In a case-crossover study that examined health and driving data for about 3,000 drivers in British Columbia, researchers found similar rates of ED visits for syncope before the dates of car crashes (1.6%) and before control dates (1.2%).
“An emergency visit for syncope did not appear to increase the risk of subsequent traffic crash,” lead author John A. Staples, MD, MPH, clinical associate professor of general internal medicine at the University of British Columbia, Vancouver, said in an interview.
The findings were published online in the Canadian Journal of Cardiology.
Case-crossover study
Syncope prompts more than 1 million visits to EDs in the United States each year. About 9% of patients with syncope have recurrence within 1 year.
Some jurisdictions legally require clinicians to advise patients at higher risk for syncope recurrence to stop driving temporarily. But guidelines about when and whom to restrict are not standardized, said Dr. Staples.
“I came to this topic because I work as a physician in a hospital and, a few years ago, I advised a young woman who suffered a serious injury after she passed out while driving and crashed her car,” he added. “She wanted to know if she could drive again and when. I found out that there wasn’t much evidence that could guide my advice to her. That is what planted the seed that eventually grew into this study.”
The researchers examined driving data from the Insurance Corporation of British Columbia and detailed ED visit data from regional health authorities. They included licensed drivers who were diagnosed with syncope and collapse at an ED between 2010 and 2015 in their study. The researchers focused on eligible participants who were involved in a motor vehicle collision between August 2011 and December 2015.
For each patient, the date of the crash was used to establish three control dates without crashes. The control dates were 26 weeks, 52 weeks, and 78 weeks before the crash. The investigators compared the rate of emergency visit for syncope in the 28 days before the crash with the rate of emergency visit for syncope in the 28 days before each control date.
An emergency visit for syncope occurred in 47 of 3,026 precrash intervals and 112 of 9,078 control intervals. This result indicated that syncope was not significantly associated with subsequent crash (adjusted odds ratio, 1.27; P = .18).
In addition, there was no significant association between syncope and crash in subgroups considered to be at higher risk for adverse outcomes after syncope, such as patients older than 65 years and patients with cardiovascular disease or cardiac syncope.
Gaps in data
“It’s a complicated study design but one that’s helpful to understand the temporal relationship between syncope and crash,” said Dr. Staples. “If we had found that the syncope visit was more likely to occur in the 4 weeks before the crash than in earlier matched 4-week control periods, we would have concluded that syncope transiently increases crash risk.”
Dr. Staples emphasized that this was a real-world study and that some patients with syncope at higher risk for a car crash likely stopped driving. “This study doesn’t say there’s no relationship between syncope and subsequent crash, just that our current practices, including current driving restrictions, seem to do an acceptable job of preventing some crashes.”
Limitations of the study influence the interpretation of the results. For example, the data sources did not indicate how patients modified their driving, said Dr. Staples.
Also lacking is information about how physicians identified which patients were at heightened risk for another syncope episode and advised those patients not to drive. “Now would be a good time to start to think about what other studies are needed to better tailor driving restrictions for the right patient,” said Dr. Staples.
‘A messy situation’
In a comment, Deepak L. Bhatt, MD, MPH, professor of cardiovascular medicine at Icahn School of Medicine at Mount Sinai, New York, called the conclusions “well thought out.” He said the study addressed a common, often perplexing problem in a practical way. Dr. Bhatt was not involved in the research.
Dr. Deepak Bhatt
“This study is trying to address the issue of what to do with people who have had syncope or fainting and have had a car crash. In general, we don’t really know what to do with those people, but there’s a lot of concern for many reasons, for both the patient and the public. There are potential legal liabilities, and the whole thing, generally speaking, tends to be a messy situation. Usually, the default position physicians take is to be very cautious and conservative, and restrict driving,” said Dr. Bhatt.
The study is reassuring, he added. “The authors have contextualized this risk very nicely. Physicians worry a lot about patients who have had an episode of syncope while driving and restrict their patients’ driving, at least temporarily. But as a society, we are much more permissive about people who drive drunk or under the influence, or who drive without seat belts, or who speed, or text while driving. So, within that larger context, we are extremely worried about this one source of risk that is probably less than these other sources of risk.”
Most of the time, the cause of the syncope is benign, said Dr. Bhatt. “We rule out the bad things, like a heart attack or cardiac arrest, seizure, and arrhythmia. Afterwards, the risk from driving is relatively small.” The study results support current practices and suggest “that we probably don’t need to be excessive with our restrictions.
“There is going to be a wide variation in practice, with some physicians wanting to be more restrictive, but there is a lot of subjectivity in how these recommendations are acted on in real life. That’s why I think this study really should reassure physicians that it’s okay to use common sense and good medical judgment when giving advice on driving to their patients,” Dr. Bhatt concluded.
The study was supported by the Canadian Institutes of Health Research and the Heart and Stroke Foundation Canada. Dr. Staples and Dr. Bhatt reported no relevant financial relationships.
A version of this article first appeared on Medscape.com.