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Syncope patients weren't more likely to crash their car than people who had visited the emergency department (ED) for other reasons, a population-based study from Canada showed.

Across the Vancouver area, 9.2% of patients had a motor vehicle accident in the year after presenting for a first-ever episode of syncope and collapse whereas that rate was 10.1% in a matched group who had presented the same month at the same ED with other conditions (adjusted hazard ratio [aHR] 0.93, 95% CI 0.87-1.01).

That was true looking only at the first 30 days post-visit (aHR 1.07, 95% CI 0.84-1.36) and for higher risk groups:

• Seniors (aHR 0.99 for age 66-85, 95% CI 0.83-1.17, and aHR 0.71 for age 86 and up, 95% CI 0.36-1.39)
• Cardiogenic syncope (aHR 1.15, 95% CI 0.86-1.52)
• Canadian Syncope Risk Score ≥1 (aHR 1.00, 95% CI 0.85-1.19)

"More stringent driving restrictions after syncope may not be warranted," wrote John Staples, MD, MPH, of the University of British Columbia in Vancouver, and colleagues in reporting the results in .

While the study suggested syncope is not a "unique harbinger" of car accident risk, don't tell patients to fire up their engines just yet, argued an accompanying

"Considering the study's implications, there is an elephant in the (emergency) room," wrote Cary Gross, MD, of Yale School of Medicine in New Haven, Connecticut, and an associate editor for the journal, and Mark Rosekind, PhD, of Johns Hopkins School of Public Health in Baltimore.

The ED patients in the study were right with the syncope patients in having more crashes than the general population in Staples' study, with incidence rates of 13.2 and 12.2 per 100 driver-years versus 8.2 crashes per 100 driver-years.

That's a 50% increased risk for both groups who'd been in the ED regardless of the reason, Gross and Rosekind pointed out.

The difference of the study's findings compared with prior work typically using the general population as a comparator, or no comparator at all, shows the complexity of the issue and need for more data, they noted.

"The larger question raised by these findings is how to identify patients who may be at a higher safety risk for MVC [motor vehicle crash] when driving after an ED visit, and perhaps, after any acute illness in general," the editorialists noted.

"Yet it is not practical to advise every patient discharged from the ED that they cannot drive," they concluded. "Our task is to collect data that will continue to advance clinical guidance and inform policy to make all patients and roads safer."

The study used 2010-2015 universal health insurance data in British Columbia, along with data from the Insurance Corporation of British Columbia, the sole provider of drivers' licenses and mandatory basic vehicle insurance for the province.

Across all six urban EDs in the Vancouver area, 9,223 patients presenting during the study period for syncope and collapse were age- and sex-matched to four control patients (total 34,366) visiting the same ED in the same month for other conditions. Median age was 54, women comprised 51.3% of the cohort; and 11.5% lived in rural areas. All study patients had drivers licenses.

It's possible that "individuals may have curtailed their road exposure (i.e., miles or hours of driving per week) after syncope because they were instructed by a physician to temporarily cease driving, because they had independent concerns about syncope and driving, or because an underlying condition prompting syncope made driving unappealing (e.g., severe hypovolemia from intractable vomiting)," the researchers noted.

However, physicians documented having given to only 1.4% of patients in the syncope group, and their traffic violations and rate of presentation for traffic injury in the year after index visit was similar between groups -- "suggesting no substantial difference in subsequent road exposure," according to the researchers.

If physicians are advising only the highest risk patients to curtail driving, it's working, they concluded.

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