Linking Type and Extent of Head Trauma to Cavum Septum Pellucidum in Older Adults With and Without Alzheimer Disease and Related Dementias

BACKGROUND AND OBJECTIVES

Cavum septum pellucidum (CSP) is a common but nonspecific MRI finding in individuals with prior head trauma. The type and extent of head trauma related to CSP, CSP features specific to head trauma, and the impact of brain atrophy on CSP are unknown. We evaluated CSP cross-sectionally and longitudinally in healthy and clinically impaired older adults who underwent detailed lifetime head trauma characterization.

METHODS

This is an observational cohort study of University of California, San Francisco Memory and Aging Center participants (healthy controls [HCs], those with Alzheimer disease or related dementias [ADRDs], subset with traumatic encephalopathy syndrome [TES]). We characterized traumatic brain injury (TBI) and repetitive head impacts (RHI) through contact/collision sports. Study groups were no RHI/TBI, prior TBI only, prior RHI only, and prior RHI + TBI. We additionally looked within TBI (1, 2, or 3+) and RHI (1-4, 5-10, and 11+ years). All underwent baseline MRI, and 67% completed a second MRI (median follow-up = 5.4 years). CSP measures included grade (0-4) and length (millimeters). Groups were compared on likelihood of CSP (logistic regression, odds ratios [ORs]) and whether CSP length discriminated groups (area under the curve [AUC]).

RESULTS

Our sample included 266 participants (N = 160 HCs, N = 106 with ADRD or TES; age 66.8 ± 8.2 years, 45.3% female). Overall, 123 (49.8%) participants had no RHI/TBI, 52 (21.1%) had TBI only, 41 (16.6%) had RHI only, 31 (12.6%) had RHI + TBI, and 20 were classified as those with TES (7.5%). Compared with no RHI/TBI, RHI + TBI (OR 3.11 [1.23-7.88]) and TES (OR 11.6 [2.46-54.8]) had greater odds of CSP. Approximately 5-10 years (OR 2.96 [1.13-7.77]) and 11+ years of RHI (OR 3.14 [1.06-9.31]) had higher odds of CSP. CSP length modestly discriminated participants with 5-10 years (AUC 0.63 [0.51-0.75]) and 11+ years of prior RHI (AUC 0.69 [0.55-0.84]) from no RHI/TBI (cut point = 6 mm). Strongest effects were noted in analyses of American football participation. Longitudinally, CSP grade was unchanged in 165 (91.7%), and length was unchanged in 171 (95.5%) participants.

DISCUSSION

Among older adults with and without neurodegenerative disease, risk of CSP is driven more by duration (years) of RHI, especially American football, than number of TBI. CSP length (≥6 mm) is relatively specific to individuals who have had substantial prior RHI. Neurodegenerative disease and progressive atrophy do not clearly influence development or worsening of CSP.

Healthy Days at Home Among Older Medicare Beneficiaries With Traumatic Brain Injury Requiring Inpatient Rehabilitation

OBJECTIVE

The objectives of this study were to characterize and identify correlates of healthy days at home (HDaH) before and after TBI requiring inpatient rehabilitation. Setting: Inpatient hospital, nursing home, and home health services.

PARTICIPANTS

Average of n= 631 community-dwelling fee-for-service age 66+ Medicare beneficiaries across 30 replicate samples who were hospitalized for traumatic brain injury (TBI) between 2012 and 2014 and admitted to an inpatient rehabilitation facility (IRF) within 72 hours of hospital discharge.

DESIGN

Retrospective study using data from Medicare claims supplemented with data from the National Trauma Databank.

MAIN MEASURES

The primary outcome, HDaH, was calculated as time alive not using inpatient hospital, nursing home, and home health services in the year before TBI hospitalization and after IRF discharge.

RESULTS

We found HDaH declined from 93.2% in the year before TBI hospitalization to 65.3% in the year after IRF discharge (73.6% among survivors only). Most variability in HDaH was: (1) in the first 3 months after discharge and (2) by discharge disposition, with persons discharged from IRF to another acute hospital having the worst prognosis for utilization and death. In negative binomial regression models, the strongest predictors of HDaH in the year after discharge were rehabilitation Functional Independence Measure mobility score (β = 0.03; 95% CI, 0.002-0.06) and inpatient Charlson Comorbidity Index score (β = - 0.06; 95% CI, -0.13 to 0.001). Dual Medicaid eligible was associated with less HDaH among survivors (β = - 0.37; 95% CI, -0.66 to -0.07).

CONCLUSION

In this study, among community-dwelling older adults with TBI, we found a notable decrease in the proportion of time spent alive at home without higher-level care after IRF discharge compared to before TBI. The finding that physical disability and comorbidities were the biggest drivers of healthy days alive in this population suggests that a chronic disease management model is required for older adults with TBI to manage their complex health care needs.

Prognostic Value of Frailty for Outcome Following Traumatic Brain Injury: A Systematic Review and Meta-Analysis

Frailty is a known predictor of negative health outcomes. The role of frailty in predicting outcomes after traumatic brain injury (TBI), however, is unclear. This systematic review aimed to evaluate the association between frailty and adverse outcomes in patients with TBI. We identified relevant articles that investigated the relationship between frailty and outcomes in patients with TBI by searching PubMed/MEDLINE, Web of Science, Scopus, and EMBASE from inception until 23 March 2023. To evaluate the risk of bias in the included studies, we utilized the Newcastle-Ottawa Scale (NOS). In addition, quantitative synthesis and meta-analyses were performed. We identified 12 studies that met our inclusion criteria; three were prospective. Of included studies, eight had low risk, three had moderate risk, and one had high risk of bias. Frailty was significantly associated with death in five studies, with an increased risk of in-hospital death and complications observed in frail patients. Frailty was associated with longer hospital stays and unfavorable outcome measured by the Extended Glasgow Outcome Scale (GOSE) in four studies. The meta-analysis found that higher frailty significantly increased the odds of non-routine discharge and unfavorable outcome as measured by GOSE scores of 4 or lower. The pooled odds ratio (OR) for non-routine discharge, was 1.80, with a 95% confidence interval (CI) of 1.15-2.84; and for unfavorable outcome, it was 1.91, with a 95% CI of 1.09-3.36. The analysis, however, did not find a significant predictive role for frailty on death (30-day or in-hospital death). The OR for higher frailty and death was 1.42 with a 95% CI of 0.92-2.19. Frailty should be considered in the evaluation of patients with TBI to identify those who may be at increased risk of negative outcomes.

Association Between Insomnia and Mental Health and Neurocognitive Outcomes Following Traumatic Brain Injury

We previously described five trajectories of insomnia (each defined by a distinct pattern of insomnia severity over 12 months following traumatic brain injury [TBI]). Our objective in the present study was to estimate the association between insomnia trajectory status and trajectories of mental health and neurocognitive outcomes during the 12 months after TBI. In this study, participants included N = 2022 adults from the Federal Inter-agency Traumatic Brain Injury Repository database and Transforming Research and Clinical Knowledge in TBI (TRACK-TBI) study. The following outcome measures were assessed serially at 2 weeks, and 3, 6, and 12 months post-injury: Insomnia Severity Index, Patient Health Questionnaire, Post-Traumatic Stress Disorder (PTSD) Checklist for Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5), Patient Reported Outcomes Measurement Information System-Pain, and Quality of Life After Brain Injury-Overall Scale. Neurocognitive performance was assessed at 2 weeks, and 6 and 12 months using the Wechsler Adult Intelligence Scales Processing Speed Index and the Trails Making Test Parts A and B. Results indicated that greater insomnia severity was associated with greater abnormality in mental health, quality of life, and neuropsychological testing outcomes. The pattern of insomnia over time tracked the temporal pattern of all these outcomes for all but a very small number of participants. Notably, severe insomnia at 3 or 6 months post-TBI was a risk factor for poor recovery at 12 months post-injury. In conclusion, in this well-characterized sample of individuals with TBI, insomnia severity generally tracked severity of depression, pain, PTSD, quality of life, and neurocognitive outcomes over 12 months post-injury. More intensive sleep assessment is needed to elucidate the nature of these relationships and to help inform best strategies for intervention.

Traumatic Brain Injury and Long-Term Risk of Stroke Among US Military Veterans

BACKGROUND

Traumatic brain injury (TBI) is associated with significant morbidity, but the association of TBI with long-term stroke risk in diverse populations remains less clear. Our objective was to examine the long-term associations of TBI with stroke and to investigate potential differences by age, sex, race and ethnicity, and time since TBI diagnosis.

METHODS

Retrospective cohort study of US military veterans aged 18+ years receiving healthcare in the Veterans Health Administration system between October 1, 2002 and September 30, 2019. Veterans with TBI were matched 1:1 to veterans without TBI on age, sex, race and ethnicity, and index date, yielding 306 796 veterans with TBI and 306 796 veterans without TBI included in the study. In primary analyses, Fine-Gray proportional hazards models adjusted for sociodemographics and medical/psychiatric comorbidities were used to estimate the association between TBI and stroke risk, accounting for the competing risk of mortality.

RESULTS

Participants were a mean age of 50 years, 9% were female, and 25% were of non-White race and ethnicity. Overall, 4.7% of veterans developed a stroke over a median follow-up of 5.2 years. Veterans with TBI had 1.69 times (95% CI, 1.64-1.73) increased risk of any stroke (ischemic or hemorrhagic) compared to veterans without TBI. This increased risk was highest in the first-year post-TBI diagnosis (hazard ratio [HR], 2.16 [95% CI, 2.03-2.29]) but remained elevated for 10+ years. Similar patterns were observed for secondary outcomes, with associations of TBI with hemorrhagic stroke (HR, 3.92 [95% CI, 3.59-4.29]) being stronger than with ischemic stroke (HR, 1.56 [95% CI, 1.52-1.61]). Veterans with both mild (HR, 1.47 [95% CI, 1.43-1.52]) and moderate/severe/penetrating injury (HR, 2.02 [95% CI, 1.96-2.09]) had increased risk of stroke compared to veterans without TBI. Associations of TBI with stroke were stronger among older compared to younger individuals (P interaction-by-age<0.001) and were weaker among Black veterans compared to other race and ethnicities (P interaction-by-race<0.001).

