Blast Overpressure Longitudinal Study (BLES)

Blast Overpressure Longitudinal Exposure Study (BLES)

The goal of this observational study is to learn about the impact of low-level blast exposure in U.S. Special Operations Forces personnel. The main questions it aims to answer are:

What advanced brain imaging changes are related to clinical presentation after low-level blast exposure? What are the relationships between low-level blast exposure and common groups of symptoms after concussion?

Participants will:

• Undergo advanced brain imaging
• Answer questionnaires
• Complete clinical tests
• Provide blood, urine, and saliva samples
• Wear blast sensors

Study Overview

• Status: Not yet recruiting
• Conditions: Low-level Blast Exposure

Detailed Description

Participants in this observational study are active-duty U.S. Special Operations Forces personnel between the ages of 18 and 50. This study is designed to characterize the neurological and clinical effects associated with repeated low-level blast exposure (LLBE) in this population. Concerns have emerged that cumulative exposure to sub-concussive blast overpressure (BOP), even in the absence of a diagnosable concussion, may be associated with subtle changes in brain structure and function over time. Due to the nature of their operational and training environments, Special Operations Forces personnel may experience repeated LLBE and are therefore an important population for longitudinal investigation.

Participation involves in-person assessments and data collection conducted over a period of approximately 4-5 years. The schedule of study activities includes baseline, daily, weekly, monthly, quarterly, and annual assessments. Baseline and annual study visits include advanced magnetic resonance imaging (MRI) and require travel to Walter Reed National Military Medical Center. Specifically, this study includes the use of the Microstructure Anatomy Gradient for Neuroimaging with Ultrafast Scanning (MAGNUS) 3.0 Tesla MRI.

Throughout the study period, participants complete standardized questionnaires and clinical assessments and provide biological samples, including blood, urine, and saliva, at specified intervals. Participants also contribute measures on a daily, weekly, monthly, quarterly, and annual basis. They will wear blast sensors throughout their participation in the study.

The total planned enrollment for the study is approximately 250 participants across multiple sites, with an estimated 60 participants enrolled at Fort Bragg, NC. Enrollment and follow-up are expected to occur over a 4-5 year period.

• Study Type: Observational
• Enrollment (Estimated): 250

Contacts and Locations

• Study Contact: Name: Tony T Yuan, PhD; Phone Number: 214-808-8971; Email: tony.yuan@usuhs.edu
• Study Contact Backup: Name: Carrie W Hoppes, PhD; Phone Number: 571-212-4660; Email: carrie.hoppes.ctr@usuhs.edu

Study Locations

• United States
  • Maryland
    • Bethesda, Maryland, United States, 20889
      • Walter Reed National Military Medical Center
      • Contact: Tony T Yuan, PhD; Phone Number: 214-808-8971; Email: tony.yuan@usuhs.edu
  • North Carolina
    • Fort Bragg, North Carolina, United States, 28310
      • Fort Bragg
      • Contact: Rodney Saunders, MSN; Phone Number: 740-398-1391; Email: rodney.saunders.ctr@usuhs.edu
  • Texas
    • San Antonio, Texas, United States, 78236
      • Wilford Hall Ambulatory Surgical Center
      • Contact: Carrie W Hoppes, PhD; Phone Number: 571-212-4660; Email: carrie.hoppes.ctr@usuhs.edu

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult
• Accepts Healthy Volunteers: Yes

• Sampling Method: Non-Probability Sample

Study Population

The target population is 250 SOF personnel, particularly those who are regularly exposed to occupational low-level blast exposure. Approximately 10% of the sample will be recruited as a control group of low/no exposure personnel.

Description

Inclusion Criteria:

• Active duty
• U.S. SOF personnel
• 18-50 years old

Exclusion Criteria:

• Subjects will be excluded only if their participation will significantly interfere with validity of data collection or safety during the study (e.g., they have conditions that might result in harm or injury during research procedures).
• Example: pregnancy (balance considerations)
• Example: being unable to undergo MRI testing (i.e., they have non-MRI compatible devices, imbedded metal fragments such as shrapnel, and/or severe claustrophobia; these MRI contraindications will be screened using an MRI Safety Questionnaire)

Study Plan

How is the study designed?

