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Brenda Hemmelgarn
Linda E Lévesque
Samy Suissa


Cohort study, case-control analysis, diabetes, elderly, injurious motor vehicle crash, pharmacoepidemiology



Studies of the risk of motor vehicle crash associated with diabetes have produced conflicting results.


To assess whether the use of anti-diabetic drugs among the elderly increases the risk of motor vehicle crash.


The computerized databases of the various universal insurance programs of Québec were linked to form a cohort of all 224,734 elderly drivers that was followed from 1990-1993. Using a nested case-control approach, all 5,579 drivers involved in an injurious crash (cases) and a random sample of 13,300 control subjects were identified. Exposure to anti-diabetic drugs was assessed in the year preceding the index date, namely the date of the crash for the cases and a randomly selected date during follow-up for the controls.


The adjusted rate ratio of an injurious crash was 1.4 (95% CI: 1.0-2.0) for current users of insulin monotherapy relative to non-users and 1.3 (95% CI: 1.0-1.7) for sulfonylurea and metformin combined. Monotherapy, using either a sulfonylurea or metformin, was not associated with an increased risk. There was a dose-response effect in subjects using high doses of combined oral therapy (RR 1.4; 95% CI: 1.0-2.0).  For  users  of  insulin  monotherapy  or  of  high  doses  of  combined  oral  therapy,  the  increase corresponds to an excess rate of 32 crashes per 10,000 elderly drivers per year.


Elderly  drivers treated  with  insulin  monotherapy or  a  combination of  sulfonylurea and  metformin, especially at high doses, have a small increased risk of injurious crashes. There is no increased risk associated with any regimen of oral monotherapy

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