Cognitive decline in older adults with a history of traumatic brain injury

Accelerated Aging after Traumatic Brain Injury: An ENIGMA Multi-Cohort Mega-Analysis

OBJECTIVE

The long-term consequences of traumatic brain injury (TBI) on brain structure remain uncertain. Given evidence that a single significant brain injury event increases the risk of dementia, brain-age estimation could provide a novel and efficient indexing of the long-term consequences of TBI. Brain-age procedures use predictive modeling to calculate brain-age scores for an individual using structural magnetic resonance imaging (MRI) data. Complicated mild, moderate, and severe TBI (cmsTBI) is associated with a higher predicted age difference (PAD), but the progression of PAD over time remains unclear. We sought to examine whether PAD increases as a function of time since injury (TSI) and if injury severity and sex interacted to influence this progression.

METHODS

Through the ENIGMA Adult Moderate and Severe (AMS)-TBI working group, we examine the largest TBI sample to date (n = 343), along with controls, for a total sample size of n = 540, to replicate and extend prior findings in the study of TBI brain age. Cross-sectional T1w-MRI data were aggregated across 7 cohorts, and brain age was established using a similar brain age algorithm to prior work in TBI.

RESULTS

Findings show that PAD widens with longer TSI, and there was evidence for differences between sexes in PAD, with men showing more advanced brain age. We did not find strong evidence supporting a link between PAD and cognitive performance.

INTERPRETATION

This work provides evidence that changes in brain structure after cmsTBI are dynamic, with an initial period of change, followed by relative stability in brain morphometry, eventually leading to further changes in the decades after a single cmsTBI. ANN NEUROL 2024;96:365-377.

Detecting and Predicting Cognitive Decline in Individuals with Traumatic Brain Injury: A Longitudinal Telephone-Based Study

Traumatic brain injuries (TBIs) can lead to long-lasting cognitive impairments, and some survivors experience cognitive decline post-recovery. Early detection of decline is important for care planning, and understanding risk factors for decline can elucidate targets for prevention. While neuropsychological testing is the gold standard approach to characterizing cognitive function, there is a need for brief, scalable tools that are capable of detecting clinically significant changes in post-TBI cognition. This study examines whether a clinically significant change can be detected using the Brief Test of Adult Cognition by Telephone (BTACT) in a sample of individuals with chronic TBI and investigates whether potentially modifiable factors are associated with cognitive decline. Ninety participants aged 40 or older with complicated mild-to-severe TBI participated in two telephone-based study visits ∼1 year apart. Demographic, head trauma exposure, comorbid medical conditions, physical, and psychosocial functioning data were collected via self-report. The BTACT, a brief measure of global cognitive function, was used to assess cognitive performance across six domains. A reliable change index for quantifying clinically significant changes in BTACT performance was calculated. Results revealed cognitive decline in 10-27% of participants across various cognitive domains. More specifically, only depressive symptoms, including depressed affect and anhedonia, were significantly associated with cognitive decline after correcting for multiple comparisons using false discovery rate (FDR). Other factors such as the number of blows to the head, male gender, dyspnea, increased anxiety symptoms, seizures, illicit drug use, and fewer cardiovascular comorbidities should be considered hypothesis generating. Importantly, age was not a significant predictor of cognitive decline, which challenges the assumption that cognitive decline is solely related to the natural aging process. It suggests that there are unique factors associated with TBI that impact cognitive function, and these factors can affect individuals across the lifespan. The BTACT is a brief and sensitive tool for identifying clinically meaningful changes in cognitive function over a relatively brief period (i.e., 1 year) in a sample of individuals in the chronic stages of TBI (i.e., x̄ = 6.7 years post-TBI). Thus, the BTACT may be useful in surveillance efforts aimed at understanding and detecting decline, particularly in situations where in-person cognitive screening is impractical or unfeasible. We also identified potentially modifiable targets for the prevention of post-TBI cognitive decline. These findings can offer insights into treatment goals and preventive strategies for individuals at risk for cognitive decline, as well as help to facilitate early identification efforts.

The Cognitive Profile of Elderly Patients With Mild Traumatic Brain Injury: A Role for Cognitive Reserve?

OBJECTIVE

To assess cognitive status in elderly patients with mild traumatic brain injury (mTBI) in the subacute phase, examine the role of cognitive reserve, and investigate associations with cognitive complaints, mental distress, and functional outcomes.

SETTING

A level 1 trauma center in the Netherlands.

PARTICIPANTS

A total of 52 individuals with mTBI and 42 healthy controls.

DESIGN

A prospective observational cohort study.

MAIN MEASURES

Neuropsychological assessment in the subacute phase (2 weeks to 6 months post-injury) to objectively measure the cognitive functioning, the Head Injury Symptom Checklist for subjective cognitive complaints, the Hospital Anxiety and Depression Scale for anxiety and depression, the Cognitive Reserve Index questionnaire for cognitive reserve, the Community Integration Questionnaire for community integration, and the Glasgow Outcome Scale Extended for functional outcome.

RESULTS

Cognitive impairments were observed in memory ( P < .001) and attention, processing speed and executive control ( P < .001). Cognitive reserve was not associated with neuropsychological test performance, except for one test measuring working memory. The relationship between injury severity and cognitive outcome was not moderated by cognitive reserve. Elderly patients reported significantly more complains than healthy controls regarding forgetfulness, concentration problems, and slowness. Complaints of concentration were associated with cognitive impairment. All cognitive complaints were significantly correlated with mental distress.

CONCLUSIONS

Cognitive impairments may be present in elderly patients in the subacute phase after mTBI, and these impairments were not significantly associated with cognitive reserve. This suggests that cognitive reserve might not serve as a protective factor against the effects of mTBI in the elderly. Concentration complaints may serve as a specific indicator for cognitive impairment, while complaints of memory and mental slowness may represent more generic indicators of mental distress. These findings highlight the importance of careful screening in older adults with mTBI, guiding clinicians toward specific treatment targets encompassing cognitive impairment, diminished mental well-being, or both.

Bradykinin 2 Receptors Mediate Long-Term Neurocognitive Deficits After Experimental Traumatic Brain Injury

The kallikrein-kinin system is one of the first inflammatory pathways to be activated following traumatic brain injury (TBI) and has been shown to exacerbate brain edema formation in the acute phase through activation of bradykinin 2 receptors (B2R). However, the influence of B2R on chronic post-traumatic damage and outcome is unclear. In the current study, we assessed long-term effects of B2R-knockout (KO) after experimental TBI. B2R KO mice (heterozygous, homozygous) and wild-type (WT) littermates (n = 10/group) were subjected to controlled cortical impact (CCI) TBI. Lesion size was evaluated by magnetic resonance imaging up to 90 days after CCI. Motor and memory function were regularly assessed by Neurological Severity Score, Beam Walk, and Barnes maze test. Ninety days after TBI, brains were harvested for immunohistochemical analysis. There was no difference in cortical lesion size between B2R-deficient and WT animals 3 months after injury; however, hippocampal damage was reduced in B2R KO mice (p = 0.03). Protection of hippocampal tissue was accompanied by a significant improvement of learning and memory function 3 months after TBI (p = 0.02 WT vs. KO), whereas motor function was not influenced. Scar formation and astrogliosis were unaffected, but B2R deficiency led to a gene-dose-dependent attenuation of microglial activation and a reduction of CD45+ cells 3 months after TBI in cortex (p = 0.0003) and hippocampus (p < 0.0001). These results suggest that chronic hippocampal neurodegeneration and subsequent cognitive impairment are mediated by prolonged neuroinflammation and B2R. Inhibition of B2R may therefore represent a novel strategy to reduce long-term neurocognitive deficits after TBI.

Sexual Dimorphism in Age-Dependent Neurodegeneration After Mild Head Trauma in Drosophila : Unveiling the Adverse Impact of Female Reproductive Signaling

Environmental insults, including mild head trauma, significantly increase the risk of neurodegeneration. However, it remains challenging to establish a causative connection between early-life exposure to mild head trauma and late-life emergence of neurodegenerative deficits, nor do we know how sex and age compound the outcome. Using a Drosophila model, we demonstrate that exposure to mild head trauma causes neurodegenerative conditions that emerge late in life and disproportionately affect females. Increasing age-at-injury further exacerbates this effect in a sexually dimorphic manner. We further identify Sex Peptide (SP) signaling as a key factor in female susceptibility to post-injury brain deficits. RNA sequencing highlights a reduction in innate immune defense transcripts specifically in mated females during late life. Our findings establish a causal relationship between early head trauma and late-life neurodegeneration, emphasizing sex differences in injury response and the impact of age-at-injury. Finally, our findings reveal that reproductive signaling adversely impacts female response to mild head insults and elevates vulnerability to late-life neurodegeneration.

