Motor vehicle crashes obesity and seat belt use: a deadly combination?

BACKGROUND Previous studies indicate that compared with lean adults, obese persons are more likely to improperly wear a lap belt across the abdomen. Improper lap belt positioning could result in severe abdominal injuries and a related increase in death. We hypothesized that adult nonobese-belted occupants involved in motor vehicle crashes (MVC) have lower mortality and lower frequency of abdominal injury than obese-belted and obese-nonbelted occupants. METHODS A national population-based cohort of adult (>/=16 years) nonobese (body mass index, BMI <30 kg/m) and obese (BMI >/=30 kg/m) MVC occupants included in the National Automotive Sampling System Crashworthiness Data System for 2003 was studied. The study population was divided into nonobese-belted, nonobese-nonbelted, obese-belted, and obese-nonbelted MVC occupants. The primary outcome was 30-day mortality. The secondary outcome was intra-abdominal injury (IAI). Crude odds ratios and 95% confidence intervals were calculated. Multivariate logistic regression analysis was used to adjust estimates for significant occupant, vehicle, and crash-related factors. RESULTS Occupants (10,656) were in the National Automotive Sampling System-Crashworthiness Data System database for 2003 and 9,313 occupants were eligible for analysis. BMI and seat belt use records were available for 7,459. Lack of seat belt use conferred an increased odds of death and IAI compared with nonbelted occupants for both obese (9.71 [5.08-18.56]) and nonobese (5.26 [3.07-9.03]) occupants. Neither mortality nor IAI was increased in obese-belted occupants compared with nonobese-belted occupants. CONCLUSION Proper seat belt use should be encouraged without concern for increases in morbidity or mortality among obese motor vehicle occupants.