CONCLUSIONS

Veterans with prior TBI are at increased long-term risk for stroke, suggesting they may be an important population to target for primary stroke prevention measures.

Blood Biomarkers in Neurodegenerative Diseases: Implications for the Clinical Neurologist

Blood-based biomarkers offer a major advance in the clinical evaluation of neurodegenerative diseases. Currently, research studies have reported robust assays of blood markers for the detection of amyloid and tau pathologies specific to Alzheimer disease (amyloid-β peptides, and p-tau) and nonspecific blood markers of neuronal (neurofilament light, β-synuclein, and ubiquitin-C-terminal-hydrolase-L1) and glial degeneration (glial fibrillary acidic protein) that can measure key pathophysiologic processes in several neurodegenerative diseases. In the near future, these markers may be used for screening, diagnosis, or disease and treatment response monitoring. Blood-based biomarkers for neurodegenerative diseases have been rapidly implemented in research, and they have the potential to enter clinical use soon in different clinical settings. In this review, we will describe the main developments and their potential implications for the general neurologist.

Alzheimer's pathology is associated with altered cognition, brain volume, and plasma biomarker patterns in traumatic encephalopathy syndrome

BACKGROUND

Traumatic encephalopathy syndrome (TES) is a clinical phenotype sensitive but non-specific to underlying chronic traumatic encephalopathy (CTE) neuropathology. However, cognitive symptoms of TES overlap with Alzheimer's disease (AD), and features of AD pathology like beta-amyloid (Aβ) plaques often co-occur with CTE, making clinical-to-pathological conclusions of TES diagnoses challenging. We investigated how Alzheimer's neuropathological changes associated with cognition, brain volume, and plasma biomarkers in patients with repetitive head impacts (RHI)/TES, clinical AD, or typically aging controls.

METHODS

We studied 154 participants including 33 with RHI/TES (age 61.5 ± 11.5, 100% male, 11/33 Aβ[ +]), 62 with AD and no known prior RHI (age 67.1 ± 10.2, 48% male, 62/62 Aβ[ +]), and 59 healthy controls without RHI (HC; age 73.0 ± 6.2, 40% male, 0/59 Aβ[ +]). Patients completed neuropsychological testing (memory, executive functioning, language, visuospatial) and structural MRI (voxel-based morphometry analysis), and provided plasma samples analyzed for GFAP, NfL, IL-6, IFN-γ, and YKL-40. For cognition and plasma biomarkers, patients with RHI/TES were stratified as Aβ[ +] or Aβ[ -] and compared to each other plus the AD and HC groups (ANCOVA adjusting for age and sex). Differences with at least a medium effect size (Cohen's d > 0.50) were interpreted as potentially meaningful.

RESULTS

Cognitively, within the TES group, Aβ[ +] RHI/TES performed worse than Aβ[-] RHI/TES on visuospatial (p = .04, d = 0.86) and memory testing (p = .07, d = 0.74). Comparing voxel-wise brain volume, both Aβ[ +] and Aβ[ -] RHI/TES had lower medial and anterior temporal lobe volume than HC and did not significantly differ from AD. Comparing plasma biomarkers, Aβ[ +] RHI/TES had higher plasma GFAP than HC (p = .01, d = 0.88) and did not significantly differ from AD. Conversely, Aβ[ -] RHI/TES had higher NfL than HC (p = .004, d = 0.93) and higher IL-6 than all other groups (p's ≤ .004, d's > 1.0).

CONCLUSIONS

Presence of Alzheimer's pathology in patients with RHI/TES is associated with altered cognitive and biomarker profiles. Patients with RHI/TES and positive Aβ-PET have cognitive and plasma biomarker changes that are more like patients with AD than patients with Aβ[ -] RHI/TES. Measuring well-validated Alzheimer's biomarkers in patients with RHI/TES could improve interpretation of research findings and heighten precision in clinical management.

Systematic Review, Meta-Analysis, and Population Attributable Risk of Dementia Associated with Traumatic Brain Injury in Civilians and Veterans

Traumatic brain injury (TBI) is an established risk factor for dementia. However, the magnitude of risk is highly variable across studies. Identification of sub-populations at highest risk, with careful consideration of potential sources of bias, is urgently needed to guide public health policy and research into mechanisms and treatments. We conducted a systematic review and meta-analysis of risk of all-cause dementia after all-severity TBI. We assessed for effect of participant age and sex, veteran status, research methods, and region. The search window covered January 1990 to January 2019. We followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) reporting guidelines. Thirty-two studies met inclusion criteria. Data were pooled using random effects models. Population attributable risk (PAR) of dementia due to TBI in the U.S. was calculated by sex and veteran status. Pooled risk ratio (RR) for dementia after TBI was 1.66 (95% confidence interval 1.42-1.93). Younger age, male sex, and studies from Asia were associated with significantly higher risk; veteran status was not. Risk of dementia associated with "head injury/trauma" was not significantly different from that associated with "TBI" diagnosis specifically. PAR of dementia due to TBI among U.S. veterans was twice that of the general U.S. population, largely due to the high prevalence of TBI exposure in the majority male veteran population. This meta-analysis found that TBI is associated with nearly 70% increased risk of dementia. Risk may be highest among younger adults, men, and cohorts in Asia. Efforts to prevent TBI and also to prevent post-TBI dementia are of high importance. Additionally, improved methods for diagnosing and tracking TBI on a public health level, such as national registries, may improve the quality and generalizability of future epidemiological studies investigating the association between TBI and dementia.

Associations of Preexisting Vascular Risk Factors With Outcomes After Traumatic Brain Injury: A TRACK-TBI Study

OBJECTIVE

To evaluate associations of preinjury vascular risk factors with traumatic brain injury (TBI) outcomes.

SETTING

The level 1 trauma center-based T ransforming R esearch a nd C linical K nowledge in TBI (TRACK-TBI) Study.

PARTICIPANTS

A total of 2361 acute TBI patients 18 years or older who presented to the emergency department within 24 hours of head trauma warranting clinical evaluation with a noncontrast head CT between February 26, 2014, and August 8, 2018.

DESIGN

A multicenter prospective cohort study.

MAIN MEASURES

Vascular risk factors (hypertension, diabetes, hyperlipidemia, and smoking) were assessed at baseline by self- or proxy-report and chart review. The primary outcome was the 6-month Glasgow Outcome Scale-Extended TBI version (GOSE-TBI). Secondary 6-month outcomes included the Rivermead Post-Concussion Symptoms Questionnaire (RPQ), the Satisfaction with Life Scale (SWLS), and the 18-item Brief Symptom Inventory Global Severity Index (BSI-18-GSI).

RESULTS

Mean age of participants was 42 years, 31% were women, and 16% were Black. Current smoking was the most common vascular risk factor (29%), followed by hypertension (17%), diabetes (8%), and hyperlipidemia (6%). Smoking was the only risk factor associated with worse scores on all 4 outcome indices. Hypertension and diabetes were associated with worse RPQ scores, and hypertension was associated with worse BSI-18-GSI scores (all P < .05). Compared with individuals with no vascular risk factors, individuals with 1 but not 2 or more vascular risk factors had significantly worse GOSE-TBI and SWLS scores, while a higher burden of vascular risk factors was significantly associated with worse RPQ and BSI-18-GSI scores.

CONCLUSION

Our study found that preinjury vascular risk factors, especially smoking, are associated with worse outcomes after TBI. Aggressive postinjury treatment of vascular risk factors may be a promising strategy to improve TBI outcomes.

Feasibility and Utility of a Flexible Outcome Assessment Battery for Longitudinal Traumatic Brain Injury Research: A TRACK-TBI Study

The effects of traumatic brain injury (TBI) are difficult to measure in longitudinal cohort studies, because disparate pre-injury characteristics and injury mechanisms produce variable impairment profiles and recovery trajectories. In preparation for the Transforming Research and Clinical Knowledge in TBI (TRACK-TBI) study, which followed patients with injuries ranging from uncomplicated mild TBI to coma, we designed a multi-dimensional Flexible outcome Assessment Battery (FAB). The FAB relies on a decision-making algorithm that assigns participants to a Comprehensive (CAB) or Abbreviated Assessment Battery (AAB) and guides test selection across all phases of recovery. To assess feasibility of the FAB, we calculated the proportion of participants followed at 2 weeks (2w) and at 3, 6, and 12 months (3m, 6m, 12m) post-injury who completed the FAB and received valid scores. We evaluated utility of the FAB by examining differences in 6m and 12m Glasgow Outcome Scale-Extended (GOSE) scores between participant subgroups derived from the FAB-enabled versus traditional approach to outcome assessment applied at 2w. Among participants followed at 2w (n = 2094), 3m (n = 1871), 6m (n = 1736), and 12m (n = 1607) post-injury, 95-99% received valid completion scores on the FAB, in full or in part, either in person or by telephone. Level of function assessed by the FAB-enabled approach at 2w was associated with 6m and 12m GOSE scores (proportional odds p < 0.001). These findings suggest that the participant classification methodology afforded by the FAB may enable more effective data collection to improve detection of natural history changes and TBI treatment effects.

Medical and Psychiatric Risk Factors for Dementia in Veterans with and without Traumatic Brain Injury (TBI): A Nationwide Cohort Study

BACKGROUND

Traumatic brain injury (TBI) is a risk factor for dementia and is common, especially among Veterans. It is unknown whether TBI exposure moderates the effect of other common medical/psychiatric comorbidities that are also risk factors for dementia. If treatable or preventable risk factors have a different impact on TBI-exposed Veterans, then this may have important public health implications for dementia prevention.

