Fall-related brain injuries and the risk of dementia in elderly people: a population-based study

Is dementia more likely following traumatic brain injury? A systematic review

BACKGROUND

The association between traumatic brain injury (TBI) and dementia is controversial, and of growing importance considering the ageing demography of TBI.

OBJECTIVE

To review the scope and quality of the existing literature investigating the relationship between TBI and dementia.

METHODS

We conducted a systematic review following PRISMA guidelines. Studies that compared TBI exposure and dementia risk were included. Studies were formally assessed for quality with a validated quality-assessment tool.

RESULTS

44 studies were included in the final analysis. 75% (n = 33) were cohort studies and data collection was predominantly retrospective (n = 30, 66.7%). 25 studies (56.8%) found a positive relationship between TBI and dementia. Clearly defined and valid measures of assessing TBI history were lacking (case-control studies-88.9%, cohort studies-52.9%). Most studies failed to justify a sample size (case-control studies-77.8%, cohort studies-91.2%), blind assessors to exposure (case-control-66.7%) or blind assessors to exposure status (cohort-3.00%). Studies that identified a relationship between TBI and dementia had a longer median follow-up time (120 months vs 48 months, p = 0.022) and were more likely to use validated TBI definitions (p = 0.01). Studies which clearly defined TBI exposure (p = 0.013) and accounted for TBI severity (p = 0.036) were also more likely to identify an association between TBI and dementia. There was no consensus method by which studies diagnosed dementia and neuropathological confirmation was only available in 15.5% of studies.

CONCLUSIONS

Our review suggests a relationship between TBI and dementia, but we are unable to predict the risk of dementia for an individual following TBI. Our conclusions are limited by heterogeneity in both exposure and outcome reporting and by poor study quality. Future studies should; (a) use validated methods to define TBI, accounting for TBI severity; (b) follow consensus agreement on criteria for dementia diagnosis; and (c) undertake follow-up that is both longitudinal, to determine if there is a progressive neurodegenerative change or static post-traumatic deficit, and of sufficient duration.

Associations of fall history and fear of falling with multidimensional cognitive function in independent community-dwelling older adults: findings from ORANGE study

BACKGROUND

Falls and fear of falling (FoF) inhibit healthy longevity and have been suggested to be associated with cognitive function. However, the domains of cognitive function that are associated with them remain controversial. It is speculated that clarifying this will help in the assessment of health status and interventions in the community.

AIM

To analyse the associations between fall history and FoF and multidimensional cognitive function in independent community-dwelling older adults.

METHODS

The data from 9759 (73.3 ± 5.4 years, 59.9% women) older individuals enrolled in the cross-sectional ORANGE study were analysed. Simple questions were used to assess fall history in the past year and current FoF. Assessments of multidimensional cognitive function were performed using the National Center for Geriatrics and Gerontology-Functional Assessment Tool (NCGG-FAT) to evaluate memory, attention, executive function, and processing speed. The independent associations of fall history and FoF with multidimensional cognitive function were assessed using multivariate linear regressions adjusted for potential confounding variables.

RESULTS

A total of 18.3% and 35.4% of participants presented with fall history and FoF, respectively. Fall history (p = 0.008) and FoF (p = 0.002) were significantly associated with memory. FoF, but not fall history was associated with attention (p = 0.004), executive function (p < 0.01), and processing speed (p < 0.01).

CONCLUSION

In independent community-dwelling older adults, fall history was associated only with the memory domain; in contrast, fear of falling was associated with multidimensional cognitive function. This study provides weak evidence suggesting the need to assess falls and FoF in all situations involving independent community-dwelling older adults.

Investigating the relationship between mild traumatic brain injury and Alzheimer's disease and related dementias: a systematic review

The objective of this systematic review is to synthesize the relevant literature published after 2016 to ascertain the current landscape of science that relates mild traumatic brain injury (mTBI) to the onset of Alzheimer's disease and related dementias (ADRD) and identify areas of need for future research. We conducted database searches and retrieved articles that were published after 2016 that utilized cognitive assessments to understand the relationship between mTBI and ADRD. We identified eight relevant articles in the review process, four of which presented a significant relationship between mTBI and disease or cognitive impairment outcomes. The studies included in this systematic review underscore the need for future research investigating a possible causal relationship between mTBI and ADRDs given the high prevalence of mTBI among brain injury patients and the lack of literature specifically addressing this issue. Future research should standardize the definitions of mTBI, AD, and ADRDs to create reliable and reproducible results that more comprehensively capture the nuances of this relationship.

Traumatic brain injury in the presence of Aβ pathology affects neuronal survival, glial activation and autophagy

Traumatic brain injury (TBI) presents a widespread health problem in the elderly population. In addition to the acute injury, epidemiological studies have observed an increased probability and earlier onset of dementias in the elderly following TBI. However, the underlying mechanisms of the connection between TBI and Alzheimer's disease in the aged brain and potential exacerbating factors is still evolving. The aim of this study was to investigate cellular injury-induced processes in the presence of amyloid β (Aβ) pathology. For this purpose, a co-culture system of cortical stem-cell derived astrocytes, neurons and oligodendrocytes were exposed to Aβ₄₂ protofibrils prior to a mechanically induced scratch injury. Cellular responses, including neurodegeneration, glial activation and autophagy was assessed by immunoblotting, immunocytochemistry, ELISA and transmission electron microscopy. Our results demonstrate that the combined burden of Aβ exposure and experimental TBI causes a decline in the number of neurons, the differential expression of the key astrocytic markers glial fibrillary acidic protein and S100 calcium-binding protein beta, mitochondrial alterations and prevents the upregulation of autophagy. Our study provides valuable information about the impact of TBI sustained in the presence of Aβ deposits and helps to advance the understanding of geriatric TBI on the cellular level.