Cognitive impairment in Chinese traumatic brain injury patients: from challenge to future perspectives

Traumatic Brain Injury (TBI) is a prevalent form of neurological damage that may induce varying degrees of cognitive dysfunction in patients, consequently impacting their quality of life and social functioning. This article provides a mini review of the epidemiology in Chinese TBI patients and etiology of cognitive impairment. It analyzes the risk factors of cognitive impairment, discusses current management strategies for cognitive dysfunction in Chinese TBI patients, and summarizes the strengths and limitations of primary testing tools for TBI-related cognitive functions. Furthermore, the article offers a prospective analysis of future challenges and opportunities. Its objective is to contribute as a reference for the prevention and management of cognitive dysfunction in Chinese TBI patients.

Feasibility of group telerehabilitation for individuals with chronic acquired brain injury: integrating clinical care and research

BACKGROUND

Acquired brain injury (ABI) is a leading cause of lifelong disability, but access to treatment in the chronic stages has significant barriers. Group-based, remotely delivered neurorehabilitation reduces costs, travel barriers, and infection risk; however, its feasibility for patients with ABI is not well-established.

OBJECTIVES

To investigate the feasibility of remotely group-based cognitive and mood therapies for persons with chronic ABI.

METHODS

Three hundred and eighty-eight adults with chronic ABI participated in group tele-neurorehabilitation modules comprising Cognitive Behavioral Therapy, Goal Management Training®, Relaxation and Mindfulness Skills Training, and/or a novel Concussion Education & Symptom Management program. Assessments comprised quantitative metrics, surveys, as well as qualitative semi-structured interviews in a subset of participants.

RESULTS

High retention, adherence, and satisfaction were observed. Facilitators of treatment included accessibility, cost-effectiveness, and convenience. Adoption of technology was high, but other people's technological interruptions were a barrier. Self-reported benefits specific to group-based format included improved mood, stress management, coping, interpersonal relationships, cognitive functioning, and present-mindedness.

CONCLUSIONS

The present study examined chronic ABI patients' perceptions of telerehabilitation. Patients found remotely delivered, group-based mood, and cognitive interventions feasible with easy technology adoption. Group format was considered a benefit. Recommendations are provided to inform design of remotely delivered ABI programs.

Deregulation of the Glymphatic System in Alzheimer's Disease: Genetic and Non-Genetic Factors

Alzheimer's disease (AD) is the most prevalent form of dementia and is characterized by progressive degeneration of brain function. AD gradually affects the parts of the brain that control thoughts, language, behavior and mental function, severely impacting a person's ability to carry out daily activities and ultimately leading to death. The accumulation of extracellular amyloid-β peptide (Aβ) and the aggregation of intracellular hyperphosphorylated tau are the two key pathological hallmarks of AD. AD is a complex condition that involves both non-genetic risk factors (35%) and genetic risk factors (58-79%). The glymphatic system plays an essential role in clearing metabolic waste, transporting tissue fluid, and participating in the immune response. Both non-genetic and genetic risk factors affect the glymphatic system to varying degrees. The main purpose of this review is to summarize the underlying mechanisms involved in the deregulation of the glymphatic system during the progression of AD, especially concerning the diverse contributions of non-genetic and genetic risk factors. In the future, new targets and interventions that modulate these interrelated mechanisms will be beneficial for the prevention and treatment of AD.

Adaptation of an evidence-based, fall-prevention, Tai Ji Quan exercise program for adults with traumatic brain injury: focus group results

INTRODUCTION

Fall risk is increased in people with traumatic brain injury (TBI).

PURPOSE

This study adapted an evidence-based fall-prevention program Tai Ji Quan: Moving for Better Balance (TJQMBB) for adults with TBI and convened an online focus group with the target population for input on its delivery, content/safety, and potential benefits.

METHODS

Fall prevention and TBI experts adapted TJQMBB. Eight adults with TBI were recruited. Participants watched demonstrations of the adapted TJQMBB exercises online over ZOOM©. Themes, subthemes, and participant quotes were extracted.

RESULTS

Five women (71%) and 2 men (29%) participated with a mean age of 45 years. Nine themes and 5 subthemes were identified. Participants recommended a learning sequence of exercise demonstration with verbal directions and visual cues, followed by simple written instructions. Participants identified physical and cognitive barriers to participation and recognized that possible balance loss during exercise was a safety issue. Potential benefits included improved balance, navigation of challenging terrain, quality of life, and social inclusion.

CONCLUSION

Participants viewed the adapted program as safe and appropriate, given modifications for physical (e.g. balance) and cognitive impairments. The TJQMBB program may be underutilized in this population due to the complexity of the exercises, but is possible with modifications.

Associations Between Traumatic Brain Injury and Cognitive Decline Among Older Male Veterans: A Twin Study

BACKGROUND AND OBJECTIVES

Traumatic brain injuries (TBIs) are associated with increased risk of dementia, but whether lifetime TBI influences cognitive trajectories in later life is less clear. Cognitive interventions after TBI may improve cognitive trajectories and delay dementia. Because twins share many genes and environmental factors, we capitalize on the twin study design to examine the association between lifetime TBI and cognitive decline.

METHODS

Participants were members of the National Academy of Sciences-National Research Council's Twin Registry of male veterans of World War II with self or proxy-reported history of TBI and with up to 4 observations over 12 years of the modified Telephone Interview for Cognitive Status (TICS-m). We used linear random-effects mixed models to analyze the association between TBI and TICS-m in the full sample and among co-twins discordant for TBI. Additional TBI predictor variables included number of TBIs, severity (loss of consciousness [LOC]), and age of first TBI (age <25 vs 25+ years [older age TBI]). Models were adjusted for age (centered at 70 years), age-squared, education, wave, twin pair, lifestyle behaviors, and medical conditions.

RESULTS

Of 8,662 participants, 25% reported TBI. History of any TBI (β = -0.56, 95% CI -0.73 to -0.39), TBI with LOC (β = -0.51, 95% CI -0.71 to -0.31), and older age TBI (β = -0.66, 95% CI -0.90 to -0.42) were associated with lower TICS-m scores at 70 years. TBI with LOC (β = -0.03, 95% CI -0.05 to -0.001), more than one TBI (β = -0.05, 95% CI -0.09 to -0.002,), and older age TBI (β = -0.06, 95% CI -0.09 to -0.03) were associated with faster cognitive decline. Among monozygotic pairs discordant for TBI (589 pairs), history of any TBI (β = -0.55, 95% CI -0.91 to -0.19) and older age TBI (β = -0.74, 95% CI -1.22 to -0.26) were associated with lower TICS-m scores at 70 years. Those with more than one TBI (β = -0.13, 95% CI -0.23 to -0.03) and older age TBI (β = -0.07, 95% CI -0.13 to -0.002) showed greater cognitive decline compared with their co-twin without TBI.

DISCUSSION

These findings support an association of the effect of TBI on cognitive score and the rapidity of cognitive decline in later life. The results in monozygotic pairs, who share all genes and many exposures, particularly in early life, provide additional evidence of a causal relationship between TBI and poorer late-life cognitive outcomes.

Adolescent traumatic brain injury leads to incremental neural impairment in middle-aged mice: role of persistent oxidative stress and neuroinflammation

Background

Traumatic brain injury (TBI) increases the risk of mental disorders and neurodegenerative diseases in the chronic phase. However, there is limited neuropathological or molecular data on the long-term neural dysfunction and its potential mechanism following adolescent TBI.

Methods

A total of 160 male mice aged 8 weeks were used to mimic moderate TBI by controlled cortical impact. At 1, 3, 6 and 12 months post-injury (mpi), different neurological functions were evaluated by elevated plus maze, forced swimming test, sucrose preference test and Morris water maze. The levels of oxidative stress, antioxidant response, reactive astrocytes and microglia, and expression of inflammatory cytokines were subsequently assessed in the ipsilateral hippocampus, followed by neuronal apoptosis detection. Additionally, the morphological complexity of hippocampal astrocytes was evaluated by Sholl analysis.

Results

The adolescent mice exhibited persistent and incremental deficits in memory and anxiety-like behavior after TBI, which were sharply exacerbated at 12 mpi. Depression-like behaviors were observed in TBI mice at 6 mpi and 12 mpi. Compared with the age-matched control mice, apoptotic neurons were observed in the ipsilateral hippocampus during the chronic phase of TBI, which were accompanied by enhanced oxidative stress, and expression of inflammatory cytokines (IL-1β and TNF-α). Moreover, the reactive astrogliosis and microgliosis in the ipsilateral hippocampus were observed in the late phase of TBI, especially at 12 mpi.

Conclusion

Adolescent TBI leads to incremental cognitive dysfunction, and depression- and anxiety-like behaviors in middle-aged mice. The chronic persistent neuroinflammation and oxidative stress account for the neuronal loss and neural dysfunction in the ipsilateral hippocampus. Our results provide evidence for the pathogenesis of chronic neural damage following TBI and shed new light on the treatment of TBI-induced late-phase neurological dysfunction.