OBJECTIVES

Determine prevalence of common medical/psychiatric comorbidities and associated risk of dementia in Veterans with versus without TBI.

DESIGN

Observational cohort.

SETTING

Nationwide Veterans Health Administrative data 2001-2019.

PARTICIPANTS

After excluding baseline dementia, Veterans age ≥55 years with TBI (N=95,139) were age/sex/race-matched 1:2 with Veterans without TBI (N=190,278).

MEASUREMENTS

We compared prevalence of hypertension, coronary artery disease (CAD), diabetes, cerebrovascular disease (CVD), epilepsy, depression, and post-traumatic stress disorder (PTSD) among Veterans with and without TBI. We calculated risk of incident dementia associated with each comorbidity using multivariable hazard ratios (HR) with Fine-Grey competing risk of death adjusted for baseline demographics. We estimated population attributable fraction (PAF) of dementia due to each comorbidity among Veterans with versus without TBI.

RESULTS

Prevalence of all comorbidities were significantly more prevalent (5.7% to 21.5% higher) among Veterans compared to those without TBI. All comorbidities were associated with increased risk of dementia in both groups. There were significant interactions between comorbidities and TBI in which HRs were slightly lower among Veterans with TBI (adjusted HRs 1.08-1.37) compared to those without TBI (adjusted HRs 1.12-2.13). Nevertheless, PAFs for dementia due to depression, hypertension, CAD, CVD, and epilepsy were slightly higher in Veterans with TBI due to their high prevalence in this group.

CONCLUSIONS

Targeting depression, hypertension, CAD, CVD, and epilepsy may be especially important for dementia risk reduction among Veterans with TBI.

Neuroinflammatory Biomarkers for Traumatic Brain Injury Diagnosis and Prognosis: A TRACK-TBI Pilot Study

The relationship between systemic inflammation and secondary injury in traumatic brain injury (TBI) is complex. We investigated associations between inflammatory markers and clinical confirmation of TBI diagnosis and prognosis. The prospective TRACK-TBI Pilot (Transforming Research and Clinical Knowledge in Traumatic Brain Injury Pilot) study enrolled TBI patients triaged to head computed tomography (CT) and received blood draw within 24 h of injury. Healthy controls (HCs) and orthopedic controls (OCs) were included. Thirty-one inflammatory markers were analyzed from plasma. Area under the receiver operating characteristic curve (AUC) was used to evaluate discriminatory ability. AUC >0.7 was considered acceptable. Criteria included: TBI diagnosis (vs. OC/HC); moderate/severe vs. mild TBI (Glasgow Coma Scale; GCS); radiographic TBI (CT positive vs. CT negative); 3- and 6-month Glasgow Outcome Scale-Extended (GOSE) dichotomized to death/greater relative disability versus less relative disability (GOSE 1-4/5-8); and incomplete versus full recovery (GOSE <8/ = 8). One-hundred sixty TBI subjects, 28 OCs, and 18 HCs were included. Markers discriminating TBI/OC: HMGB-1 (AUC = 0.835), IL-1b (0.795), IL-16 (0.784), IL-7 (0.742), and TARC (0.731). Markers discriminating GCS 3-12/13-15: IL-6 (AUC = 0.747), CRP (0.726), IL-15 (0.720), and SAA (0.716). Markers discriminating CT positive/CT negative: SAA (AUC = 0.767), IL-6 (0.757), CRP (0.733), and IL-15 (0.724). At 3 months, IL-15 (AUC = 0.738) and IL-2 (0.705) discriminated GOSE 5-8/1-4. At 6 months, IL-15 discriminated GOSE 1-4/5-8 (AUC = 0.704) and GOSE <8/ = 8 (0.711); SAA discriminated GOSE 1-4/5-8 (0.704). We identified a profile of acute circulating inflammatory proteins with potential relevance for TBI diagnosis, severity differentiation, and prognosis. IL-15 and serum amyloid A are priority markers with acceptable discrimination across multiple diagnostic and outcome categories. Validation in larger prospective cohorts is needed. ClinicalTrials.gov Registration: NCT01565551.

Effects of age and time since injury on traumatic brain injury blood biomarkers: a TRACK-TBI study

Older adults have the highest incidence of traumatic brain injury globally. Accurate blood-based biomarkers are needed to assist with diagnosis of patients across the spectrum of age and time post-injury. Several reports have suggested lower accuracy for blood-based biomarkers in older adults, and there is a paucity of data beyond day-1 post-injury. Our aims were to investigate age-related differences in diagnostic accuracy and 2-week evolution of four leading candidate blood-based traumatic brain injury biomarkers-plasma glial fibrillary acidic protein, ubiquitin carboxy-terminal hydrolase L1, S100 calcium binding protein B and neuron-specific enolase-among participants in the 18-site prospective cohort study Transforming Research And Clinical Knowledge in Traumatic Brain Injury. Day-1 biomarker data were available for 2602 participants including 2151 patients with traumatic brain injury, 242 orthopedic trauma controls and 209 healthy controls. Participants were stratified into 3 age categories (young: 17-39 years, middle-aged: 40-64 years, older: 65-90 years). We investigated age-stratified biomarker levels and biomarker discriminative abilities across three diagnostic groups: head CT-positive/negative; traumatic brain injury/orthopedic controls; and traumatic brain injury/healthy controls. The difference in day-1 glial fibrillary acidic protein, ubiquitin carboxy-terminal hydrolase L1 and neuron-specific enolase levels across most diagnostic groups was significantly smaller for older versus younger adults, resulting in a narrower range within which a traumatic brain injury diagnosis may be discriminated in older adults. Despite this, day-1 glial fibrillary acidic protein had good to excellent performance across all age-categories for discriminating all three diagnostic groups (area under the curve 0.84-0.96; lower limit of 95% confidence intervals all >0.78). Day-1 S100 calcium-binding protein B and ubiquitin carboxy-terminal hydrolase L1 showed good discrimination of CT-positive versus negative only among adults under age 40 years within 6 hours of injury. Longitudinal blood-based biomarker data were available for 522 hospitalized patients with traumatic brain injury and 24 hospitalized orthopaedic controls. Glial fibrillary acidic protein levels maintained good to excellent discrimination across diagnostic groups until day 3 post-injury irrespective of age, until day 5 post-injury among middle-aged or younger patients and until week 2 post-injury among young patients only. In conclusion, the blood-based glial fibrillary acidic protein assay tested here has good to excellent performance across all age-categories for discriminating key traumatic brain injury diagnostic groups to at least 3 days post-injury in this trauma centre cohort. The addition of a blood-based diagnostic to the evaluation of traumatic brain injury, including geriatric traumatic brain injury, has potential to streamline diagnosis.

Multi-Modal Biomarkers of Repetitive Head Impacts and Traumatic Encephalopathy Syndrome: A Clinicopathological Case Series

Traumatic encephalopathy syndrome (TES) criteria were developed to aid diagnosis of chronic traumatic encephalopathy (CTE) pathology during life. Interpreting clinical and biomarker findings in patients with TES during life necessitates autopsy-based determination of the neuropathological profile. We report a clinicopathological series of nine patients with previous repetitive head impacts (RHI) classified retrospectively using the recent TES research framework (100% male and white/Caucasian, age at death 49-84) who completed antemortem neuropsychological evaluations, T1-weighted magnetic resonance imaging, diffusion tensor imaging (n = 6), (18)F-fluorodeoxyglucose-positron emission tomography (n = 5), and plasma measurement of neurofilament light (NfL), glial fibrillary acidic protein (GFAP), and total tau (n = 8). Autopsies were performed on all patients. Cognitively, low test scores and longitudinal decline were relatively consistent for memory and executive function. Medial temporal lobe atrophy was observed in all nine patients. Poor white matter integrity was consistently found in the fornix. Glucose hypometabolism was most common in the medial temporal lobe and thalamus. Most patients had elevated plasma GFAP, NfL, and total tau at their initial visit and a subset showed longitudinally increasing concentrations. Neuropathologically, five of the nine patients had CTE pathology (n = 4 "High CTE"/McKee Stage III-IV, n = 1 "Low CTE"/McKee Stage I). Primary neuropathological diagnoses (i.e., the disease considered most responsible for observed symptoms) were frontotemporal lobar degeneration (n = 2 FTLD-TDP, n = 1 FTLD-tau), Alzheimer disease (n = 3), CTE (n = 2), and primary age-related tauopathy (n = 1). In addition, hippocampal sclerosis was a common neuropathological comorbidity (n = 5) and associated with limbic-predominant TDP-43 proteinopathy (n = 4) or FTLD-TDP (n = 1). Memory and executive function decline, limbic system brain changes (atrophy, decreased white matter integrity, hypometabolism), and plasma biomarker alterations are common in RHI and TES but may reflect multiple neuropathologies. In particular, the neuropathological differential for patients with RHI or TES presenting with medial temporal atrophy and memory loss should include limbic TDP-43. Researchers and clinicians should be cautious in attributing cognitive, neuroimaging, or other biomarker changes solely to CTE tau pathology based on previous RHI or a TES diagnosis alone.

Prognostic value of day-of-injury plasma GFAP and UCH-L1 concentrations for predicting functional recovery after traumatic brain injury in patients from the US TRACK-TBI cohort: an observational cohort study

BACKGROUND

The prognostic value of glial fibrillary acidic protein (GFAP) and ubiquitin C-terminal hydrolase L1 (UCH-L1) as day-of-injury predictors of functional outcome after traumatic brain injury is not well understood. GFAP is a protein found in glial cells and UCH-L1 is found in neurons, and these biomarkers have been cleared to aid in decision making regarding whether brain CT should be performed after traumatic brain injury. We aimed to quantify their prognostic accuracy and investigate whether these biomarkers contribute novel prognostic information to existing clinical models.

