Symptom Trajectories After Military Blast Exposure and the Influence of Mild Traumatic Brain Injury

Background: Blast-related mild traumatic brain injury (blast mTBI) is a signature wound of recent US military conflicts in the Middle East, but the relatedness of postconcussive symptoms (PCS) to the blast mTBI is unclear, and longitudinal symptom data are sparse. Objectives: To characterize postdeployment symptom levels and trajectories and to determine relationship to blast mTBI. Methods: A total of 216 participants within 2 years of blast exposure during deployment underwent structured interviews or algorithmic questionnaires for blast mTBI. Detailed symptom inventories for PCS, pain, posttraumatic stress disorder, and depression were taken serially at enrollment, 6 months, and 12 months later. Repeated-measure analysis of variance models were built. Results: Up to 50% of participants had at least 1 high-grade blast mTBI (with posttraumatic amnesia), 31% had low-grade only, and 19% had neither. Within the entire cohort, all 4 composite symptom scores started high and stayed unchanged. Between blast mTBI groups, symptom scores differed at every time point with some evidence of convergence over time. The PCS groups, different by definition to start, diverged further over time with those initially more symptomatic becoming relatively more so. Conclusions: History of blast mTBI accompanied by posttraumatic amnesia is associated with greater nonspecific symptoms after deployment, and prognosis for improvement when symptoms are prominent is poor.