Cardiovascular autonomic regulation correlates with cognitive performance in patients with a history of traumatic brain injury

BACKGROUND AND OBJECTIVE

Traumatic brain injury (TBI) may afflict brain areas contributing to both cardiovascular autonomic regulation and cognitive performance. To evaluate possible associations between both functions in patients with a history of TBI (post-TBI-patients), we determined correlations between cardiovascular autonomic regulation and cognitive function in post-TBI-patients.

METHODS

In 86 post-TBI-patients (33.1 ± 10.8 years old, 22 women, 36.8 ± 28.9 months after injury), we monitored RR intervals (RRI), systolic and diastolic blood pressures (BPsys, BPdia), and respiration (RESP) at rest. We calculated parameters of total cardiovascular autonomic modulation (RRI-standard-deviation (RRI-SD), RRI-coefficient-of-variation (RRI-CV), RRI-total-powers), sympathetic (RRI-low-frequency-powers (RRI-LF), normalized (nu) RRI-LF-powers, BPsys-LF-powers) and parasympathetic modulation (root-mean-square-of-successive-RRI-differences (RMSSD), RRI-high-frequency-powers (RRI-HF), RRI-HFnu-powers), sympathetic-parasympathetic balance (RRI-LF/HF-ratios), and baroreflex sensitivity (BRS). We used the Mini-Mental State Examination and Clock Drawing Test (CDT) to screen the general global and visuospatial cognitive function, and applied the standardized Trail Making Test (TMT)-A assessing visuospatial abilities and TMT-B assessing executive function. We calculated correlations between autonomic and cognitive parameters (Spearman's rank correlation test; significance: P < 0.05).

RESULTS

CDT values positively correlated with age (P = 0.013). TMT-A values inversely correlated with RRI-HF-powers (P = 0.033) and BRS (P = 0.043), TMT-B values positively correlated with RRI-LFnu-powers (P = 0.015), RRI-LF/HF-ratios (P = 0.036), and BPsys-LF-powers (P = 0.030), but negatively with RRI-HFnu-powers (P = 0.015).

CONCLUSIONS

In patients with a history of TBI, there is an association between decreased visuospatial and executive cognitive performance and reduced parasympathetic cardiac modulation and baroreflex sensitivity with relatively increased sympathetic activity. Altered autonomic control bears an increased cardiovascular risk; cognitive impairment compromises quality of life and living conditions. Thus, both functions should be monitored in post-TBI-patients.

From Homeostasis to Pathology: Decoding the Multifaceted Impact of Aquaporins in the Central Nervous System

Aquaporins (AQPs), integral membrane proteins facilitating selective water and solute transport across cell membranes, have been the focus of extensive research over the past few decades. Particularly noteworthy is their role in maintaining cellular homeostasis and fluid balance in neural compartments, as dysregulated AQP expression is implicated in various degenerative and acute brain pathologies. This article provides an exhaustive review on the evolutionary history, molecular classification, and physiological relevance of aquaporins, emphasizing their significance in the central nervous system (CNS). The paper journeys through the early studies of water transport to the groundbreaking discovery of Aquaporin 1, charting the molecular intricacies that make AQPs unique. It delves into AQP distribution in mammalian systems, detailing their selective permeability through permeability assays. The article provides an in-depth exploration of AQP4 and AQP1 in the brain, examining their contribution to fluid homeostasis. Furthermore, it elucidates the interplay between AQPs and the glymphatic system, a critical framework for waste clearance and fluid balance in the brain. The dysregulation of AQP-mediated processes in this system hints at a strong association with neurodegenerative disorders such as Parkinson's Disease, idiopathic normal pressure hydrocephalus, and Alzheimer's Disease. This relationship is further explored in the context of acute cerebral events such as stroke and autoimmune conditions such as neuromyelitis optica (NMO). Moreover, the article scrutinizes AQPs at the intersection of oncology and neurology, exploring their role in tumorigenesis, cell migration, invasiveness, and angiogenesis. Lastly, the article outlines emerging aquaporin-targeted therapies, offering a glimpse into future directions in combatting CNS malignancies and neurodegenerative diseases.

Epidemiology of Dog Walking-Related Injuries among Adults Presenting to US Emergency Departments, 2001-2020

PURPOSE

Dog walking is a popular daily activity, yet information regarding its injury burden is limited. This study describes the epidemiology of injuries related to leash-dependent dog walking among adults presenting to US emergency departments from 2001 to 2020.

METHODS

A retrospective analysis was performed using the National Electronic Injury Surveillance System database to identify adults (≥18 yr) presenting to US emergency departments with leash-dependent dog walking-related injuries between 2001 and 2020. Outcomes included annual estimates of injury incidence, injury characteristics, and risk factors for sustaining a fracture or traumatic brain injury (TBI). Weighted estimates and 95% confidence intervals (CI) were generated using National Electronic Injury Surveillance System sample weights.

RESULTS

Between 2001 and 2020, an estimated 422,659 adults presented to US emergency departments with injuries related to leash-dependent dog walking. The annual incidence increased more than fourfold during this period ( n = 7282 vs n = 32,306, P < 0.001). Most patients were women (75%) and adults age 40 to 64 yr (47%), with a mean age of 53 ± 0.5 yr. Patients commonly injured their upper extremity (51%) and were injured while falling when pulled or tripped by the leash (55%). The three most common injuries were finger fracture (6.9%), TBI (5.6%), and shoulder sprain/strain (5.1%). On multivariate analysis, fracture risk among dog walkers was higher in adults age ≥65 yr (odds ratio [OR], 2.1; 95% CI, 1.8-2.5) and women (OR, 1.5; 95% CI, 1.3-1.7). Risk of TBI was also elevated among older dog walkers (OR, 1.6; 95% CI, 1.3-2.0).

CONCLUSIONS

Dog walking is associated with a considerable and rising injury burden. Dog owners should be informed of this injury potential and advised on risk-reduction strategies.

Neuropsychological Impairments in Patients With Post-traumatic Epilepsy: A Scoping Review

OBJECTIVES

To date, the research on the prognosis of the neuropsychological function of patients with post-traumatic seizure (PTE) is sparse. This study aimed to systematically map the literature's extent, range, and characteristics regarding PTE and neuropsychological impairments.

METHODS

A systematic literature search was conducted in CINAHL, Cochrane, Embase, Medline, PubMed, Scopus, Web of Science, and ScienceDirect databases. The search terms were related to PTE and neuropsychological impairments.

RESULTS

This scoping review included seven studies, two of which examined the impact of PTE on neuropsychological outcomes. Among the three studies that used neuropsychological assessments, attention/concentration, and memory were the most frequently assessed domains. Only one study reported a significant difference between PTE and non-PTE patients. The cognitive rating scale findings in the other four studies were similar, indicating that patients with PTE performed worse than those without PTE.

CONCLUSIONS

The results of this review suggest that patients with PTE may have neuropsychological function impairments. More attention needs to be paid to older patients and those with higher brain injury and seizure severity. Additional investigation is necessary to determine the clinical characteristics of TBI and PTE and elucidate the relations between PTE and specific neuropsychological domains.

Drosophila melanogaster as a model to study age and sex differences in brain injury and neurodegeneration after mild head trauma

Repetitive physical insults to the head, including those that elicit mild traumatic brain injury (mTBI), are a known risk factor for a variety of neurodegenerative conditions including Alzheimer's disease (AD), Parkinson's disease (PD), and chronic traumatic encephalopathy (CTE). Although most individuals who sustain mTBI typically achieve a seemingly full recovery within a few weeks, a subset experience delayed-onset symptoms later in life. As most mTBI research has focused on the acute phase of injury, there is an incomplete understanding of mechanisms related to the late-life emergence of neurodegeneration after early exposure to mild head trauma. The recent adoption of Drosophila-based brain injury models provides several unique advantages over existing preclinical animal models, including a tractable framework amenable to high-throughput assays and short relative lifespan conducive to lifelong mechanistic investigation. The use of flies also provides an opportunity to investigate important risk factors associated with neurodegenerative conditions, specifically age and sex. In this review, we survey current literature that examines age and sex as contributing factors to head trauma-mediated neurodegeneration in humans and preclinical models, including mammalian and Drosophila models. We discuss similarities and disparities between human and fly in aging, sex differences, and pathophysiology. Finally, we highlight Drosophila as an effective tool for investigating mechanisms underlying head trauma-induced neurodegeneration and for identifying therapeutic targets for treatment and recovery.

Long-term health-related quality of life and independence among older survivors of serious injury

BACKGROUND

Little is known about the recovery experiences of older trauma intensive care unit (TICU) survivors and the relationship between geriatric trauma care and long-term functional ability and health-related quality of life (HRQOL).

METHODS

We conducted a prospective cohort study of 218 patients (age, ≥65 years) admitted to a Level 1 regional trauma center TICU before versus after implementation of a geriatric care bundle with protocolized geriatrics consultations (Geri-T). Survivors or their proxies were interviewed approximately 1 year after hospitalization. Outcomes included the Katz Index of Independence in Activities of Daily Living (ADLs), Lawton Instrumental Activities of Daily Living (IADLs), and EQ-5D-5L HRQOL survey. Two investigator-developed questions regarding recovery experiences were included. Differences in outcomes among survivors admitted before versus after Geri-T were analyzed using multivariable linear regression. Responses to questions about recovery experiences were qualitatively assessed using content analysis.

