Demographics, Velocity Distributions, and Impact Type as Predictors of AIS 4+ Head Injuries in Motor Vehicle Crashes

The objective of the study was to determine differences between the United States-based NASS and CIREN and Australia-based ANCIS databases in occupant-, crash-, and vehicle-related parameters for AIS 4+ head injuries in motor vehicle crashes. Logistic regression analysis was performed to examine roles of the change in velocity (DV), crash type (frontal, far-side, nearside, rear impact), seatbelt use, and occupant position, gender, age, stature, and body mass in cranial traumas. Belted and unbelted non-ejected occupant (age >16 years) data from 1997-2006 were used for the NASS and CIREN datasets, and 2000-2010 for ANCIS. Vehicle model year, and occupant position and demographics including body mass index (BMI) data were obtained. Injuries were coded using AIS 1990-1998 update. Similarities were apparent across all databases: mean demographics were close to the mid-size anthropometry, mean BMI was in the normal to overweight range, and representations of extreme variations were uncommon. Side impacts contributed to over one-half of the ensemble, implying susceptibility to head trauma in this mode. Odds of sustaining head injury increased by 4% per unit increase in DV (OR: 1.04, 95% CI: 1.03-1.04, p<0.001; adjusted for other variables); one-half for belted compared to unbelted occupants (OR: 0.48, 95% CI: 0.37-0.61, p<0.001); nearside, then far-side had significantly higher odds than frontal, and no difference by gender or position (front-left, front-right). Similar crash- and occupant-related outcomes from the two continents indicate a worldwide need to revise the translation acceleration-based head injury criterion to include the angular component in an appropriate format for improved injury assessment and mitigation.