Section 7:
Diseases of the Nervous System

Epileptic Seizures and Driving Literature Review

Epileptic seizures, which can result in abrupt loss of consciousness or loss of bodily control, place the individual at risk for motor vehicle crashes if the seizure occurs while driving. Because of the potential for rapid incapacitation of the driver, and of the unpredictability of the illness, epilepsy is one of the few medical conditions with driving restrictions that are enforced almost worldwide. The first report of a motor vehicle crash as a result of a seizure was in the early 1900s (Thakwitzer, 1906). Since then, a number of studies have reported an increased risk of crashes in individuals with epilepsy, with rates of crashes for individuals with epilepsy ranging from 1.5 (Crancer and McMurray, 1968; Keys, Martin, Barrow, and Fabing, 1961) to 1.95 (Waller, 1965) times greater than controls. More recent studies are equivocal: Taylor, Chawick, and Johnson (1996) suggest that the crash rates of individuals with epilepsy are no greater than the general population, after adjusting for age, gender, driving experience, and mileage, whereas results from Diller et al. (1998) suggest that crash rates are elevated for individuals with epilepsy (see Table 16). Table 16 provides a summary of results from older and more recent studies investigating the risk of crashes in individuals with epilepsy.

The majority, if not all, of the studies examining the crash rates of individuals with epilepsy have methodological limitations. For example, many studies are based on self-report, using questionnaire surveys or clinical interviews (Gastaut, and Zifikin, 1987; Hasegawa, Gastaut, and Zifikin, 1991; Stanaway, Johnson, and Lambie, 1983; Takeda, Kawai, Fukushima, and Yagi, 1991, Taylor, Chawick, and Johnson, 1996). In those studies, estimations of the crash rates of drivers with epilepsy may, in fact, be underestimations given the propensity for under-reporting of crashes in this population due to fear of license revocation (Andermann et al., 1988; Salinsky, Wegener, and Sinnema, 1992). In other studies, individuals with epilepsy were identified through state licensing authorities (Popkin and Waller, 1989) or crash rates of persons with epilepsy were determined through police identification following a crash; individuals were then referred for a medical evaluation on suspicion of epilepsy (Vander Lugt, 1975). In those instances, crash rates of drivers with epilepsy may be inflated because individuals with moderate to severe epilepsy are likely to be overrepresented and individuals with fully controlled or infrequent seizures are likely to be under-represented.

As noted previously, results from earlier studies (e.g., Crancer and McMurray; Keys et al., 1961; Waller, 1965) suggest that individuals with epilepsy have increased crash risks. However, recent advances have resulted in improved medications for controlling seizures. Moreover, increased understanding by the medical community and by patients of the causes and effects of epilepsy has, undoubtedly, resulted in improved seizure control for many individuals with epilepsy.

Finally, few studies take into account factors such as sex, age, and driving exposure, factors known to affect crash rates in the general driving population. Noteworthy in this regard are the findings from Taylor et al. (1996) showing no differences in crash rates between individuals with epilepsy and those in the general population, once age, gender, driving experience, and mileage were controlled. However, results from that same study indicate that individuals with epilepsy have a 40 percent increased risk of more severe crashes than non-epileptic individuals.

Table 16 Summary of Studies Examining the Risk of Crash for Individuals with Epilepsy