Epidemiology of Acquired Brain Injury

Gender Differences

The rate and etiology of injury seem to differ between genders, with TBI being more common in men (Canadian Institute for Health Information 2007; Colantonio et al. 2009; Colantonio et al. 2010; Greenwald et al. 2003). A study found that in the United States, TBI was nearly 1.4 times more common among males than females (Faul et al. 2010). Data from Ontario, Canada also shows greater rates of TBI among males (Chan et al. 2013a). The increased incidence in men may be due to greater participation in risk-taking activities, exposure to occupational hazards, and more engagement in violent behaviours than women. A cohort study found that fall-related TBIs were more common among females than males (51.7% versus 36.2%, respectively); conversely, being struck by or against an object was more common among males than females (Colantonio et al. 2010). Females have also been shown to have 33.1% lower odds of mortality after adjusting for covariates than males post brain injury (Haring et al. 2015). While another study in Spain found no gender effects for poorer outcome after severe TBI (Herrera-Melero et al. 2015).

Age and TBI

Overall, motor vehicle or related transportation accidents (MVAs) and falls are the most common causes of TBI among all age groups (Faul et al. 2010). Falls and MVAs, together, were shown to account for approximately 75% of TBIs requiring hospitalization in Ontario from 1992 to 2002 (Colantonio et al. 2009). Based on literature, falls account for approximately 35% to 42% of TBIs whereas MVAs are responsible for 12% to 17% (Colantonio et al. 2010; Faul et al. 2010).

Evidence suggests that the etiology of TBI varies with age. At one end of the spectrum are children, with a common cause of injury being non-accidental head trauma (Greenwald et al. 2003); up to two thirds of severe brain injury cases in the 0-4 year old age group were attributable to non-accidental trauma (Greenwald et al. 2003). Among low and middle income countries, younger age has been associated with a higher prevalence rate of TBI (Khan et al. 2015). Among adults, MVAs account for more than 60% of TBIs in those aged 16-25 years and 47% of TBIs in those aged 26-35 years (Colantonio et al. 2009). Children and older adults are more susceptible to injury due to falls (Colantonio et al. 2009; Faul et al. 2010). An epidemiological study conducted in the United States showed that falls accounted for 50.2% of TBIs in children (aged 0-14 years) and 60.7% of TBIs in adults aged 65 years or older (Faul et al. 2010). For those 85 years of age or older, the rate of hospitalizations in Ontario for TBIs due to falls was as high as 90% (Chan et al. 2013b). The increased risk of falls in the elderly may be linked to factors such as substance use, decreased balance and/or age-related neurological conditions such as dementia (Wagner 2001).

With increasing age, the prevalence of non-traumatic brain injuries (nTBIs) also increases; nTBIs, which exclude a primary stroke diagnosis, are more prevalent in those over the age of 40 years. In Ontario, the rate of hospitalized nTBI episodes increased with age, whereby the rates were 365 persons per 100,000 for those 65-74 years old compared to 561 persons per 100,000 for those above 85 years old (Chan et al. 2013b). Vascular insults (not captured in other national studies on stroke), brain tumours, meningitis, encephalitis, and anoxia have been found to be the most frequent causes of nTBI (Chan et al. 2013b).

There is an emerging trend of increased rates of TBI among elderly individuals which is heavily influenced by the fact that they are the fastest growing sector of the population (Chan et al. 2013a). A recent examination of the Ontario ABI Dataset found that between 2003 and 2010, there was a significant increase in TBI episodes among patients 65 to 74 years (11%), 75 to 84 years (50%) and those aged 85 years and older (63%; Chan et al. 2013a). Recent studies examining data from the United states also suggest that the highest rates of TBI were among those aged 75 years or older (Cuthbert et al. 2015; Faul et al. 2010).

Impact of Older Age on TBI and Subsequent Recovery

Those who sustain a TBI, regardless of age, may develop circulatory, digestive, or respiratory problems; have an increased risk of infection; and experience neurological complications, ranging from endocrine problems to seizures, and swallowing difficulties (Flanagan 2008). Individuals with TBI may also develop mental health concerns such as depression (Colantonio et al. 2011).

Evidence suggests that age influences the trajectory of one’s recovery following injury. Individuals in the older age bracket generally had poorer outcomes when compared to younger individuals (Marquez de la Plata et al. 2008). Pennings et al. (1993) found individuals over the age of 60 required a greater number of resources to obtain favourable outcomes compared to younger patients (≤40 years old) with a similar severity of injury. For those in the older age group, a longer length of stay in hospital was often necessary to address their slower rate of functional recovery (Chan et al. 2013a; Cifu et al. 1996). Both admission and discharge Functional Independence Measure scores from inpatient rehabiliation were lower among older adults (Chan et al. 2013b). Consequently, older adults also had a lower rate of discharge to the community (Colantonio et al. 2009).

