Risk factors for subsequent impaired driving by injured passengers

The purpose of this study was to evaluate the rate of, and risk factors for, subsequent impaired driving activity (IDA) in a cohort of injured passengers who were treated for injuries in a Canadian trauma center.

We studied adult passengers who were occupants in vehicles involved in motor vehicle crashes (MVCs) and either included in the British Columbia (BC) trauma registry (January 1, 1992-December 31, 2004) or treated in the emergency department (ED) of Vancouver General Hospital (VGH; January 1, 1999-December 31, 2003). Passengers were linked to their driver's license and hence to their driving record using personal health number and demographic information. Injured passengers were stratified into 3 groups based on their blood alcohol concentration (BAC) at time of ED presentation: group 1: BAC = 0, group 2: 0 < BAC ≤ 17.3 mM (0.08%), group 3: BAC > 17.3 mM (0.08%). Two outcome variables were studied: involvement in a subsequent IDA and time to their first subsequent IDA. IDA was defined as a criminal code conviction for impaired driving, a 24-h or 90-day license suspension for impaired driving, and/or involvement in an MVC where police cited alcohol as a factor. Time to first IDA following the index event among passenger BAC groups was compared with Kaplan-Meier survival analysis. Cox proportional hazards models were employed to examine the effect of various potential risk factors on time to engage in first IDA.

Injured passengers with any BAC at the time of ED visit were more likely to engage in IDA and had their first IDA sooner after the index event than those with zero BAC. Among this cohort of injured passengers, 12.1 percent with BAC = 0, 29.9 percent with 0 < BAC ≤ 17.3 mM (0.08%), and 37.8 percent with a BAC > 17.3 mM (0.08%) engaged in IDA. Compared to passengers with BAC = 0, group 3 passengers and group 2 passengers were 2.06 times and 1.79 times more likely to engage in future IDA. Twenty-five percent of injured passengers engaged their first IDA by 57 and 38 months in groups 2 and 3, respectively. Previous IDA and being male were also significant risk factors for future IDA. Those with a history of IDA before the index event were 2.37 times more likely to engage in subsequent IDA.

Injured alcohol-impaired passengers are at high risk for IDA and should be included in impaired driving prevention programs.