Mild traumatic brain injuries with loss of consciousness are associated with increased inflammation and pain in military personnel

Acute limbic system connectivity predicts chronic cognitive function in mild traumatic brain injury: An individualized differential structural covariance network study

Mild traumatic brain injury (mTBI) is a known risk factor for neurodegenerative diseases, yet the precise pathophysiological mechanisms remain poorly understand, often obscured by group-level analysis in non-invasive neuroimaging studies. Individual-based method is critical to exploring heterogeneity in mTBI. We recruited 80 mTBI patients and 40 matched healthy controls, obtaining high-resolution structural MRI for constructing Individual Differential Structural Covariance Networks (IDSCN). Comparisons were conducted at both the individual and group levels. Connectome-based Predictive Modeling (CPM) was applied to predict cognitive performance based on whole-brain connectivity. During the acute stage of mTBI, patients exhibited significant heterogeneity in the count and direction of altered edges, obscured by group-level analysis. In the chronic stage, the number of altered edges decreased and became more consistent, aligning with clinical observations of acute cognitive impairment and gradual improvement. Subgroup analysis based on loss of consciousness/post-traumatic amnesia revealed distinct patterns of alterations. The temporal lobe, particularly regions related to the limbic system, significantly predicted cognitive function from acute to chronic stage. The use of IDSCN and CPM has provided valuable individual-level insights, reconciling discrepancies from previous studies. Additionally, the limbic system may be an appropriate target for future intervention efforts.

Sex Differences in Postinjury Health Profiles Among U.S. Military Personnel Following Deployment-Related Concussion

Background: Women in the U.S. military are now authorized to serve in direct combat occupations. This may increase their risk of combat injuries, such as concussion, in future conflicts. Knowledge of sex differences in health profiles after concussion is paramount for military medical planning efforts. The purpose of this study was to assess sex-related differences in health profiles among U.S. military personnel following deployment-related concussion. Materials and Methods: We conducted a retrospective study of service members who sustained a concussion during combat deployment between 2004 and 2013. Postinjury diagnoses were abstracted from outpatient encounters in electronic health records for 24 months after concussion. We used hierarchical clustering to identify clusters, termed "health profiles," and logistic regression to determine whether sex predicted membership in the health profiles. Results: The study sample included 346 women and 4536 men with deployment-related concussion. Five postinjury health profiles were identified and classified as no morbidity, back pain, tinnitus/memory loss, posttraumatic stress disorder/postconcussion syndrome, and multimorbidity. Women relative to men had higher odds of membership in the back pain (odds ratio [OR] = 1.32; 95% confidence interval [CI] = 1.05-1.67) and multimorbidity profiles (OR = 1.44; 95% CI = 1.03-2.00) and lower odds than men in the tinnitus/memory loss profile (OR = 0.62; 95% CI = 0.42-0.91). Conclusions: Postinjury health profiles among U.S. service members differ by sex following deployment-related concussion, particularly with a higher burden of multimorbidity among women than men, which may require interdisciplinary care. Women also had higher odds of membership in the back pain profile and lower odds in the tinnitus/memory loss profile than men. To prepare for future military operations where women may have greater exposure to combat, continued research elucidating health-related sex differences after deployment-related concussion is imperative.

Associations of Chronic Pain With Psychosocial Outcomes After Traumatic Brain Injury: A NIDILRR and VA TBI Model Systems Collaborative Project

OBJECTIVE

To examine the differences in participation, life satisfaction, and psychosocial outcomes among individuals with traumatic brain injury (TBI) endorsing current, past, or no chronic pain.

SETTING

Community.

PARTICIPANTS

Three thousand eight hundred four TBI Model Systems participants 1 to 30 years of age postinjury classified into 1 of 3 groups based on their pain experience: current pain, past pain, no pain completed a Pain Survey at their usual follow-up appointment which on average was approximately 8 years postinjury.

DESIGN

Multisite, cross-sectional observational cohort study.

MAIN OUTCOME MEASURES

Sociodemographic and injury characteristics and psychosocial outcomes (ie, satisfaction with life, depression, anxiety, posttraumatic stress disorder [PTSD], sleep quality, community participation).