RESULTS

We reached 67% (146/218) of hospital survivors or their proxies across both groups; 126 patients were still alive and completed the survey. Mean age was 76 (SD, 8), 36% were female, and 90% were independent with ADLs preinjury. At follow-up, independence with ADLs was 76% and IADLs was 63%. The mean EQ-5D-5L index score was 0.78 (SD, 0.18). Most patients (65%) reported having not returned to preinjury functional status. Neither functional ability or HRQOL differed significantly among patients admitted before versus after Geri-T. Content analysis of open-ended questions revealed themes of activity limitations, persistent pain, and cognitive dysfunction.

CONCLUSION

Nearly one-fifth of TICU survivors experienced loss of ADL function 1 year after injury, and most reported having not returned to preinjury functional status. Nonetheless, patient-reported HRQOL was comparable to age-adjusted norms. Geri-T was not associated with differences in HRQOL or functional ability. Survivors reported persistent difficulty with activities beyond those of daily living, pain, and cognition.

LEVEL OF EVIDENCE

Prognostic and Epidemiologic, Level III.

Medial prefrontal cortex oxytocin mitigates epilepsy and cognitive impairments induced by traumatic brain injury through reducing neuroinflammation in mice

Traumatic brain injury (TBI) is a major risk factor to develop epilepsy and cognitive impairments. Neuropeptide oxytocin has been previously evidenced to produce antiepileptic effects. However, the involvement of central oxytocin in TBI-induced epileptic status and cognitive dysfunctions is not fully elucidated. In this study, we aim to investigate the role of oxytocin on a TBI model followed by seizure induction to clarify whether the epilepsy and cognitive deficits could be mitigated by oxytocin. TBI was established by weight drop and epileptic behaviors were induced by pentylenetetrazole (PTZ) injection in mice. Moreover, oxytocin was microinjected into the medial prefrontal cortex (mPFC) to observe the effects on the epilepsy and cognition. The blood-brain barrier (BBB) function and the neuroinflammation were measured by Evans Blue staining and enzyme-linked immunosorbent assays, respectively. Mice exposed to TBI demonstrate increased vulnerability to PTZ-mediated seizures and cognitive disturbances with a decrease in peripheral and brain oxytocin levels. Additionally, TBI reduces oxytocin, disrupts the BBB permeability and triggers neuroinflammation in mPFC in PTZ-treated mice. Intra-mPFC oxytocin simultaneously mitigates epilepsy and cognitive impairments. Finally, oxytocin restores BBB integrity and reduces mPFC inflammation in PTZ-treated TBI mice. These findings showed that intra-mPFC oxytocin suppressed the seizure vulnerability and cognitive deficits in TBI mice. The normalization of BBB integrity and inhibition of neuroinflammation may be involved in the antiepileptic and cognition-improved effects of oxytocin, suggesting that targeting inflammatory procedure in mPFC may decrease the risk to develop epilepsy and cognitive impairments in individuals previously experienced TBI.

Prevalence and sociodemographic characteristics of US community-dwelling older adults with communication disabilities, using the national health and aging trends survey

INTRODUCTION

Identifying the population-level prevalence of a disability group is a prerequisite to monitoring their inclusion in society. The prevalence and sociodemographic characteristics of older adults with communication disabilities (CDs) are not well established in the literature. In this study we sought to describe the prevalence and sociodemographic characteristics of community-dwelling older adults experiencing difficulties with understanding others or being understand when communicating in their usual language.

METHODS

We conducted a cross-sectional analysis of the National Health and Aging Trends Survey (2015), a nationally representative survey of Medicare beneficiaries ages ≥ 65 years old (N = 7,029). We calculated survey weight-adjusted prevalence estimates by mutually exclusive subgroups of no, hearing only, expressive-only, cognitive only, multiple CDs, and an aggregate any-CD prevalence. We described race/ethnicity, age, gender, education, marital status, social network size, federal poverty status, and supplemental insurance for all groups. Pearson's chi-squared statistic was used to compare sociodemographic characteristics between the any-CD and no-CD groups.

RESULTS

An estimated 25.3% (10.7 million) of community-dwelling older adults in the US experienced any-CDs in 2015; approximately 19.9% (8.4 million) experienced only one CD while 5.6% (2.4 million) had multiple. Older adults with CDs were more likely to be of Black race or Hispanic ethnicity as compared to older adults without CDs (Black 10.1 vs. 7.6%; Hispanic: 12.5 vs. 5.4%; P < 0.001). They also had lower educational attainment (Less than high school: 31.0 vs 12.4%; P < 0.001), lower poverty levels (<100% Federal poverty level: 23.5% vs. 11.1%; P < 0.001) and less social supports (Married: 51.3 vs. 61.0%; P < 0.001; Social network ≤ 1 person: 45.3 vs 36.0%; P < 0.001).

CONCLUSIONS

The proportion of the older adult population experiencing any-CDs is large and disproportionately represented by underserved sociodemographic groups. These findings support greater inclusion of any-CDs into population-level efforts like national surveys, public health goals, health services, and community research aimed at understanding and addressing the access needs of older adults who have disabilities in communication.

Self-perception of cognitive functions in patients with neurological impairments as measured against a translated Cognitive Change Index

The primary purpose of the study was to compare the results of neuropsychological assessments with results obtained using a translated Cognitive Change Index (CCI) on patients with diagnosed brain pathology. Our study included 54 patients diagnosed with neurologic pathology (stroke, TBI, or brain tumor) at the University Rehabilitation Institute Soca (average age = 51 years, SD = 15 years). The results of neuropsychological evaluations and anamnestic data were also obtained for the clinical subsample. Confirmatory factor analysis of the translated CCI performed on responses of 151 normative elderly participants supported a one-factor structure of the questionnaire. Cronbach's α was 0.77 in the clinical sample. A significant correlation was found between lower scores for attention and visual abilities using objective measurement tools and a person's self-assessment of impairment in their own cognitive functions (score on CCI). Individuals can perceive that their attention and visual abilities are impaired when those abilities also score low in diagnostic tests.

Postconcussion Symptoms and Neuropsychological Performance in Athletes: A Literature Review

ABSTRACT

Neuropsychological assessment is a common part of concussion evaluation and plays an important role within the context of a comprehensive multidisciplinary approach to managing sports-related concussion. A literature review has shown an assortment of cognitive domains used for evaluation of PCS with their corresponding tests. This review focuses on the various cognitive domains following single or multiple TBIs in athletes. Decreases in memory, executive function, language, psychomotor function, and self-reported cognitive function reached statistical significance in concussed athletes versus controls. Length of time since onset of symptoms correlated with worse memory function in chronic concussion athletes and more headache symptoms correlated with a worse outcome as well. However, some treatments are shown to be beneficial for restoration of cognitive function. When analyzing these results, it is imperative to be cognizant of the bias in the current literature. Further well-designed studies are needed to replicate these findings in larger more diverse samples.

Cognitive reserve index and long-term disability in patients with severe traumatic brain injury discharged from the intensive rehabilitation unit

Objectives

The "cognitive reserve" (CR) theory posits that higher premorbid cognitive activities can mitigate the effects of brain damage. This study aimed to investigate the association between CR and long-term functional autonomy in patients surviving a severe traumatic brain injury (sTBI).

Setting

Data were collected from the database of inpatients with severe acquired brain injury in a rehabilitation unit admitted from August 2012 to May 2020.

Participants

Patients that had incurred an sTBI, aged 18+ years, completing the phone Glasgow Outcome Scale-Expanded at follow-up (pGOS-E) in absence of previous brain trauma or neurological disease, or cognitive disorders were included. Patients with severe brain injury from non-traumatic etiologies were not included in the study.

Design

In this longitudinal study, all patients underwent a multidimensional assessment including the cognitive reserve index questionnaire (CRIq), the coma recovery scale-revised, the level of cognitive functioning, the Disability Rating Scale (DRS), and the Galveston Orientation and Amnesia Test at admission. At discharge, functional scales were administered again together with the Glasgow Outcome Scale. The pGOS-E was assessed at follow-up.

Main measures

pGOS-E.

Results

A total of 106 patients/caregivers underwent the pGOS-E after 5.8 [3.6] years from the event. Among them, 46 (43.4%) died after discharge, and 60 patients [men: 48 (80%); median age: 54 years; median time post-onset: 37 days; median education level: 10 years; median CRIq total score: 91] were included in the analysis exploring the association between pGOS-E and demographic data, cognitive reserve surrogates, and clinical variables at admission and discharge from the rehabilitation unit. A younger age (B = -0.035, p = 0.004) and a lower DRS category at discharge (B = -0.392, p = 0.029) were significantly related to a higher long-term functional autonomy in the multivariate analysis.

Conclusion

Long-term functional autonomy was not influenced by CR as assessed through the educational level and the CRIq.

