Impact of repeated blast exposure on active-duty United States Special Operations Forces.

United States (US) Special Operations Forces (SOF) are frequently exposed to explosive blasts in training and combat, but the effects of repeated blast exposure (RBE) on SOF brain health are incompletely understood. Furthermore, there is no diagnostic test to detect brain injury from RBE. As a result, SOF personnel may experience cognitive, physical, and psychological symptoms for which the cause is never identified, and they may return to training or combat during a period of brain vulnerability. In 30 active-duty US SOF, we assessed the relationship between cumulative blast exposure and cognitive performance, psychological health, physical symptoms, blood proteomics, and neuroimaging measures (Connectome structural and diffusion MRI, 7 Tesla functional MRI, [11C]PBR28 translocator protein [TSPO] positron emission tomography [PET]-MRI, and [18F]MK6240 tau PET-MRI), adjusting for age, combat exposure, and blunt head trauma. Higher blast exposure was associated with increased cortical thickness in the left rostral anterior cingulate cortex (rACC), a finding that remained significant after multiple comparison correction. In uncorrected analyses, higher blast exposure was associated with worse health-related quality of life, decreased functional connectivity in the executive control network, decreased TSPO signal in the right rACC, and increased cortical thickness in the right rACC, right insula, and right medial orbitofrontal cortex-nodes of the executive control, salience, and default mode networks. These observations suggest that the rACC may be susceptible to blast overpressure and that a multimodal, network-based diagnostic approach has the potential to detect brain injury associated with RBE in active-duty SOF.

Optimizing Brain Health of United States Special Operations Forces.

United States Special Operations Forces (SOF) personnel are frequently exposed to explosive blasts in training and combat. However, the effects of repeated blast exposure on the human brain are incompletely understood. Moreover, there is currently no diagnostic test to detect repeated blast brain injury (rBBI). In this "Human Performance Optimization" article, we discuss how the development and implementation of a reliable diagnostic test for rBBI has the potential to promote SOF brain health, combat readiness, and quality of life.

Automated neuropsychological assessment metrics (v4) military expanded battery: Normative data for special operations forces.

Objective: The Automated Neuropsychological Assessment Metrics (ANAM) has long been used to assess cognition in military samples before deployment and following injury. The purpose of this study was to explore the effects of various demographic factors on the ANAM4 Military Expanded (ANAM4 ME) performance of Special Operations Forces (SOF) and to provide regression-based normative data for clinicians working with SOF personnel. Method: The sample was a large active duty military sample of SOF and support personnel (n = 24,072) who were tested under a new baseline policy. Results: Performance differences based on demographic variables were generally small. In general, increasing age was associated with significantly worse performance, except on mathematical processing. Higher education level was associated with better performance on most subtests, as expected, but was associated with worse performance on spatial processing. Conclusion: This paper provides regression formulas for calculating adjusted scores based on the most relevant demographic variables, as well as base rates of obtaining one or more clearly above or below average scores across the entire ANAM4 ME battery.

Long-Term Effects of Repeated Blast Exposure in United States Special Operations Forces Personnel: A Pilot Study Protocol.

Emerging evidence suggests that repeated blast exposure (RBE) is associated with brain injury in military personnel. United States (U.S.) Special Operations Forces (SOF) personnel experience high rates of blast exposure during training and combat, but the effects of low-level RBE on brain structure and function in SOF have not been comprehensively characterized. Further, the pathophysiological link between RBE-related brain injuries and cognitive, behavioral, and physical symptoms has not been fully elucidated. We present a protocol for an observational pilot study, Long-Term Effects of Repeated Blast Exposure in U.S. SOF Personnel (ReBlast). In this exploratory study, 30 active-duty SOF personnel with RBE will participate in a comprehensive evaluation of: 1) brain network structure and function using Connectome magnetic resonance imaging (MRI) and 7 Tesla MRI; 2) neuroinflammation and tau deposition using positron emission tomography; 3) blood proteomics and metabolomics; 4) behavioral and physical symptoms using self-report measures; and 5) cognition using a battery of conventional and digitized assessments designed to detect subtle deficits in otherwise high-performing individuals. We will identify clinical, neuroimaging, and blood-based phenotypes that are associated with level of RBE, as measured by the Generalized Blast Exposure Value. Candidate biomarkers of RBE-related brain injury will inform the design of a subsequent study that will test a diagnostic assessment battery for detecting RBE-related brain injury. Ultimately, we anticipate that the ReBlast study will facilitate the development of interventions to optimize the brain health, quality of life, and battle readiness of U.S. SOF personnel.