RESULTS

Persons with current chronic pain demonstrated higher scores on measures of PTSD, anxiety, and depression, and the lower scores on measures of sleep quality, community participation and satisfaction with life. Those with resolved past pain had mean scores for these outcomes that were all between the current and no chronic pain groups, but always closest to the no pain group. After adjusting for sociodemographic and function in multivariate analysis, having current chronic pain was associated with more negative psychosocial outcomes. The largest effect sizes (ES; in absolute value) were observed for the PTSD, depression, anxiety, and sleep quality measures (ES = 0.52-0.81) when comparing current pain to past or no pain, smaller ES were observed for life satisfaction (ES = 0.22-0.37) and out and about participation (ES = 0.16-0.18). When comparing past and no pain groups, adjusted ES were generally small for life satisfaction, PTSD, depression, anxiety, and sleep quality (ES = 0.10-0.23) and minimal for participation outcomes (ES = 0.02-0.06).

CONCLUSIONS

Chronic pain is prevalent among individuals with TBI and is associated with poorer psychosocial outcomes, especially for PTSD, depression, anxiety, and sleep disturbance. The results from this study highlight the presence of modifiable comorbidities among those with chronic pain and TBI. Persons who experience persistent pain following TBI may be at greater risk for worse psychosocial outcomes.

Immunity impacts cognitive deficits across neurological disorders

Cognitive deficits are a common comorbidity with neurological disorders and normal aging. Inflammation is associated with multiple diseases including classical neurodegenerative dementias such as Alzheimer's disease (AD) and autoimmune disorders such as multiple sclerosis (MS), in which over half of all patients experience some form of cognitive deficits. Other degenerative diseases of the central nervous system (CNS) including frontotemporal lobe dementia (FTLD), and Parkinson's disease (PD) as well as traumatic brain injury (TBI) and psychological disorders like major depressive disorder (MDD), and even normal aging all have cytokine-associated reductions in cognitive function. Thus, there is likely commonality between these secondary cognitive deficits and inflammation. Neurological disorders are increasingly associated with substantial neuroinflammation, in which CNS-resident cells secrete cytokines and chemokines such as tumor necrosis factor (TNF)α and interleukins (ILs) including IL-1β and IL-6. CNS-resident cells also respond to a wide variety of cytokines and chemokines, which can have both direct effects on neurons by changing the expression of ion channels and perturbing electrical properties, as well as indirect effects through glia-glia and immune-glia cross-talk. There is significant overlap in these cytokine and chemokine expression profiles across diseases, with TNFα and IL-6 strongly associated with cognitive deficits in multiple disorders. Here, we review the involvement of various cytokines and chemokines in AD, MS, FTLD, PD, TBI, MDD, and normal aging in the absence of dementia. We propose that the neuropsychiatric phenotypes observed in these disorders may be at least partially attributable to a dysregulation of immunity resulting in pathological cytokine and chemokine expression from both CNS-resident and non-resident cells.

Neuroinflammation Profiling of Brain Cytokines Following Repeated Blast Exposure

Due to use of explosive devices and heavy weapons systems in modern conflicts, the effect of BW on the brain and body is of increasing concern. These exposures have been commonly linked with neurodegenerative diseases and psychiatric disorders in veteran populations. A likely neurobiological link between exposure to blasts and the development of neurobehavioral disorders, such as depression and PTSD, could be neuroinflammation triggered by the blast wave. In this study, we exposed rats to single or repeated BW (up to four exposures-one per day) at varied intensities (13, 16, and 19 psi) to mimic the types of blast exposures that service members may experience in training and combat. We then measured a panel of neuroinflammatory markers in the brain tissue with a multiplex cytokine/chemokine assay to understand the pathophysiological process(es) associated with single and repeated blast exposures. We found that single and repeated blast exposures promoted neuroinflammatory changes in the brain that are similar to those characterized in several neurological disorders; these effects were most robust after 13 and 16 psi single and repeated blast exposures, and they exceeded those recorded after 19 psi repeated blast exposures. Tumor necrosis factor-alpha and IL-10 were changed by 13 and 16 psi single and repeated blast exposures. In conclusion, based upon the growing prominence of negative psychological health outcomes in veterans and soldiers with a history of blast exposures, identifying the molecular etiology of these disorders, such as blast-induced neuroinflammation, is necessary for rationally establishing countermeasures and treatment regimens.

