Road traffic accident risk in patients with diabetes mellitus receiving blood glucose-lowering drugs. Prospective follow-up study.

AIM: To investigate, at a national level, whether patients using insulin or oral glucose-lowering agents had an increased risk of road traffic accidents compared with non-users.
METHODS: All Norwegians aged 18-69 years (3.1 million) were followed from April 2004 until September 2006. Information on drug prescriptions, road traffic accidents and emigration/death was obtained from the following population-based registries: the Prescription Database, the Road Accident Registry and the Central Population Registry. The exposure period was the time from the first prescription of insulin or oral glucose-lowering agent during the study period. The incidence of accidents in the exposed person-time was compared with the incidence of accidents in the unexposed person-time by standardized incidence ratio (SIR).
RESULTS: During the study period, 20 494 road traffic accidents with personal injuries were registered in Norway. One hundred and eighty-three accidents were registered for insulin users not taking oral glucose-lowering agents and 219 for users of oral blood glucose-lowering drugs without insulin. The SIR (95% confidence interval) for all ages and both genders combined were: insulin 1.4 (1.2-1.6), oral glucose-lowering agents 1.2 (1.0-1.3) and users of drugs for peptic ulcer and gastro-oesophageal reflux disease (negative comparators) 1.3 (1.2-1.4). The highest SIRs were found among the youngest insulin users (18-34 years old).
CONCLUSIONS: A slightly increased risk of being involved in a road traffic accident was observed for drivers prescribed insulin, while no increased risk was observed for drivers prescribed oral glucose-lowering agents. The increased risk observed for insulin users was similar to that observed for users of drugs for peptic ulcer and gastro-oesophageal reflux disease.