The association between injurious falls and older adults' cognitive function: the role of depressive mood and physical performance

Background

The impact of falls on cognitive function is unclear. We explored whether injurious falls are associated with cognitive decline in older adults, and evaluated the role of changes in psychological and physical health as mediators of such association.

Methods

This prospective study involved 2267 community-dwelling participants in the Swedish National study on Aging and Care in Kungsholmen (≥60 years). Data on injurious falls (ie, falls requiring medical attention) during each 3-year time interval of follow-up were obtained from national registers. Assessment of cognitive function (Mini-Mental State Examination), depressive mood (Montgomery-Åsberg Depression Rating Scale), and physical performance (walking speed) were carried out every 3 or 6 years over a 12-year follow-up. The association between falls and cognition was estimated through linear mixed-effects models, and the mediating role of changes in depressive mood and physical performance was tested using mediation analysis.

Results

After adjusting for potential confounders, individuals who experienced injurious falls had a greater annual decline in Mini-Mental State Examination in the subsequent time interval (β = −1.49, 95% CI: −1.84; −1.13), than those who did not. The association increased with the occurrence of ≥2 falls (β = −2.13, 95% CI: −2.70; −1.56). Worsening of walking speed and depressive mood explained around 26% and 8%, respectively, of the association between falls and cognitive decline.

Conclusions

Injurious falls are associated with greater cognitive decline, and this association is partly mediated by worsening of physical performance and, in a lesser extent, of depressive mood. These findings suggest that physical deficits and low mood are potential therapeutic targets for mitigating the association between falls and cognitive decline.

What does (low) education mean in terms of dementia risk? A systematic review and meta-analysis highlighting inconsistency in measuring and operationalising education

Low education is considered an important modifiable risk factor for dementia worldwide, despite the lack of a formal consensus definition of low education. The primary aim of this systematic review was to document and address the inconsistency in measuring and operationalising education in dementia studies. A secondary aim was to consider the dose of education required to reduce dementia risk. The protocol was registered at PROSPERO with registration ID CRD42018096168. CINAHL, Cochrane, PsycInfo, and Pubmed databases were searched using terms related to education, dementia and/or MCI, and incidence. Studies were eligible for inclusion if a risk ratio for education and any dementia, Alzheimer's Disease (AD), Vascular Dementia (VaD) or Mild Cognitive Impairment (MCI) was reported in a population cognitively healthy at baseline. Sample sizes for 65 studies meeting selection criteria ranged from 152 to 12,881, representing populations from 24 countries. Risk of bias, assessed using a tool designed specifically for dementia risk studies, was found to be medium or low for all studies. There were 23 continuous, 29 dichotomous, and 31 categorical operationalisations of education reported. Random effects meta-analyses from continuous operationalisations suggested each year of education reduced risk by eight percent for AD (95% CI:5-12%) and seven percent for any dementia (95% CI:6-9%). Dichotomous operationalisations indicated an increased risk for low education of 45% (95% CI:29-63%) for any dementia and 85% (95% CI:56-118%) for AD, however definitions of low education were heterogeneous, ranging from zero to 12 years. There were too few studies to produce summary ratios for VaD or MCI. We conclude that, while the evidence of an association between low education and dementia incidence is robust, inconsistency in the definition, measurement and operationalisation of education hinders the translation of this evidence into practical policy recommendations to reduce dementia risk.

Quality of life after traumatic brain injury: a cross-sectional analysis uncovers age- and sex-related differences over the adult life span

Traumatic brain injury (TBI) is the leading cause of disability in the working population and becomes increasingly prevalent in the elderly. Thus, TBI is a major global health burden. However, age- and sex-related long-term outcome regarding patient’s health-related quality of life (HRQoL) is yet not clarified. In this cross-sectional study, we present age- and sex-related demographics and HRQoL up to 10 years after TBI using the Quality of Life after Brain Injury (QOLIBRI) instrument. The QOLIBRI total score ranges from zero to 100 indicating good (≥ 60), moderate (40–59) or unfavorable (< 40) HRQoL. Two-thirds of the entire chronic TBI cohort (102 males; 33 females) aged 18–85 years reported good HRQoL up to 10 years after TBI. TBI etiology differed between sexes with females suffering more often from traffic- than fall-related TBI (p = 0.01) with increasing prevalence during aging (p = < 0.001). HRQoL (good/moderate/unfavorable) differed between sexes (p < 0.0001) with 17% more females reporting moderate outcome (p = 0.01). Specifically, older females (54–76-years at TBI) were affected, while males constantly reported good HRQoL (p = 0.017). Cognition (p = 0.014), self-perception (p = 0.009), and emotions (p = 0.016) rather than physical problems (p = 0.1) constrained older females’ HRQoL after TBI. Experiencing TBI during aging does not influence HRQoL outcome in males but females suggesting that female brains cope less well with a traumatic injury during aging. Therefore, older females need long-term follow-ups after TBI to detect neuropsychiatric sequels that restrict their quality of life. Further investigations are necessary to uncover the mechanisms of this so far unknown phenomenon.

