The Neurological Effects of Repeated Exposure to Military Occupational Blast: Implications for Prevention and Health

Proceedings, Findings, and Expert Recommendations from the Seventh Department of Defense State-of-the-Science Meeting

by Charles C. Engel, Emily Hoch, Molly Simmons

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Research Questions

  1. What is known about repeated low-level occupational blast exposure incurred during military service?
  2. What is the state of the scientific evidence on the potential neurological health effects?
  3. What are promising strategies for preventing neurological damage?
  4. What are promising tools for early detection of neurological consequences?

There has been growing concern about the risk of subconcussive neurological injuries that service members face after repeated, low-level blasts during training and in combat. To examine this risk, the current evidence base, and potentially promising methods and tools for prevention and detection, the Department of Defense held its Seventh State-of-the-Science Meeting in March 2018. The meeting featured findings from a scientific literature review, panel discussions, presentations by researchers in the field, a poster session, and working groups chaired by expert panelists that assessed the state of the science and put forward recommendations regarding policy and strategy guidance and future research directions. Experts in the field concluded that a much stronger evidence base is needed to identify the frequency of exposure, occupation-specific risk factors, appropriate exposure thresholds, potential neurological consequences, and approaches to prevent and detect injuries in service members after repeated exposure to low-level blasts.

Key Findings

There has been very little research on the frequency and effects of low-level occupational blast exposure in military populations

  • While there is little doubt that repeated military occupational blast exposure occurs, there is strikingly little empirical knowledge of its frequency and the military contexts and occupational specialties at greatest risk.
  • The literature review found no published information on military service–specific frequencies of exposure to low-level occupational blasts, and experimental animal studies may not adequately translate to real-life experiences in military contexts.
  • More information is also needed on the use of various munition systems in military training and in deployed environments. There has been no systematic effort to document blast loads associated with various munition types and military training experiences.

There is a need for more research into promising tools for preventing and detecting neurological damage from low-level blast exposure

  • Current Department of Defense and military service policies, directives, instructions, standards, and safety guidelines include weapon-specific, health-based standards that mandate the use of hearing-protection devices, limit the number of rounds fired per day, or place restrictions on firing from certain positions. Ensuring awareness of and compliance with these standards is an essential initial step toward preventing injury.
  • Numerous potentially applicable indicators of injury from low-level blast exposure are either available or in development. However, not all are applicable to military contexts. Multidiscipline collaboration and embedding researchers within units would improve efforts to identify appropriate indicators.

Recommendations

  • Enforce Department of Defense policies and standards related to low-level military occupational blast exposure, educate those responsible for applying these policies and standards, and evaluate efforts to improve compliance.
  • Develop a portfolio of high-quality studies assessing repeated, low-level occupational blast injury.
  • Prepare a large-scale population-based longitudinal study of military personnel with long-term follow-up to assess the prevalence and severity of neurological and general health outcomes after repeated, low-level military occupational blasts.
  • Transition from rodent studies to studies on larger animals, including nonhuman primate models. Animal studies should be guided by suspected symptoms and deficits, designed to identify the mechanisms that underlie clinical findings, and test approximate exposure conditions observed in human research, controlling for gender and age.
  • Studies of possible neurologic and general health effects should align with current military exposure assessment tools and protective practices and devices when feasible.
  • Catalogue, map, and make available to researchers, safety programs, and military end users unclassified weapon system–specific information, including blast pressure profiles and service member–specific load profiles.
  • Design policies and increase opportunities for the use of embedded research scientists from key disciplines within units during training and in deployed contexts.

Table of Contents

  • Chapter One

    Background

  • Chapter Two

    Literature Review Summary

  • Chapter Three

    Keynote Address

  • Chapter Four

    Discussion Panels

  • Chapter Five

    Scientific Presentation Summaries

  • Appendix A

    Planning Committee

  • Appendix B

    Meeting Agenda

  • Appendix C

    Keynote Speaker Biography

  • Appendix D

    Discussion Panel Biographies

  • Appendix E

    Poster Abstracts

  • Appendix F

    Expert Panel Biographies

  • Appendix G

    Meeting Participants

  • Appendix H

    Previous State-of-the-Science Meetings

Research conducted by

The meeting and these proceedings were sponsored by the Army Medical Research and Materiel Command. This research was conducted by the Personnel, Training, and Health Program within the RAND Arroyo Center.

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