Associations Between Multiple Remote Mild TBIs and Objective Neuropsychological Functioning and Subjective Symptoms in Combat-Exposed Veterans

Repetitive Head Injury and Cognitive, Physical, and Emotional Symptoms in Women Survivors of Intimate Partner Violence

Many women survivors of intimate partner violence (IPV) experience repetitive head injuries in their lifetime, but limited research has examined the cumulative effects of multiple head injuries on post-concussion symptom severity in this population. This study examined how number of lifetime head injuries and episodes of loss of consciousness (LOC) due to head injuries were related to current cognitive, physical, and emotional symptoms among women survivors of IPV. Cisgender women from Kentucky were recruited following a protective order against an intimate partner, including 268 women with no reported lifetime head injuries and 250 women with one or more IPV-related head injuries (mean [M] = 17.2 head injuries, standard deviation [SD] = 50.5, median [Mdn] = 4, range = 1-515; M = 1.8 LOC episodes, SD = 4.3, Mdn = 1, range = 0-35, respectively). Participants underwent in-person interviews about lifetime physical and sexual IPV history, head injury history, and current cognitive, physical, and emotional symptoms. Sociodemographic characteristics, physical and sexual IPV severity, and current symptom severity were examined in relation to number of head injuries and LOC episodes. A higher number of head injuries was associated with greater age, White race, less than high school education, unemployment, and rural residence. No sociodemographic variables differed based on number of LOC episodes. Greater number of lifetime head injuries and LOC episodes correlated significantly with physical IPV severity (rho = 0.35, p < 0.001; rho = 0.33, p < 0.001, respectively) and sexual IPV severity (rho = 0.22, p < 0.001; rho = 0.19, p = 0.003). Greater number of head injuries and LOC episodes correlated significantly with greater cognitive (rho = 0.33, p < 0.001; rho = 0.23, p < 0.001, respectively), physical (rho = 0.36, p < 0.001; rho = 0.31, p < 0.001), emotional (rho = 0.36, p < 0.001; rho = 0.18, p = 0.004), and total symptom severity (rho = 0.39, p < 0.001; rho = 0.26, p < 0.001). In group comparisons, participant groups stratified by number of head injuries (i.e., 0, 1-3, 4+) differed in total symptom severity (p < 0.001, η2 = 0.15), with greater symptom burden associated with more head injuries. Participants with and without LOC differed in symptom severity: cognitive (p < 0.001, d = 0.45), physical (p < 0.001, d = 0.60), emotional (p = 0.004, d = 0.37), and total symptom severity (p < 0.001, d = 0.53). Group differences between participants with and without LOC remained significant after controlling for sociodemographic variables and IPV severity. There was no cumulative effect of LOC, in that participants with 1 LOC episode did not differ from participants with 2 + LOC episodes (p > 0.05). Based on hierarchical regression analyses, only physical symptoms were independently related to number of head injuries (p = 0.008, ΔR2 = 0.011) and number of LOC episodes (p = 0.014, ΔR2 = 0.021) after controlling for sociodemographic characteristics and IPV severity. Among women survivors of IPV, cumulative head injuries appear related to greater symptom severity. Greater head injury history was independently related to worse physical symptoms (e.g., headaches, dizziness, sleep problems), whereas cognitive and emotional symptoms were, in part, attributable to cumulative physical and emotional trauma due to IPV. Women survivors of IPV with repetitive head injuries have unmet neurobehavioral health needs that may benefit from targeted interventions.

Sleep Quality Disturbances Are Associated with White Matter Alterations in Veterans with Post-Traumatic Stress Disorder and Mild Traumatic Brain Injury

Sleep disturbances are strongly associated with mild traumatic brain injury (mTBI) and post-traumatic stress disorder (PTSD). PTSD and mTBI have been linked to alterations in white matter (WM) microstructure, but whether poor sleep quality has a compounding effect on WM remains largely unknown. We evaluated sleep and diffusion magnetic resonance imaging (dMRI) data from 180 male post-9/11 veterans diagnosed with (1) PTSD (n = 38), (2) mTBI (n = 25), (3) comorbid PTSD+mTBI (n = 94), and (4) a control group with neither PTSD nor mTBI (n = 23). We compared sleep quality (Pittsburgh Sleep Quality Index, PSQI) between groups using ANCOVAs and calculated regression and mediation models to assess associations between PTSD, mTBI, sleep quality, and WM. Veterans with PTSD and comorbid PTSD+mTBI reported poorer sleep quality than those with mTBI or no history of PTSD or mTBI (p = 0.012 to <0.001). Poor sleep quality was associated with abnormal WM microstructure in veterans with comorbid PTSD+mTBI (p < 0.001). Most importantly, poor sleep quality fully mediated the association between greater PTSD symptom severity and impaired WM microstructure (p < 0.001). Our findings highlight the significant impact of sleep disturbances on brain health in veterans with PTSD+mTBI, calling for sleep-targeted interventions.