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.

Characteristics of fall-related traumatic brain injury in older adults

BACKGROUND

Older adults admitted for falls and its complications, including traumatic brain injury (TBI), is increasing. Recent studies have shown that those with falls who presented to the emergency department (ED) had an increased frequency of ED revisits, especially those with head trauma.

AIM

To determine the characteristics and predictors of fall-related traumatic brain injury (FRTBI) in older adults.

METHODS

Retrospective medical chart review of 339 patients aged 65 years and older admitted for TBI in 2014 due to a fall. Characteristics analysed include demographics, fall circumstances, prior ED visits, polypharmacy, readmission, functional status and specialist outpatient clinic utilisation before and after FRTBI.

RESULTS

A total of 339 (37.4%) patients admitted due to FRTBI was 65 years old and older; 112 (33.0%) for subdural haemorrhage (SDH); 227 (67.0%) for head injury (HI), with a mean age of 80 years. A total of 46 (41.1%) patients with SDH and 107 (47.1%) with HI had a previous ED visit within the last year, while 22 (19.6%) of SDH and 49 (21.6%) of HI had hospitalisation 3 months prior to FRTBI. FRTBI was associated with significant decline in activities of daily living, polypharmacy and increased specialist outpatient clinic appointments (P < 0.001). Mortality was 11 (3.2%). Mild cognitive impairment or dementia was significantly associated with admissions for FRTBI, 3.31 (95% confidence interval 1.68-6.51, P = 0.001) using adjusted logistic regression.

CONCLUSION

FRTBI is associated with significant functional decline and increased resource utilisation with almost half of the patients having had prior ED visits or hospitalisation. Future studies should focus on falls risk assessment and interventions for high-risk older adults prior to discharge from ED and hospital, and its impact on readmissions due to FRTBI.

Is traumatic brain injury a risk factor for neurodegeneration? A meta-analysis of population-based studies

Background

To determine the association of prior traumatic brain injury (TBI) with subsequent diagnosis of neurodegeneration disease.

Methods

All studies from 1980 to 2016 reporting TBI as a risk factor for diagnoses of interest were identified by searching PubMed, Embase, study references, and review articles. The data and study design were assessed by 2 investigators independently. A meta-analysis was performed by RevMan 5.3.

Results

There were 18 studies comprising 3,263,207 patients. Meta-analysis revealed a significant association of prior TBI with subsequent dementia. The pooled odds ratio (OR) for TBI on development of dementia, FTD and TDP-43 associated disease were 1.93 (95% CI 1.47–2.55, p < 0.001), 4.44 (95% CI 3.86–5.10, p < 0.001), and 2.97 (95% CI 1.35–6.53, p < 0.001). However, analyses of individual diagnoses found no evidence that the risk of Alzheimer’s disease, and Parkinson’s disease in individuals with previous TBI compared to those without TBI.

Conclusions

History of TBI is not associated with the development of subsequent neurodegeneration disease. Care must be taken in extrapolating from these results because no suitable criteria define post TBI neurodegenerative processes. Therefore, further research in this area is needed to confirm these questions and uncover the link between TBI and neurodegeneration disease.

Traumatic Brain Injury, Chronic Traumatic Encephalopathy, and Alzheimer Disease

Traumatic brain injury (TBI) is a major health and economic burden. With increasing aging population, this issue is expected to continue to rise. Neurodegenerative disorders are more common with aging population in general regardless of history of TBI. Recent evidence continues to support a relation between a TBI and neurocognitive decline later in life (such as in athletes and military). This article summarizes the pathologic and clinical effects of TBI (regardless of severity) on the later development of dementia in individuals 65 years or older.

Injury cascades in TBI-related neurodegeneration

Traumatic brain injury (TBI) is a widely recognized risk factor for neurodegenerative disease. The purpose of this review is to provide an update on the state of the science related to injury cascades in TBI-related neurodegeneration. Acute and chronic pathological outcomes of TBI are similar to those seen in several neurodegenerative conditions, suggesting common linking pathways. Initial research described severe TBI patients with post-mortem identification of abnormal proteins, such as amyloid deposits. History of mild TBI (mTBI) is less consistently associated with heightened risk of neurodegenerative outcomes, but specific populations with complicated medical histories and comorbidities may be more susceptible. Our understanding of a pathological signature associated with repetitive mTBI and/or subclinical brain trauma advanced significantly over the past decade, and is now commonly referred to as chronic traumatic encephalopathy. We discuss hypotheses linking TBI to neurodegenerative disease, and the importance of considering factors like injury severity, timing of injury (early life versus older age), injury frequency, and repetitive subclinical brain trauma when extrapolating results from current literature to certain populations. We describe the challenges to obtaining the data necessary for accurate epidemiological research and determination of true risk magnitude, and note the importance of developing treatment-based approaches to risk mitigation.