METHODS

We enrolled patients from the Transforming Research and Clinical Knowledge in Traumatic Brain Injury (TRACK-TBI) observational cohort study. TRACK-TBI includes patients 17 years and older who are evaluated for TBI at 18 US level 1 trauma centres. All patients receive head CT at evaluation, have adequate visual acuity and hearing preinjury, and are fluent in either English or Spanish. In our analysis, we included participants aged 17-90 years who had day-of-injury plasma samples for measurement of GFAP and UCH-L1 and completed 6-month assessments for outcome due to traumatic brain injury with the Glasgow Outcome Scale-Extended (GOSE-TBI). Biomarkers were analysed as continuous variables and in quintiles. This study is registered with ClinicalTrials.gov, NCT02119182.

FINDINGS

We enrolled 2552 patients from Feb 26, 2014, to Aug 8, 2018. Of the 1696 participants with brain injury and data available at baseline and at 6 months who were included in the analysis, 120 (7·1%) died (GOSE-TBI=1), 235 (13·9%) had an unfavourable outcome (ie, GOSE-TBI ≤4), 1135 (66·9%) had incomplete recovery (ie, GOSE-TBI <8), and 561 (33·1%) recovered fully (ie, GOSE-TBI=8). The area under the curve (AUC) of GFAP for predicting death at 6 months in all patients was 0·87 (95% CI 0·83-0·91), for unfavourable outcome was 0·86 (0·83-0·89), and for incomplete recovery was 0·62 (0·59-0·64). The corresponding AUCs for UCH-L1 were 0·89 (95% CI 0·86-0·92) for predicting death, 0·86 (0·84-0·89) for unfavourable outcome, and 0·61 (0·59-0·64) for incomplete recovery at 6 months. AUCs were higher for participants with traumatic brain injury and Glasgow Coma Scale (GCS) score of 3-12 than for those with GCS score of 13-15. Among participants with GCS score of 3-12 (n=353), adding GFAP and UCH-L1 (alone or combined) to each of the three International Mission for Prognosis and Analysis of Clinical Trials in traumatic brain injury models significantly increased their AUCs for predicting death (AUC range 0·90-0·94) and unfavourable outcome (AUC range 0·83-0·89). However, among participants with GCS score of 13-15 (n=1297), adding GFAP and UCH-L1 to the UPFRONT study model modestly increased the AUC for predicting incomplete recovery (AUC range 0·69-0·69, p=0·025).

INTERPRETATION

In addition to their known diagnostic value, day-of-injury GFAP and UCH-L1 plasma concentrations have good to excellent prognostic value for predicting death and unfavourable outcome, but not for predicting incomplete recovery at 6 months. These biomarkers contribute the most prognostic information for participants presenting with a GCS score of 3-12.

FUNDING

US National Institutes of Health, National Institute of Neurologic Disorders and Stroke, US Department of Defense, One Mind, US Army Medical Research and Development Command.

Plasma P-tau181 and P-tau217 in Patients With Traumatic Encephalopathy Syndrome With and Without Evidence of Alzheimer Disease Pathology

BACKGROUND AND OBJECTIVES

Traumatic encephalopathy syndrome (TES) has overlapping clinical symptoms with Alzheimer disease (AD). AD pathology commonly co-occurs with chronic traumatic encephalopathy (CTE) pathology. There are currently no validated CTE biomarkers. AD-specific biomarkers such as plasma P-tau181 and P-tau217 may help to identify patients with TES who have AD pathology.

METHODS

We measured plasma P-tau181 and P-tau217 (Meso Scale Discovery electrochemiluminescence) in patients with TES, mild cognitive impairment/dementia with biomarker-confirmed AD ("AD"), and healthy controls ("HC"). Patients underwent amyloid-beta (Aβ)-PET and a subset underwent tau-PET using [18F]Flortaucipir. We compared plasma P-tau levels controlling for age and sex and also performed AUC analyses to evaluate the accuracy of group differentiation. In patients with TES, we evaluated associations between plasma P-tau, years of repetitive head impact exposure, and tau-PET. Four TES patients with autopsy-confirmed CTE were described qualitatively.

RESULTS

The sample included 131 participants (TES, N = 18; AD, N = 65; HC, N = 48). Aβ(+) patients with TES (N = 10), but not Aβ(-) TES, had significantly higher plasma P-tau levels than HC (P-tau181: p < 0.001, d = 1.34; P-tau217: p < 0.001, d = 1.59). There was a trend for Aβ(+) TES having higher plasma P-tau than Aβ(-) TES (P-tau181: p = 0.06, d = 1.06; P-tau217: p = 0.09, d = 0.93). AUC analyses showed good classification of Aβ(+) TES from HC for P-tau181 (AUC = 0.87 [0.71-1.00]) and P-tau217 (AUC = 0.93 [0.86-1.00]). Plasma P-tau217 showed fair differentiation of Aβ(+) TES from Aβ(-) TES (AUC = 0.79 [0.54-1.00], p = 0.04), whereas classification accuracy of P-tau181 was slightly lower and not statistically significant (AUC = 0.71 [0.46-0.96], p = 0.13). Patients with AD had higher tau-PET tracer uptake than Aβ(+) TES and were well differentiated using P-tau181 (AUC = 0.81 [0.68-0.94]) and P-tau217 (AUC = 0.86 [0.73-0.98]). Plasma P-tau correlated with the tau-PET signal in Aβ(+) TES but not in Aβ(-) TES, and there was no association between plasma P-tau and years of repetitive head impact exposure. TES patients with severe CTE and no AD at autopsy had low P-tau181 and P-tau217 levels.

DISCUSSION

Measuring P-tau181 and P-tau217 in plasma may be a feasible and scalable fluid biomarker for identifying AD pathology in TES. Low plasma P-tau levels may be used to increase clinical suspicion of CTE over AD as a primary pathology in TES. Currently, there is no support for P-tau181 or P-tau217 as in vivo biomarkers of CTE tau. Larger studies of patients with pathologically confirmed CTE are needed.

CLASSIFICATION OF EVIDENCE

This study provides Class III evidence that (1) among patients with TES and abnormal Aβ-PET scans, elevated plasma P-tau can differentiate between affected individuals and HCs; (2) low plasma P-tau may help identify patients with TES who do not have Alzheimer; and (3) plasma P-tau181 and P-tau217 are not useful biomarkers of patients with TES who do not have AD.

Comparison Groups Matter in Traumatic Brain Injury Research: An Example with Dementia

The association between traumatic brain injury (TBI) and risk for Alzheimer's disease and related dementias (ADRD) has been investigated in multiple studies yet reported effect sizes have varied widely. Large differences in comorbid and demographic characteristics between individuals with and without TBI could result in spurious associations between TBI and poor outcomes, even when control for confounding is attempted. Yet, inadvertent control for post-TBI exposures (e.g., psychological and physical trauma) could result in an underestimate of the effect of TBI. Choice of the unexposed or comparison group is critical to estimating total associated risk. The objective of this study was to highlight how selection of the comparison group impacts estimates of the effect of TBI on risk for ADRD. Using data on veterans aged ≥55 years obtained from the Veterans Health Administration (VA) for years 1999-2019, we compared risk of ADRD between veterans with incident TBI (n=9,440) and 1) the general population of veterans who receive care at the VA (All VA)(n=119,003); 2) veterans who received care at a VA emergency department (VA ED)(n=111,342); and 3) veterans who received care at a VA ED for non-TBI trauma (VA ED NTT)(n=65,710). In inverse probability of treatment weighted models, TBI was associated with increased risk of ADRD compared to All VA (HR 1.94; 95% CI 1.84, 2.04), VA ED (HR 1.42; 95% CI 1.35, 1.50), and VA ED NTT (HR 1.12; 95% CI 1.06, 1.18). The estimated effect of TBI on incident ADRD was strongly impacted by choice of the comparison group.

Cognitive Outcome 1 Year After Mild Traumatic Brain Injury: Results From the TRACK-TBI Study

BACKGROUND AND OBJECTIVES

The objectives of this study were to develop and establish concurrent validity of a clinically relevant definition of poor cognitive outcome 1 year after mild traumatic brain injury (mTBI), to compare baseline characteristics across cognitive outcome groups, and to determine whether poor 1-year cognitive outcome can be predicted by routinely available baseline clinical variables.

METHODS

Prospective cohort study included 656 participants ≥17 years of age presenting to level 1 trauma centers within 24 hours of mTBI (Glasgow Coma Scale score 13-15) and 156 demographically similar healthy controls enrolled in the Transforming Research and Clinical Knowledge in TBI (TRACK-TBI) study. Poor 1-year cognitive outcome was defined as cognitive impairment (below the ninth percentile of normative data on ≥2 cognitive tests), cognitive decline (change score [1-year score minus best 2-week or 6-month score] exceeding the 90% reliable change index on ≥2 cognitive tests), or both. Associations of poor 1-year cognitive outcome with 1-year neurobehavioral outcomes were performed to establish concurrent validity. Baseline characteristics were compared across cognitive outcome groups, and backward elimination logistic regression was used to build a prediction model.

RESULTS

Mean age of participants with mTBI was 40.2 years; 36.6% were female; 76.6% were White. Poor 1-year cognitive outcome was associated with worse 1-year functional outcome, more neurobehavioral symptoms, greater psychological distress, and lower satisfaction with life (all p < 0.05), establishing concurrent validity. At 1 year, 13.5% of participants with mTBI had a poor cognitive outcome vs 4.5% of controls (p = 0.003). In univariable analyses, poor 1-year cognitive outcome was associated with non-White race, lower education, lower income, lack of health insurance, hyperglycemia, preinjury depression, and greater injury severity (all p < 0.05). The final multivariable prediction model included education, health insurance, preinjury depression, hyperglycemia, and Rotterdam CT score ≥3 and achieved an area under the curve of 0.69 (95% CI 0.62-0.75) for the prediction of a poor 1-year cognitive outcome, with each variable associated with >2-fold increased odds of poor 1-year cognitive outcome.

