Severely obese truckers have about a 50 percent higher accident rate in their first two years on the job than their colleagues who are a normal weight, according to researchers at the University of Minnesota-Morris.
The findings are based on health interviews and job records collected from 744 new drivers who trained at Schneider National trucking company. Researchers compared the body mass index of study participants with detailed company records tracking the truckers' on-the-job accident reports.
Stephen Burks, an associate professor of economics and management at Morris, led the study. Burks' team analyzed the weight and accident data in a couple of different ways. He said researchers tried to account for the number of miles each trucker drove and the specific type of work they were doing at the time of the accident.
"And they all tell a consistent story," Burks said. "It's roughly a 50 percent increase in accident risk for drivers of BMI of 35 and above."
For a 5-foot-10-inch person, that's a weight of 245 pounds or more.
Most of the accidents in the study were minor. But the risk also extended to accidents that were more severe, including incidents that must be reported to the Department of Transportation and accidents that the trucking company classified as severe, "which are ones which they would be extremely concerned about as managers," Burks said.
The study didn't reveal why the accident rate is higher for severely obese truckers. But Burks said it is well-established in other research that obese truckers have high rates of obstructive sleep apnea. That's a condition that causes daytime fatigue due to disrupted sleeping.
"It means that your body never gets fully restored of deep sleep," Burks said. "And so that suppresses your immune system and causes various kinds of potential co-morbidities as the doctors say, risk of stroke and heart attack, and it means you're always sleepy when you're trying to work."
Heavy truckers may also have movement limitations, Burks said, that could affect their performance.
The findings are published in the journal Accident Analysis & Prevention.