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Photo of Christopher Rhea
Photo of Christopher Rhea

Dr. Christopher Rhea (Kinesiology) received new funding from the Henry M. Jackson Foundation for the project “INVestigating traIning assoCiated blasT pAthology (INVICTA).”

The majority of combat injuries sustained during the conflicts in Iraq and Afghanistan (OEF and OIF) were associated with explosive blast events and head trauma, including traumatic brain injury (TBI), was present in most (64%-78%) service members with combat injuries. Exposure to blasts has lead to unprecedented rates of head injury among service members and TBI is considered a signature wound of these recent conflicts. Notably, 97% of individuals diagnosed with mild TBI were injured by blast exposure. For these reasons, operational, research, and medical leaders have become increasingly concerned that repeated exposure to low-levels of blast overpressure may have both acute and cumulative long-term effects.

At this point, little is known about the biological mechanisms that lead to brain damage and altered functioning among some individuals who have been exposed to explosive blast events. Conducting systematic studies of individuals who have been exposed to blast events in actual combat situations presents tremendous logistical challenges, so the researchers sought an alternative way to study biological and functional effects of blast exposure on military service members.

Study by the researchers group of combat troops who had served in OIF/OEF demonstrated that 2/3 of all exposures to blast events actually occurred as a part of their training. Using this information, and building on data gained from a previous study of individuals using explosives to breach entryways, the researchers initiated studies of service members who are exposed to repeated low-level blast events when they fire heavy weapons as a regular part of their combat training exercises. Every year, Service Members involved in routine combat training will be exposed to multiple low-level blast exposures. For example, heavy weapons training (HWT) instructors will experience 100-150 blast exposures during a 3-year assignment. Using the training programs as a natural experiment, we conducted studies to determine if there might be changes in functional or cognitive ability that occur in some individuals after exposure to these HWT blast events and found that short-term difficulties with some tasks, including the ability to recall information across time, were present in nearly 1/5 service members after exposure.

This study, which represents the continuation of our group’s current I-TAB study and includes several additional research tools, will expand current knowledge regarding the biological mechanisms that underlie the neurological impact of repetitive low-level blast exposures. The researchers will use validated measures of blast exposure level and compare these with changes in clinical, physiological, and behavioral findings in the service members enrolled in this study. Researchers will examine possible blast-related changes in biological markers using blood samples collected before and after blast-exposure and correlate important changes with the measured level of blast exposure and with changes in functioning that are detected through the tests we administer.

The findings from this study will inform further long-term studies by the researchers’ group that will examine relationships between blast-exposure, acute neurological and biological findings and the risk of developing chronic-progressive degenerative conditions that may resemble chronic traumatic encephalopathy (CTE). In addition to informing other research, this study will provide direct evidence to military leadership to support decision-making regarding service member safety and the optimization of force preparedness.

 
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