Repeated Low-Level Blast Exposure: A Descriptive Human Subjects Study.

The relationship between repeated exposure to blast overpressure and neurological function was examined in the context of breacher training at the U.S. Marine Corps Weapons Training Battalion Dynamic Entry School. During this training, Students are taught to apply explosive charges to achieve rapid ingress into secured buildings. For this study, both Students and Instructors participated in neurobehavioral testing, blood toxin screening, vestibular/auditory testing, and neuroimaging. Volunteers wore instrumentation during training to allow correlation of human response measurements and blast overpressure exposure. The key findings of this study were from high-memory demand tasks and were limited to the Instructors. Specific tests showing blast-related mean differences were California Verbal Learning Test II, Automated Neuropsychological Assessment Metrics subtests (Match-to-Sample, Code Substitution Delayed), and Delayed Matching-to-Sample 10-second delay condition. Importantly, apparent deficits were paralleled with functional magnetic resonance imaging using the n-back task. The findings of this study are suggestive, but not conclusive, owing to small sample size and effect. The observed changes yield descriptive evidence for potential neurological alterations in the subset of individuals with occupational history of repetitive blast exposure. This is the first study to integrate subject instrumentation for measurement of individual blast pressure exposure, neurocognitive testing, and neuroimaging.

Physical readiness and obesity among male U.S. Navy personnel with limited exercise availability while at sea.

OBJECTIVE: To evaluate differences in physical readiness and obesity in worksites with inherent limitations in exercise availability, utilizing data from U.S. Navy personnel assigned to submarines. METHODS: Cross-sectional study utilizing height, weight, and Physical Readiness Test (PRT) scores of 26,341 individuals assigned to small submarines (SS), large submarines (LS), and aircraft carriers (AC). RESULTS: PRT failure rates were 3.4% (AC), 1.5% (LS), and 2.9% (SS). Prevalence of obesity was 15.1% (AC), 16.9% (LS), and 17.8% (SS). The adjusted prevalence odds ratio of obesity was increased on SS and LS compared to AC, 1.25 (96% CI = 1.14, 1.31) and 1.17 (95% CI = 1.06, 1.29), respectively. CONCLUSIONS: Despite limitations in exercise availability, submarine personnel performance on the PRT was similar to that of AC personnel. Although the prevalence of obesity on submarines was slightly higher, it remains below U.S. nonmilitary comparison data. Although limited access to exercise has the potential for adverse health effects in worker populations, in our cohort of young men, the changes in both physical readiness and obesity were small. Further research on a more diverse group of workers is warranted.

Estimated incidence of multiple sclerosis among United States Armed Forces personnel using the Defense Medical Surveillance System.

BACKGROUND: The comprehensive longitudinal medical records of the U.S. Armed Forces provide a valuable tool to study the epidemiology of multiple sclerosis (MS) in persons from a diverse demography. OBJECTIVE: This study's objectives were to estimate the frequencies, incidence rates (IRs), trends, and correlates of MS among active component U.S. military members from 2000 to 2009. METHODS: An International Classification of Diseases, 9th Revision, code algorithm was used to identify MS cases from the Defense Medical Surveillance System database. IRs were determined by dividing the number of cases of MS by the total person-time of the active component during each year. RESULTS: During the 10-year period, there were 1,827 incident cases of MS with an overall IR of 12.9 per 100,000 person-years (p-yrs). Black non-Hispanics had a higher IR: (18.3 per 100,000 p-yrs) than White non-Hispanics (12.5 per 100,000 p-yrs). The incidence of MS by birth month and geographic home did not show a clear trend of seasonality or latitudinal gradient. CONCLUSIONS: This investigation is the first longitudinal study of MS incidence in U.S. Armed Forces personnel. The study demonstrates higher IRs than seen in other populations and reveals a novel pattern of MS incidence by race.

Headache disorders in the millennium cohort: epidemiology and relations with combat deployment.

OBJECTIVE: Characterize migraine and other headache disorders within a large population-based US military cohort, with an emphasis on the temporal association between military deployment and exposure to combat. BACKGROUND: Little research has been published on the prevalence of headache disorders in the US military population, especially in relation to overseas deployments and exposure to combat. A higher than expected prevalence of migraine has previously been reported among deployed US soldiers in Iraq, suggesting an association. Headache disorders, including migraine, could have important effects on the performance of service members. METHODS: A total of 77,047 US active-duty, Reserve, and National Guard members completed a baseline questionnaire between July 2001 to June 2003 for the Millennium Cohort Study. Headache disorders were assessed using the following survey-based measures: self-reported history of provider-diagnosed migraine, recurrent severe headache within the past year, and recent headaches/bothered a lot within the past 4 weeks. Follow-up surveys were completed on average 3 years after baseline (mean=2.7 years; range=11.4 months to 4.5 years). RESULTS: The overall male and female prevalence of self-reported headache conditions at baseline were: provider-diagnosed migraine, 6.9% and 20.9%, respectively; recurrent severe headache, 9.4% and 22.3%, respectively; and bothered a lot by headaches, 3.4% and 10.4%, respectively. Combat deployers had significantly higher odds of any new-onset headache disorders than non-deployers (adjusted odds ratios=1.72 for men, 1.84 for women; 95% confidence intervals, 1.55-1.90 for men, 1.55-2.18 for women), while deployers without combat exposure did not. CONCLUSIONS: Deployed personnel with reported combat exposure appear to represent a higher risk group for new-onset headache disorders. The identification of populations at higher risk of development of headache provides support for targeted interventions.

Systematic review of military motor vehicle crash-related injuries.

CONTEXT: Motor vehicle crashes account for nearly one third of U.S. military fatalities annually. The objective of this review is to summarize the published evidence on injuries due specifically to military motor vehicle (MMV) crashes. EVIDENCE ACQUISITION: A search of 18 electronic databases identified English language publications addressing MMV crash-related injuries between 1970 and 2006 that were available to the general public. Documents limited in distribution to military or government personnel were not evaluated. Relevant articles were categorized by study design. EVIDENCE SYNTHESIS: The search identified only 13 studies related specifically to MMV crashes. Most were case reports or case series (n=8); only one could be classified as an intervention study. Nine of the studies were based solely on data from service-specific military safety centers. CONCLUSIONS: Few studies exist on injuries resulting from crashes of military motor vehicles. Epidemiologic studies that assess injury rates, type, severity, and risk factors are needed, followed by studies to evaluate targeted interventions and prevention strategies. Interventions currently underway should be evaluated for effectiveness, and those proven effective in the civilian community, such as graduated driver licensing, should be considered for implementation and evaluation in military populations.

Multiple sclerosis presenting as neurological decompression sickness in a U.S. navy diver.

A case of clinically definite multiple sclerosis presenting as neurological decompression sickness is presented. A 23-yr-old U.S. Navy diver experienced onset of hypesthesia of the left upper trunk approximately 19 h after making two SCUBA dives. She did not seek medical attention until 3 wk later, at which time she was diagnosed with possible neurological decompression sickness. She was treated with hyperbaric oxygen, but demonstrated no improvement. Further evaluation led to the diagnosis of multiple sclerosis. This case underscores the potential similarity in neurological presentation between multiple sclerosis and decompression sickness. The differential diagnosis of neurological decompression sickness, particularly in atypical cases, should include multiple sclerosis. The appropriateness of medically clearing multiple sclerosis patients for diving is discussed.