Traumatic brain injury: Epidemiology, classification, and pathophysiology
- J Claude Hemphill, III, MD, MAS
J Claude Hemphill, III, MD, MAS
- Professor of Neurology
- University of California, San Francisco
Traumatic brain injury (TBI) is the leading cause of death in North America for individuals between the ages of 1 and 45. Many survivors live with significant disabilities, resulting in major socioeconomic burden as well. In 2000, the economic impact of TBI in the United States was estimated to be $9.2 billion in lifetime medical costs and $51.2 billion in productivity losses .
The focus of this topic is on the epidemiology, pathophysiology and classification of TBI. Other aspects of traumatic head injury are discussed separately. (See "Management of acute severe traumatic brain injury" and "Concussion and mild traumatic brain injury" and "Intracranial epidural hematoma in adults" and "Post-traumatic seizures and epilepsy" and "Subdural hematoma in adults: Etiology, clinical features, and diagnosis" and "Skull fractures in adults".)
The overall incidence of TBI in the United States was estimated to be 538.2 per 100,000 population, or around 1.5 million new cases in 2003 . Somewhat lower rates are reported in Europe (235 per 100,000) and Australia (322 per 100,000) [2,3].
Rates of TBI are highest in the very young (age group zero to four years) and in adolescents and young adults (15 to 24 years); there is another peak in incidence in the elderly (age >65 years) . Approximately 78 percent of TBI are treated in the emergency department only; 19 percent of patients require hospitalization, and 3 percent are fatal. Most cases treated in emergency departments occur in the very young (ages zero to four years), while hospitalization rates are highest in patients older than 65 years.
As with most traumatic injuries, the incidence of TBI is significantly higher in men compared to women, with ratios that vary between 2.0 to 1 and 2.8 to 1 [4-7]. For severe TBI, the gender ratio is more pronounced, 3.5 to 1. Lower socioeconomic status, alcohol and drug use, and underlying psychiatric and cognitive disorders are also risk factors for head injury [7,8].
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