Introduction Occupational exposure to repetitive, low-level blasts in military training and combat has been tied to subconcussive injury and poor health outcomes for service members. Most low-level blast studies to date have focused on explosive breaching and firing heavy weapon systems; however, there is limited research on the repetitive blast exposure and physiological effects that mortarmen experience when firing mortar weapon systems. Motivated by anecdotal symptoms of mortarmen, the purpose of this paper is to characterize this exposure and its resulting neurocognitive effects in order to provide preliminary findings and actionable recommendations to safeguard the health of mortarmen. Materials and Methods In collaboration with the U.S. Army Rangers at Fort Benning, blast exposure, symptoms, and pupillary light reflex were measured during 3 days of firing 81 mm and 120 mm mortars in training. Blast exposure analysis included the examination of the blast overpressure (BOP) and cumulative exposure by mortarman position, as well as comparison to the 4 psi safety threshold. Pupillary light reflex responses were analyzed with linear mixed effects modeling. All neurocognitive results were compared between mortarmen (n = 11) and controls (n = 4) and cross-compared with blast exposure and blast history. Results Nearly 500 rounds were fired during the study, resulting in a high cumulative blast exposure for all mortarmen. While two mortarmen had average BOPs exceeding the 4 psi safety limit (Fig. 2), there was a high prevalence of mTBI-like symptoms among all mortarmen, with over 70% experiencing headaches, ringing in the ears, forgetfulness/poor memory, and taking longer to think during the training week (n ≥ 8/11). Mortarmen also had smaller and slower pupillary light reflex responses relative to controls, with significantly slower dilation velocity (P < 0.05) and constriction velocity (P < 0.10). Conclusion Mortarmen experienced high cumulative blast exposure coinciding with altered neurocognition that is suggestive of blast-related subconcussive injury. These neurocognitive effects occurred even in mortarmen with average BOP below the 4 psi safety threshold. While this study was limited by a small sample size, its results demonstrate a concerning health risk for mortarmen that requires additional study and immediate action. Behavioral changes like ducking and standing farther from the mortar when firing can generally help reduce mortarmen BOP exposure, but we recommend the establishment of daily cumulative safety thresholds and daily firing limits in training to reduce cumulative blast exposure, and ultimately, improve mortarmen’s quality of life and longevity in service.

中文翻译：

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陆军游骑兵迫击炮兵的重复性低水平爆炸暴露和神经认知效应

引言 在军事训练和战斗中职业暴露于重复性低强度爆炸与服役人员的脑震荡损伤和健康状况不佳有关。迄今为止，大多数低水平爆炸研究都集中在爆炸性破坏和发射重型武器系统上；然而，关于迫击炮手在发射迫击炮武器系统时所经历的重复爆炸暴露和生理影响的研究有限。受迫击炮手轶事症状的启发，本文的目的是描述这种暴露及其导致的神经认知影响，以提供初步发现和可操作的建议，以保护迫击炮手的健康。材料和方法 与本宁堡的美国陆军游骑兵合作，爆炸暴露，症状，在训练中发射 81 毫米和 120 毫米迫击炮的 3 天期间测量瞳孔光反射。爆炸暴露分析包括检查爆炸超压 (BOP) 和迫击炮手位置的累积暴露，以及与 4 psi 安全阈值的比较。用线性混合效应模型分析瞳孔光反射反应。所有神经认知结果都在迫击炮手 (n = 11) 和对照组 (n = 4) 之间进行了比较，并与爆炸暴露和爆炸历史进行了交叉比较。结果 在研究期间发射了近 500 发子弹，导致所有迫击炮手的累积爆炸暴露量很高。虽然两名迫击炮兵的平均 BOP 超过 4 psi 安全限值（图 2），但所有迫击炮兵中 mTBI 样症状的患病率很高，超过 70% 的人出现头痛、耳鸣、健忘/记忆力差，并且在训练周期间思考时间更长 (n ≥ 8/11)。与对照组相比，迫击炮手的瞳孔光反射反应也更小、更慢，扩张速度 (P < 0.05) 和收缩速度 (P < 0.10) 明显更慢。结论 迫击炮手经历了高累积爆炸暴露，同时神经认知发生改变，这表明爆炸相关的次脑震荡损伤。这些神经认知效应甚至发生在平均 BOP 低于 4 psi 安全阈值的迫击炮手身上。虽然这项研究受到样本量小的限制，但其结果表明迫击炮手存在着令人担忧的健康风险，需要进一步研究并立即采取行动。射击时躲避和远离迫击炮等行为改变通常有助于减少迫击炮兵 BOP 暴露，