Inflammatory cytokines associated with mild traumatic brain injury and clinical outcomes: a systematic review and meta-analysis

Mild traumatic brain injuries (mTBIs) trigger a neuroinflammatory response, which leads to perturbations in the levels of inflammatory cytokines, resulting in a distinctive profile. A systematic review and meta-analysis were conducted to synthesize data related to levels of inflammatory cytokines in patients with mTBI. The electronic databases EMBASE, MEDLINE, and PUBMED were searched from January 2014 to December 12, 2021. A total of 5,138 articles were screened using a systematic approach based on the PRISMA and R-AMSTAR guidelines. Of these articles, 174 were selected for full-text review and 26 were included in the final analysis. The results of this study demonstrate that within 24 hours, patients with mTBI have significantly higher levels of Interleukin-6 (IL-6), Interleukin-1 Receptor Antagonist (IL-1RA), and Interferon-γ (IFN-γ) in blood, compared to healthy controls in majority of the included studies. Similarly one week following the injury, patients with mTBI have higher circulatory levels of Monocyte Chemoattractant Protein-1/C-C Motif Chemokine Ligand 2 (MCP-1/CCL2), compared to healthy controls in majority of the included studies. The results of the meta-analysis also confirmed these findings by demonstrating significantly elevated blood levels of IL-6, MCP-1/CCL2, and Interleukin-1 beta (IL-1β) in the mTBI population compared to healthy controls (p < 0.0001), particularly in the acute stages (<7 days). Furthermore, it was found that IL-6, Tumor Necrosis Factor-alpha (TNF-α), IL-1RA, IL-10, and MCP-1/CCL2 were associated with poor clinical outcomes following the mTBI. Finally, this research highlights the lack of consensus in the methodology of mTBI studies that measure inflammatory cytokines in the blood, and also provides direction for future mTBI research.

Loss of Consciousness and Righting Reflex Following Traumatic Brain Injury: Predictors of Post-Injury Symptom Development (A Narrative Review)

Identifying predictors for individuals vulnerable to the adverse effects of traumatic brain injury (TBI) remains an ongoing research pursuit. This is especially important for patients with mild TBI (mTBI), whose condition is often overlooked. TBI severity in humans is determined by several criteria, including the duration of loss of consciousness (LOC): LOC < 30 min for mTBI and LOC > 30 min for moderate-to-severe TBI. However, in experimental TBI models, there is no standard guideline for assessing the severity of TBI. One commonly used metric is the loss of righting reflex (LRR), a rodent analogue of LOC. However, LRR is highly variable across studies and rodents, making strict numeric cutoffs difficult to define. Instead, LRR may best be used as predictor of symptom development and severity. This review summarizes the current knowledge on the associations between LOC and outcomes after mTBI in humans and between LRR and outcomes after experimental TBI in rodents. In clinical literature, LOC following mTBI is associated with various adverse outcome measures, such as cognitive and memory deficits; psychiatric disorders; physical symptoms; and brain abnormalities associated with the aforementioned impairments. In preclinical studies, longer LRR following TBI is associated with greater motor and sensorimotor impairments; cognitive and memory impairments; peripheral and neuropathology; and physiologic abnormalities. Because of the similarities in associations, LRR in experimental TBI models may serve as a useful proxy for LOC to contribute to the ongoing development of evidence-based personalized treatment strategies for patients sustaining head trauma. Analysis of highly symptomatic rodents may shed light on the biological underpinnings of symptom development after rodent TBI, which may translate to therapeutic targets for mTBI in humans.

Deployment-related concussion and long-term health-related quality of life among US military personnel

PURPOSE

To examine the relationship between deployment-related concussion and long-term health-related quality of life (HRQoL) among injured US military personnel.

METHODS

The study sample included 810 service members with deployment-related injuries between 2008 and 2012 who responded to a web-based longitudinal health survey. Participants were categorized into three injury groups: concussion with loss of consciousness (LOC; n = 247), concussion without LOC (n = 317), or no concussion (n = 246). HRQoL was measured using the 36-Item Short Form Health Survey physical and mental component summary (PCS and MCS) scores. Current post-traumatic stress disorder (PTSD) and depression symptoms were examined. Multivariable linear regression models assessed the effects of concussion on PCS and MCS scores, while controlling for covariates.

RESULTS

A lower PCS score was observed in participants with concussion with LOC (B =  - 2.65, p = 0.003) compared with those with no history of concussion. Symptoms of PTSD (PCS: B =  - 4.84, p < 0.001; MCS: B =  - 10.53, p < 0.001) and depression (PCS: B =  - 2.85, p < 0.001; MCS: B =  - 10.24, p < 0.001) were the strongest statistically significant predictors of lower HRQoL.