Number of groups / cohorts

2

Cohorts and Interventions

Group / Cohort
High exposure (experimental); Special Operations Forces personnel with higher occupational blast overpressure exposure as measured by blast sensor(s)
Low/No exposure (control); Special Operations Forces personnel with lower occupational blast overpressure exposure as measured by blast sensor(s)

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Effective axonal radii mapping	The primary outcome measure in this study will be effective axonal radii (r_eff) mapping derived from ultra-high performance diffusion magnetic resonance imaging using the MAGNUS system and its correlations to low-level blast exposure.	At baseline and annually through study completion, an average of 5 years

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Ohio State University TBI Identification Method	The Ohio State University TBI Identification Method is a standardized approach for collecting an individual's comprehensive history of traumatic brain injuries through a structured interview lasting 3-5 minutes.	At baseline and annually through study completion, an average of 5 years
Concussion Clinical Profiles Screening	The Concussion Clinical Profiles Screening (CP Screen) tool will be used to measure the five concussion clinical subtypes (profiles) and two modifiers. The CP Screen is a 29-item post-concussion symptom inventory. Subjects rate the severity of 29 symptoms on a scale from 0 (None [Not experiencing this symptom.]) to 3 (Severe). The CP Screen total score is a sum of the 29 items (range 0 to 87, higher scores mean a worse outcome). Subscale scores range from 0 to 15 for vestibular, ocular-motor, anxiety/mood, and post-traumatic headache (migraine); 0 to 9 for cognitive; 0 to 12 for sleep; and 0 to 6 for cervical spine.	At baseline and annually through study completion, an average of 5 years
Neurobehavioral Symptom Inventory	The Neurobehavioral Symptom Inventory (NSI) is a 22-item post-concussion symptom inventory. The NSI total score is a sum of the 22 items (range 0 to 88, higher scores mean a worse outcome).	At baseline and weekly through study completion, an average of 5 years
Headache Impact Test	The Headache Impact Test (HIT-6) is a 6-item assessment of the negative impact of headaches. The HIT-6 total score is a sum of the 6 items (range 36 to 78, higher scores mean a worse outcome).	At baseline and weekly through study completion, an average of 5 years
modified Military Concussion Readiness Inventory for Dizziness and Balance	The modified Military Concussion Readiness Inventory for Dizziness and Balance (MCRI-DB) is a military-specific measure of the handicapping effects dizziness and imbalance (similar to the Dizziness Handicap Inventory). The modified MCRI-DB total score is a sum of the 25 items (range 0 to 100, higher scores mean a worse outcome).	At baseline and quarterly through study completion, an average of 5 years
Composite Autonomic Symptom Score (COMPASS) 31	The Composite Autonomic Symptom Score (COMPASS) 31 is a 31-item self-reported evaluation that measures autonomic symptoms across six domains: orthostatic intolerance, vasomotor, secretomotor, gastrointestinal (combining constipation, diarrhea, and gastroparesis domains), bladder, and pupillomotor. The COMPASS-31 total score is a sum of the 31 items (range 0 to 100, higher scores mean a worse outcome).	At baseline and annually through study completion, an average of 5 years
Pittsburgh Sleep Quality Index	The Pittsburgh Sleep Quality Index (PSQI) is a 18-item self-reported evaluation of sleep quality to distinguish between "good" and "poor" sleepers, and identify significant sleep disturbances of various types. There are an additional five items for evaluating sleep quality, as reported by a bed partner/roommate. The PSQI total score is a sum of the 18 items (range 0 to 21, higher scores mean a worse outcome).	PSQI at baseline and annually through study completion, an average of 5 years
Brief Pittsburgh Sleep Quality Index	The Brief Pittsburgh Sleep Quality Index (B-PSQI) is a 6-item self-reported evaluation of sleep quality to distinguish between "good" and "poor" sleepers, and identify significant sleep disturbances of various types. The B-PSQI total score is a sum of the 6 items (range 0 to 21, higher scores mean a worse outcome).	B-PSQI monthly through study completion (except at baseline and annually when the 18-item PSQI [see above] will be used), an average of 5 years
STOP-Bang	The STOP-Bang questionnaire will be used as a screening instrument for obstructive sleep apnea. It uses a yes/no checklist for snoring, tiredness, observed apnea, high blood pressure, BMI, age, neck circumference, and gender (male sex). Scores on the STOP-Bang range from 0 to 8 (higher scores mean a worse outcome) with ≥3 indicating a positive screening.	At baseline and annually through study completion, an average of 5 years
