The Effects of Chronic Exposure to Low-Level Blasts
Condition: Tramatic Brain Injury
MeSH terms: Brain Injuries
Study type: Observational

Summary: 
      Background:

      - Repeated exposure to explosions may lead to changes in the way that people think or feel.
      Breachers (people trained to use explosives to get into buildings) are exposed to repeated
      blasts as part of their job. Researchers want to study how they might be affected by blast
      exposure. Breachers will be compared with other groups who have different levels of exposure
      to repeated blasts. Information will also be obtained from spouses or close companions.

      Objectives:

      - To study the effects of repeated exposure to low-level blasts on thinking, memory,
      behavior, and brain function.

      Eligibility:

        -  Experienced military and civilian breachers, experienced active duty artillery
           operators, and active duty military without frequent blast exposure, 18 and 60 years of
           age.

        -  Spouses or close companions of these individuals.

      Design:

        -  Participants will be screened with a physical exam and medical history. Blood samples
           will be collected and a urine pregnancy test will be required of participants (not
           companions) before MRI scanning.

        -  Participants will spend up to 5-days as a NIH clinic outpatient, with about 6 hours of
           tests each day. Tests will include the following:

        -  Medical and professional history, with questions about exposures to blasts

        -  Tests of thinking, memory, and concentration

        -  Balance tests

        -  Hearing tests

        -  Imaging studies, such as magnetic resonance imaging, to look at the brain

        -  Overnight sleep study to monitor brain waves

        -  Blood samples

        -  Participants will return 1 year later for a 3-day followup visit. Some of the tests from
           before will be repeated. A spouse or close companion (if available) will be asked to
           complete questionnaires or have a telephone interview....
    

Detailed description: 
      The purpose of this study is to evaluate the cognitive and neurophysiological effects of
      chronic exposure to repeated low-level blast overpressure. Previous studies show converging
      evidence for a neurophysiological effect from cumulative exposure to blast, which is
      consistent with subjective reports of cognitive impairment by individuals trained to use
      explosives to gain entry to structures (breachers). This study will expand on these findings
      by examining a larger cohort of experienced breachers and artillery personnel who may be
      incurring a cumulative effect of low-level blast exposure over the course of several years.
      We will evaluate up to 20 participants from each of three groups: breachers, artillery
      personnel, and unexposed individuals. Additionally, we will ask each of the above to bring a
      close companion for a set of questionnaires and an interview to capture changes in
      functioning that participants may not be able to self-assess. Participants will travel to the
      NIH for evaluation of cognitive and neurophysiological measures. The procedures include
      neuropsychological testing, blood analysis for biomarkers, vestibular and auditory testing,
      and neuroimaging studies using diffusion tensor imaging, susceptibility weighted imaging,
      perfusion imaging, functional magnetic resonance imaging, and, where there is evidence of a
      sleep disorder, polysomnography. This study will be conducted in collaboration with the Naval
      Medical Research Center (NMRC) and the Walter Reed Army Institute of Research (WRAIR) under a
      Research Collaborative Agreement. The complementary DoD protocol will be reviewed by the DoD
      IRB and includes this NIH protocol. The complementary DoD protocol includes data collection
      at field settings, activity NIH is not engaged in and not described in this protocol.
    

Observational model: Cohort
Time perspective: Prospective
Sampling method: Probability Sample
Study population: 
        120 total: 20 breachers, 20 artillery, 20 unexposed controls, and 60 companions
      
Keywords: Military; Traumatic Brain Injury; Cognitive Testing; Neuroimaging; Natural History; Brain Function