Risk for broad-spectrum neuropsychiatric disorders after mild traumatic brain injury in a cohort of US Air Force personnel.

BACKGROUND: Military personnel are at increased risk for traumatic brain injury (TBI) from combat and non-combat exposures. Sequelae of moderate-to-severe TBI are well described, but the literature remains conflicted regarding whether mild TBI (mTBI) results in lasting brain injury and functional impairments. This study assessed risk for a range of neuropsychiatric disorders presenting after mTBI while adjusting for the potential confounds of depression and post-traumatic stress disorder (PTSD). METHODS: A historical prospective association study was conducted utilising electronic demographic, medical and military-specific data for over 49,000 active duty US Air Force service members (Airmen). This study utilised diagnostic codes considered by an expert panel to be indicative of mTBI to identify cases. Cox proportional hazards modelling calculated HRs for neuropsychiatric outcomes while controlling for varying lengths of follow-up and potentially confounding variables. RESULTS: Airmen with mTBI were at increased risk for specific neuropsychiatric disorders compared with a similarly injured non-mTBI control group. HRs for memory loss/amnesia, cognitive disorders, schizophrenia, PTSD, and depression were significantly elevated and remained so for at least 6 months post-mTBI, even after eliminating those with previous neuropsychiatric diagnoses. CONCLUSIONS: mTBI was positively associated with neuropsychiatric disorders in this population of primarily young adult males; with increased HRs 6 months post-mTBI. The results support that mTBI is distinguished from moderate-to-severe TBI in terms of risk for developing neuropsychiatric disorders. Further, these findings suggest the importance of screening for psychiatric and cognitive disorders post-mTBI in general medical practice.

Neurologically-related sequelae associated with mild traumatic brain injury.

OBJECTIVE: Mild traumatic brain injury (mTBI) accounts for more than 75% of traumatic brain injuries every year. This study examines the temporal association between non-blast mTBI and the onset of neurologic sequelae to illuminate risks of post-concussive syndrome, epilepsy and chronic pain. METHODS: A large historical prospective study was conducted utilizing electronically-recorded demographic, medical and military-specific data for over half a million active duty US Air Force Airmen. This study utilized diagnostic codes to identify mTBI exposures, two control groups and three post-mTBI time periods. Adjusted hazard ratios (HRs) were calculated using Cox proportional hazards modelling. RESULTS: HRs were higher when mTBI exposed Airmen were compared with the full cohort and lower when compared with the other injured group. When compared to the other injured group, mTBI was positively associated with epilepsy/recurrent seizure outcomes, post-concussive syndrome and pain disorders. HRs tended to be highest within the first 30 days and decreased over time. CONCLUSIONS: Findings support that mTBI may have a prolonged neurological impact. Findings are also likely generalizable to young adult populations with exposure to non-blast related mTBI, including civilians, as those included in this study were young adults with a high prevalence of recreational/sports and motor vehicle injuries.

Airmen with mild traumatic brain injury (mTBI) at increased risk for subsequent mishaps.

BACKGROUND: Little is known regarding long-term performance decrements associated with mild Traumatic Brain Injury (mTBI). The goal of this study was to determine if individuals with an mTBI may be at increased risk for subsequent mishaps. METHODS: Cox proportional hazards modeling was utilized to calculate hazard ratios for 518,958 active duty U.S. Air Force service members (Airmen) while controlling for varying lengths of follow-up and potentially confounding variables. Two non-mTBI comparison groups were used; the second being a subset of the original, both without head injuries two years prior to study entrance. RESULTS: Hazard ratios indicate that the causes of increased risk associated with mTBI do not resolve quickly. Additionally, outpatient mTBI injuries do not differ from other outpatient bodily injuries in terms of subsequent injury risk. CONCLUSIONS: These findings suggest that increased risk for subsequent mishaps are likely due to differences shared among individuals with any type of injury, including risk-taking behaviors, occupations, and differential participation in sports activities. Therefore, individuals who sustain an mTBI or injury have a long-term risk of additional mishaps. PRACTICAL APPLICATIONS: Differences shared among those who seek medical care for injuries may include risk-taking behaviors (Cherpitel, 1999; Turner & McClure, 2004; Turner, McClure, & Pirozzo, 2004), occupations, and differential participation in sports activities, among others. Individuals with an mTBI should be educated that they are at risk for subsequent injury. Historical data supported no lingering effects of mTBI, but more recent data suggest longer lasting effects. This study further adds that one of the longer term sequelae of mTBI may be an increased risk for subsequent mishap.

Risk for addiction-related disorders following mild traumatic brain injury in a large cohort of active-duty U.S. airmen.

OBJECTIVE: Military personnel are at increased risk for traumatic brain injury (TBI) from combat and noncombat exposures. The sequelae of moderate to severe TBI are well described, but little is known regarding long-term performance decrements associated with mild TBI. Furthermore, while alcohol and drug use are well known to increase risk for TBI, little is known regarding the reverse pattern. The authors sought to assess possible associations between mild TBI and addiction-related disorders in active-duty U.S. military personnel. METHOD: A historical prospective study was conducted using electronically recorded demographic, medical, and military data for more than a half million active-duty U.S. Air Force service members. Cases were identified by ICD-9-CM codes considered by an expert panel to be indicative of mild TBI. Outcomes included ICD-9-CM diagnoses of selected addiction-related disorders. Cox proportional hazards modeling was used to calculate hazard ratios while controlling for varying lengths of follow-up and potential confounding variables. RESULTS: Airmen with mild TBI were at increased risk for certain addiction-related disorders compared with a similarly injured non-mild TBI comparison group. Hazards for alcohol dependence, nicotine dependence, and nondependent abuse of drugs or alcohol were significantly elevated, with a consistent decrease over time. CONCLUSIONS: A novel finding of this study was the initial increased risk for addiction-related disorders that decreased with time, thus eroding war fighter performance in a military population. Moreover, these results suggest that mild TBI is distinguished from moderate to severe TBI in terms of timing of the risk, indicating that there is a need for screening and prevention of addiction-related disorders in mild TBI. Screening may be warranted in military troops as well as civilians at both short- and long-term milestones following mild TBI.