Older age at the time of injury has also been associated with poorer performance on various cognitive domains (Senathi-Raja et al. 2010). A study by Ashman and Mascialino (2008) specifically noted that deficits in encoding and retention of verbal information, as well as inattention, were more common and more serious post TBI in those over the age of 65. It has been postulated, for those who are older at time of injury, less neuronal plasticity may negatively affect the brain’s ability to compensate or adapt in the same way a younger brain does post injury (Senathi-Raja et al. 2010).

Mosenthal et al. (2002) found older subjects (>64 years of age) had a significantly higher mortality rate than their younger peers regardless of the severity of TBI sustained (p<0.001). Study authors suggested this increase in mortality may be attributable to multiple factors including pre-existing comorbidities, post-injury complications, and the intrinsic properties of aging itself (Mosenthal et al. 2002). Evidently, for older patients with TBI, their recovery may be challenging. This is largely because aging is often accompanied by a number of chronic comorbidities (e.g., diabetes, arthritis, cardiovascular disease and/or cerebrovascular disease; Colantonio et al. 2011). Such factors are rarely taken into account when assessing the impact an ABI has on an older person (Colantonio et al. 2004; Rapoport & Feinstein 2000); however, these pre-existing health issues may impede the recovery of patients living with an ABI if left unresolved.

A recent study examined the recovery of patients with TBI in inpatient rehabilitation facilities (Dijkers et al. 2013). The study found that adults aged 65 years or older who had less severe injuries received fewer hours of therapy and had shorter lengths of stay compared to other patients with TBI. These patients gained less functional ability during their stay and were likely to have a higher mortality rate (Dijkers et al. 2013). Hence, issues regarding therapy intensity and care may be important when examining successful recovery potential among older adults.

Impact of Aging with an Established ABI

Few studies have examined the effects of ABI on life expectancy; however, it has been suggested that a person with TBI who recovers during the acute period may still have a substantially reduced life expectancy and a poorer outcome (Colantonio et al. 2009; Ratcliff et al. 2005). One of the strongest predictors of post-acute mortality is the patient’s age at the time of injury (Colantonio et al. 2009). Sustaining an ABI in the younger years may shorten one’s life by 10 years (Corrigan et al. 2007). Further, Ratcliff et al. (2005) found an ABI doubled long-term mortality risk for all age groups, even though many survived 20 or more years post injury. It is also important to consider that persons with TBI may be at risk for subsequent falls due to balance, mobility, and cognitive impairments, as well as environmental challenges. Coupled with the effects of aging, these risk factors together may result in a patient sustaining yet another injury (Chan et al. 2013c).

The Impact of ABI on Survivors and the healthcare system

Assessing the impact that an ABI may have on individuals as they age is difficult as survivors can live for several decades post injury. This is particularly true for children and adolescents who sustain an injury. Unfortunately, longitudinal studies assessing the impact of the injury on the individual and their families is challenging due to the cost, and the number of participants lost to follow-up.

To provide some perspective on the financial burden associated with injury, the annual medical costs of patients hospitalized with a TBI in Ontario, in the first year of follow up, was approximately $120.7 million, which translates into a mean cost of $32,132 per patient (Chen et al. 2012). The cost, including follow-up services (e.g. inpatient rehabilitation), exceeded $150,000 per patient. These injuries are costly to the system, and unfortunately some costs are a result of alternative level of care (ALC) days. ALC is when patients occupy hospital beds even when they do not require the level of intensity of resources/services being provided in that particular care setting (Chen et al. 2012); for example, this commonly occurs while patients are awaiting a placement in a long-term care facility. In Ontario, from 2007 to 2009, the total number of days spent as ALC among patients with TBI increased from 15,606 to 22,637 days (Chen et al. 2012). Furthermore, the use of health care resources may also depend on multiple factors. Fu et al. (2015) found, in Canada, there was a 29% increase in hospitalization among those aged 65 years or older with TBI between the years 2006 and 2011. Hammond et al. (2015) found that this increased risk of rehospitalization was related to older age, history of seizures, history of brain injuries, and other comorbid medical conditions. Rural residence and psychiatric comorbidity have also been shown to be predictors of rehospitalization (Saverino et al. 2016).

Unfortunately, data indicates that a large proportion of individuals with a brain injury do not appear to be accessing all the rehabilitation services that they need. The Ontario Brain Injury Association survey conducted in 2005 examined the number of individuals using services compared to those who aren’t (OBIA 2007).The main reasons given for the gaps between service need and use were long waiting lists, lack of available and appropriate services, lack of training about the cognitive and behavioural needs of patients, and poor coordination of services (Chen et al. 2012; Minnes et al. 2010). Particularly noteworthy is the apparent lack of access to services for psychological issues; those with pre-existing comorbid conditions, such as psychosocial and psychiatric problems, are at an increased risk of mortality following injury (Colantonio et al. 2009), and thus should have access to care in a timely manner.