Clinical research findings from the long-term impact of military-relevant brain injury consortium-Chronic Effects of Neurotrauma Consortium (LIMBIC-CENC) 2013-2021

This is a summary of the published research from the 14 observational, longitudinal and big-data, epidemiological studies supported by the LIMBIC-CENC program from 2013-2021 examining the long-term effects of combat-related traumatic brain injury (TBI). Findings from these 43 primary and secondary analyses include: 1) unique fluid, advanced neuroimaging and electrophysiologic biomarkers associated with mild traumatic brain injury (mTBI), number of mTBIs and related dysfunction, 2) increases in a range of chronic difficulties, including neurosensory, sleep, pain, cognitive deficits, behavioral disorders, overall symptom burden, healthcare costs and service-connected disability, associated with mTBI, all-severity traumatic brain injury (TBI), blast exposure, and number of mTBIs, and 3) increases in the risk for suicide and neurodegeneration, including dementia and Parkinson's disease, associated with mTBI and all-severity TBI. Ongoing LIMBIC-CENC longitudinal and epidemiologic research will clarify, confirm and expand upon these findings.

Perspectives on Primary Blast Injury of the Brain: Translational Insights Into Non-inertial Low-Intensity Blast Injury

Most traumatic brain injuries (TBIs) during military deployment or training are clinically "mild" and frequently caused by non-impact blast exposures. Experimental models were developed to reproduce the biological consequences of high-intensity blasts causing moderate to severe brain injuries. However, the pathophysiological mechanisms of low-intensity blast (LIB)-induced neurological deficits have been understudied. This review provides perspectives on primary blast-induced mild TBI models and discusses translational aspects of LIB exposures as defined by standardized physical parameters including overpressure, impulse, and shock wave velocity. Our mouse LIB-exposure model, which reproduces deployment-related scenarios of open-field blast (OFB), caused neurobehavioral changes, including reduced exploratory activities, elevated anxiety-like levels, impaired nesting behavior, and compromised spatial reference learning and memory. These functional impairments associate with subcellular and ultrastructural neuropathological changes, such as myelinated axonal damage, synaptic alterations, and mitochondrial abnormalities occurring in the absence of gross- or cellular damage. Biochemically, we observed dysfunctional mitochondrial pathways that led to elevated oxidative stress, impaired fission-fusion dynamics, diminished mitophagy, decreased oxidative phosphorylation, and compensated cell respiration-relevant enzyme activity. LIB also induced increased levels of total tau, phosphorylated tau, and amyloid β peptide, suggesting initiation of signaling cascades leading to neurodegeneration. We also compare translational aspects of OFB findings to alternative blast injury models. By scoping relevant recent research findings, we provide recommendations for future preclinical studies to better reflect military-operational and clinical realities. Overall, better alignment of preclinical models with clinical observations and experience related to military injuries will facilitate development of more precise diagnosis, clinical evaluation, treatment, and rehabilitation.

Research Letter: PTSD Symptom Severity and Multiple Traumatic Brain Injuries Are Associated With Elevated Memory Complaints in Veterans With Histories of Mild TBI

OBJECTIVE

The evaluation of memory complaints in mild traumatic brain injury (mTBI) remains an important clinical consideration, especially in the context of comorbid psychiatric symptoms such as posttraumatic stress disorder (PTSD). We compared subjective memory complaints in veterans with and without a history of mTBI, examined ratings between those with single versus multiple mTBIs, and investigated associations between memory complaints and PTSD symptom severity.

METHODS

117 outpatient veterans (mTBI: n = 79 [single mTBI: n = 22, multiple mTBI: n = 57], military controls [MCs]: n = 38) completed a TBI history assessment, the Prospective-Retrospective Memory Questionnaire (PRMQ), and the PTSD Checklist-Military Version (PCL-M).

RESULTS

Hierarchical multiple regression showed that greater PCL-M scores significantly predicted elevated PRMQ-Total scores, accounting for 38% of the variance explained (P < .001). mTBI status predicted an additional 5% of variance in memory complaints (P < .01). The multiple-mTBI group endorsed more memory complaints than either MCs (P < .01) or the single-mTBI group (P < .05), who did not differ from MCs (P > .50).

