Head injury and aging: the importance of bleeding injuries.

The current study analyzed 1993-2007 data from NASS/CDS (National Automotive Sampling System / Crashworthiness Data System) to explore the types of serious head injuries sustained by adult motor vehicle crash occupants and how the types of head injuries sustained shifted with age. The purpose was to determine which head injuries are most important for older occupants by identifying specific injuries that become more likely for aging occupants and taking into consideration previous reports on the potential outcome of those injuries for an older population. Results confirmed previous reports that older head injury victims in motor vehicle collisions were more likely to sustain bleeding injuries than younger head injury victims. The current study showed that, in particular, the rate of extra-axial bleeding injury (which includes epidural, subdural, and subarachnoid bleeding) increased with age. The increase in extra-axial bleeding injury rate was especially prominent in relatively low Delta-V crashes. Among the extra-axial bleeding injuries that had increased odds of injury for older occupants, subdural hematoma and subarachnoid hemorrhage were notable, with increased odds of injury for occupants age 50 to 69 as well as for occupants age 70 and older. The importance of subdural hematoma for aging occupants is emphasized by previous studies showing its high mortality rate, while the impact of subarachnoid hemorrhage is linked in previous studies to its aggravating effect on other injuries. The results highlight a need to further explore the injury mechanisms of subdural hematoma and subarachnoid hemorrhage in older occupants in order to define age-adjusted injury tolerance and develop countermeasures.