Chapter 1 - Epidemiology of traumatic brain injury

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Abstract

Traumatic brain injury (TBI) is a leading cause of death, and in a recent analysis it was found that nearly one-third of all injury-related deaths in the US have at least one diagnosis of TBI (CDC-Quickstats, 2010). This chapter presents the burden of TBI as regards age group, gender, costs, race, emergency department (ED) visits, hospitalizations, and deaths. Injury trends over a 15 year period are examined. Rehabilitation estimates and disability estimates are also available. Through good epidemiology we can better understand the causes of TBI and design more effective intervention programs to reduce injury. Important sources of evidence for this chapter include mostly studies from the US because of their leading work in the epidemiology of this important injury.

Section snippets

Overview: importance of injury and traumatic brain injury

In 2009, injury was the leading cause of death in the US for persons aged 1–44 years (CDC, 2009). Because the burden of injury is concentrated among these younger and middle age groups, the impact on disability-adjusted life years lost for injury is approximately 15% in the US. Meanwhile, the impact of injury on mortality for all age groups is approximately 10% (Murray and Lopez, 1997). Injuries are classified into the two categories of unintentional and intentional injuries, or

Overall traumatic brain injury rates

The overall incidence rate of TBI in the US for 2002–2006 was 579 per 100 000 persons, or approximately 1.7 million cases per year (Faul et al., 2010). This estimate includes all levels of TBI severity. The TBI-related hospitalization rate in the US was 93.8 per 100 000 persons. In a meta-analysis that included data from the 1990s and the 2000s, the TBI hospitalization rate in Europe was calculated to be 235 per 100 000 persons (Tagliaferri et al., 2005). However, methodological differences and

Definitions

According to the US Centers for Disease Control and Prevention (CDC), a TBI is caused by a bump, blow, or jolt to the head or a penetrating head injury that disrupts the normal function of the brain. Not all blows or jolts to the head result in a TBI. Exposures to blasts, and the accompanying overpressure wave, are a leading cause of TBI for active duty military personnel in war zones (Champion et al., 2009). The severity of a TBI may range from mild to severe. Signs and symptoms vary by

Cost: burden of injury

The economic cost of TBI in the US is measured by combining the costs of two major cost categories (Finkelstein et al., 2006). The first is direct cost and includes the cost of deaths within and outside of the medical system and the costs of medical treatments of hospitalized and nonhospitalized TBI patients. The second category of cost is called productivity costs. Parts of these costs are lost wages and fringe benefits due to the incapacity to work and the absence from the workplace or

Severity measures

The most common severity assessment for TBI is the Glasgow Coma Scale score (GCS) (Teasdale and Jennett, 1974, Shah and Kelly, 2003). This score is commonly used in prehospital settings and in EDs and is the total of three combined scores: Glasgow Motor, Glasgow Verbal, and Glasgow Eye movement. Each component of the score identifies the patient's crude functional status. It has also been shown to be a useful system in determining TBI severity (Evans, 2006). Early severity classification of TBI

Emergency department rates

The majority of TBIs are identified in the emergency department (ED). Of the 1.7 million people in the US who are annually diagnosed with a TBI, 1 365 000, or 80%, were treated in EDs and released alive (Faul et al., 2010). TBIs represent 1.4% of all visits seen in an ED and 4.8% of the total injuries presented in an ED (Faul et al., 2010). Treatment in the ED begins with diagnostic procedures. Upon presentation of advanced symptoms of TBI in an ED, computed tomography (CT) scans are used to

Hospitalizations

In the US, of the 1.7 million people, on average, who are diagnosed annually with a TBI, 275 000 (16%) were treated in a hospital setting and were discharged (Faul et al., 2010). Using surveillance data from 11 states, 74.9% of the all hospitalized TBI patients had a mild TBI (Langlois et al., 2003). Another 9.6% of hospitalized TBI patients were classified as having a moderate or severe TBI, with 5.7% having an unknown severity score (Langlois et al., 2003). Although treatment options vary

Deaths

Approximately 52 000 US residents die as a result of TBI annually (Faul et al., 2010). Nearly one-third (Quickstats, 2010) or 30.5% (Faul et al., 2010) of all injury-related deaths involve a TBI. In trauma centers, where the most severe TBI patients are treated, mortality has been reported to be as high as 50% of all trauma-related deaths (Dutton et al., 2010).