Neck Disability Index	The Neck Disability Index (NDI) is a 10-item self-reported evaluation that measures how neck pain impacts daily life and the level of self-perceived disability in individuals with neck pain. The NDI total score is a sum of the 10 items (range 0 to 50, higher scores mean a worse outcome).	At baseline and annually through study completion, an average of 5 years
PTSD Checklist for DSM-5 (PCL-5)	The PTSD Checklist for DSM-5 (PCL-5) is a 20-item self-report instrument designed to evaluate the 20 symptoms of PTSD as outlined in the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5). The PCL-5 total score is a sum of the 20 items (range 0 to 80, higher scores mean a worse outcome).	At baseline and annually through study completion, an average of 5 years
General Anxiety Disorder (GAD-7)	The General Anxiety Disorder (GAD-7) is a 7-item assessment for identifying likely cases of generalized anxiety disorder. The GAD-7 total score is a sum of the 7 items (range 0 to 21, higher scores mean a worse outcome).	At baseline and annually through study completion, an average of 5 years
Patient Health Questionnaire (PHQ-9)	The Patient Health Questionnaire (PHQ-9) is a 9-item assessment for evaluating the presence and severity of depressive symptoms. The PHQ-9 total score is a sum of the 9 items (range 0 to 27, higher scores mean a worse outcome).	At baseline and annually through study completion, an average of 5 years
Quality of Life after Brain Injury (QOLIBRI)	The Quality of Life after Brain Injury (QOLIBRI) evaluates health-related quality of life in individuals following TBI, incorporating the individual's perspective on their health, functioning, and well-being. The QOLIBRI consists of 37 items divided into four scales: Cognition, Self, Daily Life and Autonomy, and Social Relationships. The QOLIBRI total score is a sum of the 37 items (range 0 to 100, higher scores mean a better outcome).	At baseline and annually through study completion, an average of 5 years
Caffeine Consumption Questionnaire - Revised	The Caffeine Consumption Questionnaire - Revised is a six-page self-report measure to estimate caffeine consumption. This outcome measure can be scored in three ways: a conservative estimate using minimum caffeine concentration values, a mean estimate based on average concentrations, and a liberal estimate using maximum concentration values.	At baseline and weekly through study completion, an average of 5 years
Supplement Frequency Questionnaire	The Supplement Frequency Questionnaire is a one-page survey that assesses supplement use across 16 categories over the past year. The 16 categories are: multivitamins (one-a-day, B-complex, antioxidant); vitamins A, C, E, B-12, and D; beta-carotene; folic acid; calcium; selenium; iron; zinc; fish oil/omega-3 fatty acids; and garlic. This outcome measure can be scored by calculating total nutrient intake for each nutrient from supplements by multiplying frequency × duration × default dose.	At baseline and annually through study completion, an average of 5 years
Alcohol Use Disorders Identification Test - Consumption (AUDIT-C)	The Alcohol Use Disorders Identification Test - Consumption (AUDIT-C) is a screening tool used to identify hazardous drinking and potential alcohol use disorders. The AUDIT-C total score is a sum of the 3 items (range 0 to 12, higher scores mean a worse outcome).	At baseline and annually through study completion, an average of 5 years
Penn State Cigarette Dependence Index	The Penn State Cigarette Dependence Index is a 10-item measure of nicotine dependence. The Penn State Cigarette Dependence Index total score is a sum of the 10 items (range 0 to 20, higher scores mean a worse outcome).	At baseline and annually through study completion, an average of 5 years
Penn State Electronic Cigarette Dependence Index	The Penn State Electronic Cigarette Dependence Index is a 10-item measure of nicotine dependence. The Penn State Electronic Cigarette Dependence Index total score is a sum of the 10 items (range 0 to 20, higher scores mean a worse outcome).	At baseline and annually through study completion, an average of 5 years
Penn State Nicotine Pouch Dependence Index	The Penn State Nicotine Pouch Dependence Index is a 10-item measure of nicotine dependence. The Penn State Nicotine Pouch Dependence Index total score is a sum of the 10 items (range 0 to 20, higher scores mean a worse outcome).	At baseline and annually through study completion, an average of 5 years
Military Acute Concussion Evaluation 2 (MACE2)	The Military Acute Concussion Evaluation 2 (MACE2) is the standard of care for concussion screening and diagnosis in the military, and consists of: description of incident (potentially concussive event); alteration of consciousness or memory; symptoms; history of concussion, headache disorder or migraine, depression, anxiety, or other behavioral health concerns; cognitive exam; neurological exam; and Vestibular/Ocular Motor Screening (VOMS; see below). The MACE2's multiple measurements will be aggregated to arrive at one reported value - positive or negative.	At baseline and annually through study completion, an average of 5 years