Association of life-course traumatic brain injury with dementia risk: A nationwide twin study

INTRODUCTION

The impact of life-course traumatic brain injury (TBI) on dementia is unclear.

METHODS

Within the Swedish Twin Registry (STR), 35,312 dementia-free twins were followed for up to 18 years. TBI history was identified via medical records. Data were analyzed using generalized estimating equation (GEE) and conditional logistic regression.

RESULTS

In multi-adjusted GEE models, the odds ratio (OR, 95% confidence interval [CI]) of dementia was 1.27 (1.03-1.57) for TBI at any age, 1.55 (1.04-2.31) for TBI at 50 to 59 years, and 1.67 (1.12-2.49) for TBI at 60 to 69 years. Cardiometabolic diseases (CMDs) increased dementia risk associated with TBI at age 50 to 69 years. The ORs in GEE and conditional logistic regression did not differ significantly (P = .37).

DISCUSSION

TBI, especially between ages 50 and 69 years, is associated with an increased risk of dementia, and this is exacerbated among people with CMDs. Genetic and early-life environmental factors may not account for the TBI-dementia association.

Overview of the meningeal lymphatic vessels in aging and central nervous system disorders

In the aging process and central nervous system (CNS) diseases, the functions of the meningeal lymphatic vessels (MLVs) are impaired. Alterations in MLVs have been observed in aging-related neurodegenerative diseases, brain tumors, and even cerebrovascular disease. These findings reveal a new perspective on aging and CNS disorders and provide a promising therapeutic target. Additionally, recent neuropathological studies have shown that MLVs exchange soluble components between the cerebrospinal fluid (CSF) and interstitial fluid (ISF) and drain metabolites, cellular debris, misfolded proteins, and immune cells from the CSF into the deep cervical lymph nodes (dCLNs), directly connecting the brain with the peripheral circulation. Impairment and dysfunction of meningeal lymphatics can lead to the accumulation of toxic proteins in the brain, exacerbating the progression of neurological disorders. However, for many CNS diseases, the causal relationship between MLVs and neuropathological changes is not fully clear. Here, after a brief historical retrospection, we review recent discoveries about the hallmarks of MLVs and their roles in the aging and CNS diseases, as well as potential therapeutic targets for the treatment of neurologic diseases.

Chronic Cognitive and Cerebrovascular Function after Mild Traumatic Brain Injury in Rats

Severe traumatic brain injury (TBI) results in cognitive dysfunction in part due to vascular perturbations. In contrast, the long-term vasculo-cognitive pathophysiology of mild TBI (mTBI) remains unknown. We evaluated mTBI effects on chronic cognitive and cerebrovascular function and assessed their interrelationships. Sprague-Dawley rats received midline fluid percussion injury (n = 20) or sham (n = 21). Cognitive function was assessed (3- and 6-month novel object recognition [NOR], novel object location [NOL], and temporal order object recognition [TOR]). Six-month cerebral blood flow (CBF) and cerebral blood volume (CBV) using contrast magnetic resonance imaging (MRI) and ex vivo circle of Willis artery endothelial and smooth muscle-dependent function were measured. mTBI rats showed significantly impaired NOR, with similar trends (non-significant) in NOL/TOR. Regional CBF and CBV were similar in sham and mTBI. NOR correlated with CBF in lateral hippocampus, medial hippocampus, and primary somatosensory barrel cortex, whereas it inversely correlated with arterial smooth muscle-dependent dilation. Six-month baseline endothelial and smooth muscle-dependent arterial function were similar among mTBI and sham, but post-angiotensin 2 stimulation, mTBI showed no change in smooth muscle-dependent dilation from baseline response, unlike the reduction in sham. mTBI led to chronic cognitive dysfunction and altered angiotensin 2-stimulated smooth muscle-dependent vasoreactivity. The findings of persistent pathophysiological consequences of mTBI in this animal model add to the broader understanding of chronic pathophysiological sequelae in human mild TBI.

Risk Factors for Alzheimer Disease Development After Traumatic Brain Injury: A Preliminary Study

Traumatic brain injury (TBI) is increasingly recognized as a major risk factor for developing neurocognitive disorders, though this association remains controversial. Determination of risk factors for post-traumatic neurodegeneration in patients with TBI is critical given the high incidence of TBI. We hypothesized that cardiovascular and metabolic comorbidities, in addition to TBI severity, are associated with the risk of post-traumatic development of Alzheimer disease dementia (ADD). A case-controlled retrospective study was conducted using medical records and medical insurance data of 5642 patients with TBI admitted to a tertiary trauma center over a 12-year period, to assess risk factors of developing ADD after TBI. Logistic regression shows that presence of post-traumatic amnesia ( P= 0.03) and chronic vascular lesions ( P= 0.04) are significantly associated with development of ADD after TBI. This innovative preliminary study is the first to explore risk factors for post-traumatic ADD. Further association studies are essential to optimize care following TBI.

Cognitive functioning following traumatic brain injury in older adults: associations with social participation and health-related quality of life

OBJECTIVES

To describe objective and subjective cognitive functioning older adults who sustained TBI at age 65 or over, and to determine whether cognitive functioning is associated with health-related quality of life (HRQoL) and social participation.

METHOD

The sample consisted of 40 individuals with TBI (mean age = 73 years; 65% mild, 35% moderate/severe TBI). On average 15 months post-injury, they completed measures of objective and subjective cognitive functioning (Telephone Interview for Cognitive Status-Modified, Alphaflex, Medical Outcomes Study Cognitive Functioning Scale), HRQoL (SF-12), and social participation (Participation Assessment with Recombined Tools - Objective).

RESULTS

Mean score for objective cognitive functioning was lower than normative values, while mean scores for executive functioning and subjective cognitive functioning were comparable to normative values. There was no relationship between objective and subjective measures. Subjective cognitive functioning and (to a lesser extent) global objective cognitive functioning were significantly associated with mental HRQoL but not with physical HRQoL or social participation.

CONCLUSION

These results underscore the importance of considering both subjective perception and objective performance when assessing and intervening on cognition to promote better mental HRQoL in older adults with TBI.

Environmental enrichment improves traumatic brain injury-induced behavioral phenotype and associated neurodegenerative process

Traumatic brain injury (TBI) causes persistent cognitive impairment and neurodegeneration. Environmental enrichment (EE) refers to a housing condition that promotes sensory and social stimulation and improves cognition and motor performance but the underlying mechanisms responsible for such beneficial effects are not well defined. In this study, anesthetized adult rats received either a moderate-to-severe controlled cortical impact (CCI) or sham surgery and then were housed in either EE or standard conditions. The results showed a significant increase in protein nitration and oxidation of lipids, impaired cognition and motor performance, and augmented N-methyl-d-aspartate receptor subtype-1 (NMDAR1) levels. However, EE initiated 24 h after CCI resulted in reduced oxidative insult and microglial activation and significant improvement in beam-balance/walk performance and both spatial learning and memory. We hypothesize that following TBI there is an upstream activation of NMDAR that promotes oxidative insult and an inflammatory response, thereby resulting in impaired behavioral functioning but EE may exert a neuroprotective effect via sustained downregulation of NMDAR1.

Traumatic brain injury and post-traumatic stress disorder are not associated with Alzheimer's disease pathology measured with biomarkers

INTRODUCTION

Epidemiological studies report an association between traumatic brain injury (TBI) and post-traumatic stress disorder (PTSD) and clinically diagnosed Alzheimer's disease (AD). We examined the association between TBI/PTSD and biomarker-defined AD.

METHODS

We identified 289 non-demented veterans with TBI and/or PTSD and controls who underwent clinical evaluation, cerebrospinal fluid (CSF) collection, magnetic resonance imaging (MRI), amyloid beta (Aβ) and tau positron emission tomography, and apolipoprotein E testing. Participants were followed for up to 5.2 years.

RESULTS

Exposure groups (TBI, PTSD, and TBI + PTSD) had higher prevalence of mild cognitive impairment (MCI: P < .0001) and worse Mini-Mental State Examination scores (PTSD: P = .008; TBI & PTSD: P = .009) than controls. There were no significant differences in other cognitive scores, MRI volumes, Aβ or tau accumulation, or in most longitudinal measures.

DISCUSSION

TBI and/or PTSD were not associated with elevated AD biomarkers. The poorer cognitive status of exposed veterans may be due to other comorbid pathologies.

The Bidirectional Link Between Sleep Disturbances and Traumatic Brain Injury Symptoms: A Role for Glymphatic Dysfunction?

