The impact of repetitive exposure to low-level blast on neurocognitive function in Canadian Armed Forces' breachers, snipers, and military controls.

Abstract

Objective: The primary aim of this study was to evaluate whether military occupations with repetitive exposure to low-level blast (i.e., breachers and snipers) display poorer neurocognitive status compared to military controls without prior occupational engagement as breachers and/or snipers, and whether that effect is mediated by self-reported mental health symptoms.

Method: With data collected from Canadian Armed Forces (CAF) breachers and snipers and sex- and age-matched CAF controls (n = 112), mental health was assessed using the PCL-5 (PTSD) and the Brief Symptoms Inventory, and neurocognitive function based on a set of computerized tasks (i.e., four-choice reaction time task, delayed matching-to-sample, n-back, Stroop). Directed Acyclic Graphs (DAGs) were created to establish a causal framework describing the potential effect of occupation on neurocognitive function while considering mental health. Factor analysis modeling was used to establish the latent construct of neurocognitive function, which was then incorporated into student-t models for effect estimation, following assumptions derived from causal inference principles.

Results: Our results demonstrated that it is snipers specifically who displayed lower neurocognitive performance compared to breachers and controls. Critically, this effect was not mediated by mental health status. In fact, mental health was generally better in both breachers and snipers when compared to controls.

Conclusions: When the focus is on occupations with repetitive exposure to low-level blast, the snipers in particular are impacted most in terms of neurocognitive function. We speculate that this might be due to additional impact of recoil forces exacerbating the effect of blast overpressure on the nervous system.