ABIEBR :: 2.1 Epidemiology of Acquired Brain Injury

2.1 Epidemiology of Acquired Brain Injury

2.1.1 Prevalence

Acquired Brain injury (ABI), particularly of the traumatic brain injury (TBI) type, is one of the leading causes of death and lifelong disability in North America, particularly in children and adolescents (Greenwald et al., 2003; Thurman et al., 1999). In developed Western countries, incidence figures for TBI are estimated to be 250-300 per 100,000 population (Campbell, 2000; Liss & Willer, 1990). It is estimated that the annual incidence of TBI in the United States ranges from 1.4 to 1.5 million (Thurman et al., 1999; Zaloshnja et al., 2008). In Ontario, the Ontario Brain Injury Association (2004) estimates that the total annual number of brain injuries is over 18,000 with nearly 4,000 injuries occurring annually in the pediatric population alone (0-14 years). Given the potential for damage caused by the primary and secondary insults to the brain, it has been argued that no two head injuries are neuropathologically alike (Liss & Willer, 1990).

2.1.2 Gender Differences in Causes of Injury

Traumatic brain injuries are three times more common in men (Greenwald et al., 2003). It has been reported that the highest rate of injury occurs in young men between the ages of 15 and 24 (Murdoch & Theodoros, 2001). Numbers released by CIHI indicate that males (of all ages) are at a higher risk of sustaining an ABI when compared to females (CIHI 2004). (see Figure 2.1)

Figure 2.1: Head Injury Admission by Gender in Canada (2003-2004)

The increased incidence in men may result from greater risk-taking activities, occupational hazards and more violence related injuries when compared with women. The estimated incidence of traumatic brain injury doubles between the ages of 5 and 14 years and peaks in both males and females during adolescence and early adulthood to approximately 250 per 100,000; 20% of these are moderate or severe traumatic brain injuries.

2.1.3 Age and TBI

Evidence suggests that the etiology of TBIvaries with age. Overall, motor vehicle or related transportation accidents and falls comprise the most common cause of TBI. Transportation accidents, particularly for young males (15 to 24 years), by some estimates account for more than 50% of all head injuries (Murdoch & Theodoros, 2001). Child abuse, sporting accidents, and falls are the most common causes of TBI in children while falls are the most common causes of TBI in the elderly (see Figure 2.2) (Murdoch & Theodoros, 2001; Tokutomi et al., 2008; Mosenthal et al., 2002; Rapoport & Feinstein, 2000; Wagner, 2001).

The increased risk of falls in the elderly may be linked to decreased balance and neuronal loss that accompanies the aging process (Wagner, 2001). Non-traumatic brain injuries are more prevelant in those over the age of 40.  Vascular insults, brain tumors, meningitis, encephalitis, anoxia have been found to be the most frequent causes of non-TBIs (ABI Dataset Pilot Project Team, 2009).

Figure 2.2: Causes of ABIs as Reported by CIHI in Canada (2003-2004)

Although the incidence of TBI is greater in younger patients (<60 years of age) when compared with the elderly (see Figure 2.3), older ABI/TBI victims usually show greater severity of injury and higher mortality rates (see Figure 2.4) (Wagner, 2001; Tokutomi et al., 2008; Ashman et al., 2008; Mosenthal et al., 2002).

Figure 2.3: Numbers of ABIs Admitted to Hospital as reported by CIHI in Canada (2003-2004)

Figure 2.4: Number of Hospital Deaths Related to ABI as reported by CIHI in Canada (2003-2004)

2.1.3.1 Impact of Older Age on TBI and Subsequent Recovery

Those who sustain a TBI, regardless of age, may develop circulatory, digestive or respiratory problems, be diagnosed with neurological issues such as endocrine problems, seizures, swallowing difficulties, and with some an increased risk of infection (Flanagan 2008). However, those 65 and older at the time of injury are more likely to report dizziness and weakness. Pennings et al. (1993) found individuals over the age of 60 required a greater number of resources to obtain favorable outcomes compared to younger patients (40 years old or younger) with similar severities of injury.  In a cohort study of Senathi-Raja et al. (Senathi-Raja et al., 2010) the authors concluded that older age at the time of injury was associated with poorer performance on various cognitive domains.  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 in the same way a younger brain does post injury (Senathi-Raja et al., 2010).