Mild traumatic brain injury (mTBI), often referred to as concussion, is a major cause of morbidity and mortality worldwide. Sleep disturbances are common after mTBI. Moreover, subjects who develop subjective sleep complaints after mTBI also report more severe somatic, mental health, and cognitive impairment and take longer to recover from mTBI sequelae. Despite many previous studies addressing the role of sleep in post-mTBI morbidity, the mechanisms linking sleep to recovery after mTBI remain poorly understood. The glymphatic system is a brainwide network that supports fluid movement through the cerebral parenchyma and the clearance of interstitial solutes and wastes from the brain. Notably, the glymphatic system is active primarily during sleep. Clearance of cellular byproducts related to somatic, mental health, and neurodegenerative processes (e.g., amyloid-β and tau, among others) depends in part on intact glymphatic function, which becomes impaired after mTBI. In this viewpoint, we review the current knowledge regarding the association between sleep disturbances and post-mTBI symptoms. We also discuss the role of glymphatic dysfunction as a potential link between mTBI, sleep disruption, and posttraumatic morbidity. We outline a model where glymphatic dysfunction and sleep disruption caused by mTBI may have an additive effect on waste clearance, leading to cerebral dysfunction and impaired recovery. Finally, we review the novel techniques being developed to examine glymphatic function in humans and explore potential interventions to alter glymphatic exchange that may offer a novel therapeutic approach to those experiencing poor sleep and prolonged symptoms after mTBI.

Lipoxins in the Nervous System: Brighter Prospects for Neuroprotection

Lipoxins (LXs) are generated from arachidonic acid and are involved in the resolution of inflammation and confer protection in a variety of pathological processes. In the nervous system, LXs exert an array of protective effects against neurological diseases, including ischemic or hemorrhagic stroke, neonatal hypoxia-ischemia encephalopathy, brain and spinal cord injury, Alzheimer's disease, multiple sclerosis, and neuropathic pain. Lipoxin administration is a potential therapeutic strategy in neurological diseases due to its notable efficiency and unique superiority regarding safety. Here, we provide an overview of LXs in terms of their synthesis, signaling pathways and neuroprotective evidence. Overall, we believe that, along with advances in lipoxin-related drug design, LXs will bring brighter prospects for neuroprotection.

Traumatic Brain Injury Is Associated With Both Hemorrhagic Stroke and Ischemic Stroke: A Systematic Review and Meta-Analysis

Background

Traumatic brain injury (TBI) is considered a risk factor for the development of stroke (Hemorrhagic Stroke and Ischemic Stroke). We performed this systemic review and meta-analysis to determine the association of prior TBI with the subsequent diagnosis of stroke.

Methods

We systematically searched PubMed, EMBASE, and the Cochrane Library for cohort studies involving TBI patients who subsequently developed stroke. Study selection, data extraction, and quality assessment were performed by two separate researchers. Data were analyzed with random-effects models, and a secondary analysis stratified by the type of stroke was performed.

Results

Of the 741 identified studies, 6 studies were eligible for inclusion, with more than 2,200,000 participants. TBI predicted the occurrence of stroke in the random-effect model, with a relative risk of 2.14 (95% CI 1.97–2.32, P < 0.001). Furthermore, in the analysis of each type of stroke, TBI was associated with the incidence of ischemic stroke (RR 1.351 95% CI 1.212–1.506, P < 0.001), and TBI was associated with an even greater increase in the incidence of hemorrhagic stroke (RR 6.118 95% CI 5.265–7.108, P < 0.001).

Conclusion

Our meta-analysis showed that TBI was associated with a more than two-fold increase in the risk of stroke. However, owing to the high degree of heterogeneity, decisions should be made on a patient-by-patient basis. The occurrence of TBI is associated with the development of both hemorrhagic and ischemic stroke, and the risk of hemorrhagic stroke is much higher than that of ischemic stroke in TBI patients.

Advanced brain age in deployment-related traumatic brain injury: A LIMBIC-CENC neuroimaging study

OBJECTIVE

To determine if history of mild traumatic brain injury (mTBI) is associated with advanced or accelerated brain aging among the United States (US) military Service Members and Veterans.

METHODS

Eight hundred and twenty-two participants (mean age = 40.4 years, 714 male/108 female) underwent MRI sessions at eight sites across the US. Two hundred and one participants completed a follow-up scan between five months and four years later. Predicted brain ages were calculated using T1-weighted MRIs and then compared with chronological ages to generate an Age Deviation Score for cross-sectional analyses and an Interval Deviation Score for longitudinal analyses. Participants also completed a neuropsychological battery, including measures of both cognitive functioning and psychological health.

RESULT

In cross-sectional analyses, males with a history of deployment-related mTBI showed advanced brain age compared to those without (t(884) = 2.1, p = .038), while this association was not significant in females. In follow-up analyses of the male participants, severity of posttraumatic stress disorder (PTSD), depression symptoms, and alcohol misuse were also associated with advanced brain age.

CONCLUSION

History of deployment-related mTBI, severity of PTSD and depression symptoms, and alcohol misuse are associated with advanced brain aging in male US military Service Members and Veterans.

Association of Traumatic Brain Injury With Mortality Among Military Veterans Serving After September 11, 2001

IMPORTANCE

Emerging evidence suggests that harmful exposures during military service, such as traumatic brain injury (TBI), may contribute to mental health, chronic disease, and mortality risks.

OBJECTIVE

To assess the mortality rates and estimate the number of all-cause and cause-specific excess deaths among veterans serving after the September 11, 2001, terrorist attacks (9/11) with and without exposure to TBI.

DESIGN, SETTING, AND PARTICIPANTS

This cohort study analyzed administrative and mortality data from January 1, 2002, through December 31, 2018, for a cohort of US military veterans who served during the Global War on Terrorism after the 9/11 terrorist attacks. Veterans who served active duty after 9/11 with 3 or more years of care in the Military Health System or had 3 or more years of care in the Military Health System and 2 or more years of care in the Veterans Health Administration were included for analysis. The study used data from the Veterans Affairs/Department of Defense Identity Repository database, matching health records data from the Military Health Service Management Analysis and Reporting tool, the Veterans Health Administration Veterans Informatics and Computing Infrastructure, and the National Death Index. For comparison with the total US population, the study used the Centers for Disease Control and Prevention WONDER database. Data analysis was performed from June 16 to September 8, 2021.

EXPOSURE

Traumatic brain injury.

MAIN OUTCOMES AND MEASURES

Multivariable, negative binomial regression models were used to estimate adjusted all-cause and cause-specific mortality rates for the post-9/11 military veteran cohort, stratified by TBI severity level, and the total US population. Differences in mortality rates between post-9/11 military veterans and the total US population were used to estimate excess deaths from each cause of death.

RESULTS

Among 2 516 189 post-9/11 military veterans (2 167 736 [86.2%] male; and 45 324 [1.8%] American Indian/Alaska Native, 160 178 [6.4%], Asian/Pacific Islander, 259 737 [10.3%] Hispanic, 387 926 [15.4%] non-Hispanic Black, 1 619 834 [64.4%] non-Hispanic White, and 43 190 [1.7%] unknown), 17.5% had mild TBI and 3.0% had moderate to severe TBI; there were 30 564 deaths. Adjusted, age-specific mortality rates were higher for post-9/11 military veterans than for the total US population and increased with TBI severity. There were an estimated 3858 (95% CI, 1225-6490) excess deaths among all post-9/11 military veterans. Of these, an estimated 275 (95% CI, -1435 to 1985) were not exposed to TBI, 2285 (95% CI, 1637 to 2933) had mild TBI, and 1298 (95% CI, 1023 to 1572) had moderate to severe TBI. Estimated excess deaths were predominantly from suicides (4218; 95% CI, 3621 to 4816) and accidents (2631; 95% CI, 1929 to 3333). Veterans with moderate to severe TBI accounted for 33.6% of total excess deaths, 11-fold higher than would otherwise be expected.

CONCLUSIONS AND RELEVANCE

This military veteran cohort experienced more excess mortality compared with the total US population than all combat deaths from 9/11/01 through 9/11/21, concentrated among individuals exposed to TBI. These results suggest that a focus on what puts veterans at risk for accelerated aging and increased mortality is warranted.

The influence of cognitive reserve in the protection of the cognitive status after an acquired brain injury: A systematic review

BACKGROUND

Cognitive Reserve (CR) hypothesis was introduced to account for the variability in cognitive performance of patients with similar degrees of brain injury or pathology. The individual variability of CR is modulated by the interaction of innate capacities and exposures throughout life, which can act as protectors against neuropathology's clinical effects. Individuals with higher CR appear to have better cognitive performance after a brain injury. The present review aimed to identify and map the scientific evidence available in literature regarding CR's influence in protecting the cognitive status after an Acquired Brain Injury (ABI).

METHOD

A systematic review was performed for published studies until October 2020 in PubMed, Scopus, and CINAHL electronic databases. Studies regarding CR's influence in protecting the cognitive status after an ABI were included in this review. The Newcastle-Ottawa Scale was used to assess risk of bias in the included studies. This systematic review was recorded in the International Prospective Register of Systematic Reviews (PROSPERO) under the number CRD42021236594.

RESULTS

Twenty-one studies published between 2003 and 2020 were selected and analyzed. The literature analysis showed that CR has a positive effect on cognitive status after an ABI. Various proxies were used to estimate CR, including estimated premorbid IQ, education, occupation attainment, socioeconomic status, leisure activities, bilingualism, and social integration. CR proxies constitute a set of variables that may have a significant influence on cognitive status. Higher CR levels were associated with lower cognitive impairment after an ABI.

