“People who have concussions often have slower reaction times as a result, and do more poorly on tests of thinking skills after their injury than their peers without concussions," says the senior study author Julianne Schmidt, PhD, an associate professor of kinesiology and a certified athletic trainer at the University of Georgia in Athens. “Our study suggests that complicated driving skills, the kind involving split-second reaction times that could mean the difference between life and death, are the ones that may take the longest to regain after you have a concussion — even when all of your symptoms have resolved,” Dr. Schmidt says. For the study, researchers asked 28 college students with valid driver’s licenses to complete two simulated driving scenarios in a lab. Half the participants had sustained a concussion, and they were compared with people the same age and sex who had similar driving histories but no head injury. In the first scenario, a stoplight changed from green to yellow, requiring participants to quickly choose whether to brake or accelerate. People who had sustained concussions took 0.24 seconds longer to react, or the equivalent of 15.6 feet of stopping distance under the test circumstances, compared with those who hadn’t experienced head injuries.
Slow Response to Pedestrians in Street
In the second scenario, a child ran into the street, forcing participants to instantly decide whether to swerve or break to avoid a collision. Participants in the concussion group took 0.6 seconds longer to react, or the equivalent of 3.3 feet in stopping distance under the circumstances in this scenario. A separate test of reaction time that required participants to hit the spacebar on a keyboard when they saw a specific word on the computer screen didn’t find a meaningful difference between the concussion group and the other participants. “This could mean traditional reaction time tests aren’t the best measure of driving responsiveness and readiness,” Schmidt says. “And that could have important public safety implications, considering more than 3 million people have sports-related concussions in the United States each year.” This pilot study hasn’t been published or peer-reviewed, and the results haven’t been independently verified. It may have had too few participants to detect some small but statistically meaningful differences between the participants who sustained concussions and people who didn’t. Some previous studies have found that people have delayed reaction times that impair driving ability in the days immediately after a concussion. But less is known about how long this lasts, when it’s safe for people to get behind the wheel, or how to accurately test driving ability after a concussion, says the lead study author, Landon Lempke, a doctoral candidate at the University of Georgia.
Earlier Studies Found Driving Impaired After Concussions
A study published in 2015 in Accident Analysis and Prevention used mental health exams, simulated maze driving tests, and other assessments to examine driving fitness 24 hours after a concussion and again two weeks later. The concussion patients took longer to complete tests at 24 hours than a control group of participants who didn’t have brain injuries. After two weeks, less than half the concussion patients had returned to driving, often citing symptoms like headaches, pain, and dizziness. Injury severity and lower scores on the tests done at 24 hours only partially explained how long it took concussion patients to return to driving, the authors of this study concluded. An older study, published in Neuropsychology, asked patients with concussions as well as a control group without brain injuries to watch videos of traffic scenes filmed from a driver’s point of view and identify potential hazards as quickly as possible. People with concussions were slower to spot hazards that the other participants. More recently, a review published in March 2020 in Sports Medicine found that people can have slowed reaction times for three to more than eight weeks after a concussion, but that these deficits can resolve given more time. Organizations such as the Centers for Disease Control and Prevention and the National Athletic Trainers Association offer guidelines for when concussion patients can safely return to sports, school, and work. But there aren’t any guidelines for resumption of driving, says Alexander Crizzle, PhD, MPH, the director of the driving simulation laboratory at the University of Saskatchewan in Saskatoon. RELATED: Post-Concussion Syndrome, What You Need to Know
Cognitive Tests Can Help Determine Readiness to Drive
“Usually, people are told not to drive for 24 hours after a concussion or even longer if they are still having symptoms,” Dr. Crizzle says. “However, typically the onus is on the person to not drive if they don’t feel it’s safe.” Patients who don’t do well on standard clinical tests for detecting impairments in cognition, motor skills, and visual skills after a concussion may want to avoid driving until subsequent tests show these deficits have resolved, Crizzle says. Tests used to assess athletes after sports concussions that focus on reaction times and other symptoms may also help determine road readiness. “Reaction time in general is an important cognitive and motor skill needed to stop the vehicle and stop at lights or signs, as well as to react to moving roadway traffic, whether that’s cars, trucks, cyclists, or pedestrians,” Crizzle says. “An impaired ability to process information quickly and made a quick movement can increase the risk of a motor vehicle accident,” he adds. RELATED: Does My Child Have a Concussion?
With Therapy, Lost Driving Skills May Be Relearned
Most people who sustain a concussion may be able to safely resume driving and other daily activities after an initial period of rest to let the brain recover, says Mark Ettenhofer, PhD, an assistant research scientist in the department of psychiatry at the University of California in San Diego. People who have prolonged symptoms that keep them off the road may improve with targeted interventions like occupational or physical therapy, says Dr. Ettenhofer. “A patient who has slowed reaction times or problems with other thinking skills may benefit from cognitive rehabilitation, which involves practicing different cognitive activities,” Ettenhofer says. “On the other hand, a patient who is experiencing persistent problems with balance, dizziness, or eye movements may benefit from vestibular rehabilitation, which involves practicing and training a different set of skills,” Ettenhofer adds.
