A study has confirmed what many in trucking already believed -- that there's a direct connection between a truck driver's crash risk and his or her body mass index. Obese truckers, during their first two years on the road, are 43% to 55% more likely to be involved in a crash when compared against those truckers with a normal BMI.

Stephen Burks of the University of Minnesota-Morris, a former truck driver and behavioral economist, has been working with Schneider National for more than a decade to study truck driver health and safety.

According to an article by Science Now, it was two years ago that Burks and his team decided to study drivers' BMI numbers and see how that related to crash rates.

They asked 744 rookie drivers with Schneider National for their height and weight, and from that information calculated the each driver's individual BMI. Those with a BMI higher than 25 are considered overweight, while those with a BMI greater than 30 were considered obese.

The study followed the drivers for two years.

"That's when the data stood up and shouted at us," Jon Anderson, a biostatistician at the University of Minnesota-Morris told Science Now. "We found really clear evidence that the highest-BMI drivers are at higher risk of having an accident."

During their first two years on the road, drivers with a BMI higher than 35 ("severely obese") were 43% to 55% more likely to crash than were drivers with a normal BMI, the team reports in the November issue of Accident Analysis & Prevention.

Drivers who are overweight or obese, but not severely, did not appear to be at higher risk. The study does not indicate why. "The relationship held even when the researchers corrected for number of miles on the road, geographic location, age, and other crash risk factors," stated the article by Science Now.

Some ideas behind the increased risk may include sleep apnea, limited agility, or fatigue associated with obesity, according to the article.