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History of fainting associated with double the risk of motor vehicle crashes

Do you have a history of fainting or passing out? A new study suggests you may be nearly twice as likely to be involved in a motor vehicle crash, according to an article published online by JAMA Internal Medicine.

Syncope is a sudden loss of consciousness. Although it resolves quickly on its own, syncope is a threat to public safety if it occurs when someone is driving a motor vehicle. Because about a third of patients with syncope will have a recurrence within three years, it can be tough for physicians to judge which patients with syncope are fit to drive.

Anna-Karin Numé, M.D., of Copenhagen University Gentofte Hospital, Denmark, and coauthors looked at whether patients with syncope had a greater risk of motor vehicle crashes than the general population. Their study included 41,039 Danish residents with a first-time diagnosis of syncope from 2008 through 2012. The patients were an average age of 66, about half of them were female and nearly 35 percent had underlying cardiovascular disease.

Of the 41,093 patients with syncope, 4.4 percent – or 1,791 patients – had a motor vehicle crash, many of which led to injury and a few deaths, according to the results.

Compared to the general population of Denmark, patients with syncope had almost double the risk of a motor vehicle crash. That increased risk persisted during the follow-up period and the five-year crash risk after syncope was 8.2 percent compared with 5.1 percent in the general population.

The authors acknowledge some limitations of their study, including that data regarding the circumstances of the traffic crash were unavailable. They also note that only a small proportion of patients with syncope had a motor vehicle crash.

“Since the absolute crash risk was relatively small, whether syncope should lead to restrictions on a patient’s ability to drive is a difficulty policy question that must balance multiple considerations. Syncope should be considered as one of several factors in a broad assessment of fitness to drive rather than an absolute criterion,” the study concludes.

Commentary: Syncope and the Risk of Subsequent Motor Vehicle Crash

“Applying the findings of Numé et al to individual patients requires further clinical judgment, since no patient is exactly the average and since some patients with syncope can be diagnosed and cured. At a minimum, physicians could consider asking patients about driving when eliciting a medical history. … Numé et al provide a timely reminder for clinicians to consider traffic safety when managing a patient with syncope. Doing so will not clarify the diagnosis but might help prevent a life-threatening complication,” write Donald A. Redelmeier, M.D., F.R.C.P.C., M.S.H.S.R., and Sheharyar Raza, H.B.Sc., of the University of Toronto, Canada, in a related commentary.