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.

Does traumatic brain injury hold the key to the Alzheimer's disease puzzle?

INTRODUCTION

Neurodegenerative disorders have been a graveyard for hundreds of well-intentioned efforts at drug discovery and development. Concussion and other traumatic brain injuries (TBIs) and Alzheimer's disease (AD) share many overlapping pathologies and possible clinical links.

METHODS

We searched the literature since 1995 using MEDLINE and Google Scholar for the terms concussion, AD, and shared neuropathologies. We also studied a TBI animal model as a supplement to transgenic (Tg) mouse AD models for evaluating AD drug efficacy by preventing neuronal losses. To evaluate TBI/AD pathologies and neuronal self-induced cell death (apoptosis), we are studying brain extracellular vesicles in plasma and (-)-phenserine pharmacology to probe, in animal models of AD and humans, apoptosis and pathways common to concussion and AD.

RESULTS

Neuronal cell death and a diverse and significant pathological cascade follow TBIs. Many of the developing pathologies are present in early AD. The use of an animal model of concussion as a supplement to Tg mice provides an indication of an AD drug candidate's potential for preventing apoptosis and resulting progression toward dementia in AD. This weight drop supplementation to Tg mouse models, the experimental drug (-)-phenserine, and plasma-derived extracellular vesicles enriched for neuronal origin to follow biomarkers of neurodegenerative processes, each and in combination, show promise as tools useful for probing the progression of disease in AD, TBI/AD pathologies, apoptosis, and drug effects on rates of apoptosis both preclinically and in humans. (-)-Phenserine both countered many subacute post-TBI pathologies that could initiate clinical AD and, in the concussion and other animal models, showed evidence consistent with direct inhibition of neuronal preprogrammed cell death in the presence of TBI/AD pathologies.

DISCUSSION

These findings may provide support for expanding preclinical Tg mouse studies in AD with a TBI weight drop model, insights into the progression of pathological targets, their relations to apoptosis, and timing of interventions against these targets and apoptosis. Such studies may demonstrate the potential for drugs to effectively and safely inhibit preprogrammed cell death as a new drug development strategy for use in the fight to defeat AD.

Increased Rates of Mild Traumatic Brain Injury Among Older Adults in US Emergency Departments, 2009-2010

OBJECTIVE

To estimate rates of emergency department (ED) visits for mild traumatic brain injury (TBI) among older adults. We defined possible mild TBI cases to assess underdiagnoses.

DESIGN

Cross-sectional.

SETTING

National sample of ED visits in 2009-2010 captured by the National Hospital Ambulatory Medical Care Survey.

PARTICIPANTS

Aged 65 years and older.

MEASUREMENTS

Mild TBI defined by International Classification of Diseases, Ninth Revision, Clinical Modification, codes (800.0x-801.9x, 803.xx, 804.xx, 850.xx-854.1x, 950.1x-950.3x, 959.01) and a Glasgow Coma Scale score of 14 or more or missing, excluding those admitted to the hospital. Possible mild TBI was defined similarly among those without mild TBI and with a fall or motor vehicle collision as cause of injury. We calculated rates of mild TBI and examined factors associated with a diagnosis of mild TBI.

RESULTS

Rates of ED visits for mild TBI were 386 per 100 000 among those aged 65 to 74 years, 777 per 100 000 among those aged 75 to 84 years, and 1205 per 100 000 among those older than 84 years. Rates for women (706/100 000) were higher than for men (516/100 000). Compared with a possible mild TBI, a diagnosis of mild TBI was more likely in the West (odds ratio = 2.31; 95% confidence interval, 1.02-5.24) and less likely in the South/Midwest (odds ratio = 0.52; 95% confidence interval, 0.29-0.96) than in the Northeast.

CONCLUSIONS

This study highlights an upward trend in rates of ED visits for mild TBI among older adults.

What is the Relationship of Traumatic Brain Injury to Dementia?

There is a long history linking traumatic brain injury (TBI) with the development of dementia. Despite significant reservations, such as recall bias or concluding causality for TBI, a summary of recent research points to several conclusions on the TBI-dementia relationship. 1) Increasing severity of a single moderate-to-severe TBI increases the risk of subsequent Alzheimer's disease (AD), the most common type of dementia. 2) Repetitive, often subconcussive, mild TBIs increases the risk for chronic traumatic encephalopathy (CTE), a degenerative neuropathology. 3) TBI may be a risk factor for other neurodegenerative disorders that can be associated with dementia. 4) TBI appears to lower the age of onset of TBI-related neurocognitive syndromes, potentially adding "TBI cognitive-behavioral features". The literature further indicates several specific risk factors for TBI-associated dementia: 5) any blast or blunt physical force to the head as long as there is violent head displacement; 6) decreased cognitive and/or neuronal reserve and the related variable of older age at TBI; and 7) the presence of apolipoprotein E ɛ4 alleles, a genetic risk factor for AD. Finally, there are neuropathological features relating TBI with neurocognitive syndromes: 8) acute TBI results in amyloid pathology and other neurodegenerative proteinopathies; 9) CTE shares features with neurodegenerative dementias; and 10) TBI results in white matter tract and neural network disruptions. Although further research is needed, these ten findings suggest that dose-dependent effects of violent head displacement in vulnerable brains predispose to dementia; among several potential mechanisms is the propagation of abnormal proteins along damaged white matter networks.

