Traumatic brain injury in older adults: shining light on a growing public health crisis

The population distribution in the United States is changing from a broad base of younger individuals with few individuals living to older adulthood to a much more even distribution throughout the lifespan (United States Census Bureau, 2018). A similar transformation has occurred when looking at new onset traumatic brain injury (TBI). While improved car safety features have resulted in a decrease in motor vehicle accident-related TBIs, the number of older adults presenting to emergency departments (EDs) for evaluation of TBI has increased by at least 60% with a 2009–2010 estimate showing ∼20 million older adults evaluated annually for TBI (Albrecht et al., 2016). In addition to a rising number of ED visits, older adults have rising levels of hospitalisations and death following TBI. In fact, as of 2013, adults 75 years and older sustained the highest number of TBIs—exceeding that of infants (Taylor, Bell, Breiding, & Xu, 2017). These growing numbers have created a public health priority and this issue of the International Review of Psychiatry attempts to shine light on this crisis, which deserves the same advocacy and specialised focus as sports- and military-related TBI. These individuals, as well as those aging with a TBI sustained earlier in life, warrant a focussed approach to scientific study and treatment that is informed by, yet distinct from, that of TBI in disparate populations.

From pre-injury risk factors to presenting symptoms and future complications, there exists a nuanced set of geriatric-specific factors to consider in those with new onset TBI at an older age. In the era of individualised medicine, patient characteristics and clinically relevant biomarkers are used to guide care and a one-size-fits-all approach to treatment is viewed as antiquated. There is a common assumption that older adults do worse after new onset TBI. This is supported in the current issue in a study by Abdulle and Van der Naalt, which found that half of elderly participants with new onset mild TBI (mTBI) showed incomplete recovery at 6 months post-injury. One possible explanation for these worse outcomes is highlighted in this issue by Erler et al., who found that older adults had lower levels of participation in rehabilitation activities 5 years post-moderate-to-severe TBI. While on the whole older adults may do worse after TBI, there is a growing literature base that supports the belief that a subset of older adults exhibit at least equivalent outcomes to younger (Peters, 2016; Peters & Gardner, 2018). In this issue, Richey et al. examined a sample of adults with new onset mTBI presenting to an ED and found that older adults had at least equivalent 6-month outcome trajectories to younger adults in regards to functional recovery, post-concussive symptoms, and depressive symptoms. These studies should not be viewed in opposition, but rather the importance of a focussed examination of individual, patient-level factors for predicting outcome should be highlighted, as should the importance of TBI definition and severity.

Two articles in this issue examine the specific issue of sleep disturbances following TBI in older adults. This is an extremely important neuropsychiatric symptom given the mounting evidence that during sleep the brain enhances glymphatic pathway clearance of metabolites and modulates activity of astrocytes (Kim, Nam, & Song, 2018). In this issue, Albrecht and Wickwire show that older adults diagnosed with TBI were more likely than those without to have new onset sleep disorders both before and after the TBI. Also in this issue, Ledger et al. examined gender effects on the frequency of sleep disturbances and found a greater impact of TBI on sleep disturbances in older females than males. Given the connection between sleep and brain recovery, it is essential to include screening and education on sleep disorders in the clinical setting and include sleep disruption as a variable in the research setting.

As the brain has a finite capacity for recovery and adaptation, a brain after TBI may have fewer resources to devote to the aging process. This may result in an alteration in how the brain handles “normal” aging rather than the onset of a new neurodegenerative process. In addition, it is increasingly clear that there is an association in some individuals between a history of TBI and later onset of neurodegenerative illness, which may be heightened if the TBI is experienced later in life (Barnes et al., 2018; Gardner et al., 2014). In this issue, Joyce et al. did not find an increased risk of developing Parkinson’s disease or poorer motor scores in those with a history of TBI. However, in those diagnosed with Parkinson’s disease, they did find a negative correlation between number of TBIs and cognition (executive function, memory, and language) and a positive correlation with depressive symptoms. One of the articles in this issue, by Pradeep, Bray, et al., sought to analyse the impact of TBI on the accuracy of clinician-diagnosed Alzheimer’s Disease using neuropathological findings at autopsy as the gold standard comparator. They found that TBI history was associated with an increased false positive rate of Alzheimer’s disease diagnosis. Although further research is needed on the topic, these articles highlight the importance of TBI screening in the memory care setting, as well as the need for clinical guidance on how this history may impact clinical presentation and diagnostic accuracy.

The last topic covered in this issue is the connection between TBI and neurodegenerative decline in athletes. In a critical review of the literature by Schaffert et al., studies investigating the dose-response relationship between cognitive decline and head injury in National Football League (NFL) players generated mixed findings. The authors highlight the inconsistencies in the measures of head injury exposure. They suggest that further research is needed to understand the relationship between sports-related concussions and the risk of long-term cognitive decline and neurodegenerative disease in aging NFL players. Drawing from the literature showing the importance of age at first exposure (AFE) to future cognitive decline in football players (Alosco et al., 2017), Bryant et al. utilised data from the Professional Fighters Brain Health study and found positive correlations between earlier AFE and smaller bilateral hippocampal and posterior corpus callosum volumes, decreased processing speed and psychomotor speed, and higher measures of depression and impulsivity in fighters. Results differed based on whether fighters were active or retired. These athlete-based studies are essential for clinicians, governing bodies, parents, and athletes to make informed decisions about return-to-play, age at first play, etc. In addition, these large sports entities are a great potential advocate for further study of TBI in older adults in the general population.

This issue of the International Review of Psychiatry is an important step towards further recognition and devoted study of TBI in older adults. Further work is needed to develop clinical care guidelines for older adults with TBI and a focussed approach is needed. Integrating research methods (e.g. informant interviews, home visits) utilised in geriatric dementia research could go a long way to make TBI clinical research relevant to the older adult. With the aging population, the need to understand the impact of age on TBI outcomes will only become more important.