If heart disease, diabetes, hypertension, stroke and other diseases caused by being overweight aren’t enough to encourage Americans to shed pounds, a new study says that obese drivers are also at a higher risk of dying in a severe automobile accident.

The study, posted online before upcoming publication in the American Journal of Emergency Medicine, finds that a moderately obese driver faces a 21 percent increased risk of death in a severe automobile crash, while the risk of not surviving the crash increases to 56 percent for “morbidly obese” drivers.

The study, partially funded by the Federal Highway Administration, marks the first time the effect of body mass on crash outcome has been significantly factored into such evaluations. Drivers were grouped based on body mass index -- weight in kilograms divided by height in meters squared -- into underweight, normal, overweight, slightly obese, moderately obese and morbidly obese categories. Surprisingly, underweight and normal-weight drivers were found to be at an even greater risk of dying than their counterparts carrying an extra 10 pounds.

"The severity and patterns of crash injuries depend on a complex interaction of biomechanical factors, including deceleration velocity at impact, seatbelt and airbag use, vehicle type and weight, and type of impact," said the primary author on the study, Dr. Dietrich Jehle, professor of emergency medicine at the University at Buffalo School of Medicine and Biomedical Sciences and at Erie County Medical Center.

Jehle and colleagues set out to investigate the relationship between driver body size and risk of crash-related fatality by analyzing data in the national Fatality Analysis Reporting System database. To be included in the database, a crash must involve, "a vehicle traveling on a roadway customarily open to the public and must result in the death of an occupant of a vehicle or a nonmotorist." From the 168,049 drivers in severe motor vehicle crashes entered in the database, 155,584 met the criteria for inclusion in the analysis. 

As a result of the study, Jehle concludes that body type should be part of the vehicle safety design process. To save more lives, he suggests extending the range of adjustable seats, as well as encouraging moderately and morbidly obese individuals to buy larger vehicles with more space between the seat and the steering column.

He also recommended that manufacturers design and test vehicle interiors with obese dummies, and testing with a 50-percentile (BMI 24.3) male dummy that better represents the average American man.

"Crash-test dummies have saved lives and provided invaluable data on how human bodies react to crashes,” Jehle said, "but they are designed to represent normal-weight individuals. If they represented our overweight American society, there could be further improvements in vehicle design that could decrease mortality. It would improve safety for the one-third of the U.S. population that is obese. For underweight and normal-weight individuals, placing airbags within the seatbelt also might be protective."

Jehle says he expects the issue to get worse for overweight drivers. "The rate of obesity is continuing to rise,” he says. “So it is imperative that car designs are modified to protect the obese population, and that crash tests are done using a full range of dummy sizes.”

[Source: InsideLine]