In the United States in 2015, there were 6,296,000 police-reported motor vehicle crashes (MVC) resulting in 2,443,000 injuries and 35,485 deaths, making this activity one of the most dangerous activities people engage in (1). Many factors contribute causally to MVC, and it is unclear how many of these MVC can be related directly to impaired driving ability after a mild traumatic brain injury (mTBI)/sports-related concussion (SRC). However, one can certainly have a reasonable concern that the impaired cognitive processes found in mTBI/SRC, such as delayed reaction time, decreased concentration, and visual disturbances may lead to more MVC. These cognitive processes needed for safe driving, if impaired, may make an already dangerous activity even more dangerous. Despite this, the question of when it is safe to drive after mTBI has not, at this point in time, been answered. Consensus statements regarding mild traumatic brain injuries do not give return to driving recommendations (2,3). Clinicians treating mTBI need to address the topic of return to driving after concussion, and the answer is not immediately available. This article reviews the relevant research literature regarding this topic.
An online literature review was conducted searching the terms “driving, safety, concussion, sports related concussion and mild traumatic brain injury” in PubMed, Embase, and Cochrane library. With these inquiries, relatively little research was found directly addressing the question of the timing of driving safety after concussion. A total of 11 articles were found which looked at various aspects of the question, but none of them sought to answer the question directly.
It has been well-established that driving performance depends on an individual’s ability to perform several different classes of cognitive tasks, and impairment in cognitive functioning is a predictor of worse driving outcomes (4,5). Much of the research in this area has been conducted in individuals with traumatic brain injuries (TBI), specifically moderate-to-severe TBI (6). However, given that mTBI/SRC affects many of the same cognitive domains as moderate-to-severe TBI, some of the evidence from this body of literature can be applied to mTBI. A meta-analysis of computerized neurocognitive testing showed that mTBI/SRC impacts neurocognitive tests, and that some of the same cognitive centers affected in TBI also are affected in mTBI/SRC though less severe (7,8). Despite knowing that mTBI/SRC affects cognitive function and can impair driving, how long these impairments last is still in question. It is up to the clinicians to decide when it is safe for patients to drive after mTBI/SRC and to provide education regarding return to driving. A recent publication of a quality improvement project by Stuart et al. (2016) points out that, at least among the clinic visits for concussion in their study, less than 10% of these visits had documented driving recommendations. It is interesting to note that there are probably many reasons for such a low rate of giving driving recommendations to patients. However, as noted above, there are no clear guidelines or consensus statements regarding the timing of driving safety after mTBI/SRC, so it has not been entirely clear what recommendations should be given to the patient (9).
Several factors make the question of “when is it safe to drive after mTBI/SRC?” difficult to answer. Direct testing of an individual’s driving performance on the road is impractical and potentially dangerous. Therefore, surrogate tests are used to predict driving performance. Some of these tests include self-reported questionnaires, nonstandardized assessments, questionnaires completed by next-of-kin, and simulator tests. All of these tests come with their own inherent level of inconsistency and imperfection which was supported by a meta-analysis of these various tests, which found that none of these tests were suitable to predict safe return to driving (10). There are some standardized assessments currently being used, which enable clinicians to detect impairment in cognitive function, but it is unclear what level of impairment is significant enough to correlate with poorer driving outcomes (10,11). The decision regarding return to driving also is nuanced in that decisions must be weighed against the potential harms of removing an activity which provides a level of independence, allows access to social activities, and increases mobility. Doing so can potentially lead to social isolation, depression, and anxiety (12,13).
Attitudes and expectations of individuals regarding their recovery after mTBI vary. In a study of 81 patients in Australia with mTBI/SRC recruited from the emergency department, the patients were surveyed regarding their expectations for recovery after mTBI. Almost half of them did not intend to moderate their driving exposure post-injury (14). In a survey of 223 collegiate student-athletes who had experienced a mTBI/SRC in the past, only 43.8% of them endorsed refraining from driving after the injury (15). Baker et al. (16) reported that only 26 of 60 participants in their study had returned to driving 2 wk postinjury, showing the variability in attitudes and cautiousness toward return to driving.
