The Explosive Ordinance Disposal (EOD) community within the US Military is a specialized force in charge of the most fundamental aspects of the military operations in combat which include disarming and safely disposing explosive threats. EOD technicians have provided critical protection for our military and civilians exposed to improvised explosive devices (IEDs), which became the signature threat of both Afghan and Iraq wars. The nature of the job puts EOD technicians at high risk for blast exposures (from training and combat) resulting in traumatic brain injury (TBI) and sub-concussive head impact. Further, this population is exposed to high levels of combat with psychologically traumatic events. Given the groups neurological and psychological risk factors as well as their critical role in combat, we hypothesized that EOD technicians will present with increased psychological and neurobehavioral symptoms as well decreased cognitive functioning compared to other military personnel.

Participants were recruited from a military hospital with at least one diagnosed mild traumatic brain injury (MTBI). Exclusion criteria included TBI greater then mild severity and invalid performance on the Rey-15. Final sample included 10 EOD and 90 other military.

CognCognitive measures included Hopkins Verbal Learning Test-Reviseitive measures included Hopkins Verbal Learning Test-Revised (HVLT-R); DKEFS Color Word Condition 4 Switching (CW4), Trail Making Condition 3 Letter Sequencing (TM3) and Condition 4 Switching (TM4), and Paced Auditory Serial Addition Test (PASAT). Self-report measures included the Neurobehavioral Symptom Inventory (NSI), Key Behaviors Change Inventory (KBCI), Post-Traumatic Stress Disorder Checklist (PCL-M), Patient Health Questionnaire (PHQ), Combat Exposure Scale (CES) and Blast Exposure Threshold Survey (BETS). The Ohio State University Traumatic Brain Injury Identification Method (OSU) assessed TBI history.

EOD were older (EOD M=38.4, SD=4.06; Others M=33.32, SD=8.08; p=0.05), had a higher pre-morbid IQ (EOD M=110.90, SD=7.64; Other M=101.59, SD=10.55; p=0.008), more combat deployments (EOD M=5.5, SD=2.37; Others M=3.55, SD=2.98; p=0.049) and exposure to wartime atrocities (CES, p=0.003). They had greater number of MTBI (OSU EOD M=6.67, SD=3.33; Other M=3.67, SD=2.34; p=0.007), blast related MTBI (OSU-TBI EOD M=2.33, SD=1.63; Other M=0.67, SD=0.91; p<0.001), and exposure to large explosives (BETS p<0.0001). EOD reported better attention skills (KBCI Inattention, p=0.016, d=0.82; Impulsivity p=0.047, d=0.67). There was a trend for EOD to have lower neurobehavioral symptoms (NSI Total, d=0.32), post-traumatic stress (PCL d=0.39), and depression (PHQ d=0.50); however, despite the moderate effect sizes (p’s >0.05). EOD presented with significantly better scores on DKEFS TMT3 (p=0.037, d=0.70), HVLT-R-Total (p=0.001, d=1.10), HVLT-R-Delayed (p=0.03, d=0.74), and attention/executive functioning skills (PASAT p=0.001, d=1.12). DKEFTS CW4 Switching (d=0.51) and TMT4 Switching were approaching significance (d=0.61) with EOD performing better.

As expected, the EOD sample in this study had higher number of combat deployments, greater exposure to combat atrocities (e.g., death), higher levels of exposure to large explosives, as well as a higher number of MTBI. Inconsistent with our hypotheses, despite these psychological and neurological risk factors, EOD performed better on cognitive measures of memory, attention and executive functioning. They also reported less problems with inattention and impulsivity. Results may reflect the impact of psychological and cognitive resiliency.