Applying Systems Biology Methodology To Identify Genetic Factors Possibly Associated with Recovery after Traumatic Brain Injury

Traumatic brain injury (TBI) is one of the leading causes of morbidity and mortality worldwide. It is linked with a number of medical, neurological, cognitive, and behavioral sequelae. The influence of genetic factors on the biology and related recovery after TBI is poorly understood. Studies that seek to elucidate the impact of genetic influences on neurorecovery after TBI will lead to better individualization of prognosis and inform development of novel treatments, which are considerably lacking. Current genetic studies related to TBI have focused on specific candidate genes. The objectives of this study were to use a system biology-based approach to identify biologic processes over-represented with genetic variants previously implicated in clinical outcomes after TBI and identify unique genes potentially related to recovery after TBI. After performing a systematic review to identify genes in the literature associated with clinical outcomes, we used the genes identified to perform a systems biology-based integrative computational analysis to ascertain the interactions between molecular components and to develop models for regulation and function of genes involved in TBI recovery. The analysis identified over-representation of genetic variants primarily in two biologic processes: response to injury (cell proliferation, cell death, inflammatory response, and cellular metabolism) and neurocognitive and behavioral reserve (brain development, cognition, and behavior). Overall, this study demonstrates the use of a systems biology-based approach to identify unique/novel genes or sets of genes important to the recovery process. Findings from this systems biology-based approach provide additional insight into the potential impact of genetic variants on the underlying complex biological processes important to TBI recovery and may inform the development of empirical genetic-related studies for TBI. Future studies that combine systems biology methodology and genomic, proteomic, and epigenetic approaches are needed in TBI.

Head Injury as a Risk Factor for Dementia and Alzheimer's Disease: A Systematic Review and Meta-Analysis of 32 Observational Studies

BACKGROUND

Head injury is reported to be associated with increased risks of dementia and Alzheimer's disease (AD) in many but not all the epidemiological studies. We conducted a systematic review and meta-analysis to estimate the relative effect of head injury on dementia and AD risks.

METHODS

Relevant cohort and case-control studies published between Jan 1, 1990, and Mar 31, 2015 were searched in PubMed, Web of Science, Scopus, and ScienceDirect. We used the random-effect model in this meta-analysis to take into account heterogeneity among studies.

RESULTS

Data from 32 studies, representing 2,013,197 individuals, 13,866 dementia events and 8,166 AD events, were included in the analysis. Overall, the pooled relative risk (RR) estimates showed that head injury significantly increased the risks of any dementia (RR = 1.63, 95% CI 1.34-1.99) and AD (RR = 1.51, 95% CI 1.26-1.80), with no evidence of publication bias. However, when considering the status of unconsciousness, head injury with loss of consciousness did not show significant association with dementia (RR = 0.92, 95% CI 0.67-1.27) and AD (RR = 1.49, 95% CI 0.91-2.43). Additionally, this positive association did not reach statistical significance in female participants.

CONCLUSIONS

The findings from this meta-analysis indicate that head injury is associated with increased risks of dementia and AD.

Glycosylation and other PTMs alterations in neurodegenerative diseases: Current status and future role in neurotrauma

Traumatic brain injuries (TBIs) present a chief public health threat affecting nations worldwide. As numbers of patients afflicted by TBI are expected to rise, the necessity to increase our understanding of the pathophysiological mechanism(s) as a result of TBI mounts. TBI is known to augment the risk of developing a number of neurodegenerative diseases (NDs) such as Alzheimer's disease (AD) and Parkinson's disease (PD). Hence, it is rational to assume that a common mechanistic ground links the pathophysiology of NDs to that of TBIs. Through this review, we aim to identify the protein-protein interactions, differential proteins expression, and PTMs, mainly glycosylation, that are involved in the pathogenesis of both ND and TBI. OVID and PubMed have been rigorously searched to identify studies that utilized advanced proteomic platforms (MS based) and systems biology tools to unfold the mechanism(s) behind ND in an attempt to unveil the mysterious biological processes that occur postinjury. Various PTMs have been found to be common between TBI and AD, whereas no similarities have been found between TBI and PD. Phosphorylated tau protein, glycosylated amyloid precursor protein, and many other modifications appear to be common in both TBI and AD. PTMs, differential protein profiles, and altered biological pathways appear to have critical roles in ND processes by interfering with their pathological condition in a manner similar to TBI. Advancement in glycoproteomic studies pertaining to ND and TBI is urgently needed in order to develop better diagnostic tools, therapies, and more favorable prognoses.

