Syncope and the Risk of Subsequent Motor Vehicle Crash: A Population-Based Retrospective Cohort Study

Abstract

Importance: Medical driving restrictions are burdensome, yet syncope recurrence while driving can cause a motor vehicle crash (MVC). Few empirical data inform current driving restrictions after syncope.

Objective: To examine MVC risk among patients visiting the emergency department (ED) after first-episode syncope.

Design, setting, and participants: A population-based, retrospective observational cohort study of MVC risk after first-episode syncope was performed in British Columbia, Canada. Patients visiting any of 6 urban EDs for syncope and collapse were age- and sex-matched to 4 control patients visiting the same ED in the same month for a condition other than syncope. Patients' ED medical records were linked to administrative health records, driving history, and detailed crash reports. Crash-free survival among individuals with syncope was then compared with that among matched control patients. Data analyses were performed from May 2020 to March 2022.

Exposures: Initial ED visit for syncope.

Main outcomes and measures: Involvement as a driver in an MVC in the year following the index ED visit. Crashes were identified using insurance claim data and police crash reports.

Results: The study cohort included 43 589 patients (9223 patients with syncope and 34 366 controls; median [IQR] age, 54 [35-72] years; 22 360 [51.3%] women; 5033 [11.5%] rural residents). At baseline, crude MVC incidence rates among both the syncope and control groups were higher than among the general population (12.2, 13.2, and 8.2 crashes per 100 driver-years, respectively). In the year following index ED visit, 846 first crashes occurred in the syncope group and 3457 first crashes occurred in the control group, indicating no significant difference in subsequent MVC risk (9.2% vs 10.1%; adjusted hazard ratio [aHR], 0.93; 95% CI, 0.87-1.01; P = .07). Subsequent crash risk among patients with syncope was not significantly increased in the first 30 days after index ED visit (aHR, 1.07; 95% CI, 0.84-1.36; P = .56) or among subgroups at higher risk of adverse events after syncope (eg, age >65 years; cardiogenic syncope; Canadian Syncope Risk Score ≥1).

Conclusions and relevance: The findings of this population-based retrospective cohort study suggest that patients visiting the ED with first-episode syncope exhibit a subsequent crash risk no different than the average ED patient. More stringent driving restrictions after syncope may not be warranted.

Figure 1.. Cumulative Motor Vehicle Crash Incidence

Cumulative crash incidence calculated using the Kaplan-Meier survival function to account for censoring events. ED indicates emergency department.

Figure 2.. Forest Plot Results for Selected Subgroup Analyses

Squares depict the adjusted HR point estimate; horizontal lines depict the 95% CIs. Results of the main analysis and the subgroup analyses for sex, age, residential neighborhood population density, and ED disposition compare all 9223 patients in the syncope group with all 34 366 patients in the control group. Subgroup analyses based on variables available only in medical record review (cardiovascular disease, syncope causes, Canadian Syncope Risk Score, San Francisco Syncope Rule score, physician driving advice) compare the 9112 patients who had a completed medical record review in the syncope group with 34 366 patients in the control group. ED indicates emergency department and TLOC indicates transient loss of consciousness.