With financial and technical support from CDC for statewide TBI surveillance systems, seven States (Arizona, Colorado, Minnesota, Missouri, New York [excluding New York City], Oklahoma, and South Carolina) compiled data for TBI-related hospitalizations and deaths that occurred in 1994. As a result, these States have been able to provide more complete descriptions of the incidence, severity, causes, and outcomes of TBI currently occurring among their residents. During 1994, the seven States had 32,112 reported cases of TBI collectively; among persons with these injuries, 5,442 (16.9 percent of all reported TBIs) died without being admitted to a hospital, while 26,670 (83.0 percent) were admitted. Among those who were hospitalized, 1,802 (5.6 percent of all TBIs) died while receiving acute care. Thus, a total of 7,244 TBIs (22.6 percent of all reported TBIs) were fatal.

The annual unadjusted incidence rate of TBI for all seven States combined was 90.9 per 100,000 population (91.8 per 100,000, age-adjusted to the 1990 U.S. population). The crude rate of hospitalizations for TBI in the seven States combined was 75.5 per 100,000. The overall TBI-related death rate was 20.7 per 100,000 (Figure 6). In an assessment of State-specific rates of TBI, serious nonfatal injuries requiring hospitalization were far more common than injuries resulting in death in all seven States. The median age at the time of injury was 32 years. The incidence rate of TBI was highest among persons 75 years of age and older (191.1 per 100,000) and among persons 15-24 years (145.1 per 100,000) (Figure 7). Most TBIs (21,423 or 66.7 percent) occurred among males, with the rate among males (124.1 per 100,000) being about twice the rate among females (59.1 per 100,000).

View figure 6.

Serious nonfatal traumatic brain injuries requiring hospitalization greatly outnumber fatal traumatic brain injuries in seven States.

View figure 7.

Teenagers, young adults, and people over 75 are far more likely than others to sustain a traumatic brain injury, primarily because of motor vehicle crashes and violence among youths, and falls among the elderly.

Transportation-related crashes (involving motor vehicles, bicycles, pedestrians, and recreational vehicles) accounted for 49 percent of all TBIs; falls accounted for an additional 26 percent (Figure 8). Firearm-use accounted for 10 percent of all TBIs in the seven States, and assaults not involving firearms accounted for 8 percent of reported injuries. Nearly two-thirds of firearm-related TBIs (66.5 percent) were classified as suicidal in intent (Figure 9).

View figure 8.

Motor vehicle crashes are by far the leading cause of traumatic brain injury in these seven States and nationally as well. Shootings cause less than 10 percent of all traumatic brain injuries, yet they are the leading cause of TBI-related death.

View figure 9.

The majority of firearm-related traumatic brain injury represent suicides or suicide attempts, although more than a fourth are the result of assaults by others.

The leading causes of TBI varied by age in the seven States. Falls were by far the leading cause of TBI among persons aged 75 years and older (at a rate of 126.6 per 100,000), whereas transportation led the list for persons aged 15-24 years (97.9 per 100,000) (Figure 10). Analysis also revealed that the severity of injury and the outcome varied depending on the cause. For example, 90.4 percent of firearm-related TBIs resulted in death, but only 10.2 percent of fall-related TBI proved fatal (Figure 11).

View figure 10.

Peak incidence rates in youths are largely related to motor vehicle crashes, whereas peak rates in the elderly are largely related to falls.

View figure 11.

People injured in motor vehicle crashes, falls, or assaults without a firearm have a much greater chance of surviving than do those injured in a shooting.

The consistency of findings in these seven States, located in different regions of the United States, suggests that these data may be broadly representative of the Nation as a whole. The epidemiologic patterns of TBI described in this report also resemble those from an analysis of 1994 National Hospital Discharge Survey (NHDS) data, which obtained hospital discharge data from a sample of 478 participating hospitals located across the United States. The crude TBI-related hospitalization rate estimated in the NHDS was 94 per 100,000 population.2 The combined TBI-related hospitalization rate obtained from Arizona, Colorado, Minnesota, Missouri, New York State, Oklahoma, and South Carolina is approximately 20 percent lower than the corresponding rate estimated from the NHDS. Different sampling and other methods that may explain this rate difference have not yet been elucidated.