Traumatic brain injury and age at onset of cognitive impairment in older adults

There is a deficiency of knowledge regarding how traumatic brain injury (TBI) is associated with age at onset (AAO) of cognitive impairment in older adults. Participants with a TBI history were identified from the Alzheimer's disease neuroimaging initiative (ADNI 1/GO/2) medical history database. Using an analysis of covariance (ANCOVA) model, the AAO was compared between those with and without TBI, and potential confounding factors were controlled. The AAO was also compared between those with mild TBI (mTBI) and moderate or severe TBI (sTBI). Lastly, the effects of mTBI were analyzed on the AAO of participants with clinical diagnoses of either mild cognitive impairment (MCI) or Alzheimer's disease (AD). The AAO for a TBI group was 68.2 ± 1.1 years [95 % confidence interval (CI) 66.2-70.3, n = 62], which was significantly earlier than the AAO for the non-TBI group of 70.9 ± 0.2 years (95 % CI 70.5-71.4, n = 1197) (p = 0.013). Participants with mTBI history showed an AAO of 68.5 ± 1.1 years (n = 56), which was significantly earlier than the AAO for the non-TBI group (p = 0.032). Participants with both MCI and mTBI showed an AAO of 66.5 ± 1.3 years (95 % CI 63.9-69.1, n = 45), compared to 70.6 ± 0.3 years for the non-TBI MCI group (95 % CI 70.1-71.1, n = 935) (p = 0.016). As a conclusion, a history of TBI may accelerate the AAO of cognitive impairment by two or more years. These results were consistent with reports of TBI as a significant risk factor for cognitive decline in older adults, and TBI is associated with an earlier AAO found in patients with MCI or AD.

Role of apolipoprotein E polymorphism as a prognostic marker in traumatic brain injury and neurodegenerative disease: a critical review

OBJECT

The difference in course and outcome of several neurodegenerative conditions and traumatic injuries of the nervous system points toward a possible role of genetic and environmental factors as prognostic markers. Apolipoprotein E (Apo-E), a key player in lipid metabolism, is recognized as one of the most powerful genetic risk factors for dementia and other neurodegenerative diseases. In this article, the current understanding of APOE polymorphism in various neurological disorders is discussed.

METHODS

The English literature was searched for various studies describing the role of APOE polymorphism as a prognostic marker in neurodegenerative diseases and traumatic brain injury. The wide ethnic distribution of APOE polymorphism was discussed, and the recent meta-analyses of role of APOE polymorphism in multiple diseases were analyzed and summarized in tabular form.

RESULTS

Results from the review of literature revealed that the distribution of APOE is varied in different ethnic populations. APOE polymorphism plays a significant role in pathogenesis of neurodegeneration, particularly in Alzheimer’s disease. APOE ε4 is considered a marker for poor prognosis in various diseases, but APOE ε2 rather than APOE ε4 has been associated with cerebral amyloid angiopathy-related bleeding and sporadic Parkinson’s disease. The role of APOE polymorphism in various neurological diseases has not been conclusively elucidated.

CONCLUSIONS

Apo-E is a biomarker for various neurological and systemic diseases. Therefore, while analyzing the role of APOE polymorphism in neurological diseases, the interpretation should be done after adjusting all the confounding factors. A continuous quest to look for associations with various neurological diseases and wide knowledge of available literature are required to improve the understanding of the role of APOE polymorphism in these conditions and identify potential therapeutic targets.

The association of traumatic brain injury with rate of progression of cognitive and functional impairment in a population-based cohort of Alzheimer's disease: the Cache County Dementia Progression Study

BACKGROUND

There is limited research on factors that influence the rate of progression in Alzheimer's disease (AD). A history of traumatic brain injury (TBI) is associated with an increased risk for AD, but its role on the rate of dementia progression after the onset of AD has not been examined.

METHODS

A population-based cohort of 325 persons with incident AD was followed for up to 11 years. The sample was 65% female with a mean (SD) age of dementia onset = 84.4 (6.4) years. History of TBI was categorized as number, severity (with or without loss of consciousness), and timing in relation to dementia onset (within ten years or more than ten years). Cognition was assessed by the Consortium to Establish a Registry of AD battery, and functional ability was assessed by the Clinical Dementia Rating Sum of Boxes.

RESULTS

In linear mixed models, a history of TBI within ten years of onset showed faster progression of functional impairment (LR x2 = 10.27, p = 0.006), while those with TBI more than ten years before dementia onset had higher scores on a measure of list learning (β = 1.61, p = 0.003) and semantic memory (β = 0.75, p = 0.0035).

CONCLUSIONS

History of TBI and its recency may be a useful factor to predict functional progression in the course of AD.

Falls and cognitive decline in Mexican Americans 75 years and older

Background

Little is known about long-term emotional and cognitive consequences of falls. We examined the association between falls and subsequent cognitive decline, and tested the hypothesis that depression would mediate any falls–cognition association among cognitively intact Hispanic Elders.

Methods

We used data from the Hispanic Established Population for the Epidemiological Study of the Elderly to examine change in Mini Mental State Examination (MMSE) scores over the 6-year period according to number of falls. All participants (N=1,119) had MMSE scores ≥21 and complete data on Center for Epidemiologic Studies of Depression Scale, social and demographic factors, medical conditions (diabetes, heart attack, stroke, and hypertension), and hand grip muscle strength.

