As blanket bans on commercial driving licenses for people with diabetes come under increasing fire, a new study leaves the debate on safety at a crossroads.

The study, which appeared in the May issue of Diabetes Care, assessed the crash risks of a variety of commercial drivers in Canada. Drivers of single- and multi-unit trucks were surveyed by phone and broken up into one of four categories: those with diabetes who used insulin; those with diabetes who did not use insulin and did not have complications; those with diabetes who did not use insulin and had some sort of complication; and drivers who had no diabetes at all.

Crashes were found to be rare in any group, with only a small fraction of drivers reporting more than one incident a year.

Among drivers of single-unit trucks, those with diabetes who did not use insulin and had no complications were found to be almost 68 percent more likely to crash as those with no diabetes. The study's authors suggest this increase in risk may be the product of hypoglycemia induced by certain oral agents. This finding particularly surprised researchers because the oral agents taken by many people with diabetes who are not using insulin are not generally associated with an increased risk of hypoglycemia.

Single-unit drivers with diabetes who were on insulin or who were not on insulin and had complications, however, showed no substantial increase in crash risk. Nonetheless, the researchers urge members of these groups to exercise caution.

The study's authors credit the low accident rate among insulin-dependent commercial drivers to this group's vigorous self-regulation efforts, which keeps most type 1s from driving their trucks when they feel their symptoms are at their most dangerous.