Proportion of Injured Drivers Presenting to a Tertiary Care Emergency Department Who Engage in Future Impaired Driving Activities

Abstract

Objective: We determined the rate of, and predictive factors for, subsequent impaired driving activity (IDA) by injured drivers treated in a Canadian tertiary care emergency department (ED) following a motor vehicle crash (MVC).

Methods: We retrospectively identified all drivers injured in a MVC who presented to our tertiary care, urban ED (1999–2003) and had their blood alcohol content (BAC) measured. Injured drivers were categorized by BAC: group 1, BAC = 0; group 2, 0 < BAC ≤ 17.3 mM (80 mg/dL, legal limit); and group 3, BAC > 17.3 mM. IDA was defined as any of the following: a conviction for impaired driving; a 24-h or 90-day license suspension for impaired driving; involvement in alcohol-related MVC. Time to IDA following the index event between groups was compared with Kaplan-Meier survival analyses. Effects of covariates on time to IDA were analyzed using Cox proportional hazards models.

Results: During the study period, 1489 injured drivers met study criteria: 1171 in group 1, 51 in group 2, and 267 in group 3. During an average follow-up of 52.4 months, 82 (30.7%) group 3 drivers engaged in subsequent IDA, compared with 80 (6.8%) group 1 drivers (p < 0.0001). Youth, male gender, history of previous IDA, and the number of previous IDA events were all associated with a significant increase in subsequent IDA. A history of IDA was the strongest predictor of future IDA in group 1 (440% increase risk) and in group 3 (80% increased risk). The magnitude of BAC elevation above the legal limit was not predictive of future IDA. Conclusions: A high portion of injured impaired drivers who present to hospital engage in repeat IDA following discharge. Besides impairment at time of hospital visit, the best predictor of future IDA is a history of IDA prior to the index event.

Keywords:

• Traffic crashes
• Alcohol
• Impaired driving

ACKNOWLEDGMENTS

The authors would like to recognize the BC Trauma Registry, Vancouver General Hospital for the contribution of data towards this project.

Notes

∗ p < 0.05.

∗∗ p < 0.01 in comparison with Gp1 drivers (BAC = 0). (Unpaired t-test for comparison of mean age. Fisher's exact test for comparison of proportions.)

∗The hazard ratio is the relative risk of having the outcome for someone with the risk factor versus someone without. In the case of a score, the hazard ratio estimates the relative risk associated with a one-point increase in the score.