An Estimated 5.3 Million Americans - a little more than 2 percent of the U.S. population - currently live with disabilities resulting from traumatic brain injury.   Every 21 Seconds, One Person in the U.S. Sustains a Traumatic Brain Injury     Traumatic brain injury (TBI) Definition:   An insult to the brain, not of degenerative or congenital nature caused by an external physical force that may produce a diminished or altered state of consciousness, which results in an impairment of cognitive abilities or physical functioning. It can also result in the disturbance of behavioral or emotional functioning.     Acquired brain injury (ABI) Definition:   Injury to the brain which is not hereditary, congenital or degenerative that has occurred after birth. (Includes anoxia, aneurysms, infections to the brain and stroke.) 1.5 Million Americans sustain a traumatic brain injury each year1 Each year, 80,000 Americans experience the onset of long-term disability following TBI.1 More than 50,000 people die every year as a result of TBI.1 The risk of TBI is highest among adolescents, young adults and those older than 75.2 After one brain injury, the risk for a second injury is three times greater; after the second injury, the risk for a third injury is eight times greater.3     The Cost of Brain Injury The cost of traumatic brain injury in the United States is estimated to be $48.3 billion annually. Hospitalization accounts for $31.7 billion, and fatal brain injuries cost the nation $16.6 billion each year.