Body mass index and injury risk among US children 9-15 years old in motor vehicle crashes

Objective: To determine the relationship between body mass index (BMI) and injury risk among US children in motor vehicle crashes. Design: Cross-sectional study using data from the Partners for Child Passenger Safety study, a child-focused crash surveillance system. Participants: A probability sample of children, 9-15 years of age, involved in crashes in parent-operated vehicles between 1 December 2000 and 31 December 2006. Main outcome measure: The odds ratio of Abbreviated Injury Severity (AIS) 2+ injuries ( overall and body region specific) by BMI category: underweight, normal, overweight, and obese. Results: The study sample included 3232 children in 2873 vehicles, representing a population estimate of 54 616 children in 49 037 vehicles. Approximately 15% (n=502) sustained an AIS 2+ injury to any body region; 34% of the children were overweight or obese. There was no overall increase in injury risk by BMI; however, body region differences were found. In multivariate logistic regression, compared with normal weight children, the odds of sustaining an AIS 2+ injury to the extremities for overweight and obese children was 2.64 (95% CI 1.64 to 4.77) and 2.54 (95% CI 1.15 to 5.59), respectively. Conclusions: Although overweight and obese children are not at increased overall risk of injury, they are at increased risk of injury to the lower and upper extremities. This increased risk may be due to a combination of physiology, biomechanical forces, and vehicle design.