DISCUSSION

Poor 1-year cognitive outcome is common, affecting 13.5% of patients with mTBI vs 4.5% of controls. These results highlight the need for better understanding of mechanisms underlying poor cognitive outcome after mTBI to inform interventions to optimize cognitive recovery.

Traumatic Brain Injury and Risk of Neurodegenerative Disorder

Traumatic brain injury (TBI), particularly of greater severity (i.e., moderate to severe), has been identified as a risk factor for all-cause dementia and Parkinson's disease, with risk for specific dementia subtypes being more variable. Among the limited studies involving neuropathological (postmortem) confirmation, the association between TBI and risk for neurodegenerative disease increases in complexity, with polypathology often reported on examination. The heterogeneous clinical and neuropathological outcomes associated with TBI are likely reflective of the multifaceted postinjury acute and chronic processes that may contribute to neurodegeneration. Acutely in TBI, axonal injury and disrupted transport influences molecular mechanisms fundamental to the formation of pathological proteins, such as amyloid-β peptide and hyperphosphorylated tau. These protein deposits may develop into amyloid-β plaques, hyperphosphorylated tau-positive neurofibrillary tangles, and dystrophic neurites. These and other characteristic neurodegenerative disease pathologies may then spread across brain regions. The acute immune and neuroinflammatory response involves alteration of microglia, astrocytes, oligodendrocytes, and endothelial cells; release of downstream pro- and anti-inflammatory cytokines and chemokines; and recruitment of peripheral immune cells. Although thought to be neuroprotective and reparative initially, prolongation of these processes may promote neurodegeneration. We review the evidence for TBI as a risk factor for neurodegenerative disorders, including Alzheimer's dementia and Parkinson's disease, in clinical and neuropathological studies. Further, we describe the dynamic interactions between acute response to injury and chronic processes that may be involved in TBI-related pathogenesis and progression of neurodegeneration.

Trajectories of Insomnia in Adults After Traumatic Brain Injury

IMPORTANCE

Insomnia is common after traumatic brain injury (TBI) and contributes to morbidity and long-term sequelae.

OBJECTIVE

To identify unique trajectories of insomnia in the 12 months after TBI.

DESIGN, SETTING, AND PARTICIPANTS

In this prospective cohort study, latent class mixed models (LCMMs) were used to model insomnia trajectories over time and to classify participants into distinct profile groups. Data from the Transforming Research and Clinical Knowledge in Traumatic Brain Injury (TRACK-TBI) study, a longitudinal, multisite, observational study, were uploaded to the Federal Interagency Traumatic Brain Injury Repository (FITBIR) database. Participants were enrolled at 1 of 18 participating level I trauma centers and enrolled within 24 hours of TBI injury. Additional data were obtained directly from the TRACK-TBI investigators that will be uploaded to FITBIR in the future. Data were collected from February 26, 2014, to August 8, 2018, and analyzed from July 1, 2020, to November 15, 2021.

EXPOSURES

Traumatic brain injury.

MAIN OUTCOMES AND MEASURES

Insomnia Severity Index assessed serially at 2 weeks and 3, 6, and 12 months thereafter.

RESULTS

The final sample included 2022 participants (1377 [68.1%] men; mean [SD] age, 40.1 [17.2] years) from the FITBIR database and the TRACK-TBI study. The data were best fit by a 5-class LCMM. Of these participants, 1245 (61.6%) reported persistent mild insomnia symptoms (class 1); 627 (31.0%) initially reported mild insomnia symptoms that resolved over time (class 2); 91 (4.5%) reported persistent severe insomnia symptoms (class 3); 44 (2.2%) initially reported severe insomnia symptoms that resolved by 12 months (class 4); and 15 (0.7%) initially reported no insomnia symptoms but had severe symptoms by 12 months (class 5). In a multinomial logistic regression model, several factors significantly associated with insomnia trajectory class membership were identified, including female sex (odds ratio [OR], 1.65 [95% CI, 1.02-2.66]), Black race (OR, 2.36 [95% CI, 1.39-4.01]), history of psychiatric illness (OR, 2.21 [95% CI, 1.35-3.60]), and findings consistent with intracranial injury on computed tomography (OR, 0.36 [95% CI, 0.20-0.65]) when comparing class 3 with class 1.

CONCLUSIONS AND RELEVANCE

These results suggest important heterogeneity in the course of insomnia after TBI in adults. More work is needed to identify outcomes associated with these insomnia trajectory class subgroups and to identify optimal subgroup-specific treatment approaches.

The Effect of Sex and Wealth on Population Attributable Risk Factors for Dementia in South Africa

Background and Aims: South Africa is a middle-income country with high levels of income inequality and a rapidly aging population and increasing dementia prevalence. Little is known about which risk factors for dementia are important and how they differ by social determinants of health as well as key demographic characteristics such as sex and wealth. We sought to calculate the population attributable risks (PARs) for established potentially modifiable risk factors for dementia among these different groups.

Methods: We obtained risk factor prevalence from population-based surveys for established dementia risk factors (diabetes, midlife hypertension, midlife obesity, physical inactivity, depression, smoking, low educational attainment, social isolation). We used relative risk estimates reported in previous meta-analyses and estimated PARs using Levin's formula and accounting for communality. We tested for one-way and two-way interactions by sex and wealth using Pearson's χ2. In stratified analyses, we performed tests for trend using logistic regression.

Results: The prevalence of established risk factors for dementia ranged from 5% for depression to 64% for low education. After accounting for communality, the risk factors contributing the greatest PAR were low education (weighted PAR 12%, 95% CI 7% to 18%), physical inactivity (9, 5–14%), and midlife hypertension (6, 5–14%). Together, 45% of dementia cases may be attributable to modifiable risk factors (95% CI 25–59%). We found significant interactions (p < 0.005) between sex, wealth, or both (sex ^* wealth) and each risk factor except social isolation and physical activity. Low education was inversely associated with wealth in both male and female. The PAR for midlife hypertension, obesity, and diabetes was associated with increasing wealth, and was higher in female. In contrast, the PAR for smoking was higher in male (8% vs. 2%) and was associated with increasing wealth among female only. We found that either a strategy of large reductions in selected risk factors with the highest PAR (midlife hypertension, smoking, physical inactivity) or small reductions across all risk factors could potentially reduce dementia cases by as many as 250,000 by 2050.

Discussions: The potential impact on dementia risk by decreasing exposure to established dementia risk factors is large and differs by sex and social determinants of health like wealth. Risk factor PAR should inform national and local health policy dementia initiatives in South Africa including which risk factors to target in the whole population and which to target in high-risk groups for maximum public health benefit.

FAIR Data Reuse in Traumatic Brain Injury: Exploring Inflammation and Age as Moderators of Recovery in the TRACK-TBI Pilot

The guiding principle for data stewardship dictates that data be FAIR: findable, accessible, interoperable, and reusable. Data reuse allows researchers to probe data that may have been originally collected for other scientific purposes in order to gain novel insights. The current study reuses the Transforming Research and Clinical Knowledge for Traumatic Brain Injury (TRACK-TBI) Pilot dataset to build upon prior findings and ask new scientific questions. Specifically, we have previously used a multivariate analytics approach to multianalyte serum protein data from the TRACK-TBI Pilot dataset to show that an inflammatory ensemble of biomarkers can predict functional outcome at 3 and 6 months post-TBI. We and others have shown that there are quantitative and qualitative changes in inflammation that come with age, but little is known about how this interaction affects recovery from TBI. Here we replicate the prior proteomics findings with improved missing value analyses and non-linear principal component analysis and then expand upon this work to determine whether age moderates the effect of inflammation on recovery. We show that increased age correlates with worse functional recovery on the Glasgow Outcome Scale-Extended (GOS-E) as well as increased inflammatory signature. We then explore the interaction between age and inflammation on recovery, which suggests that inflammation has a more detrimental effect on recovery for older TBI patients.

Association of remote mild traumatic brain injury with cortical amyloid burden in clinically normal older adults

We investigated whether clinically normal older adults with remote, mild traumatic brain injury (mTBI) show evidence of higher cortical Aβ burden. Our study included 134 clinically normal older adults (age 74.1 ± 6.8 years, 59.7% female, 85.8% white) who underwent Aβ positron emission tomography (Aβ-PET) and who completed the Ohio State University Traumatic Brain Injury Identification questionnaire. We limited participants to those reporting injuries classified as mTBI. A subset (N = 30) underwent a second Aβ-PET scan (mean 2.7 years later). We examined the effect of remote mTBI on Aβ-PET burden, interactions between remote mTBI and age, sex, and APOE status, longitudinal Aβ accumulation, and the interaction between remote mTBI and Aβ burden on memory and executive functioning. Of 134 participants, 48 (36%) reported remote mTBI (0, N = 86; 1, N = 31, 2+, N = 17; mean 37 ± 23 years since last mTBI). Effect size estimates were small to negligible for the association of remote mTBI with Aβ burden (p = .94, η2 < 0.01), and for all interaction analyses. Longitudinally, we found a non-statistically significant association of those with remote mTBI (N = 11) having a faster rate of Aβ accumulation (B = 0.01, p = .08) than those without (N = 19). There was no significant interaction between remote mTBI and Aβ burden on cognition. In clinically normal older adults, history of mTBI is not associated with greater cortical Aβ burden and does not interact with Aβ burden to impact cognition. Longitudinal analyses suggest remote mTBI may be associated with more rapid cortical Aβ accumulation. This finding warrants further study in larger and more diverse samples with well-characterized lifelong head trauma exposure.

Depression in Older Adults 12 Months Following Traumatic Brain Injury: A TRACK-TBI Study

OBJECTIVE

To investigate depression at 12 months following traumatic brain injury (TBI) in older compared with younger adults.

DESIGN

Prospective longitudinal cohort study of persons with medically documented mild, moderate, and severe TBI at 12 months post-injury.

SETTING

Eighteen participating Level One trauma centers in the U.S.

PARTICIPANTS

1,505 participants with TBI and primary outcome data at 12-month follow-up.