Findings from several studies appear to support this premise that elderly ABI patients do not do as well. Marquez de la Plata (2008) in a study examining the effects of TBI over a 5 year time period found those in the oldest age group (40 to 85) had poorer outcomes when compared to the younger groups.  They also reported that those individuals who declined post injury and post rehabilitation tended to be in the two older age groups (>26 years). Cognitive impairments, such as performing poorly on tests of word fluency, visual and verbal memory, abstract reasoning and processing speed, are more common and more serious post ABI in those over the age of 65 (Ashman et al., 2008).  For those in the older age group, a longer length of stay in hospital is often necessary to address their slower rates of functional gain (Cifu et al., 1996).

Aging is often accompanied by a number of chronic conditions such as diabetes, arthritis, cardiovascular disease or cerebrovascular disease.  These comorbid conditions are rarely taken into account when assessing the impact an ABI has on an older person (Rapoport & Feinstein, 2000; Colantonio et al., 2004).  These pre-existing health issues may also contribute to increased lengths of rehabilitation stay and a reduction in functional gains as measured by the Glasgow Outcome Scale (Dijkers et al. 2008, Mosenthal et al. 2002). Further, Mosenthal et al. (2002) found older subjects (>64 years of age) had a significantly higher mortality rate (p<0.001) than their younger peers regardless of the level of ABI sustained.  Study authors suggested this increase in deaths may have been the result of medical complications occurring post injury (Mosenthal et al., 2002).

2.1.3.2 Impact of Aging with an Established ABI

Few studies have examined the effects of an ABI on life expectancy; however, it has been suggested that sustaining an ABI in the younger years could shorten one’s life by 10 years (Corrigan et al., 2007).  Ratcliff et al. (2005) found an ABI doubled mortality risk, even though many survived 20+ years post injury. Older adults who sustain an ABI are also at an increased risk (compared to the general population) of a shortened life expectancy (Flanagan, 2008; Ratcliff et al., 2005).

Another area that has garnered a great deal of discussion is the potential link between TBI and Alzheimer’s disease or dementia. Unfortunately study results are mixed (Trudel et al., 2008; Rapoport & Feinstein, 2000).  It has not yet been shown that individuals who sustain an ABI early in life are at greater risk of developing Alzheimer’s disease or dementia post injury. T o date study findings are inconclusive, confusing and often contradictory. More research is needed.

There is very little consistency from study to study regarding the measures that are used to assess patients. There is also the question of the ineffectiveness of using existing measures as they may not be adaptable and appropriate to use with an older population (Dijkers et al., 2008). Coupled with this is the lack of consistency in how aging is defined or how an older population is defined.  Is it 50 and up, 65 and up or is it 70 and up?  More research is needed along with agreed upon definitions and guidelines.

2.1.4 The Impact of ABIon Survivors and Family Members

To assess the impact an ABI may have on individuals as they age is difficult.  Unlike stroke, which has a typical onset later in life, survivors of ABI typically live for several decades post-injury? Thus, because the lives of most survivors of moderate to severe TBI involve chronic, life-long disabilities with varying degrees of dependence, the cost in suffering, family burden, and financial burden to society can be very high for the injured individual. This is particularly true in children and adolescents who are more likely than adults to survive following a TBI; however, longitudinal studies to assess the impact the injury has on the individual, their family, and their community are expensive and the risk that a significant number of  subjects will be lost to follow-up. 

Current data indicates large proportionsof brain injury patients do not appear to be fully accessing the rehabilitation services that they need. The following three figures (Figures 2.5 to 2.7) present the results from an Ontario Brain Injury Association survey conducted in 2005 on the number of adults, youth (15-19yrs) and children using services versus those not using services (Ontario Brain Injury Association, 2007).

Figure 2.5: Service Use and the Perceived Need for Services among Adults with ABI, 2005

Figure 2.6: Service Use vs Perceived Need for Services among Youth (15-19) with ABI, 2005

Figure 2.7: Service Use vs Perceived Need for Services among Children with ABI, 2005

Particularly noteworthy is the apparent lack of access to services for psychological issues.  The perceived need for increased rehabilitation services is in contrast to the current  contraction of rehabilitation services.