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Life-threatening alcohol-related traffic crashes in adverse weather: a double-matched case–control analysis from Canada
  1. Donald A Redelmeier,
  2. Fizza Manzoor
  1. Medicine, Sunnybrook Health Sciences Centre, Toronto, Ontario, Canada
  1. Correspondence to Dr Donald A Redelmeier; dar{at}


Importance Drunk driving is a major cause of death in North America, yet physicians rarely counsel patients on the risks of drinking and driving.

Objective To test whether the risks of a life-threatening alcohol-related traffic crash were further accentuated by adverse weather.

Design Double matched case–control analysis of hospitalised patients.

Setting Canada’s largest trauma centre between 1 January 1995 and 1 January 2015.

Participants Patients hospitalised due to a life-threatening alcohol-related traffic crash.

Exposure Relative risk of a crash associated with adverse weather estimated by evaluating the weather at the place and time of the crash (cases) compared with the weather at the same place and time a week earlier and a week later (controls).

Results A total of 2088 patients were included, of whom the majority were drivers injured at night. Adverse weather prevailed among 312 alcohol-related crashes and was significantly more frequent compared with control circumstances. The relative risk of a life-threatening alcohol-related traffic crash was 19% higher during adverse weather compared with normal weather (95% CI: 5 to 35, p=0.006). The absolute increase in risk amounted to 43 additional crashes, extended to diverse groups of patients, applied during night-time and daytime, contributed to about 793 additional patient-days in hospital and was distinct from the risks for drivers who were negative for alcohol.

Conclusions Adverse weather was associated with an increased risk of a life-threatening alcohol-related traffic crash. An awareness of this risk might inform warnings to patients about traffic safety and counselling alternatives to drinking and driving.

  • preventive medicine
  • primary care
  • substance misuse
  • trauma management
  • neurological injury

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  • Contributors The lead author (DAR) wrote the first draft. Both authors (DAR, FM) contributed to study design, manuscript preparation, data analysis, results interpretation, critical revisions and final decision to submit. The lead author (DAR) had full access to all the data in the study, takes responsibility for the integrity of the data and is accountable for the accuracy of the analysis.

  • Funding This article was supported by a Canada Research Chair in Medical Decision Sciences, the Canadian Institutes of Health Research, the Ontario Ministry of Transportation and the Comprehensive Research Experience for Medical Students program at the University of Toronto.

  • Competing interests None declared.

  • Ethics approval The study protocol was approved by the Research Ethics Board of Sunnybrook Health Sciences Center including a waiver for direct patient consent.

  • Provenance and peer review Not commissioned; externally peer reviewed.

  • Data sharing statement No additional data are available.

  • Patient consent for publication Not required.

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