INTERVENTION

Not applicable.

MAIN OUTCOME MEASURE

Patient Health Questionnaire-9 (PHQ-9).

RESULTS

PHQ-9 total scores were significantly lower for older adults (age≥65)(M = 3.2) as compared with younger adults (age<65)(M = 5.0) (B = -1.63, p < .001), indicating less depressive symptoms in older adults. Age did not interact with education, sex, race/ethnicity, psychiatric history, substance use, or GCS severity to impact PHQ-9 scores. Of the 29% of older adults who endorsed symptoms consistent with depression, 14% were classified as minor depression and 15% as major depression. The odds of older adults falling in the major depression vs. no depression group was significantly lower (decreased by 56%) as compared with younger adults (OR = 0.44, p =.001).

CONCLUSIONS

At 12-months post-TBI, older adults endorse lower depressive symptoms than their younger counterparts and are less likely to experience major depression; however, over one-fourth of older adults endorsed symptoms consistent with depression, warranting evaluation and treatment.

Prevalence of Lifetime History of Traumatic Brain Injury among Older Male Veterans Compared with Civilians: A Nationally Representative Study

Traumatic brain injury (TBI) is common among older adults as well as among veterans in the United States and can increase risk for dementia. We compared prevalence of TBI in older male veterans and civilians using a nationally representative sample. We examined data from 599 male respondents to the 2014 wave of the Health and Retirement Study (HRS), a nationally representative survey of older adults, randomly selected to participate in a comprehensive TBI survey. Respondents self-reported no injury, non-TBI head/neck injury (NTI), or TBI. We used weighted analyses to examine prevalence of injury and relative risk of injury subtypes. Among male veterans, we found a national prevalence of more than 70% for lifetime history of any head/neck injury (TBI plus NTI), 14.3% for multiple NTI, and 36% for lifetime history of at least one TBI. In contrast, prevalence estimates for male civilians were 58% for lifetime history of head/neck injury, 4.8% for multiple NTI, and 45% for lifetime history of at least one TBI (all comparisons, p < 0.001). Male civilians have higher self-reported TBI prevalence, whereas male veterans have higher self-reported NTI and multiple-NTI prevalence. Further research on drivers of the unexpectedly higher prevalence of lifetime history of TBI in male civilians, as well as on mechanisms and sequelae of the highly prevalent non-TBI head/neck injuries among older male veterans, is warranted.

Blood biomarkers of traumatic brain injury and cognitive impairment in older veterans

OBJECTIVE

To determine whether blood-based biomarkers can differentiate older veterans with and without traumatic brain injury (TBI) and cognitive impairment (CogI).

METHODS

We enrolled 155 veterans from 2 veterans' retirement homes: 90 without TBI and 65 with TBI history. Participants were further separated into CogI groups: controls (no TBI, no CogI), n = 60; no TBI with CogI, n = 30; TBI without CogI, n = 30; and TBI with CogI, n = 35. TBI was determined by the Ohio State University TBI Identification Method. CogI was defined as impaired cognitive testing, dementia diagnosis, or use of dementia medication. Blood specimens were enriched for CNS-derived exosomes. Proteins (neurofilament light [NfL], total tau, glial fibrillary acidic protein [GFAP], α-synuclein, β-amyloid 42 [Aβ42], and phosphorylated tau [p-tau]) and cytokines (tumor necrosis factor-α [TNF-α], interleukin-6 [IL-6], and interleukin-10) were measured using ultrasensitive immunoassays.

RESULTS

Veterans were, on average, 79 years old. In participants with TBI history, 65% had mild TBI; average time from most recent TBI was 37 years. In adjusted analyses, the TBI and CogI groups differed on CNS-enriched exosome concentration of p-tau, NfL, IL-6, TNF-α (all p < 0.05), and GFAP (p = 0.06), but not on Aβ42 or other markers. Adjusted area under the curve (AUC) analyses found that all significantly associated biomarkers combined separated TBI with/without CogI (AUC, 0.85; 95% confidence interval [CI], 0.74-0.95) and CogI with/without TBI (AUC, 0.88; 95% CI, 0.77-0.99).

CONCLUSIONS

Increased levels of blood-based, CNS-enriched exosomal biomarkers associated with TBI and CogI can be detected even decades after TBI.

CLASSIFICATION OF EVIDENCE

This study provides Class II evidence that in veterans with a history of TBI, CNS-enriched exosome concentration of p-tau, NfL, IL-6, and TNF-α are associated with CogI.

Neuropathological correlates of structural and functional imaging biomarkers in 4-repeat tauopathies

Neurodegenerative dementia syndromes are characterized by spreading of pathological protein deposition along syndrome-specific neural networks. Structural and functional MRI measures can assess the integrity of these networks and have been proposed as biomarkers of disease progression for clinical trials. The relationship between in vivo imaging measures and pathological features, at the single subject level, remains largely unknown. Patient-specific maps of atrophy and seed-based intrinsic connectivity disruption, as compared to normal controls, were obtained for 27 patients subsequently diagnosed with progressive supranuclear palsy (n = 16, seven males, age at death 68.9 ± 6.0 years, imaging-to-pathology interval = 670.2 ± 425.1 days) or corticobasal degeneration (n = 11, two males, age at death 66.7 ± 5.4 years, imaging-to-pathology interval = 696.2 ± 482.2 days). A linear mixed effect model with crossed random effects was used to test regional and single-subject level associations between post-mortem regional measures of neurodegeneration and tau inclusion burden, on the one hand, and regional volume loss and seed-based intrinsic connectivity reduction, on the other. A significant association was found between tau inclusion burden and in vivo volume loss, at the regional level and independent of neurodegeneration severity, in both progressive supranuclear palsy [n = 340 regions; beta 0.036; 95% confidence interval (CI): 0.001, 0.072; P = 0.046] and corticobasal degeneration (n = 215 regions; beta 0.044; 95% CI: 0.009, 0.079; P = 0.013). We also found a significant association between post-mortem neurodegeneration and in vivo volume loss in both progressive supranuclear palsy (n = 340 regions; beta 0.155; 95% CI: 0.061, 0.248; P = 0.001) and corticobasal degeneration (n = 215 regions; beta 0.277; 95% CI: 0.104, 0.450; P = 0.002). We found a significant association between regional neurodegeneration and intrinsic connectivity dysfunction in corticobasal degeneration (n = 215 regions; beta 0.074; 95% CI: 0.005, 0.143; P = 0.035), but no other associations between post-mortem measures of tauopathy and intrinsic connectivity dysfunction reached statistical significance. Our data suggest that in vivo structural imaging measures reflect independent contributions from neurodegeneration and tau burden in progressive supranuclear palsy and corticobasal degeneration. Seed-based measures of intrinsic connectivity dysfunction showed less reliable predictive value when used as in vivo biomarkers of tauopathy. The findings provide important guidance for the use of imaging biomarkers as indirect in vivo assays of microscopic pathology.

Screening for Lifetime History of Traumatic Brain Injury Among Older American and Irish Adults at Risk for Dementia: Development and Validation of a Web-Based Survey

BACKGROUND

Traumatic brain injury (TBI) is an established risk factor for dementia but mechanisms are uncertain. Accurate TBI exposure classification is critical for cognitive aging research studies seeking to discover mechanisms and treatments of post-TBI dementia. Brief TBI screens, commonly used in epidemiological studies of cognitive aging, are insensitive, leading to exposure mis-classification. Comprehensive TBI interviews, while more sensitive, may be impractical.

OBJECTIVE

We aimed to develop and validate a scalable, self-administered, comprehensive, web-based, TBI exposure survey for use in international cognitive aging research.

METHODS

We adapted a gold-standard comprehensive TBI interview (the Ohio State University TBI Identification Method; OSU TBI-ID) into a self-administered web-based survey for older adults (Older Adult modification of the OSU TBI-ID; OA OSU TBI-ID). We assessed reliability of our web-based survey versus the gold-standard interview among 97 older adults with normal cognition and mild cognitive impairment (MCI). In addition, we assessed sensitivity of the National Alzheimer's Coordinating Center Uniform Data Set (NACC UDS) brief TBI screen versus the interview among 70 older adults with normal cognition.

RESULTS

Our OA OSU TBI-ID web-based survey had good to excellent reliability versus the interview (κ 0.66-0.73; ICCs 0.68-0.81) even among the sub-set with MCI (κ 0.74-0.88; ICCs 0.76-0.85), except for several age-at-injury variables. The NACC UDS brief TBI screen missed 50% of TBI exposures identified using the OSU TBI-ID interview.

CONCLUSION

The OSU TBI-ID interview and web-based survey may facilitate more accurate TBI exposure classification in cognitive aging research thereby accelerating discovery of targetable mechanisms of post-TBI dementia.

Tau PET and multimodal brain imaging in patients at risk for chronic traumatic encephalopathy

OBJECTIVE

To characterize individual and group-level neuroimaging findings in patients at risk for Chronic Traumatic Encephalopathy (CTE).

METHODS

Eleven male patients meeting criteria for Traumatic Encephalopathy Syndrome (TES, median age: 64) underwent neurologic evaluation, 3-Tesla MRI, and PET with [18F]-Flortaucipir (FTP, tau-PET) and [11C]-Pittsburgh compound B (PIB, amyloid-PET). Six patients underwent [18F]-Fluorodeoxyglucose-PET (FDG, glucose metabolism). We assessed imaging findings at the individual patient level, and in group-level comparisons with modality-specific groups of cognitively normal older adults (CN). Tau-PET findings in patients with TES were also compared to a matched group of patients with mild cognitive impairment or dementia due to Alzheimer's disease (AD).