CONCLUSION

Concussion with LOC was significantly associated with lower HRQoL in the physical domain. These findings affirm that concussion management should integrate physical and psychological care to improve long-term HRQoL and warrant a more detailed examination of causal and mediating mechanisms. Future research should continue to incorporate patient-reported outcomes and long-term follow-up of military service members to further define the lifelong impact of deployment-related concussion.

Cytokine Profiles Differentiate Symptomatic from Asymptomatic PTSD in Service Members and Veterans with Chronic Traumatic Brain Injury

Traumatic brain injuries (TBI) and posttraumatic stress disorder (PTSD) are commonly observed comorbid occurrences among military service members and veterans (SMVs). In this cross-sectional study, SMVs with a history of TBI were stratified into symptomatic and asymptomatic PTSD groups based on posttraumatic stress checklist-civilian (PCL-C) total scores. Blood-based biomarkers were assessed, and significant differential markers were associated with scores from multiple neurobehavioral self-report assessments. PCL-C cutoffs were total scores >50 (PTSD symptomatic) and <25 (asymptomatic). Cytokines IL6, IL8, TNFα, and IL10 were significantly elevated (p < 0.05−0.001) in the TBI+/PTSD symptomatic group compared to the TBI+/asymptomatic group. Cytokine levels of IL8, TNFα, and IL10 were strongly associated with PCL-C scores (0.356 < r > 0.624 for all, p < 0.01 for all), while TNFα and IL10 were additionally associated with NSI totals (r = 0.285 and r = 0.270, p < 0.05, respectively). This is the first study focused on PTSD symptom severity to report levels of circulating pro-inflammatory IL8, specifically in SMVs with TBI. These data suggest that within the military TBI population, there are unique cytokine profiles that relate to neurobehavioral outcomes associated with TBI and PTSD.

The Role of Neuroinflammation in Neuropsychiatric Disorders Following Traumatic Brain Injury: A Systematic Review

BACKGROUND

Neuropsychiatric symptoms are common following traumatic brain injury (TBI), but their etiological onset remains unclear. Mental health research implicates neuroinflammation in the development of psychiatric disorders. The presence of neuroinflammatory responses after TBI thus prompts an investigation of their involvement in the emergence of neuropsychiatric disorders postinjury.

OBJECTIVE

Review the literature surrounding the role of neuroinflammation and immune response post-TBI in the development of neuropsychiatric disorders.

METHODS

A search of scientific databases was conducted for original, empirical studies in human subjects. Key words such as "neuroinflammation," "TBI," and "depression" were used to identify psychopathology as an outcome TBI and the relation to neuroinflammatory response.

RESULTS

Study results provide evidence of neuroinflammation mediated post-TBI neuropsychiatric disorders including anxiety, trauma/stress, and depression. Inflammatory processes and stress response dysregulation can lead to secondary cell damage, which promote the development and maintenance of neuropsychiatric disorders postinjury.

CONCLUSION

This review identifies both theoretical and empirical support for neuroinflammatory response as feasible mechanisms underlying neuropsychiatric disorders after TBI. Further understanding of these processes in this context has significant clinical implications for guiding the development of novel treatments to reduce psychiatric symptoms postinjury. Future directions to address current limitations in the literature are discussed.

The Quality of Life and the Bio-Molecular Profile in Working Environment: A Systematic Review

Working life is characterised by various requirements and degrees of control in meeting these demands. The imbalance of these elements with workers’ resources can result in work-related stress involving the repeated activation of stress response systems. Modifications in the bio-molecular profile may represent a biological signature of individuals’ life experiences and provide evidence on pathways through which such stressors can result in health outcomes. The aim of our systematic review is to characterize the quality of life (QOL) and the bio-molecular profile in the working population, to highlight if the alteration observed might be related to the working conditions. The article query was performed on PubMed, Embase, and Cochrane CENTRAL and results have been presented according to three molecular pathways involved in the stress response: oxidative stress, inflammation, and neuroendocrine activation. The epidemiological sample has been sub-grouped into “clinical” and “non-clinical” populations according to the presence of a diagnosis of psychological disorders. Besides some critical issues, the review highlights the importance of developing a valid array of biological indicators, measurable in non-invasive matrices, sensitive to both derangements from physiological conditions and stress reduction, useful for identifying those groups at higher risk of health outcomes and, eventually, promoting workers’ wellbeing.

