More medical conditions mean more crashes: Driver study

Drivers with several health issues, such as obesity, diabetes, heart disease and high blood pressure, are more likely to be involved in a crash than truckers with only one condition.

While this conclusion may seem obvious, the numbers are striking. Of about 38,000 drivers whose medical and crash records were studied, those with three or more ailments had a crash frequency of 93 incidents per million miles compared to 29 per million miles for all drivers.

"All of the research up until this point has just been looking at one single condition," says Matthew Thiese, the report's lead author. "If you have 'x condition,' how much more likely are you to have a crash? This is the first study that actually looks at [multiple conditions] in concert."

Thiese, assistant professor at the University of Utah Rocky Mountain Center for Occupational and Environmental Health, says, "If you have one condition, regardless of which one, you increase your crash risk, but when you get up to the three or four, it’s even worse. It has a knock-on effect. That’s information for employers to say, 'Look, not only are we losing people because of medical certification issues, but we’re also having people who are more likely to be involved in a crash when they get into these higher numbers. It would be helpful to try and encourage drivers, in whatever way that is, to reduce their number of conditions."

Thiese adds: "People with four conditions, shouldn't even be driving." This is borne out by his research showing that only 82 drivers fit in the category of having three conditions. The relatively low number is because many of the drivers who reach this level of infirmity, have already been reassigned to non-driving jobs, left the industry voluntarily or were denied medical certification. The study used millions of data points much of it from Road Ready, a company that provides health history information to Department of Transportation examiners and transportation companies. Driver names were scrubbed. "The list we used [of medical conditions] came in 2010 from the Medical Review Board for the Federal Motor Carrier Safety Administration. They had a list of 13 maladies, and they said, 'These are the conditions we think,  as medical professionals, that there’s an increased risk.' They actually came out and said that if you have three of these conditions, you should only get a six-month card. If you have four conditions, you shouldn’t be medically certified." Until now, however, that risk had not been quantified.