Mild traumatic brain injury in the United States, 1998--2000.

PRIMARY OBJECTIVE: To determine the incidence and epidemiology of emergency department (ED)-attended mild traumatic brain injury (mTBI) in the US.

RESEARCH DESIGN: Secondary analysis of ED visits for mTBI in the National Hospital Ambulatory Medical Care Survey for 1998--2000.

METHODS AND PROCEDURES: MTBI defined by International Classification of Diseases, 9th Revision, Clinical Modification (ICD9-CM) codes for 'skull fracture', 'concussion', 'intracranial injury of unspecified nature' and 'head injury, unspecified'.

MAIN OUTCOME AND RESULTS: The average incidence of mTBI was 503.1/100000, with peaks among males (590/100000), American Indians/Alaska Natives (1,026/100000) and those <5 years of age (1,115.2/100000). MTBI incidence was highest in the Midwest region (578.4/10000) and in non-urban areas (530.9/100000) of the US. Bicycles and sports accounted for 26.4% of mTBI in the 5-14 age group.

CONCLUSIONS: The national burden of mTBI is significant and the incidence higher than that reported by others. Possible explanations are discussed. Bicycle and sports-related injuries are an important and highly preventable cause of mTBI underscoring the need to promote prevention programmes on a national level.