Adults 65 years and older and children ages four and under have the highest rate of TBI hospitalization or death due to the risk of falls. Adolescents ages 15 to 19 years old are at risk due to bike accidents and sports-related head injuries. Others at a higher risk for concussion include: Those involved in a motor vehicle accident Military personnel due to exposure to explosive devices Anyone involved in a car accident Victims of physical abuse Individuals who had a previous concussion or Second Impact Syndrome (SIS), in which the victim suffers a second head injury before they have fully recovered from the first, such as athletes who return to their sport after a concussion.