Blood Biomarkers Predict Future Cognitive Decline after Military-Related Traumatic Brain Injury

BACKGROUND

Traumatic brain injury (TBI) has been associated with increased likelihood of late-life dementia; however, the mechanisms driving this relationship are elusive. Blood-based biomarkers may provide insight into these mechanisms and serve as useful prognostic indicators of cognitive recovery or decline following a TBI.

OBJECTIVE

The aim of this study was to examine blood biomarkers within one year of TBI and explore their relationship with cognitive decline.

METHODS

Service members and veterans (n=224) without injury (n=77), or with history of bodily injury (n=37), uncomplicated mild TBI (n=55), or more severe TBI (n=55), underwent a blood draw and neuropsychological assessment within one year of their injury as part of a case-control study. A subsample (n=87) completed follow-up cognitive assessment.

RESULTS

In the more severe TBI group, baseline glial fibrillary acidic protein (p=.008) and ubiquitin C-terminal hydrolase-L1 (p=.026) were associated with processing speed at baseline, and baseline ubiquitin C-terminal hydrolase-L1 predicted change in immediate (R2Δ=.244, p=.005) and delayed memory (R2Δ=.390, p=.003) over time. In the mild TBI group, higher baseline tau predicted greater negative change in perceptual reasoning (R2Δ=.188, p=.033) and executive functioning (R2Δ=.298, p=.007); higher baseline neurofilament light predicted greater negative change in perceptual reasoning (R2Δ=.211, p=.012).

CONCLUSION

Baseline ubiquitin C-terminal hydrolase-L1 strongly predicted memory decline in the more severe TBI group, while tau and neurofilament light strongly predicted decline in the mild TBI group. A panel including these biomarkers could be particularly helpful in identifying those at risk for future cognitive decline following TBI.

White Matter Abnormalities and Cognitive Deficit After Mild Traumatic Brain Injury: Comparing DTI, DKI, and NODDI

White matter (WM) disruption is an important determinant of cognitive impairment after mild traumatic brain injury (mTBI), but traditional diffusion tensor imaging (DTI) shows some limitations in assessing WM damage. Diffusion kurtosis imaging (DKI) and neurite orientation dispersion and density imaging (NODDI) show advantages over DTI in this respect. Therefore, we used these three diffusion models to investigate complex WM changes in the acute stage after mTBI. From 32 mTBI patients and 31 age-, sex-, and education-matched healthy controls, we calculated eight diffusion metrics based on DTI (fractional anisotropy, axial diffusivity, radial diffusivity, and mean diffusivity), DKI (mean kurtosis), and NODDI (orientation dispersion index, volume fraction of intracellular water (Vic), and volume fraction of the isotropic diffusion compartment). We used tract-based spatial statistics to identify group differences at the voxel level, and we then assessed the correlation between diffusion metrics and cognitive function. We also performed subgroup comparisons based on loss of consciousness. Patients showed WM abnormalities and cognitive deficit. And these two changes showed positive correlation. The correlation between Vic of the splenium of the corpus callosum and Digit Symbol Substitution Test scores showed the smallest p-value (p = 0.000, r = 0.481). We concluded that WM changes, especially in the splenium of the corpus callosum, correlate to cognitive deficit in this study. Furthermore, the high voxel count of NODDI results and the consistency of mean kurtosis and the volume fraction of intracellular water in previous studies and our study showed the functional complementarity of DKI and NODDI to DTI.

Role of Inflammation in Traumatic Brain Injury-Associated Risk for Neuropsychiatric Disorders: State of the Evidence and Where Do We Go From Here

In the past decade, there has been an increasing awareness that traumatic brain injury (TBI) and concussion substantially increase the risk for developing psychiatric disorders. Even mild TBI increases the risk for depression and anxiety disorders such as posttraumatic stress disorder by two- to threefold, predisposing patients to further functional impairment. This strong epidemiological link supports examination of potential mechanisms driving neuropsychiatric symptom development after TBI. One potential mechanism for increased neuropsychiatric symptoms after TBI is via inflammatory processes, as central nervous system inflammation can last years after initial injury. There is emerging preliminary evidence that TBI patients with posttraumatic stress disorder or depression exhibit increased central and peripheral inflammatory markers compared with TBI patients without these comorbidities. Growing evidence has demonstrated that immune signaling in animals plays an integral role in depressive- and anxiety-like behaviors after severe stress or brain injury. In this review, we will 1) discuss current evidence for chronic inflammation after TBI in the development of neuropsychiatric symptoms, 2) highlight potential microglial activation and cytokine signaling contributions, and 3) discuss potential promise and pitfalls for immune-targeted interventions and biomarker strategies to identify and treat TBI patients with immune-related neuropsychiatric symptoms.