CONCLUSIONS

Although more research is necessary for a complete understanding of CR's impact on cognition, the synthesis of these studies confirmed that there is evidence on the beneficial impact of CR on cognitive status after an ABI. These findings support CR's cognitive status role following an ABI and may provide additional information for prognosis and rehabilitation plans.

ENIGMA brain injury: Framework, challenges, and opportunities

Traumatic brain injury (TBI) is a major cause of disability worldwide, but the heterogeneous nature of TBI with respect to injury severity and health comorbidities make patient outcome difficult to predict. Injury severity accounts for only some of this variance, and a wide range of preinjury, injury-related, and postinjury factors may influence outcome, such as sex, socioeconomic status, injury mechanism, and social support. Neuroimaging research in this area has generally been limited by insufficient sample sizes. Additionally, development of reliable biomarkers of mild TBI or repeated subconcussive impacts has been slow, likely due, in part, to subtle effects of injury and the aforementioned variability. The ENIGMA Consortium has established a framework for global collaboration that has resulted in the largest-ever neuroimaging studies of multiple psychiatric and neurological disorders. Here we describe the organization, recent progress, and future goals of the Brain Injury working group.

Multiple Past Concussions in High School Hockey Players: Examining Cognitive Functioning and Symptom Reporting

OBJECTIVE

To investigate (1) if there are meaningful differences in baseline preseason cognitive functioning or symptom reporting between high school ice hockey players with and without prior concussions and (2) determine which health history variables predict symptom reporting.

DESIGN

Cross-sectional study.

SETTING

High schools across the state of Maine.

PARTICIPANTS

Participants were 1616 male high school ice hockey players (mean age = 15.6 years; SD = 1.5 years) who completed baseline testing between 2009 and 2015.

INDEPENDENT VARIABLES

Athletes were grouped according to their self-reported concussion history [0 (n = 1136), 1 (n = 321), 2 (n = 112), or 3+ (n = 47) previous concussions].

MAIN OUTCOME MEASURES

Cognitive functioning was measured by the Immediate Post-Concussion Assessment and Cognitive Testing (ImPACT) battery, and symptom ratings were obtained from the Post-Concussion Symptom Scale.

RESULTS

There were no statistically significant differences between groups in cognitive functioning as measured by ImPACT. The group with ≥3 prior concussions endorsed higher total symptom scores, but the effect sizes were small and not statistically significant. In a multivariate model, prior treatment for headaches (not necessarily migraines), prior treatment for a psychiatric condition, and prior treatment for substance/alcohol use all significantly predicted total symptom scores, with concussion history being the weakest independent predictor.

CONCLUSIONS

Players with a history of prior concussions performed similarly to players with no prior concussions on cognitive testing. Health history factors were more strongly associated with symptom reporting than concussion history.

Current Concepts in Intracranial Interstitial Fluid Transport and the Glymphatic System: Part II-Imaging Techniques and Clinical Applications

The glymphatic system is a recently discovered network unique to the central nervous system that allows for dynamic exchange of interstitial fluid (ISF) and cerebrospinal fluid (CSF). As detailed in part I, ISF and CSF transport along paravascular channels of the penetrating arteries and possibly veins allow essential clearance of neurotoxic solutes from the interstitium to the CSF efflux pathways. Imaging tests to investigate this neurophysiologic function, although challenging, are being developed and are reviewed herein. These include direct visualization of CSF transport using postcontrast imaging techniques following intravenous or intrathecal administration of contrast material and indirect glymphatic assessment with detection of enlarged perivascular spaces. Application of MRI techniques, including intravoxel incoherent motion, diffusion tensor imaging, and chemical exchange saturation transfer, is also discussed, as are methods for imaging dural lymphatic channels involved with CSF efflux. Subsequently, glymphatic function is considered in the context of proteinopathies associated with neurodegenerative diseases and traumatic brain injury, cytotoxic edema following acute ischemic stroke, and chronic hydrocephalus after subarachnoid hemorrhage. These examples highlight the substantial role of the glymphatic system in neurophysiology and the development of certain neuropathologic abnormalities, stressing the importance of its consideration when interpreting neuroimaging investigations. © RSNA, 2021.

Orientation of neurites influences severity of mechanically induced tau pathology

Chronic traumatic encephalopathy is a neurodegenerative disease associated with repeated traumatic brain injury (TBI). Chronic traumatic encephalopathy is a tauopathy, in which cognitive decline is accompanied by the accumulation of neurofibrillary tangles of the protein tau in patients' brains. We recently found that mechanical force alone can induce tau mislocalization to dendritic spines and loss of synaptic function in in vitro neuronal cultures with random cell organization. However, in the brain, neurons are highly aligned, so here we aimed to determine how neuronal organization influences early-stage tauopathy caused by mechanical injury. Using microfabricated cell culture constructs to control the growth of neurites and an in vitro simulated TBI device to apply controlled mechanical deformation, we found that neuronal orientation with respect to the direction of a uniaxial high-strain-rate stretch injury influences the degree of tau pathology in injured neurons. We found that a mechanical stretch applied parallel to the neurite alignment induces greater mislocalization of tau proteins to dendritic spines than does a stretch with the same strain applied perpendicular to the neurites. Synaptic function, characterized by the amplitude of miniature excitatory postsynaptic currents, was similarly decreased in neurons with neurites aligned parallel to stretch, whereas in neurons aligned perpendicular to stretch, it had little to no functional loss. Experimental injury parameters (strain, strain rate, direction of stretch) were combined with a standard viscoelastic solid model to show that in our in vitro model, neurite work density during stretch correlates with tau mislocalization. These findings suggest that in a TBI, the magnitude of brain deformation is not wholly predictive of neurodegenerative consequences of TBI but that deformation relative to local neuronal architecture and the neurite mechanical energy during injury are better metrics for predicting trauma-induced tauopathy.

Duration of post-traumatic amnesia is uniquely associated with memory functioning in chronic moderate-to-severe traumatic brain injury

BACKGROUND

Disrupted memory circuitry may contribute to post-traumatic amnesia (PTA) after traumatic brain injury (TBI). It is unclear whether duration of PTA (doPTA) uniquely impacts memory functioning in the chronic post-injury stage.

OBJECTIVE

To examine the relationship between doPTA and memory functioning, independent of other cognitive abilities, in chronic moderate-to-severe TBI.

METHODS

Participants were 82 individuals (median chronicity = 10.5 years) with available doPTA estimates and neuropsychological data. Composite memory, processing speed (PS), and executive functioning (EF) performance scores, as well as data on subjective memory (SM) beliefs, were extracted. DoPTA-memory associations were evaluated via linear modeling of doPTA with memory performance and clinical memory status (impaired/unimpaired), controlling for PS, EF and demographic covariates. Interrelationships between doPTA, objective memory functioning, and SM were assessed.

RESULTS

DoPTA was significantly related to memory performance, even after covariate adjustment. Impairment in memory, but not PS or EF, was associated with a history of longer doPTA. SM was associated with memory performance, but unrelated to doPTA.

CONCLUSIONS

Findings suggest a specific association between doPTA-an acute injury phenomenon-and chronic memory deficits after TBI. Prospective studies are needed to understand how underlying mechanisms of PTA shape distinct outcome trajectories, particularly functional abilities related to memory processing.

Distant histories of mild traumatic brain injury exacerbate age-related differences in white matter properties

We examined associations of distant histories of mild traumatic brain injury (mTBI) with non-linear and linear trajectories of white matter (WM) properties across a wide age range (23-77). Diffusion tensor imaging (DTI) data obtained from 171 Veterans with histories of clinically diagnosed mTBIs and 115 controls were subjected to tractography, isolating 20 major WM tracts. Non-linear and linear effects of age on each tract's diffusion properties were examined in terms of their interactions with group (mTBI and control). The non-linear model revealed 7 tracts in which the mTBI group's DTI metrics rapidly deviated from control trajectories in middle and late adulthoods, despite the injuries having occurred in the late 20s, on average. In contrast, no interactions between prior injuries and age were detected when examining linear trajectories. Distant mTBIs may thus accelerate normal age-related trajectories of WM degeneration much later in life. As such, life-long histories of head trauma should be assessed in all patients in their mid-to-late adulthoods, whether neurologically healthy or presenting with seemingly unrelated neuropathology.

Glial AP1 is activated with aging and accelerated by traumatic brain injury

The emergence of degenerative disease after traumatic brain injury is often described as an acceleration of normal age-related processes. Whether similar molecular processes occur after injury and in age is unclear. Here we identify a functionally dynamic and lasting transcriptional response in glia, mediated by the conserved transcription factor AP1. In the early post-TBI period, glial AP1 is essential for recovery, ensuring brain integrity and animal survival. In sharp contrast, chronic AP1 activation promotes human tau pathology, tissue loss, and mortality. We show a similar process activates in healthy fly brains with age. In humans, AP1 activity is detected after moderate TBI and correlates with microglial activation and tau pathology. Our data provide key molecular insight into glia, highlighting that the same molecular process drives dynamic and contradictory glia behavior in TBI, and possibly age, first acting to protect but chronically promoting disease.

