Risk Factors for Mild Traumatic Brain Injury among US Army Soldiers

Abstract

The Defense and Veterans Brain Injury Center (2015 DVBIC) reported more than 120,000 mild traumatic brain injury (mTBI) cases since the year 2000 among active duty US Army personnel. Increasing evidence suggests mTBI as a risk factor for development of mental health disorders (MHD) and post-traumatic stress disorder (PTSD). PURPOSE: To determine risk factors for mTBI, PTSD, and MHD and the association of mTBI and non-head injuries with subsequent PTSD and MHD among US Army active duty Soldiers. METHODS: This prospective cohort study utilized the Total Army Injury and Health Outcomes Database (TAIHOD) to analyze soldiers’ (N=1,261,297) medical encounter data between 2002 and 2011. International Classification of Diseases, Ninth Revision [ICD-9] codes were used to identify outcomes of interest: mTBI (CDC surveillance definition for mTBI), PTSD (ICD-9-CM 309.81), and MHD (ICD-9-CM codes to identify depression and anxiety, while excluding the diagnostic code of PTSD [ICD-9-CM 309.81]). Non-head (torso, spine, extremity) injuries were identified by ICD-9-CM codes using the Barell Injury Diagnosis Matrix. RESULTS: From 2002 to 2011 incident mTBI, PTSD, and MHD were found in: 79,505, 71,454, and 285,731 soldiers, respectively. The average injury rate per 1000 soldier years for mTBI, PTSD, and MHD were 17.23, 15.37, and 67.99, respectively. Sustaining a prior (>12 mos.) non-head injury was a significant risk factor for subsequent mTBI (OR 9.82, 95% CI 9.62-10.02). MTBI was associated with increased risk for both subsequent (>12 mos.) PTSD (OR 5.67, 95% CI 5.37-5.98) and MHD (OR 2.99, 95% CI 2.89-3.10). Non-head injury was associated with an increased risk for PTSD (OR 2.15, 95% CI 2.10-2.19) and MHD (OR 2.17, 95% CI 2.15-2.20) to a lesser degree than mTBI. CONCLUSION: Soldiers are at greater risk for developing PTSD and other MHDs for more than a year after an mTBI exposure versus non-head injuries. Identifying populations at risk for mTBI, and those with a previous mTBI exposure, are important consideration for mental health surveillance and intervention programs for both military and civilians. The views, opinions and/or findings contained herein are those of the authors and should not be construed as an official Department of the Army position, or policy.