The incidence of TBI is high, but just how high is not known,
primarily because many head injuries are not included in official
statistics and because definitions of TBI, of disability and of recovery
vary across the respective research groups and agencies that track
TBI incidence. For example, what clearly affects any of the estimates
of TBI incidence is that many people with mild injuries do not gain
access to the health care system, because, as was discussed above,
many such injuries are labeled incorrectly or are ignored.
These individuals with TBI are not included in hospital-based estimates.
Further, many of these individuals -- in unknown numbers -- have all
the symptoms of TBI and do not know the cause of their symptoms. Because
the problems in living triggered by TBI are not seen by them as being
a result of TBI they are not counted in household surveys that ask
if "anyone in the household has experienced a TBI".
In a presentation in 1995, Dr. David Thurman of the Centers for Disease
Control and Prevention reviewed data regarding incidence and mortality
rates due to TBI, covering the past 20 years. Based on current data,
he estimates that 250,000 hospitalizations occur yearly, with 70,000
of these occurrences experiencing long-term disability and 60,000
dying. The direct costs of such injuries plus lost earnings Thurman
estimates at nearly $40 billion yearly.
Thurman acknowledges that these data are under-estimates, as hospitalization
rates have decreased due to more stringent admission criteria in recent
years (and, as discussed above, many people with TBI's do not reach
the hospital's doors at all). Also, the one-quarter million hospitalizations
estimated by Thurman do not include those whose medical contact was
in the hospital's emergency room or clinic, or in a physician's office.
Interestingly, the incidence rates have fallen since the 1970's. Then,
annual rates hovered around 200 per 100,000. In the early 1990's,
the incidence in several studies approximated 100 per 100,000. This
precipitous drop Thurman attributes to the changed rates for hospitalization
mentioned above and also to a real drop in injuries, based on fewer
transportation-related accidents, which now are the cause of half
of all TBIs.
Who is the typical person with TBI? Historically, the 'average' brain
injury has been depicted as happening to a young male. The ratio of
males to females has been estimated to be as high as 4:1; Thurman's
data suggest a 2:1 ratio. Although these data well describe people
with head injuries who have been hospitalized, recent data based on
interviewing people with head injuries living in the community indicate
that the ratio of head injured males to females in the non-hospitalized
population is closer to 3:2.
This may be the case partly because females are more likely to receive
blows to the head (for example, through spousal abuse) that are not
viewed as serious enough to send them to the hospital, but the cumulative
effects lead eventually to serious consequences in day-to-day functioning.
In looking at the age of those who are injured, Thurman's data suggest
that indeed young people are at high risk. Those who are 15 to 24
have an annual rate of TBI of 169 injuries per 100,000. However, those
younger than 15 have relatively low annual rates (about 80 per 100,000),
while those of retirement age have the second highest rate (124 per
100,000). What these data suggest is that although teenage and young
adult males top the list of those most likely to be injured, TBI is
more of an "equal opportunity" nemesis than myths would have it.
