Neurocognitive Performance Deficits Related to Immediate and Acute Blast Overpressure Exposure

Abstract

Addressing the concerns surrounding blast injury for the military community is a pressing matter. Specifically, sub-concussive blast effects, or those blast effects which do not yield a medical diagnosis but can result in symptom reporting and negative self-reported outcomes, are becoming increasingly important. This work evaluates explosive blast overpressure and impulse effects at the sub-concussive level on neurocognitive performance assessed with the Defense Automated Neurobehavioral Assessment (DANA) across seven breacher training courses conducted by the US Military. The results reported here come from 202 healthy, male military volunteer participants. Findings indicate that the neurocognitive task appearing most sensitive to identifying performance change is the DANA Procedural Reaction Time (PRT) subtask which may involve a sufficient level of challenge to reliably detect a small, transient cognitive impairment among a healthy undiagnosed population. The blast characteristic that was consistently associated with performance change was peak overpressure. Overall, this study provides evidence that increasing blast overpressure, defined as peak overpressure experienced in a training day, can lead to transient degradations in neurocognitive performance as seen on the DANA PRT subtask, which may generalize to other capabilities.

Keywords: blast; breacher; cognition; military; practice effect.

Figure 1

Adjusted* change score means (and standard error bars) for Immediate and Acute performance by DANA subtest. Change score are plotted over time for participants exposed to >5 psi peak overpressure (“High,” black), and participants exposed to 5 psi or less peak overpressure (“Low,” gray). In both PRT and GNG, the “High” exposure group mean performance change was statistically different from the “Low” group; participants with higher peak overpressure exposure have a reduced level of improvement. Further analyses (regression) resulted in statistically significant differences between “High” and “Low” groups in PRT at the Immediate and Acute time point in PRT and at the Acute time point in GNG as indicated below by “+.” ^*Mean values estimated from regression using “High” and “Low” peak overpressure exposure groups.

Figure 2

Peak overpressure exposure (psi) and acute PRT performance change (ms) scatter plot with regression line (black line), confidence interval (gray line), and prediction interval (dotted gray lines). Regression line illustrates association between higher peak overpressure and larger acute PRT performance change scores (indicating slower performance at the end of the training day compared to baseline). The confidence interval marks the boundary which contains the true best fit line with 95% probability. The predication interval shows the range of predicted performance values with corresponding peak overpressure exposure levels with 95% probability. Immediate PRT performance (not pictured) shows a similar trend (i.e., higher peak overpressure associated with larger Immediate PRT performance change scores), but with slightly less gradient.