Results

At baseline, participants’ mean age was 80.8 years (range, 74–109), mean education was 6.3 years (range, 0–17), and mean MMSE was 25.2 (range, 21–30). Of the 1,119 participants, 15.8% experienced one fall and 14.4% had two or more falls. In mixed model analyses, having two or more falls was associated with greater decline in MMSE score (estimate =−0.81, standard error =0.19, P<0.0001) compared to having no fall, after adjusting for age, sex, marital status, and education. The magnitude of the association decreased (estimate =−0.65, standard error =0.19, P=0.0007) when adjustment was made for high depressive symptoms, suggesting a possible mediating effect of depression on the falls–cognition association. Female sex, high level of education, and high performance in hand grip muscle strength were associated with a slower decline in MMSE scores.

Conclusion

Having two or more falls was independently associated with steeper decline in cognition over 6 years, with a possible mediating effect of depression on the falls–cognition association.

Older adults with acquired brain injury: a population based study

Background

Acquired brain injury (ABI), which includes traumatic (TBI) and non-traumatic brain injury (nTBI), is a leading cause of death and disability worldwide. The objective of this study was to examine the trends, characteristics, cause of brain injury, and discharge destination of hospitalized older adults aged 65 years and older with an ABI diagnosis in a population with universal access to hospital care. The profile of characteristics of patients with TBI and nTBI causes of injury was also compared.

Methods

A population based retrospective cohort study design with healthcare administrative databases was used. Data on acute care admissions were obtained from the Discharge Abstract Database and patients were identified using the International Classification of Diseases – Version 10 codes for Ontario, Canada from April 1, 2003 to March 31, 2010. Older adults were examined in three age groups – 65 to 74, 75 to 84, and 85+ years.

Results

From 2003/04 to 2009/10, there were 14,518 episodes of acute care associated with a TBI code and 51, 233 episodes with a nTBI code. Overall, the rate of hospitalized TBI and nTBI episodes increased with older age groups. From 2007/08 to 2009/10, the percentage of patients that stayed in acute care for 12 days or more and the percentage of patients with delayed discharge from acute care increased with age. The most common cause of TBI was falls while the most common type of nTBI was brain tumours. The percentage of patients discharged to long term care and complex continuing care increased with age and the percentage discharged home decreased with age. In-hospital mortality also increased with age. Older adults with TBI and nTBI differed significantly in demographic and clinical characteristics and discharge destination from acute care.

Conclusions

This study showed an increased rate of acute care admissions for both TBI and nTBI with age. It also provided additional support for falls prevention strategies to prevent injury leading to cognitive disability with costly human and economic consequences. Implications for increased numbers of people with ABI are discussed.

Risk for late-life re-injury, dementia and death among individuals with traumatic brain injury: a population-based study

OBJECTIVES

To determine the association of self-reported traumatic brain injury (TBI) with loss of consciousness (LOC) with late-life re-injury, dementia diagnosis and mortality.

DESIGN

Ongoing longitudinal population-based prospective cohort study.

SETTING

Seattle-area integrated health system.

PARTICIPANTS

4225 dementia-free individuals age 65 and older were randomly selected and enrolled between 1994 and 2010. Participants were seen every 2 years, with mean (range) follow-up of 7.4 (0-16) years. 606 (14%) participants reported a lifetime history of TBI with LOC at enrolment. 3466 participants provided information regarding lifetime history of TBI and completed at least one follow-up visit.

MAIN OUTCOME MEASURES

Self-reported TBI with LOC after study entry, incident all-cause dementia and Alzheimer's disease (AD), and all-cause mortality.

RESULTS

There were 25 567 person-years of follow-up. History of TBI with LOC reported at study enrolment was associated with increased risk for TBI with LOC during follow-up, with adjusted HRs ranging from 2.54 (95% CI 1.42 to 4.52) for those reporting first injury before age 25 to 3.79 (95% CI 1.89 to 7.61) for those with first injury after age 55. History of TBI with LOC was not associated with elevated risk for developing dementia or AD. There was no association between baseline history of TBI with LOC and mortality, though TBI with LOC since the previous study visit ('recent TBI') was associated with increased mortality (HR 2.12, 95% CI 1.62 to 2.78).

CONCLUSIONS

Individuals aged 65 or older who reported a history of TBI with LOC at any time in their lives were at elevated risk of subsequent re-injury. Recent TBI with LOC sustained in older adulthood was associated with increased risk for mortality. Findings support the need for close clinical monitoring of older adults who sustain a TBI with LOC.

Traumatic brain injury: special problem, special care

External physical insult, an accidental blow, acceleration followed by rapid deceleration, or explosive blasts can cause traumatic brain injury (TBI). During the last few years, experts have realized that even mild blows to the head can cause lasting damage. Better understanding of how TBI occurs has improved the probability of survival for those with the most serious injuries. Graded using the Glasgow Coma Scale, TBI may leave its sufferers awake, in periods of alertness interspersed with cognitive confusion, or deep in coma. Falls recently displaced motor vehicle accidents as the leading cause of TBI. Elders are at high risk for falls and TBI, and they may be unaware of possible lasting complications. Pharmacologic therapies for patients who have suffered TBI are, by necessity, individualized.

Traumatic Brain Injury in the Elderly: Is it as Bad as we Think?

