December 07, 2009 20:06 ET

Link found between glycemic control and road crashes in diabetics

Attention: Assignment Editor, Health/Medical Editor, Media Editor, News Editor, Transportation Editor TORONTO, ONTARIO, MEDIA ADVISORY--(Marketwire - Dec. 7, 2009) - A new study in PLoS Medicine led by Sunnybrook Health Sciences Centre researcher, Dr. Donald Redelmeier, suggests an adverse association between tighter glycemic control and higher risk of a motor vehicle crash for adult drivers who have diabetes mellitus.

Using a population-based case control analysis over a two year period in Ontario (January 1, 2005 to January 1, 2007), Dr. Redelmeier and colleagues from the University of Toronto studied diabetic drivers and examined the connection between measured glycosylated hemoglobin (HbA1c) drivers and the risk of a motor vehicle crash.

Of the 795 total drivers studied, one-in-fourteen had been involved in a crash. The mean HbA1c (a measure of diabetes control over about 8-12 weeks) was lower for those in a crash than those who were crash-free. That is, lower HbA1c levels predicted higher crash risk. In addition, the risk of a crash quadrupled when a driver had a history of severe hypoglycemia that required outside help.

Careful blood glucose control is a fundamental part of diabetes care to reduce complications. Some driving licensing authorities also require adults who hold commercial licenses to document glycemic control. The authors question such licensing policies, saying that "the data suggest that a patient's HbA1c level is neither necessary nor sufficient for determining fitness-to-drive."

Says Redelmeier, "There seems to be a common assumption that if blood glucose levels are not strictly controlled there is an increased risk that the driver could become impaired by retinopathy, neuropathy, or hyperglycemia. However, this popular belief is one theory that does not appear to be fully supported by evidence."

Redelmeier, who is also a Professor of Medicine and Physician at Sunnybrook (Canada's largest trauma centre) states, "The basic implication of our study is to underscore the difficulty in judging fitness-to-drive in adults with diabetes mellitus. This pitfall calls into question traffic laws that prevail in the United States, United Kingdom, Canada, Germany, Holland, Australia, and other countries."

The study was supported by the Canada Research Chair in Medical Decision Sciences.

The results of the study are published in the December 8, 2009 issue of the Public Library of Science (PLoS) Medicine.


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