The association between seatbelt use and trauma outcomes: Does body mass index matter?

National Highway Traffic Safety Administration (NHTSA) reports that seat belt use results in a significant decrease in MVC mortality. The rate of obesity is currently extensive. There is limited data on the impact of seat belt use and body mass index (BMI) on mortality and trauma outcomes following MVCs. This study aimed to evaluate the impact of seat belt use and BMI on outcomes in adult trauma patients.

A four-year review using our Level I Trauma Center registry. Patients were divided by BMI into normal weight BMI < 25 (NL-BMI), overweight BMI 25-29.9, and obese BMI ≥ 30. Groupings were subdivided by seat belt use into patients wearing a seat belt at the time of injury (seatbeltPOS) and those who were not (seatbeltNEG).

11,792 patients involved in MVCs were included in our study. 4515 (38.3%) were NL-BMI, 4583 (38.9%) were overweight, and 2694 (22.8%) were obese. SeatbeltPOS patients had significantly lower mortality compared to seatbeltNEG, regardless of BMI, with 12/1394 (0.86%) in seatbeltPOS compared to 274/10,398 (2.64%) deaths in seatbeltNEG patients (p ≪ 0.001). Evaluated by BMI, overweight and obese seatbeltPOS patients had significantly less deaths 7/900 (0.78%) vs overweight and obese seatbeltNEG patients 179/6377 (2.81%) (p = 0.0004). NL-BMI seatbeltPOS patients also had significantly lower mortality 5/494 (1.01%) compared to NL-BMI seatbeltNEG patients 95/4021 (2.36%), (p = 0.048).

Use of a seat belt reduced Trauma Center mortality regardless of BMI. Seat belts should be used by all patients as a mechanism to significantly reduce mortality.