Prognosis and Diagnostic Biomarkers of Mild Traumatic Brain Injury: Current Status and Future Prospects

Mild traumatic brain injury (mTBI) is the most prevalent type of TBI (80-90%). It is characterized by a loss consciousness for less than 30 minutes, post-traumatic amnesia for less than 24 hours, and Glasgow Coma Score of 13-15. Accurately diagnosing mTBIs can be a challenge because the majority of these injuries do not show noticeable or visible changes on neuroimaging studies. Appropriate determination of mTBI is tremendously important because it might lead in some cases to post-concussion syndrome, cognitive impairments including attention, memory, and speed of information processing problems. The scientists have studied different methods to improve mTBI diagnosis and enhanced approaches that would accurately determine the severity of the trauma. The present review focuses on discussing the role of biomarkers as potential key factors in diagnosing mTBI. The present review focuses on 1) protein based peripheral and CNS markers, 2) genetic biomarkers, 3) imaging biomarkers, 4) neurophysiological biomarkers, and 5) the studies and clinical trials in mTBI. Each section provides information and characteristics on different biomarkers for mTBI.

Oxygen Metabolism-induced Stress Response Underlies Heart-brain Interaction Governing Human Consciousness-breaking and Attention

Neuroscientists have emphasized visceral influences on consciousness and attention, but the potential neurophysiological pathways remain under exploration. Here, we found two neurophysiological pathways of heart-brain interaction based on the relationship between oxygen-transport by red blood cells (RBCs) and consciousness/attention. To this end, we collected a dataset based on the routine physical examination, the breaking continuous flash suppression (b-CFS) paradigm, and an attention network test (ANT) in 140 immigrants under the hypoxic Tibetan environment. We combined electroencephalography and multilevel mediation analysis to investigate the relationship between RBC properties and consciousness/attention. The results showed that RBC function, via two independent neurophysiological pathways, not only triggered interoceptive re-representations in the insula and awareness connected to orienting attention but also induced an immune response corresponding to consciousness and executive control. Importantly, consciousness played a fundamental role in executive function which might be associated with the level of perceived stress. These results indicated the important role of oxygen-transport in heart-brain interactions, in which the related stress response affected consciousness and executive control. The findings provide new insights into the neurophysiological schema of heart-brain interactions.

Correlation between Mild Traumatic Brain Injury-Induced Inflammatory Cytokines and Emotional Symptom Traits: A Systematic Review

Both mild traumatic brain injuries (mTBI) and systemic injuries trigger a transient neuroinflammatory response that result in similar clinical outcome. The ensuing physical, cognitive, and emotional symptoms fail to subside in approximately 15–20% of the concussed population. Emotional impairments, particularly depression, anxiety, and post-traumatic stress disorder (PTSD), are commonly associated with poor recovery following mTBI. These emotional impairments also have a significant neuroinflammatory component. We hypothesized that the inflammatory cytokines seen in mTBI patients with emotional symptoms would coincide with those commonly seen in patients with emotional symptoms without mTBI. A systematic review was conducted to identify the most common neuroinflammatory cytokines in the mTBI population with psychological symptoms (depression, anxiety, PTSD). The electronic databases EMBASE, MEDLINE, Cochrane Central Register of Controlled Trials (CENTRAL), PUBMED, and PSYCINFO were searched from data inception to 31 August 2021. A systematic screening approach was employed from screening to data analysis. A total of 994 articles were screened, 108 were selected for full article review, and 8 were selected for data analysis. The included studies consisted of 875 patients of which 81.3% were male. The mean sample size of patients with at least one mTBI was 73.8 ± 70.3 (range, 9–213), with a mean age of 33.9 ± 4.8 years. The most common cytokines associated with poor psychological outcomes involving PTSD and/or depression in the chronic mTBI population were IL-6, TNFα, IL-10, and CRP.