Civil engineering airman at increased risk for injuries and injury-related musculoskeletal disorders.

BACKGROUND: With the advent of electronic records, the opportunity to conduct research on workplace-related injuries and musculoskeletal disorders has increased dramatically. The purpose of this study was to examine the United States Air Force Civil Engineering career field to determine if they are negatively impacted by their work environment. Specifically, the objective of this study was to determine if enlisted Civil Engineering Airmen (n = 25,385) were at increased risk for injury or injury-related musculoskeletal disorders compared to enlisted Information Management/Communications Airmen (n = 28,947). METHODS: Using an historical prospective design, electronic data were assembled and analyzed using Cox's proportional hazards modeling. Models were stratified by gender and adjusted for race/ethnicity, marital status, birth year, and deployment status. RESULTS: Male Civil Engineers were observed to be at greater risk for both inpatient injury-related musculoskeletal disorders (HR = 1.86; 95% CI = 1.54-2.26) and injuries (HR = 1.77; 95% CI = 1.48-2.11), while female Civil Engineers were more than double the risk for both inpatient injury-related musculoskeletal disorders (HR = 2.18; 95% CI = 1.28-3.73) and injuries (HR = 2.22; 95% CI = 1.27-3.88) compared to Information Management/Communications Airmen. CONCLUSIONS: Although analyses do not allow exploration of specific causes, they highlight the utility of using electronic data to identify occupations for further evaluation. Based on these results, additional resources were allocated to survey Civil Engineers on their physical work demands and job requirements to identify key problem areas for further study and mitigation.

Aircraft type and other risk factors for spinal disorders: data from 19,673 military cockpit aircrew.

INTRODUCTION: Many assume that exposure to flight in high-performance aircraft (HPA) or rotary wing aircraft (RWA) increases the risk of spinal disorders compared to other fixed wing aircraft (FWA). However, this association has yet to be confirmed. This study explores the relationship between flight in different aircraft and the development of lumbar and cervical spine disorders. METHODS: The flight records of 19,673 U.S. Air Force (USAF) cockpit aircrew officers were examined for entries with a spinal disorder diagnosis in an existing aircrew health information database. Univariate and multivariate analyses were employed to examine the association between aircraft type, other variables, and spinal disorders. RESULTS: In stratified analysis of HPA and FWA, but not RWA categories, statistically significant unadjusted associations were observed between flight hours and cervical [HPA: odds ratio (OR) = 2.80, FWA: OR = 4.73] and lumbar disorders (HPA: OR = 2.46, FWA: OR = 3.01). After adjustment for birth year in a stratified multivariate analysis, these associations were no longer statistically significant. In all three aircraft types, statistically significant adjusted associations were observed between older birth year category and both cervical (HPA: OR = 3.82, FWA: OR = 5.88) and lumbar disorders (HPA: OR = 4.16, RWA: OR = 2.96, FWA: OR = 2.39). DISCUSSION: The risk produced by exposure to HPA, RWA, or FWA as measured by flight hours may be overshadowed by that produced by birth year, which was the strongest predictor for spinal disorders in this study. Future endeavors should more closely examine the association between age and accrual of flight hours in various aircraft types in order to accurately direct preventive measures.

Fatigue and stimulant use in military fighter aircrew during combat operations.

INTRODUCTION: Fatigue in military aviation is a significant safety and operational problem resulting in diminished alertness and performance. Research demonstrates that stimulant medications maintain alertness and performance in sleep-deprived aircrew. However, these studies control many of the variables present during combat operations. Few studies have evaluated fatigue or the factors and effects associated with stimulant use in fighter aircrew during combat operations. METHODS: The study consisted of three questionnaires administered to 29 deployed F-1 5E aircrew participants. An initial questionnaire compiled demographic and sleep behavior data. Pre- and postflight questionnaires for each sortie collected substance use, fatigue, and physical symptoms data. Regression analysis identified variables associated with in-flight stimulant use. RESULTS: Surveys were completed for 111 sorties averaging 7.6 h in duration. Stimulants were used on 35% of sorties an average of 2.8 h after takeoff. Stimulant use was associated with a decrease in in-flight and postflight fatigue without significant differences in postflight symptoms. Sorties airborne during the circadian trough, longer sortie durations, and preflight hypnotic use displayed statistically significant associations with in-flight stimulant use. CONCLUSIONS: In-flight stimulants decrease fatigue during combat operations without significant postflight symptoms. During combat, stimulants were used earlier, at lower doses, and on shorter sorties than previously thought. The factors associated with stimulant use are potentially modifiable by improving training and aircrew scheduling practices. Furthermore, current policies authorizing stimulant use, based primarily on sortie duration, should also consider hypnotic use, inconsistent aircrew scheduling, and circadian disruption.