Low-Level Blast Exposure in Humans A Systematic Review of Acute and Chronic Effects.

There is growing concern that military breaching and training and firing artillery and mortars, grenades, and shoulder-fired weapons may have some type of cumulative deleterious effects. There are anecdotal reports of those with repetitive exposure to low-level blast complaining of various symptoms, as well as increasing empirical evidence. The purpose of this report is to provide a systematic review of the literature on repetitive lowlevel blast as it pertains to military and police training protocols. An extensive literature search was conducted, resulting in detailed review of 18 studies. Results suggest few consistent findings, likely due to the heterogeneity of methods, high risk of bias, and lack of reliance on objective blast-exposure data. Adverse effects, when present, dissipated over time. All studies that used blast gauges found significant associations, though only a subset actually reported using the blast-gauge data (to correlate objective exposure with outcomes). When comparing studies within an outcome domain (e.g., cognitive), findings were largely inconsistent. Research with larger sample sizes, followed longitudinally, is needed.

Hypertrophic cardiomyopathy.

Hypertrophic cardiomyopathy (HCM) is a cardiac disorder affecting 1 in 500 persons. The cardinal feature is (inappropriate) left ventricular hypertrophy in the absence of another identifiable cause. Sudden cardiac death (SCD) is the most devastating and feared complication and may be the presenting manifestation. The striking heterogeneity and unpredictability of HCM make risk stratification problematic and imprecise. Cases must be deferred to the FAA for third- or limited second-class special issuance consideration. In general, first-class and full second-class medical certification is not permitted.

US military smallpox vaccination program: occupational impact of immunizations on aircrew in Air Mobility Command, US Air Force.

CONTEXT: President George W. Bush announced a national smallpox vaccination program (SVP) on December 13, 2002, for military personnel, civilian healthcare workers, and "first responders." The program was intended to protect these individuals against exposure to weaponized smallpox. The US Air Force (USAF) began implementation of the SVP on January 7, 2003. OBJECTIVES: To determine if the SVP affected USAF personnel readiness, and, based on these results, to determine the overall safety of a large-scale SVP. METHODS: A retrospective cohort study of duty-restriction rates measured by duties not to include flying (DNIFs) of C-17 aircrews in the USAF Air Mobility Command (AMC). Data from January 2002 to May 2002 (prevaccination) and January 2003 to May 2003 (vaccination) were compiled by month from three of the 11 AMC bases. Total DNIFs associated with or attributed to the smallpox vaccine were recorded. In addition, total 2003 DNIFs in 1662 study subjects (678 [40.8%] of whom received smallpox vaccination) were recorded and compared with total 2002 DNIFs in 1602 control subjects before SVP implementation. Differences in monthly DNIF rates were calculated using the one-tailed paired t test. RESULTS: In the 678 subjects who received smallpox vaccination, 13 vaccine-related DNIFs (1.9%) occurred. Differences in DNIF rates were statistically significant (P<.05) during 2 months at one AMC base. However, the SVP did not increase overall DNIF rates in the SVP study period. CONCLUSIONS: With DNIF status as a health marker, the SVP did not impose operational constraints or adversely affect aircrew preparedness in the USAF AMC. The authors suggest that a similar SVP with comparable screening measures would indicate the overall safety of the vaccine.