January 2013

Highly obese truck drivers have higher crash risk, according to new research

Highly obese commercial truck drivers have a much higher crash rate in their first two years on the job than their normal-weight counterparts, according to research from the University of Minnesota Morris (UMM). The findings come from a multi-year study led by Stephen Burks, an associate professor of economics and management at Morris and a former truck driver.

Burks’s research team collected height and weight data from 744 new drivers during their training with a cooperating trucking firm, Schneider National, Inc., and calculated the body mass index (BMI) for each. Using the firm’s job records, the researchers tracked the drivers’ performance during their first two years on the road. They then used statistical models to estimate the relationship between crash risk and BMI, controlling for demographic characteristics and for variations in the drivers’ exposure to risks on the road.

The researchers found that drivers who are severely obese are about 50 percent more likely to be involved in a crash than drivers who have a BMI within the normal range. Drivers who were overweight but not severely obese did not appear to be at higher risk for a crash.

The study did not determine the cause for the increased crash risk, but Burks suggests the causes may include fatigue due to obstructive sleep apnea (OSA), daytime sleepiness sometimes experienced by obese individuals who don’t have OSA, and limited agility. OSA is common among commercial drivers, with prevalence estimated as high as 17 to 28 percent. “This research is a kind of prequel to the study of obstructive sleep apnea in truckers we are currently doing,” he says.

Although most crashes new drivers have are minor, the study found that a minor crash predicts a greater risk of a more serious one later. As a truckload motor carrier, Schneider National operates within a high turnover part of the driver labor market, and new drivers are always a significant fraction of the work force at firms in this large industry segment. This suggests that driver health has significant implications for public safety, the researchers say.

“We have long been aware of the correlation between BMI and work-related injuries, but seeing the correlation to crash risk caused us to redouble our efforts to address commercial driver wellness,” says Don Osterberg, senior vice president of safety and security with Schneider National. “We now have a comprehensive sleep disorder testing and treatment program and a multifaceted wellness program to address the longer-term health of our commercial drivers as a way to mitigate risk. By proactively addressing the issue of obesity, we are able to reduce healthcare and other safety costs,” he says.

The research was published in the November issue of Accident Analysis & Prevention and was covered on the “breaking science news” website of Science on October 26.

The work is part of the Truckers & Turnover Project, a multi-year study in the field of behavioral personnel economics conducted by a team of UMM faculty and students as well as faculty at other institutions in the U.S. and abroad, in cooperation with Schneider National and other firms. Work is expected to continue for several more years.