Syncope and Risk of Subsequent Motor Vehicle Crash

Quick Takes

  • Syncope while driving can cause a motor vehicle crash, but limited data inform current driving restrictions after syncope.
  • Findings from this population-based retrospective cohort study suggest that stringent driving restrictions may not be warranted.

Study Questions:

What is the motor vehicle crash (MVC) risk among patients visiting the emergency department (ED) after their first episode of syncope?


The study cohort was comprised of patients in British Columbia, Canada, visiting any one of six urban EDs for syncope and collapse. Patients were matched to four control patients visiting the same ED in the same month for a condition besides syncope. Medical records were linked to administrative health records, driving history, and crash reports. Incidence as a driver in an MVC in the year following the ED visit was then compared between individuals with syncope and matched control patients. Insurance claim data and police crash reports were used to identify crashes. Two trained medical record abstractors assessed the likelihood that syncope occurred and the likely etiology.


A total of 9,223 patients with syncope and 34,366 matched controls were included. MVC incidence rates among the syncope and control groups were higher than the general population (12.2, 13.2, and 8.2 crashes per 100 driver-years, respectively). Vasovagal was the most common cause of syncope. Following the index ED visit, 846 first crashes occurred in the syncope group and 3,457 first crashes occurred in the control group within the first year (9.2% vs. 10.1%; adjusted hazard ratio [aHR], 0.93; 95% confidence interval [CI], 0.87-1.01; p = 0.07). Crashes by patients with syncope (aHR, 1.07; 95% CI, 0.84-1.36; p = 0.56) as well as subgroups at higher risk of adverse events after syncope (e.g., age >65 years; cardiogenic syncope; Canadian Syncope Risk Score ≥1) were also not significantly increased in the first 30 days after the ED visit.


Patients visiting the ED with first-episode syncope have subsequent MVC risk similar to the average ED patient. Current driving restrictions after syncope may be too stringent.


Although syncope while driving can cause an MVC, limited data inform current driving restrictions after syncope. This extensive retrospective population cohort study demonstrated that patients visiting the ED with first-episode syncope had similar MVC risk to the average ED patient over the subsequent year. Of note, the high rate of vasovagal syncope in this study cohort (over two thirds), in part explains the nonsignificant crash risk compared to controls, as they would not normally be restricted.

Other limitations include: 1) inclusion of only patients presenting to the ED, as syncope patients are also evaluated in clinics and/or may not seek immediate attention at all; 2) physician-directed restriction or self-restriction of both syncope and control patients from driving, reducing incidence of MVCs; and 3) restriction of high-risk syncope patients, also lowering MVC incidence. Further study is warranted on the necessity of the general 6-month restriction from driving in the United States for unexplained syncope.

Clinical Topics: Arrhythmias and Clinical EP, Prevention, Implantable Devices, SCD/Ventricular Arrhythmias, Atrial Fibrillation/Supraventricular Arrhythmias

Keywords: Accidents, Traffic, Arrhythmias, Cardiac, Emergency Service, Hospital, Insurance, Accident, Medical Records, Motor Vehicles, Police, Risk Factors, Secondary Prevention, Syncope, Syncope, Vasovagal

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