Modeling the Influence of Age on Neurological Outcome and Quality of Life One Year after Traumatic Brain Injury: A Prospective Multi-Center Cohort Study

Beta2 adrenergic receptor-mediated abnormal myelopoiesis drives neuroinflammation in aged patients with traumatic brain injury

Aged patients often suffer poorer neurological recovery than younger patients after traumatic brain injury (TBI), but the mechanisms underlying this difference remain unclear. Here, we demonstrate abnormal myelopoiesis characterized by increased neutrophil and classical monocyte output but impaired nonclassical patrolling monocyte population in aged patients with TBI as well as in an aged murine TBI model. Retrograde and anterograde nerve tracing indicated that increased adrenergic input through the central amygdaloid nucleus-bone marrow axis drives abnormal myelopoiesis after TBI in a β2-adrenergic receptor-dependent manner, which is notably enhanced in aged mice after injury. Selective blockade of β2-adrenergic receptors rebalances abnormal myelopoiesis and improves the outcomes of aged mice after TBI. We therefore demonstrate that increased β2-adrenergic input-driven abnormal myelopoiesis exacerbates post-TBI neuroinflammation in the aged, representing a mechanism underlying the poorer recovery of aged patients and that blockade of β2-adrenergic receptor is a potential approach to promote neurological recovery after TBI.

The impact of age on outcome 2 years after traumatic brain injury: Case control study

BACKGROUND

Age is associated with outcome after traumatic brain injury (TBI). However, there are mixed findings across outcome domains and most studies lack controls.

OBJECTIVES

This cross-sectional study examined the association between age group (15-24 years, 25-34 years, 35-44 years, 45-54 years, 55-64 years, and 65 years or more) and outcomes 2 years after TBI in independence in daily activities, driving, public transportation use, employment, leisure activities, social integration, relationships and emotional functioning, relative to healthy controls. It was hypothesized that older individuals with TBI would have significantly poorer outcomes than controls in all domains except anxiety and depression, for which it was expected they would show better outcomes. Global functional outcome (measured using the Glasgow Outcome Scale-Extended) was also examined, and we hypothesized that older adults would have poorer outcomes than younger adults.

METHODS

Participants were 1897 individuals with TBI (mean, SD age 36.7, 17.7 years) who completed measures 2 years post-injury and 110 healthy controls (age 38.3, 17.5 years).

RESULTS

Compared to controls, individuals with TBI were less independent in most activities of daily living, participated less in leisure activities and employment, and were more socially isolated, anxious and depressed (p < 0.001). Those who were older in age were disproportionately less likely to be independent in light domestic activities, shopping and driving; and participated less in occupational activities relative to controls. Functional outcome was significantly higher in the youngest age group than in all older age groups (p < 0.001), but the younger groups were more likely to report being socially isolated (p < 0.001), depressed (p = 0.005) and anxious (p = 0.02), and less likely to be married or in a relationship (p < 0.001).

CONCLUSION

A greater focus is needed on addressing psychosocial issues in younger individuals with TBI, whereas those who are older may require more intensive therapy to maximise independence in activities of daily living and return to employment.

Early Shared Decision-Making for Older Adults with Traumatic Brain Injury: Using Time-Limited Trials and Understanding Their Limitations

Older adults account for a disproportionate share of the morbidity and mortality after traumatic brain injury (TBI). Predicting functional and cognitive outcomes for individual older adults after TBI is challenging in the acute phase of injury. Given that neurologic recovery is possible and uncertain, life-sustaining therapy may be pursued initially, even if for some, there is a risk of survival to an undesired level of disability or dependence. Experts recommend early conversations about goals of care after TBI, but evidence-based guidelines for these discussions or for the optimal method for communicating prognosis are limited. The time-limited trial (TLT) model may be an effective strategy for managing prognostic uncertainty after TBI. TLTs can provide a framework for early management: specific treatments or procedures are used for a defined period of time while monitoring for an agreed-upon outcome. Outcome measures, including signs of worsening and improvement, are defined at the outset of the trial. In this Viewpoint article, we discuss the use of TLTs for older adults with TBI, their potential benefits, and current challenges to their application. Three main barriers limit the implementation of TLTs in these scenarios: inadequate models for prognostication; cognitive biases faced by clinicians and surrogate decision-makers, which may contribute to prognostic discordance; and ambiguity regarding appropriate endpoints for the TLT. Further study is needed to understand clinician behaviors and surrogate preferences for prognostic communication and how to optimally integrate TLTs into the care of older adults with TBI.

Systemic immune response in young and elderly patients after traumatic brain injury

BACKGROUND

Traumatic brain injury (TBI) is a leading cause of death and long-term disability worldwide. In addition to primary brain damage, systemic immune alterations occur, with evidence for dysregulated immune responses in aggravating TBI outcome and complications. However, immune dysfunction following TBI has been only partially understood, especially in the elderly who represent a substantial proportion of TBI patients and worst outcome. Therefore, we aimed to conduct an in-depth immunological characterization of TBI patients, by evaluating both adaptive (T and B lymphocytes) and innate (NK and monocytes) immune cells of peripheral blood mononuclear cells (PBMC) collected acutely (< 48 h) after TBI in young (18-45 yo) and elderly (> 65 yo) patients, compared to age-matched controls, and also the levels of inflammatory biomarkers.