Military Acute Concussion Evaluation 2 (MACE2) with embedded Vestibular/Ocular Motor Screening (VOMS)	The Vestibular/Ocular Motor Screening (VOMS) is a brief clinical screening tool (<5 minutes) for vestibular and ocular motor symptoms and impairment after concussion and consists of seven items: smooth pursuits, horizontal saccades, vertical saccades, near-point convergence (NPC), horizontal vestibulo-ocular reflex (VOR), vertical VOR, and visual motion sensitivity. The VOMS' multiple measurements will be aggregated to arrive at one reported value - positive or negative.	At baseline and annually through study completion, an average of 5 years
Sway mobile device application	The Sway mobile device application (Sway Medical, Inc., Tulsa, OK) will be used to assess symptoms, cognition, and balance. Sway's multiple measurements will be aggregated to arrive at one reported value - positive or negative.	At baseline and weekly through study completion, an average of 5 years
COncussion BALance Test (COBALT)	Subjects will undergo COncussion BALance Test (COBALT) (Bertec Corporation, Columbus, OH) testing. Each of the eight conditions in the manufacturer's research-only protocol will be performed for two 20-sec trials during which errors will be recorded by the clinician and sway velocity will be recorded by the force plate. The COBALT's multiple measurements will be aggregated to arrive at two reported values - sway velocity and number of errors.	At baseline and quarterly through study completion, an average of 5 years
King-Devick Test	The King-Devick Test (King-Devick technologies, inc., Oak Brook, IL) is a short, timed assessment in which subjects rapidly read aloud single-digit numbers.	At baseline and weekly through study completion, an average of 5 years
EYE-SYNC®	The EYE-SYNC® (NeuroSync, Inc., Holliston, MA) will be used to administer the Vestibular/Ocular Motor Screening, as well as pro-saccades and anti-saccades.	At baseline and annually through study completion, an average of 5 years
PLR®-4000	The PLR®-4000 (NeurOptics, Inc., Irving, CA) will be used to measure pupil size and pupillary reactivity. Eight measurements from the device (maximum diameter, minimum diameter, percent change, latency of constriction, constriction velocity, maximum constriction velocity, dilation velocity, and time to reach 75% recovery) will be aggregated to arrive at one reported value - normal or abnormal (in comparison to published normative data).	At baseline and annually through study completion, an average of 5 years
Automated Neuropsychological Assessment Metrics (v4) Military Expanded	The Military Battery consists of Participant Information (military demographics), Sleepiness Scale, TBI Questionnaire, Mood Scale, Simple Reaction Time, Code Substitution - Learning, Procedural Reaction Time, Mathematical Processing, Matching to Sample, Code Substitution - Delayed, and Simple Reaction Time (Repeated) modules. The ANAM's multiple measurements will be aggregated to arrive at one reported value - normal or abnormal (in comparison to published normative data stratified by age [5-year increments], gender, race/ethnicity and education).	At baseline and annually through study completion, an average of 5 years
Wechsler Abbreviated Scale of Intelligence - Second Edition (WASI-II)	The Wechsler Abbreviated Scale of Intelligence - Second Edition (WASI-II) is a rapid (approximately 30-minute) assessment of cognitive functioning. A composite score, the Full Scale IQ-4 Subtest (FSIQ-4), ranges from "Very Superior" (≥130) to "Extremely Low/Impaired" (<70) and higher scores mean a better outcome.	At baseline and annually through study completion, an average of 5 years
Videonystagmography (VNG) / oculomotor and vestibular function testing	Subjects will undergo videonystagmography (VNG) / oculomotor and vestibular function testing (smooth pursuit, horizontal and vertical saccades, caloric testing, ocular and cervical vestibular-evoked myogenic potentials [oVEMP and cVEMP]) performed by a Research Audiologist. The results of this battery of testing will be aggregated to arrive at one reported value - normal or abnormal (in comparison to published normative data).	At baseline and annually through study completion, an average of 5 years
Video Head Impulse (vHIT)	Subjects will undergo video Head Impulse Test (vHIT) testing with the ICS® Impulse (Natus; Middleton, WI). This is a standard clinical test of the semicircular canals. Vestibulo-ocular reflex gain will be determined using the ratio of the area under the curve of eye velocity relative to the area under the curve of head velocity (after saccade traces are removed) from onset to offset of head velocity.	At baseline and annually through study completion, an average of 5 years
Wireless Automated Hearing Test System (WAHTS)	Subjects will undergo Wireless Automated Hearing Test System (WAHTS) (WAHTS Hearing LLC; Lebanon, NH) portable, wireless audiometry testing.	At baseline and annually through study completion, an average of 5 years