Mental and physical health, and long-term quality of life among service members injured on deployment

Background

More than 52,000 casualties have been documented in post-9/11 conflicts. Service members with extremity injuries (EIs) or traumatic brain injury (TBI) may be at particular risk for long-term deficits in mental and physical health functioning compared with service members with other injuries.

Methods

The present study combined medical records with patient reports of mental health and health-related quality of life (HRQOL) for 2,537 service members injured in overseas contingency operations who participated in the Wounded Warrior Recovery Project. Combined parallel-serial mediation models were tested to examine the pathways through which injury is related to mental and physical health conditions, and long-term HRQOL.

Results

Results revealed that injury was indirectly related to long-term HRQOL via its associations with physical health complications and mental health symptoms. Relative to TBI, EI was associated with a higher likelihood for a postinjury diagnosis for a musculoskeletal condition, which were related to lower levels of later posttraumatic stress disorder (PTSD) symptoms, and higher levels of physical and mental HRQOL. Similarly, EI was related to a lower likelihood for a postinjury PTSD diagnosis, and lower levels of subsequent PTSD symptoms, and therefore higher physical and mental HRQOL relative to those with TBI. Despite this, the prevalence of probable PTSD among those with EI was high (35%). Implications for intervention, rehabilitation, and future research are discussed.

The risk factors for insomnia and sleep-disordered breathing in military communities: A meta-analysis

BACKGROUND

Many reviews and meta-analyses had been conducted to investigate risk factors for sleep disorders in the general population. However, no similar research has been performed in the military population though insomnia and sleep-disordered breathing are quite prevalent in that population.

OBJECTIVES

To investigate risk factors for insomnia and sleep-disordered breathing in military personnel.

METHODS

A systematic literature search was performed from inception to March 2021 and 6496 records were produced. Two authors independently screened records for eligibility. Results were presented as odds ratios, and a random-effect model was used to pool results. Data analysis was performed respectively according to military personnel type (i.e., veteran, active-duty personnel). Risk factors were sorted into three categories: sociodemographic, army-specific, and comorbidity. This meta-analysis was registered in PROSPERO before data analysis (registration No: CRD42020221696).

RESULTS

Twenty-seven articles were finally included in the quantitative analysis. For sleep-disordered breathing in active-duty personnel, four sociodemographic (i.e., overweight/obesity, higher body mass index, male gender, >35 years old) and one comorbidity (i.e., depression) risk factors were identified. For insomnia in active-duty personnel, four sociodemographic (i.e., aging, alcohol dependence, white race, and female gender), two army-specific (i.e., deployment experience, combat experience), and four comorbidity (i.e., depression, post-traumatic stress disorder, traumatic brain injury, and anxiety) risk factors were identified. For insomnia in veterans, one army-specific (i.e., combat experience) and one comorbidity (i.e., post-traumatic stress disorder) risk factor was identified.

CONCLUSIONS

Several risk factors were identified for insomnia and sleep-disordered breathing in the current meta-analysis. Risk factors for veterans and active-duty personnel were partially different. Research on sleep breathing disorders remains limited, and more convincing evidence would be obtained with more relevant studies in the future.

Evaluation of an Immunomodulatory Probiotic Intervention for Veterans With Co-occurring Mild Traumatic Brain Injury and Posttraumatic Stress Disorder: A Pilot Study

Background: US military Veterans returned from Operation Enduring Freedom/Operation Iraqi Freedom/Operation New Dawn (OEF/OIF/OND) with symptoms associated with mild traumatic brain injury [mTBI; i.e., persistent post-concussive (PPC) symptoms] and posttraumatic stress disorder (PTSD). Interventions aimed at addressing symptoms associated with both physical and psychological stressors (e.g., PPC and PTSD symptoms) are needed. This study was conducted to assess the feasibility, acceptability, and safety of a probiotic intervention, as well as to begin the process of evaluating potential biological outcomes.

Methods: A pilot randomized controlled trial was implemented among US military Veterans from recent conflicts in Iraq and Afghanistan. Those enrolled had clinically significant PPC and PTSD symptoms. Participants were randomized to intervention (Lactobacillus reuteri DSM 17938) or placebo supplementation (daily for 8 weeks +/- 2 weeks) at a 1:1 ratio, stratified by irritable bowel syndrome status. Thirty-one Veterans were enrolled and randomized (15 to the placebo condition and 16 to the probiotic condition).

