ABSTRACT
Estimates of the occurrence of mild traumatic brain injury (MTBI) have ranged greatly, from 131 per 100,000 (Kraus et al., 1984) to 149 per 100,000 (Annegers et al., 1980)—or approximately 325,000 to 375,000 occurrences per year-to over 2 million occurrences per year (National Head Injury Foundation, 1993). In part because many cases of MTBI do not result in hospital admission, inclusive surveillance systems for MTBI are nonexistent and incidence estimates are often not based on reliable data. One of the best studies of incidence (Sosin, Sniezek, & Thurman, 1996) was based on a household survey of a national sample conducted through the U.S. Census Bureau. This study resulted in an estimate of 618 cases per 100,000 of mild to moderate TBI in 1991 that resulted in loss of consciousness (LOC) but not death or institutionalization. Of these, 59 per 100,000 resulted in only an overnight stay in the hospital, with an additional 460 per 100,000 resulting in no hospitalization. These data can be interpreted to indicate an annual incidence of MTBI of 519 per 100,000 or-based on a national population of 250 million-approximately 1.3 million mild brain injuries per year. This is a conservative estimate because MTBI may occur without LOC.