Traumatic brain injury in elderly patients is a neglected global disease burden. The main cause is fall, followed by motor vehicle accidents. This review article summarizes different aspects of geriatric traumatic brain injury, including epidemiology, pathology, and effects of comorbidities and pre-injury medications such as antiplatelets and anticoagulants. Functional outcome with or without surgical intervention, cognitive outcome, and psychiatric complications are discussed. Animal models are also reviewed in attempt to explain the relationship of aging and outcome, together with advances in stem cell research. Though elderly people in general did fare worse after traumatic brain injury, certain "younger elderly" people, aged 65-75 years, could have a comparable outcome to younger adults after minor to moderate head injury.

Will testing for apolipoprotein E assist in tailoring dementia risk reduction? A review

This paper aims to systematically review the influence of apolipoprotein E (ApoE) on the effects of potentially modifiable mid and late life risk factors for dementia. Scopus, Medline, PubMed, PsycINFO, and HuGE databases were searched up to November 2008. Two independent reviewers selected 94 articles from 13,122 results. Results suggest the deleterious effect of current smoking is limited only to persons without ApoE epsilon 4 (4 out of 4 studies), ApoE epsilon 4 increases the risk of dementia associated with greater fat consumption, particularly saturated fats (3 out of 4 studies), and increases the protective effect against dementia associated with HRT use (3 out of 5 with one of the non-significant studies suggesting a trend). There was evidence that ApoE does not modify the risk of dementia associated with measures of, and treatments for CVD, other dietary factors, and estradiol levels. There was inconsistent or contradictory evidence for other environmental factors reviewed. There is insufficient evidence for the recommendation of ApoE testing to assist with tailoring risk reduction recommendations for dementia.

Modifiable Midlife Risk Factors for Late-Life Cognitive Impairment and Dementia

The baby boom generation is approaching the age of greatest risk for cognitive impairment and dementia. There is growing interest in strategies to modify the environment in midlife to increase the probability of maintaining cognitive health in late life. Several potentially modifiable risk factors have been studied in relation to cognitive impairment and dementia in late life, but methodological limitations of observational research have resulted in some inconsistencies across studies. The most promising strategies are maintaining cardiovascular health, engagement in mental, physical, and social activities, using alcohol in moderation, abstaining from tobacco use, and following a heart-healthy diet. Other factors that may influence cognitive health are occupational attainment, depression, personality, exposure to general anesthesia, head injury, postmenopausal hormone therapy, non-steroidal anti-inflammatory medications, and nutritional supplements such as antioxidants. Some long-term observational studies initiated in midlife or earlier, and some randomized controlled trials, have examined the effects of specific cognitive health promotion behaviors in midlife on the risk of cognitive impairment in late life. Overall, these studies provide limited support for risk reduction at this time. Recommendations and challenges for developing effective strategies to reduce the burden of cognitive impairment and dementia in the future are discussed.

Risk of dementia associated with the ApoE epsilon4 allele and falls causing head injury without explicit traumatic brain injury

OBJECTIVES

Severe head injury (HI) and the apolipoprotein E (ApoE) epsilon4 allele are risk factors for dementia. The corresponding effect of falls causing HI without explicit traumatic brain injury (TBI) in association with the ApoE epsilon4 is not known.

MATERIALS AND METHODS

Altogether 134 persons aged 70 years or older constituted a retrospective population sample, who scored > or =26 in the MiniMental State Examination (MMSE) test at baseline and were clinically examined for dementia 9 years afterward. Fall-related HI causing superficial laceration or bruises or wounds that require suturing were prospectively recorded during the 9-year follow-up. We used Cox regression with age at the diagnosis of dementia as a dependent variable.

RESULTS

Twenty-eight (21%) subjects had falls causing HI without explicit TBI, the ApoE epsilon4 allele was seen in 44 (33%), and clinical dementia was diagnosed in 25 (19%). Adjusted for the baseline MMSE score, sex and educational status, the hazard ratio for subsequent dementia in subjects having falls with HI without explicit TBI and the ApoE epsilon4 allele as compared with those who do not possess these characteristics was 2.70 (95% confidence interval, 1.02-7.16).

CONCLUSIONS

According to the results of this small retrospective study, falls with HI without explicit TBI in connection with the ApoE epsilon4 allele is associated with subsequent dementia among older adults.

Traumatic brain injury and Alzheimer's disease: a review

In an effort to identify the factors that are involved in the pathogenesis of Alzheimer's disease (AD), epidemiological studies have featured prominently in contemporary research. Of those epidemiological factors, accumulating evidence implicates traumatic brain injury (TBI) as a possible predisposing factor in AD development. Exactly how TBI triggers the neurodegenerative cascade of events in AD remains controversial. There has been extensive research directed towards understanding the potential relationship between TBI and AD and the putative influence that apolipoprotein E (APOE) genotype has on this relationship. The aim of the current paper is to provide a critical summary of the experimental and human studies regarding the association between TBI, AD and APOE genotype. It will be shown that despite significant discrepancies in the literature, there still appears to be an increasing trend to support the hypothesis that TBI is a potential risk factor for AD. Furthermore, although it is known that APOE genotype plays an important role in AD, its link to a deleterious outcome following TBI remains inconclusive and ambiguous.