vs. immunological). Overall, musculoskeletal symptoms were reported more frequently than neurological and immunological symptoms. However, Marines with probable mTBIs (regardless of mechanism of injury) and those with probable mbTBIs specifically reported more neurological symptoms, which rose to the level of musculoskeletal symptom reporting. Among Marines with probable mTBI, those with high risk of LLB exposure also reported significantly more neurological symptoms. Our results indicate that mbTBIs and miTBIs may be fundamentally different, and that LLB may increase susceptibility to injury.