The mortality rate for people who reach a hospital alive was estimated at 30% in 1966;[2] more recent estimates place this number at 9%.[15] The number of people reaching a hospital alive has increased, perhaps due to improved prehospital care or specialized treatment centers.[14] Of those who reach the hospital alive but then die, most do so within the first two hours of arrival.[17] The sooner a TBI is diagnosed, the higher the mortality rate; this is likely due to other accompanying injuries that prove fatal.[15]