They only looked at cases in which both parties involved in the collision had been driving vehicles of similar size and types. The final dataset used covered 3,403 pairs of drivers. Almost half of these drivers were of normal weight, 1 in 3 was overweight, and almost 1 in 5 (18 percent) was obese.
The risk of fatality against victim’s estimated body mass index (BMI) were compared. BMI is used to assess whether a person is fat and is calculated by dividing one's weight in kilograms by the square of one's height in meters. An adult is said to be of normal weight if his or her BMI is between 18.5 and 24.9. Below this range, this person is considered underweight; between 25 and 29.9 is considered overweight, and 30 and above is obese.
After taking into account of factors like age and alcohol use, the researchers found that underweight drivers had higher risk of 19 percent compared to those of normal weight. The increased risk was 21, 51 and 80 percent respectively for those of BMI between 30 and 34.9, between 35 and 39.9, and those who were extremely obese with BMI of 40 and above. Obese women were at even higher risk. Among those of BMI between 35 and 39.9, the risk of death was double compared with people of normal weight.
According to the data from hospitals’ intensive-care units, obese victims in the car accidents tended to have more chest injuries and fewer head injuries, were likelier to have more complications, required longer hospital stays, and were likelier to die of their injuries. The obese drivers were more likely to leave the seatbelt unbuckled or partially fastened because it is uncomfortable. Another reason could be the passenger vehicles are well designed to protect normal-weight vehicle occupants but not for overweight or obese patients.
Taking into account of the fact that more than 33 percent of adult men and 35 percent of adult women are obese, the ability of passenger vehicles to protect overweight or obese occupants may have increasing important public health occupations.