For any driver, forgoing the seat belt is a potentially deadly decision. In the event of an accident, more force will be delivered to the body much more quickly, and unprotected drivers also have a greater chance of being thrown from the car.
"It's clear that not wearing a seat belt is associated with a higher chance of death,” said lead author Dietrich Jehle, M.D., professor of emergency medicine at the UB School of Medicine and Biomedical Sciences and associate medical director at Erie County Medical Center. “Obese drivers may find it more difficult to buckle up a standard seat belt."
Drivers were considered overweight or obese if they had a BMI (body mass index) of 25 or more, according to the World Health Organization definition of obesity. A BMI of 25-30 is defined as overweight, 30-35 slightly obese, 35-40 moderately obese and 40 morbidly obese.
Researchers found that the degree of a driver's obesity was in direct relation to the likelihood that the driver would wear a seat belt. In other words, as Jehle explained, "the more obese the driver, the less likely that seat belts were used."
Jehle stressed that the research raises questions surrounding how to make cars safer for obese drivers and how to encourage overweight or obese drivers to wear seat belts. He added that the findings also raise questions about how best to conduct crash-tests of cars – crash test dummies, after all, are not obese.
"We need to do something, since one-third of the U.S. population is overweight (not obese) and one-third is considered obese," Jehle said.
The researchers based their study on data in the national Fatality Analysis Reporting System (FARS) of the National Highway Traffic Safety Administration, which tracks motor vehicle crashes and numerous variables about the collisions, some of which are related to seat belt use. They looked at 336,913 drivers who were in a severe crash where a death occurred and controlled for confounding variables.
These finding comes from the same UB researchers who in 2010 identified obesity as a risk factor for death in a study of 155,584 drivers in severe auto crashes. In that study, they found that morbidly obese individuals are 56 percent more likely to die in a crash than individuals of normal weight.