RESULTS

All patients with TES sustained repetitive head injury participating in impact sports, ten in American football. Three patients met criteria for dementia and eight had mild cognitive impairment. Two patients were amyloid-PET positive and harbored the most severe MRI atrophy, FDG hypometabolism, and FTP-tau PET binding. Among the nine amyloid-negative patients, tau-PET showed either mildly elevated frontotemporal binding, a "dot-like" pattern, or no elevated binding. Medial temporal FTP was mildly elevated in a subset of amyloid-negative patients, but values were considerably lower than in AD. Voxelwise analyses revealed a convergence of imaging abnormalities (higher FTP binding, lower FDG, lower gray matter volumes) in frontotemporal areas in TES compared to controls.

CONCLUSIONS

Mildly elevated tau-PET binding was observed in a subset of amyloid-negative patients at risk for CTE, in a distribution consistent with CTE pathology stages III-IV. FTP-PET may be useful as a biomarker of tau pathology in CTE but is unlikely to be sensitive to early disease stages.

Association of Mild Traumatic Brain Injury With and Without Loss of Consciousness With Dementia in US Military Veterans

Importance

Traumatic brain injury (TBI) is common in both veteran and civilian populations. Prior studies have linked moderate and severe TBI with increased dementia risk, but the association between dementia and mild TBI, particularly mild TBI without loss of consciousness (LOC), remains unclear.

Objective

To examine the association between TBI severity, LOC, and dementia diagnosis in veterans.

Design, Setting, and Participants

This cohort study of all patients diagnosed with a TBI in the Veterans Health Administration health care system from October 1, 2001, to September 30, 2014, and a propensity-matched comparison group. Patients with dementia at baseline were excluded. Researchers identified TBIs through the Comprehensive TBI Evaluation database, which is restricted to Iraq and Afghanistan veterans, and the National Patient Care Database, which includes veterans of all eras. The severity of each TBI was based on the most severe injury recorded and classified as mild without LOC, mild with LOC, mild with LOC status unknown, or moderate or severe using Department of Defense or Defense and Veterans Brain Injury Center criteria. International Classification of Diseases, Ninth Revision codes were used to identify dementia diagnoses during follow-up and medical and psychiatric comorbidities in the 2 years prior to the index date.

Main Outcomes and Measures

Dementia diagnosis in veterans who had experienced TBI with or without LOC and control participants without TBI exposure.

Results

The study included 178 779 patients diagnosed with a TBI in the Veterans Health Administration health care system and 178 779 patients in a propensity-matched comparison group. Veterans had a mean (SD) age of nearly 49.5 (18.2) years at baseline; 33 250 (9.3%) were women, and 259 136 (72.5%) were non-Hispanic white individuals. Differences between veterans with and without TBI were small. A total of 4698 veterans (2.6%) without TBI developed dementia compared with 10 835 (6.1%) of those with TBI. After adjustment for demographics and medical and psychiatric comobidities, adjusted hazard ratios for dementia were 2.36 (95% CI, 2.10-2.66) for mild TBI without LOC, 2.51 (95% CI, 2.29-2.76) for mild TBI with LOC, 3.19 (95% CI, 3.05-3.33) for mild TBI with LOC status unknown, and 3.77 (95% CI, 3.63-3.91) for moderate to severe TBI.

Conclusions and Relevance

In this cohort study of more than 350 000 veterans, even mild TBI without LOC was associated with more than a 2-fold increase in the risk of dementia diagnosis. Studies of strategies to determine mechanisms, prevention, and treatment of TBI-related dementia in veterans are urgently needed.

Linguistic and Cultural Acceptability of a Spanish Translation of the Ohio State University Traumatic Brain Injury Identification Method Among Community-Dwelling Spanish-Dominant Older Adults

Objective

Our objective was to (1) evaluate the linguistic and cultural acceptability of a Spanish translation of the Ohio State University traumatic brain injury identification method (OSU TBI-ID) and (2) to assess the usability and acceptability of a tablet-based version of this instrument in a cohort of Spanish-dominant older adults.

Setting

University clinical research center and local community center.

Participants

Community-dwelling Spanish-dominant adults age 50 years or older without dementia residing in the Bay Area of California (N=22).

Design

Cross-sectional cohort study.

Main Outcome Measures

Qualitative assessment of linguistic or cultural acceptability of a Spanish translation of the OSU TBI-ID as well as usability or acceptability of a tablet-based self-administered version of this instrument.

Results

The Spanish translation had high linguistic and cultural acceptability and was further optimized based on participant feedback. Cognitive interviews to review survey wording revealed high levels of homogeneity in the clinical definitions and synonyms given by participants—for example, results for the clinical term “Quedó Inconsciente/Pérdida (temporal) de la conciencia” (To be unconscious/[Temporary] loss of consciousness) used in the survey included “perder el conocimiento” (loss of consciousness), “knockeado” (knocked out), “No es que esté dormida, porque está inconsciente, pero su corazón está todavía palpitando” (it’s not that they’re sleeping, because they’re unconscious, but their heart is still palpitating). The tablet interface had low observer-based usability, revealing that participants with <13 years of education (n=6) had more difficulty using the tablet which could be improved with minor changes to the coding of the application and minimal in-person technology support. Acceptability of the tool was low among all but 1 participant.

Conclusion

This linguistically optimized Spanish translation of the OSU TBI-ID is recommended for use as a semistructured interview among Spanish-dominant older adults. Although the tablet-based instrument may be used by interviewers as an efficient electronic case report form among older adults, further research is needed, particularly among older adults with varying levels of education, to validate this instrument as a self-administered survey.

Divergent Six Month Functional Recovery Trajectories and Predictors after Traumatic Brain Injury: Novel Insights from the Citicoline Brain Injury Treatment Trial Study

Cross-sectional approaches to outcome assessment may not adequately capture heterogeneity in recovery after traumatic brain injury (TBI). Using latent class mixed models (LCMM), a data-driven analytic that identifies groups of patients with similar trajectories, we identified distinct 6 month functional recovery trajectories in a large cohort (n = 1046) of adults 18-70 years of age with complicated mild to severe TBI who participated in the Citicoline Brain Injury Treatment Trial (COBRIT). We used multinomial logistic fixed effect models and backward elimination, forward selection, and forward stepwise selection with several stopping rules to explore baseline predictors of functional recovery trajectory. Based on statistical and clinical considerations, the seven-class model was deemed superior. Visualization of these seven functional recovery trajectories revealed that each trajectory class started at one of three recovery levels at 1 month, which, for ease of reference we labeled groups A-C: Group A, good recovery (two classes; A1 and A2); Group B, moderate disability (two classes; B1 and B2); and Group C, severe disability (three classes; C1, C2, and C3). By 6 months, these three groups experienced dramatically divergent trajectories. Group A experienced stable good recovery (A1, n = 115) or dramatic decline (A2, n = 4); Group B experienced rapid complete recovery (B1, n = 71) or gradual recovery (B2, n = 742); Group C experienced dramatic rapid recovery (C1, n = 12), no recovery (C2, n = 91), or death (C3, n = 11). Trajectory class membership was not predicted by citicoline treatment (p = 0.57). The models identified demographic, pre-injury, and injury-related predictors of functional recovery trajectory, including: age, race, education, pre-injury employment, pre-injury diabetes, pre-injury psychiatric disorder, site, Glasgow Coma Scale (GCS) score, post-traumatic amnesia, TBI mechanism, major extracranial injury, hemoglobin, and acute computed tomographic (CT) findings. GCS was the most consistently selected predictor across all models. All models also selected at least one demographic or pre-injury medical predictor. LCMM successfully identified dramatically divergent, clinically meaningful 6 month recovery trajectories with utility to inform clinical trial design.

Age and sex-mediated differences in six-month outcomes after mild traumatic brain injury in young adults: a TRACK-TBI study

Introduction: Risk factors for young adults with mTBI are not well understood. Improved understanding of age and sex as risk factors for impaired six-month outcomes in young adults is needed. Methods: Young adult mTBI subjects aged 18-39 years (18-29y; 30-39y) with six-month outcomes were extracted from the Transforming Research and Clinical Knowledge in Traumatic Brain Injury Pilot (TRACK-TBI Pilot) study. Multivariable regressions were performed for outcomes with age, sex, and the interaction factor age-group*sex as variables of interest, controlling for demographic and injury variables. Mean-differences (B) and 95% CIs are reported. Results: One hundred mTBI subjects (18-29y, 70%; 30-39y, 30%; male, 71%; female, 29%) met inclusion criteria. On multivariable analysis, age-group*sex was associated with six-month post-traumatic stress disorder (PTSD; PTSD Checklist-Civilian version); compared with female 30-39y, female 18-29y (B= -19.55 [-26.54, -4.45]), male 18-29y (B= -19.70 [-30.07, -9.33]), and male 30-39y (B= -15.49 [-26.54, -4.45]) were associated with decreased PTSD symptomatology. Female sex was associated with decreased six-month functional outcome (Glasgow Outcome Scale-Extended (GOSE): B= -0.6 [1.0, -0.1]). Comparatively, 30-39y scored higher on six-month nonverbal processing speed (Wechsler Adult Intelligence Scale-Processing Speed Index (WAIS-PSI); B= 11.88, 95% CI [1.66, 22.09]). Conclusions: Following mTBI, young adults aged 18-29y and 30-39y may have different risks for impairment. Sex may interact with age for PTSD symptomatology, with females 30-39y at highest risk. These results may be attributable to cortical maturation, biological response, social modifiers, and/or differential self-report. Confirmation in larger samples is needed; however, prevention and rehabilitation/counseling strategies after mTBI should likely be tailored for age and sex.