There is evidence to suggest that clinicians should consider recommending driving restrictions for the first 24 h postinjury to patients who have suffered an mTBI. A study conducted in 2010 by Preece et al. recruited 42 patients with diagnosed mTBI and 43 patients with only minor orthopedic injuries from the emergency department within 24 h of injury. The patients completed a computerized hazard perception test wherein they watched videos of traffic scenes filmed from the driver’s perspective, and then were asked to identify the traffic hazards by pointing and clicking with a mouse as quickly as possible. The patients who had been diagnosed with mTBI/SRC were significantly slower to identify the traffic hazards. This study does have some weaknesses. Randomization of study groups is not possible with this study design and there exists a small possibility that other conditions besides the mTBI/SRC contributed to the increased time for hazard perception in that group. Despite these weaknesses, the study suggested that patients with mTBI should be advised not to drive within the first 24 h of injury (17). These findings were strengthened by another study by Baker et al. (16) showing slower times in the occupational therapy-drive home maze test in patients with mTBI/SRC in the 24 h before taking the test, with faster times predicting a higher probability of passing an on-road driving test.
After 24 h to 48 h have passed postinjury, the patient’s symptoms may be beginning to resolve. This intermediate time, where the patient’s symptoms are resolving, can be the most difficult time for clinicians to make decisions about return to driving. A small study conducted by Schmidt et al. (11) examined driving performance in asymptomatic patients with recent mTBI using a desktop simulator. Testing was conducted within 48 h after symptom resolution. The asymptomatic patients who had experienced mTBI were relatively less able to keep their vehicle in the center of the lane and had more lane excursions, particularly around curves, than the control group. These findings were correlated with a number of covariables. Deficiencies in attention, working memory, verbal memory, psychomotor speed, motor speed, visuospatial ability, visuoconstructive skills, executive function, and cognitive flexibility were associated with poorer driving performance (measured by lane excursions) among the mTBI group compared to control. These findings provide some direction regarding which neuropsychological functions may predict driving performance and may be a future area of research. This study did not have a follow up regarding whether the individuals in the mTBI group, who had more frequent lane excursions, were at greater risk of motor vehicle crash at a later date. These findings also are supported by Cullen et al. (18) who found some evidence that the neuropsychological measures, processing speed, and cognitive flexibility predict ability to return to driving after traumatic brain injury. However, the generalizability of these findings to the population of patients with mTBI/SRC is unclear.
If one looks at the long term effects of mTBI/SRC on driving, the evidence is quite mixed. Schneider and Gouvier (7,19,20) tested young adult drivers about 7 yr after mTBI and found no evidence of impairment in a specific test looking at one task involved in driving called the useful field of view test. However, a newer study by Bernstein and Calamia (7) took a different approach and examined the effects of mTBI/SRC on self-reported driving ability. They found that the group with a history of mTBI engaged in more frequent aberrant driving behaviors, more frequent deliberate dangerous driving, and were at a higher risk of being involved in a car accident.
Given that the evidence seems to suggest impairments in the domains of psychomotor speed and reaction time negatively affect driving performance, many clinicians may opt to use computerized neurocognitive tests (CNT) as an indicator of readiness to return to driving since these domains are commonly tested in CNT. Indeed, a study by Macdonald et al. (21) showed that administering CNT and associated reaction time measurements may influence a physician’s decision to recommend a return to driving in high school-aged teens. It should be noted, however, that while this study provides insight into physician decision making, it does not correlate CNT or reaction time with actual driving performance or outcomes (21). The reliability of CNT is hotly debated, and a recent meta-analysis in the Journal of Athletic Training (2017) concluded that CNT have less than desirable reliability for a number of reasons (22).
A qualitative study by Bottari et al. (23) examined the perceptions and adaptive strategies of individuals having sustained an mTBI/SRC. It was found that individuals with postconcussive symptoms often develop strategies by trial and error to overcome their troubles with driving. Of course there is a period of time where they are driving and have not yet developed their coping strategies.
The decision regarding return to driving after mTBI/SRC is a highly nuanced, difficult decision with limited research to back up decisions. There is some evidence to suggest it may be reasonable for clinicians to consider restriction from driving for the first 24 to 48 h after mTBI/SRC. However, after the first 48 h have passed, there is insufficient evidence to make a recommendation regarding return to drive. Clinicians will have to weigh the evidence and make decisions on a case by case basis. For example, a physician may choose to recommend a return to driving in an asymptomatic patient at 7 d postinjury, whereas the same physician may choose to recommend against return to driving at 7 d in a patient still experiencing significant symptoms. There are some promising standardized assessments as well as cognitive domains which require further research in order to provide a standardized recommendation. It may be reasonable to develop supportive strategies which encourage patients who have sustained mTBI/SRC to use strategies to promote safe driving. For example, when a patient is considering a return to driving, clinicians may encourage them to drive at low traffic times, avoid night-time driving, reduce their speed, avoid driving while fatigued, and limit distractions (radio, conversations, etc.). This may reduce the temporary safety risk while they return to baseline.
The authors declare no conflict of interest and do not have any financial disclosures.
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