Mild Traumatic Brain Injury (Concussion) During Combat: Lack of Association of Blast Mechanism With Persistent Postconcussive Symptoms

Objective: To determine whether screening for a blast mechanism of concussion identifies individuals at higher risk of persistent postconcussive symptoms (PCS). Setting: United States Army post. Participants: 3952 US Army infantry soldiers were administered anonymous surveys 3 to 6 months after returning from a yearlong deployment to Iraq. Main Outcome Measures: Self-reported concussion (defined as an injury that resulted in being dazed, confused, or 'seeing stars'; not remembering the injury; or losing consciousness [knocked out]): Patient Health Questionnaire 15-item scale for physical symptoms and PCS; Posttraumatic Stress Disorder Checklist; and Patient Health Questionnaire depression module. Results: Of the 587 soldiers (14.9% of the total sample) who met criteria for concussion, 201 (34.2%) reported loss of consciousness, and 373 (63.5%) reported only an alteration of consciousness without loss of consciousness; 424 (72.2%) reported a blast mechanism, and 150 (25.6%) reported a nonblast mechanism. Among soldiers who lost consciousness, blast mechanism was significantly associated with headaches and tinnitus 3 to 6 months postdeployment compared with a nonblast mechanism. However, among the larger group of soldiers reporting concussions without loss of consciousness, blast was not associated with adverse health outcomes. Conclusions: Blast mechanism of concussion was inconsistently associated with PCS, depending on the definition of concussion utilized. A self-reported history of blast mechanism was not associated with persistent PCS for the majority of US soldiers with concussions.