Blast in Context: The Neuropsychological and Neurocognitive Effects of Long-Term Occupational Exposure to Repeated Low-Level Explosives on Canadian Armed Forces' Breaching Instructors and Range Staff

Abstract

Currently, there is strong interest within the military to better understand the effects of long-term occupational exposure to repeated low-level blast on health and performance. To gain traction on the chronic sequelae of blast, we focused on breaching—a tactical technique for gaining entry into closed/blocked spaces by placing explosives and maintaining a calculated safe distance from the detonation. Using a cross-sectional design, we compared the neuropsychological and neurocognitive profiles of breaching instructors and range staff to sex- and age-matched Canadian Armed Forces (CAF) controls. Univariate tests demonstrated that breaching was associated with greater post-concussive symptoms (Rivermead Post Concussion Symptoms Questionnaire) and lower levels of energy (RAND SF-36). In addition, breaching instructors and range staff were slower on a test that requires moving and thinking simultaneously (i.e., cognitive-motor integration). Next, using a multivariate approach, we explored the impact of other possible sources of injury, including concussion and prior war-zone deployment on the same outcomes. Concussion history was associated with higher post-concussive scores and musculoskeletal problems, whereas deployment was associated with higher post-concussive scores, but lower energy and greater PTSD symptomatology (using PCL-5). Our results indicate that although breaching, concussion, and deployment were similarly correlated with greater post-concussive symptoms, concussion history appears to be uniquely associated with altered musculoskeletal function, whereas deployment history appears to be uniquely associated with lower energy and risk of PTSD. We argue that the broader injury context must, therefore, be considered when studying the impact of repetitive low-level explosives on health and performance in military members.

Blast effects on post-concussive and mental health outcomes: Data from Canadian Armed Forces breachers and snipers

“…In earlier research involving CFSME breachers and range staff and CAF controls, 35 post-concussive symp toms were also elevated among those with a history of concussion and warzone deployment. Th e authors examined those associations in this dataset.…”

“…[11][12][13][14][15] In contrast, data collected from samples of breachers from CANSOFCOM and CFSME showed that, whereas breachers and range staff report elevated levels of postconcussive symptoms, they did not report poorer men tal health outcomes, at least as measured by the RAND SF-36 or the PCL-5. 30,35 This study was conducted to replicate and extend those findings in two ways. First, beyond PTSD (PCL-5) and a measure of emotional well-being (RAND SF-36), measures of mental health were broadened to also include the Brief Symptom Inventory (BSI-18) -a self-report measure covering nine symptom dimensions that draw on three global indices of distress including anxiety, depression, and somatization.…”

“…In a follow-up study, a largely similar battery of measures was administered to a sample of breachers and range staff recruited from the Canadian Forces School of Military Engineering (CFSME), and a group of sex-and age-matched CAF controls. 35,36 Aside from the RPQ and the RAND SF-36, the Post-Traumatic Checklist-5 (PCL-5) -a clinical measure of PTSD symptomatol ogy -was also included. 37 Compared to CAF controls, breachers and range staff scored higher on the RPQ but not on the PCL-5 or the emotional well-being sub-scale of RAND SF-36.…”

“…Self-report measures began with questions regarding occupational history, including prior head injury. 30,35 History of head injury was measured by asking each participant to indicate, via self-report, whether they experienced a set of events associated with head injury in the past (yes/no) (Table 2). A structured interview to diagnose blast-induced mTBI was not conducted.…”

A Distinct Metabolite Signature in Military Personnel Exposed to Repetitive Low-Level Blasts

“…Regardless of the mechanism, post-blast neurocognitive deficits have been demonstrated in animal models and humans ( 10 , 11 ). Repetitive low-level blasts, while unlikely to cause mechanical trauma via acceleration and/or rotation of the head, nevertheless result in neuropsychological and neurocognitive deficits and generally decreased physical and mental health ( 7 , 12 , 13 ).…”