Here is an article by Larry Kahaner from Fleet Owner Magazine published on February 3rd:

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."

hiese 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.

The cost of crashes is high, according to FMCSA statistics. Approximately 60,000 truck crashes were reported to the police over the past 5 years, with an average cost per crash of between $331,000 and $533,000. The average cost per crash involving a fatality was between $7.2 million and $11.7 million.

Thiese has two messages for carriers. "It would be great if carriers were made more aware of this so [correlation between illness and crashes] so they can help their drivers. Helping drivers takes all sorts of different forms, whether it's encouraging drivers to try and get treatment for some of these [conditions] or promoting wellness, promoting healthy eating, having these types of programs. So that’s one.

"The second is that it may be more cost beneficial to do these types of [wellness] programs because you could prevent some crashes, and you’re also more likely to have drivers maintain their medical certification. There’s no data to back it up, but I would think turnover would possibly be less, too."

Thiese wants to continue his research about driver health and hopes to study which particular diseases together are directly related to the most crashes. "We would like to give drivers, carriers, and physicians a better map to say, 'Okay, these are our top-three offenders, and if they all run together it’s way worse than if other conditions are going on.'"

He concludes: "Truck drivers and carriers do so much for us, and they face so many challenges. Hopefully this line of research can help improve drivers' quality of life and the carriers' business by providing more information and better tools to make the really tough decisions about worker health and preventing crashes."

The study, titled Multiple Conditions Increase Preventable Crash Risks Among Drivers in a Cohort Study, was supported by the National Institute of Occupational Safety and Health and appeared in the Journal of Occupational and Environmental Medicine.