RESULTS

Our data show that young respond differently than elderly to TBI, highlighting the immune unfavourable status of elderly compared to young patients. While in young only CD4 T lymphocytes are activated by TBI, in elderly both CD4 and CD8 T cells are affected, and are induced to differentiate into subtypes with low cytotoxic activity, such as central memory CD4 T cells and memory precursor effector CD8 T cells. Moreover, TBI enhances the frequency of subsets that have not been previously investigated in TBI, namely the double negative CD27- IgD- and CD38-CD24- B lymphocytes, and CD56dim CD16- NK cells, both in young and elderly patients. TBI reduces the production of pro-inflammatory cytokines TNF-α and IL-6, and the expression of HLA-DM, HLA-DR, CD86/B7-2 in monocytes, suggesting a compromised ability to drive a pro-inflammatory response and to efficiently act as antigen presenting cells.

CONCLUSIONS

We described the acute immunological response induced by TBI and its relation with injury severity, which could contribute to pathologic evolution and possibly outcome. The focus on age-related immunological differences could help design specific therapeutic interventions based on patients' characteristics.

Ageing is associated with maladaptive immune response and worse outcome after traumatic brain injury

Traumatic brain injury is increasingly common in older individuals. Older age is one of the strongest predictors for poor prognosis after brain trauma, a phenomenon driven by the presence of extra-cranial comorbidities as well as pre-existent pathologies associated with cognitive impairment and brain volume loss (such as cerebrovascular disease or age-related neurodegeneration). Furthermore, ageing is associated with a dysregulated immune response, which includes attenuated responses to infection and vaccination, and a failure to resolve inflammation leading to chronic inflammatory states. In traumatic brain injury, where the immune response is imperative for the clearance of cellular debris and survey of the injured milieu, an appropriate self-limiting response is vital to promote recovery. Currently, our understanding of age-related factors that contribute to the outcome is limited; but a more complete understanding is essential for the development of tailored therapeutic strategies to mitigate the consequences of traumatic brain injury. Here we show greater functional deficits, white matter abnormalities and worse long-term outcomes in aged compared with young C57BL/6J mice after either moderate or severe traumatic brain injury. These effects are associated with altered systemic, meningeal and brain tissue immune response. Importantly, the impaired acute systemic immune response in the mice was similar to the findings observed in our clinical cohort. Traumatic brain-injured patient cohort over 70 years of age showed lower monocyte and lymphocyte counts compared with those under 45 years. In mice, traumatic brain injury was associated with alterations in peripheral immune subsets, which differed in aged compared with adult mice. There was a significant increase in transcription of immune and inflammatory genes in the meninges post-traumatic brain injury, including monocyte/leucocyte-recruiting chemokines. Immune cells were recruited to the region of the dural injury, with a significantly higher number of CD11b⁺ myeloid cells in aged compared with the adult mice. In brain tissue, when compared with the young adult mice, we observed a more pronounced and widespread reactive astrogliosis 1 month after trauma in aged mice, sustained by an early and persistent induction of proinflammatory astrocytic state. These findings provide important insights regarding age-related exacerbation of neurological damage after brain trauma.

Aging with Traumatic Brain Injury: Deleterious Effects of Injury Chronicity Are Most Pronounced in Later Life

Understanding the effects of age on longitudinal traumatic brain injury (TBI) outcomes requires attention to both chronic and evolving TBI effects and age-related changes in health and function. The present study examines the independent and interactive effects of aging and chronicity on functional outcomes after TBI. We leveraged a well-defined cohort of individuals who sustained a moderate/severe TBI and received acute inpatient rehabilitation at specialized centers with high follow up rate as part of their involvement in the TBI Model Systems longitudinal study. We selected individuals at one of two levels of TBI chronicity (either 2 or 10 years post-injury) and used an exact matching procedure to obtain balanced chronicity groups based on age and other characteristics (N = 1993). We found that both older age and greater injury chronicity were related to greater disability, reduced functional independence, and less community participation. There was a significant age by chronicity interaction, indicating that the adverse effects of greater time post-injury were most pronounced among survivors who were age 75 or older. The inflection point at roughly 75 years of age was corroborated by post hoc analyses, dividing the sample by age at 75 years and examining the interaction between age group and chronicity. These findings point to a need for provision of rehabilitation services in the chronic injury period, particularly for those who are over 75 years old. Future work should investigate the underlying mechanisms of this interaction towards the goal of developing interventions and models of care to promote healthy aging with TBI.

Prevalence of persistent vegetative state compared to recovery, disability, and death in subjects with severe traumatic brain injury: A meta-analysis

BACKGROUND

The persistent vegetative state has drawn considerable attention since it is the poorest result apart from mortality in subjects with severe traumatic brain injury. This meta-analysis was performed to evaluate its prevalence compared to recovery, disability, and death 6 months post severe traumatic brain injury.

METHODS

A systematic-literature search up to May 2020 was performed and 19 studies were detected with 10 368 subjects. They contained data about the subject's status 6 months post severe traumatic brain injury (recovery, disability, persistent vegetative state, and death). Odds ratio (OR) with 95% confidence intervals (CIs) was calculated comparing the prevalence of persistent vegetative state to that of recovery, disability, and death; 6 months post severe traumatic brain injury using the dichotomous method with a random- or fixed-effect model.

RESULTS

Significantly higher prevalence was found of recovery (OR, 0.08; 95% CI, 0.03-0.20, P < .001); disability (OR, 0.09; 95% CI, 0.06-0.15, P < .001); and death (OR, 0.07; 95% CI, 0.04-0.11, P < .001) compared to the prevalence of persistent vegetative state. The prevalence of persistent vegetative state was variable over time. Also, the prevalence of persistent vegetative states in developing countries was much higher than in developed countries.

CONCLUSIONS

However, persistent vegetative state is the poorest result apart from mortality in subjects with severe traumatic brain injury. Its prevalence is lower than the recovery, disability, and death even in developing counties with its lower healthcare services. The prevalence was variable over time and higher in developing countries. This relationship forces us to recommend improving healthcare services to the extent that a persistent vegetative state could be avoided as much as possible.