Other Outcome Measures

Outcome Measure	Measure Description	Time Frame
quantitative EEG via the NeuroCatch®	Cognition will be explored using quantitative EEG via the NeuroCatch® (NeuroCatch Inc., Canada) brain vital sign framework. This framework includes three event-related brain potentials (ERPs): auditory N100 (auditory sensation), auditory oddball P300 (basic attention), and auditory speech processing N400 (cognitive processing). NeuroCatch's multiple measurements will be aggregated to arrive at one reported value - normal or abnormal.	At baseline and quarterly through study completion, an average of 5 years
Blast sensor-measurement of blast exposure(s)	Subjects will wear blast sensors continuously during training for the duration of their study participation. The blast sensors' multiple measurements will be aggregated to arrive at one reported value - total exposure (number of exposure events exceeding 4psi).	Daily through study completion, an average of 5 years
Self-report of blast exposure(s)	Self-report of environment (i.e., indoor/outdoor, under overhang, etc.), role (shooter/breacher, observer, instructor), position (i.e., prone supported, prone unsupported, kneeling, standing, etc.), weapon (i.e., make/model, caliber, etc.), number of rounds, date/time, and duration of training will also be collected on training days. The questionnaire-based self-report of blast exposure(s) will be aggregated to arrive at one reported value - estimated total exposure (number of exposure events).	Daily through study completion, an average of 5 years

Collaborators and Investigators

• Sponsor: Uniformed Services University of the Health Sciences
• Collaborators: The Geneva Foundation; MIT Lincoln Laboratory
• Investigators: Principal Investigator: Tony T Yuan, PhD, Uniformed Services University of the Health Sciences; Study Chair: Vincent B Ho, MD, Uniformed Services University of the Health Sciences

Study record dates

Study Major Dates

• Study Start (Estimated): May 1, 2026
• Primary Completion (Estimated): August 1, 2030
• Study Completion (Estimated): August 1, 2030

Study Registration Dates

• First Submitted: March 24, 2026
• First Submitted That Met QC Criteria: May 18, 2026
• First Posted (Actual): May 26, 2026

Study Record Updates

• Last Update Posted (Actual): May 26, 2026
• Last Update Submitted That Met QC Criteria: May 18, 2026
• Last Verified: March 1, 2026

More Information

Terms related to this study

• Keywords: magnetic resonance imaging; traumatic brain injury; concussion; blast overpressure; repeated blast exposure; low-level blast exposure
• Additional Relevant MeSH Terms: Brain Diseases; Central Nervous System Diseases; Nervous System Diseases; Wounds and Injuries; Craniocerebral Trauma; Trauma, Nervous System; Head Injuries, Closed; Wounds, Nonpenetrating; Brain Injuries; Brain Injuries, Traumatic; Brain Concussion
• Other Study ID Numbers: 25-21750; HU00012520052 (Other Grant/Funding Number: U.S. Special Operations Command)

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: NO
• IPD Plan Description: Research data may be shared, when permitted by USSOCOM, upon reasonable request to the Principal Investigator.

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No