CONCLUSIONS

Comorbid PTSD symptoms are an important factor when considering memory complaints in veterans with a reported history of mTBI. However, independent of comorbid PTSD symptoms, mTBI status-particularly in the context of repetitive neurotrauma-uniquely contributes to memory complaints. Findings suggest that veterans with a history of multiple mTBIs may be a particularly vulnerable group in need of specialized interventions and/or psychoeducation.

Number of Concussions Does Not Affect Treatment Response to Cognitive Rehabilitation Interventions Following Mild TBI in Military Service Members

OBJECTIVE

The study objective was to determine whether number of concussions would affect symptom improvement following cognitive rehabilitation (CR) interventions.

METHOD

Service members (N = 126) with concussion history completed a 6-week randomized control trial of CR interventions. Participants were stratified based on self-reported lifetime concussion frequency. Outcome measures included the Paced Auditory Serial Addition Test (PASAT), the Global Severity Index (GSI) from the Symptom Checklist-90-Revised, and the Key Behaviors Change Inventory (KBCI).

RESULTS

Mixed-model analyses of variance revealed a significant main effect for time on cognitive, psychological, and neurobehavioral functioning. A significant main effect for the number of concussions was observed for GSI and KBCI, but not PASAT. Interactions between the number of concussions and time were not significant for any of the outcome variables.

CONCLUSIONS

Over the 6-week interval, improvements were found for all participants across all outcome measures. Number of concussions did not affect improvements over time.

Poor Parental Supervision Associated With Traumatic Brain Injury and Reactive Aggression in Young Offenders

OBJECTIVE

To establish whether poor parental supervision is associated with head injury and self-reported reactive aggression (ie, aggression in response to perceived provocation or threat) in adolescents in a Young Offender's Institute, by examining correlations between these variables. Understanding this population is important, as they are at a key pivotal age for intervention to prevent lifelong reoffending.

METHODS

Ninety-six male participants aged 16 to 18 years were recruited from a UK Young Offender's Institute. Self-report measures of remembered parenting, reactive aggression, and head injury history were administered during individual interviews.

RESULTS

Seventy-four percent of participants reported having experienced a lifetime traumatic brain injury (TBI), and 46% of participants reported experiencing at least 1 TBI leading to a loss of consciousness (LOC). We found that poor parental supervision, length of LOC following TBI, and self-reported reactive aggression were all positively correlated.

CONCLUSIONS

Findings show that there are correlational relationships between poor parental supervision, length of LOC following lifetime TBI, and higher levels of self-reported reactive aggression. This suggests there may be pathways resulting from poor parental supervision leading to both TBI with LOC, and reactive aggression. We advocate for future research with longitudinal designs and larger samples to examine the nature of these interactions, and to establish whether poor parental supervision is a prospective risk factor for more TBIs leading to LOC, and reactive aggression. This is key to understanding whether parenting interventions could help to reduce the disabling effects of TBI in adolescents, and help to prevent contact with the law.

Blast in Context: The Neuropsychological and Neurocognitive Effects of Long-Term Occupational Exposure to Repeated Low-Level Explosives on Canadian Armed Forces' Breaching Instructors and Range Staff

Currently, there is strong interest within the military to better understand the effects of long-term occupational exposure to repeated low-level blast on health and performance. To gain traction on the chronic sequelae of blast, we focused on breaching—a tactical technique for gaining entry into closed/blocked spaces by placing explosives and maintaining a calculated safe distance from the detonation. Using a cross-sectional design, we compared the neuropsychological and neurocognitive profiles of breaching instructors and range staff to sex- and age-matched Canadian Armed Forces (CAF) controls. Univariate tests demonstrated that breaching was associated with greater post-concussive symptoms (Rivermead Post Concussion Symptoms Questionnaire) and lower levels of energy (RAND SF-36). In addition, breaching instructors and range staff were slower on a test that requires moving and thinking simultaneously (i.e., cognitive-motor integration). Next, using a multivariate approach, we explored the impact of other possible sources of injury, including concussion and prior war-zone deployment on the same outcomes. Concussion history was associated with higher post-concussive scores and musculoskeletal problems, whereas deployment was associated with higher post-concussive scores, but lower energy and greater PTSD symptomatology (using PCL-5). Our results indicate that although breaching, concussion, and deployment were similarly correlated with greater post-concussive symptoms, concussion history appears to be uniquely associated with altered musculoskeletal function, whereas deployment history appears to be uniquely associated with lower energy and risk of PTSD. We argue that the broader injury context must, therefore, be considered when studying the impact of repetitive low-level explosives on health and performance in military members.