Sleep in Neurologic Disorders

Sleep is a complex brain state with fundamental relevance for cognitive functions, synaptic plasticity, brain resilience, and autonomic balance. Sleep pathologies may interfere with cerebral circuit organization, leading to negative consequences and favoring the development of neurologic disorders. Conversely, the latter can interfere with sleep functions. Accordingly, assessment of sleep quality is always recommended in the diagnosis of patients with neurologic disorders and during neurorehabilitation programs. This review investigates the complex interplay between sleep and brain pathologies, focusing on diseases in which the association with sleep disturbances is commonly overlooked and whereby major benefits may derive from their proper management.

Cognitive Reserve in Individuals Aging With Traumatic Brain Injury: Independent and Interactive Effects on Cognitive Functioning

OBJECTIVE

To examine the influence of 2 temporal factors-age and injury chronicity-on the relationship between cognitive reserve (CR) and cognitive functioning in older adults with chronic traumatic brain injury (TBI).

SETTING

Outpatient research laboratory.

PARTICIPANTS

Adults, 50 years or older, with a 1- to 45-year history of moderate or severe TBI (N = 108).

DESIGN

Cross-sectional observational study.

MAIN MEASURES

CR was estimated using demographically corrected performance on a word-reading test (an approximation of premorbid IQ). Injury chronicity was operationalized as number of years since the date of injury. Composite cognitive scores were computed from performances on neuropsychological tests of processing speed, executive functioning, and memory.

RESULTS

CR was positively and significantly related to all cognitive performances independent of age, injury chronicity, and injury severity. Greater injury chronicity significantly attenuated the effect of CR on processing speed such that individuals more distal from their injury date evidenced a weaker positive relationship between CR and performance.

CONCLUSION

Temporal factors may modify associations between CR and cognition. Findings suggest that the protective effects of CR are temporally delimited, potentially contending with declines in brain reserve. The prognostic value of traditional outcome determinants should be considered in the context of injury chronicity.

Acute cognitive impairment after traumatic brain injury predicts the occurrence of brain atrophy patterns similar to those observed in Alzheimer's disease

Traumatic brain injuries (TBIs) are often followed by persistent structural brain alterations and by cognitive sequalae, including memory deficits, reduced neural processing speed, impaired social function, and decision-making difficulties. Although mild TBI (mTBI) is a risk factor for Alzheimer's disease (AD), the extent to which these conditions share patterns of macroscale neurodegeneration has not been quantified. Comparing such patterns can not only reveal how the neurodegenerative trajectories of TBI and AD are similar, but may also identify brain atrophy features which can be leveraged to prognosticate AD risk after TBI. The primary aim of this study is to systematically map how TBI affects white matter (WM) and gray matter (GM) properties in AD-analogous patterns. Our findings identify substantial similarities in the regional macroscale neurodegeneration patterns associated with mTBI and AD. In cerebral GM, such similarities are most extensive in brain areas involved in memory and executive function, such as the temporal poles and orbitofrontal cortices, respectively. Our results indicate that the spatial pattern of cerebral WM degradation observed in AD is broadly similar to the pattern of diffuse axonal injury observed in TBI, which frequently affects WM structures like the fornix, corpus callosum, and corona radiata. Using machine learning, we find that the severity of AD-like brain changes observed during the chronic stage of mTBI can be accurately prognosticated based on acute assessments of post-traumatic mild cognitive impairment. These findings suggest that acute post-traumatic cognitive impairment predicts the magnitude of AD-like brain atrophy, which is itself associated with AD risk.

Complement Drives Synaptic Degeneration and Progressive Cognitive Decline in the Chronic Phase after Traumatic Brain Injury

Cognitive deficits following traumatic brain injury (TBI) remain a major cause of disability and early-onset dementia, and there is increasing evidence that chronic neuroinflammation occurring after TBI plays an important role in this process. However, little is known about the molecular mechanisms responsible for triggering and maintaining chronic inflammation after TBI. Here, we identify complement, and specifically complement-mediated microglial phagocytosis of synapses, as a pathophysiological link between acute insult and a chronic neurodegenerative response that is associated with cognitive decline. Three months after an initial insult, there is ongoing complement activation in the injured brain of male C57BL/6 mice, which drives a robust chronic neuroinflammatory response extending to both hemispheres. This chronic neuroinflammatory response promotes synaptic degeneration and predicts progressive cognitive decline. Synaptic degeneration was driven by microglial phagocytosis of complement-opsonized synapses in both the ipsilateral and contralateral brain, and complement inhibition interrupted the degenerative neuroinflammatory response and reversed cognitive decline, even when therapy was delayed until 2 months after TBI. These findings provide new insight into our understanding of TBI pathology and its management; and whereas previous therapeutic investigations have focused almost exclusively on acute treatments, we show that all phases of TBI, including at chronic time points after TBI, may be amenable to therapeutic interventions, and specifically to complement inhibition.SIGNIFICANCE STATEMENT There is increasing evidence of a chronic neuroinflammatory response after traumatic brain injury (TBI), but little is known about the molecular mechanisms responsible for triggering and maintaining chronic inflammation. We identify complement, and specifically complement-mediated microglial phagocytosis of synapses, as a pathophysiological link between acute insult and a chronic neurodegenerative response, and further that this response is associated with cognitive decline. Complement inhibition interrupted this response and reversed cognitive decline, even when therapy was delayed until 2 months after injury. The data further support the concept that TBI should be considered a chronic rather than an acute disease condition, and have implications for the management of TBI in the chronic phase of injury, specifically with regard to the therapeutic application of complement inhibition.

Disentangling the effects of age and mild traumatic brain injury on brain network connectivity: A resting state fMRI study

INTRODUCTION

Cognitive complaints are common shortly after mild traumatic brain injury (mTBI) but may persist up to years. Age-related cognitive decline can worsen these symptoms. However, effects of age on mTBI sequelae have scarcely been investigated.

METHODS

Fifty-four mTBI patients (median age: 35 years, range 19-64 years, 67% male) and twenty age- and sex-matched healthy controls were studied using resting state functional magnetic resonance imaging in the sub-acute phase. Independent component analysis was used to identify intrinsic connectivity networks (ICNs). A multivariate approach was adopted to evaluate the effects of age and group on the ICNs in terms of (static) functional network connectivity (FNC), intensities of spatial maps (SMs) and time-course spectral power (TC).

RESULTS

We observed significant age-related changes for a) FNC: changes between 10 pairs of ICNs, mostly involving the default mode (DM) and/or the cognitive-control (CC) domains; b) SMs: intensity decrease in clusters across three domains and intensity increase in clusters across two domains, including the CC but not the DM and c) TC: spectral power decrease within the 0-0.15 Hz range and increase within the 0.20-0.25 Hz range for increasing age within networks located in frontal areas, including the anterior DM. Groups only differed for TC within the 0.065-0.10 Hz range in the cerebellar ICN and no age × group interaction effect was found.

CONCLUSIONS

We showed robust effects of age on connectivity between and within ICNs that are associated with cognitive functioning. Differences between mTBI patients and controls were only found for activity in the cerebellar network, increasingly recognized to participate in cognition. Our results suggest that to allow for capturing the true effects related to mTBI and its effects on cognitive functioning, age should be included as a covariate in mTBI studies, in addition to age-matching groups.

Understanding the relationship between cognitive performance and function in daily life after traumatic brain injury

OBJECTIVE

Cognitive impairment is a key cause of disability after traumatic brain injury (TBI) but relationships with overall functioning in daily life are often modest. The aim is to examine cognition at different levels of function and identify domains associated with disability.

METHODS

1554 patients with mild-to-severe TBI were assessed at 6 months post injury on the Glasgow Outcome Scale-Extended (GOSE), the Short Form-12v2 and a battery of cognitive tests. Outcomes across GOSE categories were compared using analysis of covariance adjusting for age, sex and education.

RESULTS

Overall effect sizes were small to medium, and greatest for tests involving processing speed (ηp 2 0.057-0.067) and learning and memory (ηp 2 0.048-0.052). Deficits in cognitive performance were particularly evident in patients who were dependent (GOSE 3 or 4) or who were unable to participate in one or more major life activities (GOSE 5). At higher levels of function (GOSE 6-8), cognitive performance was surprisingly similar across categories. There were decreases in performance even in patients reporting complete recovery without significant symptoms. Medium to large effect sizes were present for summary measures of cognition (ηp 2 0.111), mental health (ηp 2 0.131) and physical health (ηp 2 0.252).

CONCLUSIONS

This large-scale study provides novel insights into cognitive performance at different levels of disability and highlights the importance of processing speed in function in daily life. At upper levels of outcome, any influence of cognition on overall function is markedly attenuated and differences in mental health are salient.