The rates in this report are substantially lower than rates previously reported in studies conducted from 1974 to 1986 (approximately 200 cases per 100,000 population annually).7-16 In comparison, from 1979 to 1992, the TBI-associated death rate declined 22 percent, largely because of a decrease in TBI-related deaths associated with motor-vehicle crashes.3 The findings in this report and those from the NHDS suggest a decline of approximately 50 percent in combined morbidity and death during a corresponding interval, indicating a disproportionately large reduction in rates of nonfatal TBI resulting in hospitalization. This decrease may reflect successes in injury prevention efforts but may also be the result of recent changes in hospital admission policies that encourage outpatient care for less severe injuries.

This evident shift away from inpatient care underscores the need for surveillance of TBI patients treated in emergency departments and other outpatient settings. The National Center for Health Statistics National Health Interview Survey (NHIS) has provided some information on the incidence of TBI treated on an outpatient basis.1 In 1991, an estimated 1.54 million non-institutionalized U.S. civilians sustained a brain injury that resulted in loss of consciousness but was not severe enough to cause death or long-term institutionalization, according to self-reported NHIS data collected with the 1991 Injury Supplement. Of these 1.54 million persons, 25 percent received no medical care for their TBI, 49 percent received care in an emergency department or other outpatient site, 9 percent received overnight hospital care, and 16 percent were admitted to a hospital for two or more days.

CDC Estimates of Traumatic Brain Injury-Related Disability

Prevalence

The CDC's National Center for Injury Prevention and Control estimates that 5.3 million U.S. citizens (2 percent of the population) are living with disability as a result of a traumatic brain injury. This represents the prevalence of TBI disability, defined as the proportion of persons in the population at a given time who have disability resulting from a traumatic brain injury. To estimate the prevalence of disability from TBI in the United States, CDC developed a model incorporating data on the incidence of TBI, severity of injury, and likelihood of disability given a specific level of injury severity.22 Data come from several sources:

CDC estimated the incidence of TBI by using its case definition and 1970-1995 National Hospital Discharge Survey (NHDS) data, obtained from CDC's National Center for Health Statistics.

CDC estimated the severity of TBI by using NHDS data, classified according to ICD-9-CM-derived Abbreviated Injury Scale23 (ICD/AIS) scores by means of a computer algorithm (ICDMAP-90©).

Calculating the likelihood of disability following TBI at each level of severity required two data sources. For injuries occurring in 1980 or after, CDC obtained preliminary follow-up data from the Colorado TBI Registry and Follow-up System,26 which surveyed TBI survivors one year after injury and measured disability by using the Functional Independence Measure.27 For injuries that occurred before 1980, we used historical data reviewed by Kraus.

The model uses these data to estimate the number of persons alive in 1996 who had ever had a TBI that required hospitalization and resulted in long-term disability. It incorporates differences in rates across age groups, variations in injury severity, and changing patterns in hospital admissions related to severity. The model does not account for disability among people who visited emergency departments or outpatient clinics with a TBI but were not admitted to the hospital. Because of this, our estimate of 5.3 million U.S. citizens living with TBI-related disability may be low. Other restrictions in existing data and methods may also affect the accuracy of this estimate.23 Given these limitations, some variation in future estimates of the prevalence of TBI-related disability is expected.

Incidence

According to NHDS data, the annual incidence rate of TBI hospitalizations has been declining since 1975, when it peaked at 234 per 100,000 population (500,000 cases). During 1990-1995, the mean annual incidence rate for persons hospitalized with TBI and survived was 99 per 100,000 population (260,000 cases). Hospitalization incidence patterns mirrored mortality rate patterns -- the highest rates were among persons 15-24 years of age and persons over age 65. Based on preliminary data from the Colorado TBI Registry and Follow-up System,25,26 we can estimate that each year, approximately 35 percent (80,500) of the 230,000 hospitalized survivors of TBI experience the onset of long-term disability. A small but unknown proportion of the more than 1 million persons with TBI who are not hospitalized may also experience long-term disability. If we assume this proportion is only 1 percent (existing data indicate it is probably greater), an additional 10,000 persons might have long-term disability. Thus, the estimated number of persons who become disabled each year from TBI is between 80,000 and 90,000.

Executive Summary
Introduction
CDC's Traumatic Brain Injury Surveillance Program, 1989-1998
Current Data on Traumatic Brain Injury Mortality and Morbidity
CDC Estimates of Traumatic Brain Injury-Related Disability
Public Health Goals
References
Appendix: Methods Used to Produce Estimates for This Report