Traumatic brain injury after frontal crashes: relationship with body mass index.

Background: Previous studies had demonstrated that injury severity and risk of death after motor-vehicle crashes are related to human body characteristics. The purpose of this study was to clarify the relationship between body mass index (BMI) and head injury severity in front seat passengers after a frontal collision.

Methods: Data from all front seat occupants with at least one injury, older than 16 years old involved in a frontal collision from 1993 to 2005 were retrieved from the National Automotive Sampling System (NASS) database. Patient and collision characteristics were analyzed. Two cohorts were defined according to BMI < or > or =30 kg/m2.

Results: A total of 6,977 patients were included in this study, 5,918 (85%) had complete data on weight and height. Patient's mean age was 37 +/- 18 years old, the median ISS was 6, interquartile range (IQR) 15, and 61% were men. The mortality rate was positively associated to the crash delta velocity (DV) (p < 0.0001). The use of restraint system reduced the risk of death (p = 0.01). There was a significant increase in fatal outcome (p < 0.0001; RR 1.84 95% CI 1.61-2.1) and injury severity (ISS >25 p < 0.0001; RR 1.36 95% CI 1.19-1.54) in the obese cohort. Obese patients had higher chances of having a maximum head injury (Abbreviated Injury Score head = 6) than those not obese (p = 0.003; RR 1.97 95% CI 1.52-2.55).

Conclusion: Obese passengers are more likely to suffer a more severe head trauma after a frontal collision. Further studies with computational models are needed to determine the precise role of BMI on brain injury-related biomechanical metrics.