Driving simulator reveals early Parkinson's impairments that routine tests cannot detect

Driving simulator reveals early Parkinson's impairments that routine tests cannot detect

A state-of-the-art simulator uncovers the hidden driving problems of Parkinson's disease, revealing deficits missed by routine cognitive testing and highlighting the need for more realistic driving fitness assessments.

Driving simulator setup used in the experiments, consisting of a steering wheel with pedals, three monitors displaying the virtual driving environment, and a participant chair. Study: Cognitive changes associated with driving performance in Parkinson's disease detected using a driving simulator

A current oneScientific reportsThis study tested whether a proof-of-concept driving simulator could detect subtle, early driving difficulties in people with Parkinson's disease (PD) who do not have dementia. They found that despite similar average cognitive test scores, people with Parkinson's had poorer lane control and slower reaction times than people without the condition. The simulator showed driving impairments that were not fully captured by standard neuropsychological testing.

Driving requires complex integrated skills

Driving requires the rapid integration of cognitive, perceptual and motor processes. To drive safely, individuals must divide attention, maintain executive control, process visuospatial information, and manage risk. These skills support situational awareness, predicting the behavior of others, and responding appropriately to changing traffic and emotional conditions. Many driving license systems, for example in Spain, assess fitness to drive using standardized tests that assess vision, coordination, reaction time and attention. However, these tools often overlook higher-level cognitive skills that contribute to safe driving.

In Parkinson's disease, a neurodegenerative disease characterized by loss of dopaminergic function, motor symptoms are the focus of diagnosis. In mild to moderate stages of the disease, cognitive problems such as executive dysfunction, attention deficit disorder, and reduced working memory may occur. These deficits impair driving by slowing reactions, reducing accuracy in multitasking situations, and weakening the ability to plan and adapt. As a result, people with Parkinson's may struggle with sudden traffic events or complex driving environments, increasing the risk of collisions.

Traditional driving assessments rely heavily on simplified visuomotor and reaction time tasks that lack ecological validity and rarely include detailed cognitive assessments. Due to advances in simulation technology, driving simulators offer a promising opportunity to measure nuanced driving behaviors that may not be present in standard tests.

Study design and participant assessment

In this cross-sectional study, seven drivers diagnosed with Parkinson's disease were compared with seven healthy drivers matched for age and gender. All participants were under 75 years old, had a valid driver's license and had regular driving experience. PD participants met additional criteria, namely stable medication for 30 days, mild to moderate disease severity, no visual perceptual deficits, and intact global cognition.

Each participant completed a single 120-minute session that included cognitive testing and a driving simulation. The neuropsychological battery included a series of computerized reaction time tasks assessing sensory-motor speed, sustained attention, inhibitory control, decision making, and visual search.

Driving performance was evaluated using a high-fidelity simulator with three screens, realistic pedal resistance and force feedback steering. Reaction times, lane keeping, steering precision, turning accuracy and vehicle following behavior were evaluated in five driving tests. Each scenario generated quantitative metrics including lane departure, reaction times and speed differences.

Statistical analyzes included t-tests, Wilcoxon tests, analysis of covariance (ANCOVA) to separate cognitive from motor influences in reaction time tasks, linear mixed models for repeated simulator measures, and correlations to examine relationships between simulator performance, cognitive task outcomes, and PD severity.

Simulator reveals subtle driving deficits

The cognitive assessments showed that most neuropsychological test results were similar between people with Parkinson's and healthy controls. The only significant difference occurred on a symbol search test, where the PD group performed slower, indicating reduced processing speed. Reaction time tasks generally showed no differences between groups, except for one task in which PD participants responded more slowly; Further analysis confirmed that this was related to deficits in perceptual processing and sustained alertness.

In the driving simulator, the small sample size limited statistical significance, but there were clear differences in performance. PD drivers responded more slowly in one experiment and tended to drive at different speeds in another experiment. They also had a harder time maintaining lane position, spent less time in the lane, and deviated further from the center.

These impairments were closely related to disease progression, higher levodopa dose, longer disease duration, and higher disease stage, all of which were associated with poorer tracking and greater deviation. Furthermore, poorer reaction time performance was correlated with difficulty reversing, suggesting that simple reaction time measures reflect real-world driving behavior. Overall, the simulator detected visual, spatial, and attention deficits that were not captured by standard cognitive tests.

Implications for early driving assessment

The study shows that while traditional cognitive tests may appear normal in people with mild to moderate Parkinson's disease, a driving simulator can reveal significant impairments in reaction time, visuospatial control and sustained attention, all of which are essential for safe driving. The results suggest that standard assessments may miss subtle deficits that influence real-world performance. The simulator tasks were intentionally designed to mimic common driving difficulties in PD, such as: B. lane keeping, left turning and reversing, thus providing a more ecologically valid assessment environment.

Key strengths include the integration of neuropsychological testing, computer-based reaction time tasks, and simulator performance. However, the small, non-random and all-male sample limits generalizability and the simulation cannot fully replicate actual driving demands. Despite these limitations, the study demonstrates the feasibility and value of simulator-based assessments.

The results support the idea that immersive, targeted driving simulations could help detect early impairments that traditional tools miss, although several simulator differences did not reach statistical significance due to small sample sizes. This represents a step towards a more accurate assessment of fitness to drive in PD.

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