Alcohol is a major risk factor in all injuries and 30–50% of all patients hospitalized with trauma are intoxicated at the time of injury (

Mechanism (external causes)

In looking at the causes of TBI in the ED, using the latest summarized data from CDC (Faul et al., 2010), the leading causes of TBI are falls (178.4 per 100 000 persons), struck by or against events (92.7 per 100 000 persons), and motor vehicle crashes (74.7 per 100 000 persons). Among the top four mechanistic categories of injury, assaults are the least common form of TBI (50.6 per 100 000 persons) (Faul et al., 2010) (Fig. 1.5). Because external cause codes are not completed on all cases, there

Peaks within age groups

The incidence rate of TBI across age groups and mechanism of injury are highly variable and suggestive of various lifestyles and activities as people age. During the early stages and later stages of life, a person's vulnerability to falls is the greatest. In ED visits, TBI related falls for those aged 0–4 years old is 806.3 per 100 000 persons and 440.2 per 100 000 persons for those aged 75 years old and older. The majority of people with fall-related TBIs in this age group were seen in EDs and

Gender

Overall, the rate of TBI among males seen in EDs is 547.6 per 100 000 persons and among females is 385.9 per 100 000 persons. Thus, a male is more likely to incur a TBI compared to a female. For every age group category (consisting of 4 years per category), TBI is more frequent for males than females (Faul et al., 2010). The rate ratio is largest for gender in the 10–14-year-old age group (304.1 per 100 000 persons for females and 913.4 per 100 000 persons for males) and is almost at parity for

Race

Among ED visits the black racial group has the highest rate of TBI, with a reported rate of 568.7 per 100 000 persons, followed by the white racial group (456.6 per 100 000 persons) and then the American Indian, Alaskan Native, Asian, or Pacific Islander group with a rate of 345.3 per 100 000 persons (Faul et al., 2010). For all racial groups, the highest rate of TBI occurs in the 0–4 age group. For hospitalizations the black racial group has the highest rate of TBI, with a reported rate of 78.7

Traumatic brain injury in the military

In recent years the public has become more aware that TBI is an important public health issue, in part due to exposure to images of brain injured veterans from the war in Iraq and Afganistan. In fact, TBI has been labeled as the “signature injury” of the war in Iraq (Hoge et al., 2008). This public exposure, along with some high profile TBI cases, may have influenced the general public to seek medical treatment following a TBI.

TBI among US military personnel is a critical health concern for

Disability

Traumatic brain injury (TBI) is a major cause of disability in the US (Kraus et al., 1987). This disability can manifest as cognitive deficits leading to the inability or reduced ability to work and perform daily activities and may be associated with an increased need for ongoing medical care, rehabilitation, support, and services (Zaloshnja et al., 2005). It is estimated that the prevalence of TBI-related disability ranged from 2.5 to 6.5 million people in the US (Consensus Conference, 1999).

Alzheimer's disease and epilepsy

The association between TBI and Alzheimer's disease has been controversial. Some studies have shown a linkage while others have not (summarized in Jellinger, 2004). More research is needed before an association can be made between a TBI and degenerative neurologic diseases. However, an increased duration of PTA has been associated with a heightened risk for TBI complications such as post-traumatic epilepsy (Chadwick, 2005). In a study of nearly 4500 TBI patients, it was found that seizures are

Rehabilitation

Reliable national estimates of people needing rehabilitation services following a TBI are not available. However, using unrelated studies combined with national estimates of people hospitalized with a TBI, an estimate can be constructed. Given that two studies estimated the need for rehabilitative services following a TBI requiring hospitalization was 15% (Willer et al., 1990) and 30% (Thurman et al., 1999), and that the number of people hospitalized for TBI was 275 000 (Faul et al., 2010), the

Conclusions

TBI is a public health problem affecting persons of all ages regardless of sex and other demographic characteristics. Most of the causes are preventable and the cause of TBI appears to be highly dependent on the age of the person. Thus, a person's risk exposure to a TBI is susceptible to life changes. For example, younger and older people have a disproportionate amount of fall-related TBI mostly because of strength and stability issues. Meanwhile, TBIs associated with motor vehicle crashes

Disclaimer

“The findings and conclusions in this report are those of the author(s) and do not necessarily represent the official position of the Centers for Disease Control and Prevention/the Agency for Toxic Substances and Disease Registry.”

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