The epidemiology of mild, uncomplicated brain injury.

Mild brain injury accounts for a substantial proportion of all persons admitted to a hospital for brain trauma, yet the amount of information on the epidemiology of this problem is quite sparse. Data on mild brain injuries for San Diego County residents injured in 1981 were analyzed for incidence, external cause, prehospital factors, diagnoses, alcohol use, and in-hospital treatment costs. More than 80% of all San Diego County residents hospitalized for an acute brain injury had a mild uncomplicated brain injury: a rate of 130.8 per 100,000 per year. Three quarters of these had an ER Glasgow Coma Scale of 15. Rates are twice as high for males compared to females, with peak occurrence for males at ages 15-19 years. More than 40% of mild brain injuries are caused by motor-vehicle-related events. The most common diagnosis was concussion (80%) or other intracranial injury (14%). Median length of hospital stay was 2-3 days and depended on brain injury diagnosis or Glasgow Coma Scale. Although less than 30% of those aged 15 years and older were blood tested for alcohol, two thirds of those tested had a level of 100 mg% or higher. In-hospital treatment costs for concussion or other mild intracranial injury for San Diego County residents exceeded six million dollars in 1981.