Pre-injury Comorbidities Are Associated With Functional Impairment and Post-concussive Symptoms at 3- and 6-Months After Mild Traumatic Brain Injury: A TRACK-TBI Study

Introduction: Over 70% of traumatic brain injuries (TBI) are classified as mild (mTBI), which present heterogeneously. Associations between pre-injury comorbidities and outcomes are not well-understood, and understanding their status as risk factors may improve mTBI management and prognostication. Methods: mTBI subjects (GCS 13-15) from TRACK-TBI Pilot completing 3- and 6-month functional [Glasgow Outcome Scale-Extended (GOSE)] and post-concussive outcomes [Acute Concussion Evaluation (ACE) physical/cognitive/sleep/emotional subdomains] were extracted. Pre-injury comorbidities >10% incidence were included in regressions for functional disability (GOSE ≤ 6) and post-concussive symptoms by subdomain. Odds ratios (OR) and mean differences (B) were reported. Significance was assessed at p < 0.0083 (Bonferroni correction). Results: In 260 subjects sustaining blunt mTBI, mean age was 44.0-years and 70.4% were male. Baseline comorbidities >10% incidence included psychiatric-30.0%, cardiac (hypertension)-23.8%, cardiac (structural/valvular/ischemic)-20.4%, gastrointestinal-15.8%, pulmonary-15.0%, and headache/migraine-11.5%. At 3- and 6-months separately, 30.8% had GOSE ≤ 6. At 3-months, psychiatric (GOSE ≤ 6: OR = 2.75, 95% CI [1.44-5.27]; ACE-physical: B = 1.06 [0.38-1.73]; ACE-cognitive: B = 0.72 [0.26-1.17]; ACE-sleep: B = 0.46 [0.17-0.75]; ACE-emotional: B = 0.64 [0.25-1.03]), headache/migraine (GOSE ≤ 6: OR = 4.10 [1.67-10.07]; ACE-sleep: B = 0.57 [0.15-1.00]; ACE-emotional: B = 0.92 [0.35-1.49]), and gastrointestinal history (ACE-physical: B = 1.25 [0.41-2.10]) were multivariable predictors of worse outcomes. At 6-months, psychiatric (GOSE ≤ 6: OR = 2.57 [1.38-4.77]; ACE-physical: B = 1.38 [0.68-2.09]; ACE-cognitive: B = 0.74 [0.28-1.20]; ACE-sleep: B = 0.51 [0.20-0.83]; ACE-emotional: B = 0.93 [0.53-1.33]), and headache/migraine history (ACE-physical: B = 1.81 [0.79-2.84]) predicted worse outcomes. Conclusions: Pre-injury psychiatric and pre-injury headache/migraine symptoms are risk factors for worse functional and post-concussive outcomes at 3- and 6-months post-mTBI. mTBI patients presenting to acute care should be evaluated for psychiatric and headache/migraine history, with lower thresholds for providing TBI education/resources, surveillance, and follow-up/referrals. Clinical Trial Registration: www.ClinicalTrials.gov, identifier NCT01565551.

Preinjury employment status as a risk factor for symptomatology and disability in mild traumatic brain injury: A TRACK-TBI analysis

BACKGROUND

Preinjury employment status may contribute to disparity, injury risk, and recovery patterns following mild traumatic brain injury (MTBI).

OBJECTIVE

To characterize associations between preinjury unemployment, prior comorbidities, and outcomes following MTBI.

METHODS

MTBI patients from TRACK-TBI Pilot with complete six-month outcomes were extracted. Preinjury unemployment, comorbidities, injury factors, and intracranial pathology were considered. Multivariable regression was performed for employment and outcomes, correcting for demographic and injury factors. Mean-differences (B) and 95% CIs are reported. Statistical significance was assessed at p < 0.05.

RESULTS

162 MTBI patients were aged 39.8±15.4-years and 24.6% -unemployed. Unemployed patients demonstrated increased psychiatric comorbidities (45.0% -vs.- 23.8%; p = 0.010), drug use (52.5% -vs.- 21.3%; p < 0.001), smoking (62.5% -vs.- 27.0%; p < 0.001), prior TBI (78.4% -vs.- 55.0%; p = 0.012), and lower education (15.0% -vs.- 45.1% college degree; p = 0.003). On multivariable analysis, unemployment associated with decreased six-month functional outcome (Glasgow Outcome Scale-Extended: B = - 0.50, 95% CI [- 0.88, - 0.11]), increased psychiatric disturbance (Brief Symptom Inventory-18: B = 6.22 [2.33, 10.10]), postconcussional symptoms (Rivermead Questionnaire: B = 4.91 [0.38, 9.44]), and post-traumatic stress disorder (PTSD Checklist-Civilian: B = 5.99 [0.76, 11.22]). No differences were observed for cognitive measures or satisfaction with life.

CONCLUSIONS

Unemployed patients are at risk for preinjury psychosocial comorbidities, poorer six-month functional recovery and increased psychiatric/postconcussional/PTSD symptoms. Resource allocation and return precautions should be implemented to mitigate and/or prevent the decline of at-risk patients.

Age-Related Differences in Diagnostic Accuracy of Plasma Glial Fibrillary Acidic Protein and Tau for Identifying Acute Intracranial Trauma on Computed Tomography: A TRACK-TBI Study

Plasma tau and glial fibrillary acidic protein (GFAP) are promising biomarkers for identifying traumatic brain injury (TBI) patients with intracranial trauma on computed tomography (CT). Accuracy in older adults with mild TBI (mTBI), the fastest growing TBI population, is unknown. Our aim was to assess for age-related differences in diagnostic accuracy of plasma tau and GFAP for identifying intracranial trauma on CT. Samples from 169 patients (age <40 years [n = 79], age 40-59 years [n = 60], age 60 years+ [n = 30]), a subset of patients from the Transforming Research and Clinical Knowledge in TBI (TRACK-TBI) Pilot study who presented with mTBI (Glasgow Coma Scale score of 13-15), received head CT, and consented to blood draw within 24 h of injury, were assayed for hyperphosphorylated-tau (P-tau), total-tau (T-tau; both via amplification-linked enhanced immunoassay using multi-arrayed fiberoptics), and GFAP (via sandwich enzyme-linked immunosorbent assay). P-tau, T-tau, P-tau:T-tau ratio, and GFAP concentration were significantly associated with CT findings. Overall, discriminative ability declined with increasing age for all assays, but this decline was only statistically significant for GFAP (area under the receiver operating characteristic curve [AUC]: old 0.73 [reference group; ref] vs. young 0.93 [p = 0.037] or middle-aged 0.92 [p = 0.0497]). P-tau concentration consistently showed the highest diagnostic accuracy across all age-groups (AUC: old 0.84 [ref] vs. young 0.95 [p = 0.274] or middle-aged 0.93 [p = 0.367]). Comparison of models including P-tau alone versus P-tau plus GFAP revealed significant added value of GFAP. In conclusion, the GFAP assay was less accurate for identifying intracranial trauma on CT among older versus younger mTBI patients. Mechanisms of this age-related difference, including role of assay methodology, specific TBI neuroanatomy, pre-existing conditions, and anti-thrombotic use, warrant further study.

Mild TBI and risk of Parkinson disease: A Chronic Effects of Neurotrauma Consortium Study

OBJECTIVE

Our aim was to assess risk of Parkinson disease (PD) following traumatic brain injury (TBI), including specifically mild TBI (mTBI), among care recipients in the Veterans Health Administration.

METHODS

In this retrospective cohort study, we identified all patients with a TBI diagnosis in Veterans Health Administration databases from October 2002 to September 2014 and age-matched 1:1 to a random sample of patients without TBI. All patients were aged 18 years and older without PD or dementia at baseline. TBI exposure and severity were determined via detailed clinical assessments or ICD-9 codes using Department of Defense and Defense and Veterans Brain Injury Center criteria. Baseline comorbidities and incident PD more than 1 year post-TBI were identified using ICD-9 codes. Risk of PD after TBI was assessed using Cox proportional hazard models adjusted for demographics and medical/psychiatric comorbidities.

RESULTS

Among 325,870 patients (half with TBI; average age 47.9 ± 17.4 years; average follow-up 4.6 years), 1,462 were diagnosed with PD during follow-up. Compared to no TBI, those with TBI had higher incidence of PD (no TBI 0.31%, all-severity TBI 0.58%, mTBI 0.47%, moderate-severe TBI 0.75%). In adjusted models, all-severity TBI, mTBI, and moderate-severe TBI were associated with increased risk of PD (hazard ratio [95% confidence interval]: all-severity TBI 1.71 [1.53-1.92]; mTBI 1.56 [1.35-1.80]; moderate-severe TBI 1.83 [1.61-2.07]).

CONCLUSIONS

Among military veterans, mTBI is associated with 56% increased risk of PD, even after adjusting for demographics and medical/psychiatric comorbidities. This study highlights the importance of TBI prevention, long-term follow-up of TBI-exposed veterans, and the need to determine mechanisms and modifiable risk factors for post-TBI PD.

Geriatric Traumatic Brain Injury: Epidemiology, Outcomes, Knowledge Gaps, and Future Directions

This review of the literature on traumatic brain injury (TBI) in older adults focuses on incident TBI sustained in older adulthood ("geriatric TBI") rather than on the separate, but related, topic of older adults with a history of earlier-life TBI. We describe the epidemiology of geriatric TBI, the impact of comorbidities and pre-injury function on TBI risk and outcomes, diagnostic testing, management issues, outcomes, and critical directions for future research. The highest incidence of TBI-related emergency department visits, hospitalizations, and deaths occur in older adults. Higher morbidity and mortality rates among older versus younger individuals with TBI may contribute to an assumption of futility about aggressive management of geriatric TBI. However, many older adults with TBI respond well to aggressive management and rehabilitation, suggesting that chronological age and TBI severity alone are inadequate prognostic markers. Yet there are few geriatric-specific TBI guidelines to assist with complex management decisions, and TBI prognostic models do not perform optimally in this population. Major barriers in management of geriatric TBI include under-representation of older adults in TBI research, lack of systematic measurement of pre-injury health that may be a better predictor of outcome and response to treatment than age and TBI severity alone, and lack of geriatric-specific TBI common data elements (CDEs). This review highlights the urgent need to develop more age-inclusive TBI research protocols, geriatric TBI CDEs, geriatric TBI prognostic models, and evidence-based geriatric TBI consensus management guidelines aimed at improving short- and long-term outcomes for the large and growing geriatric TBI population.