What Could Happen During a Split Second? Slowed Reaction Time in Individuals with a Concussion

Slowed driving-reaction time following concussion-symptom resolution

Lempke LB, Lynall RC, Hoffman NL, Devos H, Schmidt JD. J Sport Health Sci. 2020 Sep 19;S2095-2546(20)30121-6

Take-Home Message

Asymptomatic individuals with a recent concussion had slower driving reaction time than healthy peers.

Summary

We know little about how people after a concussion experience impaired driving performance. Furthermore, our routine concussion assessments may be unable to determine if someone is safe to drive. Hence, there are no guidelines to inform medical professionals or patients on when it is safe to drive after a concussion. Therefore, the authors compared driving reaction times using a driving simulator between 14 people with a concussion (~16 days post-concussion) and 14 healthy controls matched for age, sex, and driving experience. The authors also tested whether a computerized neurocognitive assessment related to driving reaction times. The authors measured reaction time during 3 simulations: stoplight (green to yellow), evasion (avoiding approaching vehicle), and pedestrian (a person running in front of the vehicle) between groups. A composite reaction time score was based on the average reaction time from the 3 simulations. The participants with a concussion were asymptotic or returned to baseline signs and symptoms score before the evaluations. Participants completed a neurocognitive test that evaluated verbal and visual memory, psychomotor speed, RT, simple and complex attention, processing speed, cognitive flexibility, executive function, and motor speed. Healthy participants and people with a concussion had similar concussion histories, years of education, driving experience, and number of car violations and crashes. Participants with a concussion had slower composite driving reaction time scores than controls. The neurocognitive assessment scores lacked a strong relationship with driving reaction time scores.

Viewpoints

The authors found that despite the individuals being asymptomatic after a concussion, they had slower reaction times than the control group. This finding adds to the evidence that even after patients report no concussion signs and symptoms, impairments still exist. This raises concerns about driving safety for patients with a concussion. The authors estimated that the concussed individuals needed an additional 59 feet when traveling ~70mph and ~21 feet when traveling ~50mph to react to the scenarios compared to the healthy controls. Unfortunately, neurocognitive assessments lacked a strong relationship with driving reaction time. Hence, these tests may be unable to inform a clinician if a patient would have an impaired driving reaction time. This study highlights the need for assessments to address complicated activities of daily life following a concussion such as readiness to drive. Currently, medical professionals should have conversations with patients with a concussion about how their driving may be impaired even if they are feeling fine.