Results: Thresholds for feasibility, acceptability, and safety were met. Probiotic supplementation resulted in a decrease in plasma C-reactive protein (CRP) concentrations relative to the placebo group that approached statistical significance (p = 0.056). Although during the Trier Social Stress Test (TSST; administered post-supplementation) no between-group differences were found on a subjective measure of stress responsivity (Visual Analog Scale), there was a significantly larger increase in mean heart beats per minute between baseline and the math task for the placebo group as compared with the probiotic group (estimated mean change, probiotic 5.3 [95% Confidence Interval: −0.55, 11.0], placebo 16.9 [11.0, 22.7], p = 0.006).

Conclusions: Findings from this trial support the feasibility, acceptability, and safety of supplementation with an anti-inflammatory/immunoregulatory probiotic, L. reuteri DSM 17938, among Veterans with PPC and PTSD symptoms. Moreover, results suggest that CRP may be a viable inflammatory marker of interest. A larger randomized controlled trial aimed at measuring both biological and clinical outcomes is indicated.

Clinical Trial Registration:ClinicalTrials.gov, Identifier NCT02723344.

Recent Advances in Blood-Based Biomarkers of Remote Combat-Related Traumatic Brain Injury

PURPOSE OF REVIEW

Traumatic brain injury (TBI) is highly prevalent among service members and Veterans (SMVs) and associated with changes in blood-based biomarkers. This manuscript reviews candidate biomarkers months/years following military-associated TBI.

RECENT FINDINGS

Several blood-based biomarkers have been investigated for diagnostic or prognostic use to inform care years after military-associated TBI. The most promising include increased levels of plasma/serum and exosomal proteins reflecting neuronal, axonal and/or vascular injury, and inflammation, as well as altered microRNA expression and auto-antibodies of central nervous system markers. Diagnostic and prognostic biomarkers of remote TBI outcomes remain in the discovery phase. Current evidence does not yet support single or combination biomarkers for clinical diagnostic use remotely after injury, but there are promising candidates that require validation in larger, longitudinal studies. The use of prognostic biomarkers of future neurodegeneration, however, holds much promise and could improve treatments and/or preventive measures for serious TBI outcomes.

Dysregulation of inflammation, neurobiology, and cognitive function in PTSD: an integrative review

Compelling evidence from animal and human research suggest a strong link between inflammation and posttraumatic stress disorder (PTSD). Furthermore, recent findings support compromised neurocognitive function as a key feature of PTSD, particularly with deficits in attention and processing speed, executive function, and memory. These cognitive domains are supported by brain structures and neural pathways that are disrupted in PTSD and which are implicated in fear learning and extinction processes. The disruption of these supporting structures potentially results from their interaction with inflammation. Thus, the converging evidence supports a model of inflammatory dysregulation and cognitive dysfunction as combined mechanisms underpinning PTSD symptomatology. In this review, we summarize evidence of dysregulated inflammation in PTSD and further explore how the neurobiological underpinnings of PTSD, in the context of fear learning and extinction acquisition and recall, may interact with inflammation. We then present evidence for cognitive dysfunction in PTSD, highlighting findings from human work. Potential therapeutic approaches utilizing novel pharmacological and behavioral interventions that target inflammation and cognition also are discussed.

Inflammation in Post-Traumatic Stress Disorder (PTSD): A Review of Potential Correlates of PTSD with a Neurological Perspective

Post-traumatic stress disorder (PTSD) is a chronic condition characterized by symptoms of physiological and psychosocial burden. While growing research demonstrated signs of inflammation in PTSD, specific biomarkers that may be representative of PTSD such as the detailed neural correlates underlying the inflammatory responses in relation to trauma exposure are seldom discussed. Here, we review recent studies that explored alterations in key inflammatory markers in PTSD, as well as neuroimaging-based studies that further investigated signs of inflammation within the brain in PTSD, as to provide a comprehensive summary of recent literature with a neurological perspective. A search was conducted on studies published from 2009 through 2019 in PubMed and Web of Science. Fifty original articles were selected. Major findings included elevated levels of serum proinflammatory cytokines in individuals with PTSD across various trauma types, as compared with those without PTSD. Furthermore, neuroimaging-based studies demonstrated that altered inflammatory markers are associated with structural and functional alterations in brain regions that are responsible for the regulation of stress and emotion, including the amygdala, hippocampus, and frontal cortex. Future studies that utilize both central and peripheral inflammatory markers are warranted to elucidate the underlying neurological pathway of the pathophysiology of PTSD.