Driving in Parkinson's Disease: Decision on driving fitness a joint process

By Ergun Y. Uc, MD
Associate Professor
Department of Neurology, Carver College of Medicine
University of Iowa

Iowa City, Iowa USA

June/July 2010

Scope of the problem. Driving is an important instrumental activity of daily living that is essential for mobility and independence. Driving safety depends on vision, cognition, motor function, and alertness, all of which can be impaired in Parkinson's disease (PD).1

The main elements of cognitive dysfunction in PD include attention problems, executive dysfunction (e.g., planning and decision making, set-shifting), visuospatial abilities, and memory.2 Mild cognitive impairment (MCI) affects about 20% of PD patients at the time of diagnosis and more than 50% across different stages of the disease. The prevalence of dementia is about 30% and can reach up to ~80% with older age and longer disease duration. Problems with vision include decreased acuity, poor contrast sensitivity, decreased processing, and impairments in spatial and motion perception.2 Medications used to treat motor dysfunction can have adverse effects on cognition and alertness.

With increasing longevity in the society, the number of elderly and cognitively impaired drivers is rising. For example, the number of drivers over age 65 is projected to increase five-fold from 1986 to 2028 in North America, accompanied by a 3-4 fold increase in drivers with dementia.3 In parallel to these changes in the general population, the number of drivers with PD and associated cognitive impairment/dementia is expected to rise, posing added challenges for determining their driving fitness and maintaining their safe mobility.

Driving performance on standardized road tests and in simulators: Consistent with the wide variety of aforementioned risk factors, drivers with PD have shown poorer performance on road tests4-8 and driving simulator experiments9-12 compared to healthy comparisons.

Drivers with PD committed more safety errors and were more likely to classified as "unsafe" on standardized road tests.4-8 Due to lower cognitive reserve, PD patients may have increased difficulties to respond to additional challenges during driving. These challenges may include driving under low visibility conditions,12 approaching a dangerous intersection,12 driving on unfamiliar roads,6 especially if they have to find their way13 or search for landmarks.14 Distractions similar to talking on a cellular phone or talking to a passenger can deteriorate their driving ability further.10,15 In general, driving is primarily a visuomotor process and dual tasks with high visual demands have greater degradation effect on driving in PD.

Impairments in vision and cognition have been shown as the main predictors of driving safety and performance on empirical testing on the road or in the driving simulator.4-15 However, motor dysfunction also contributes to driving safety,8 especially when speed of movement is a critical factor, as in responding to sudden hazards.9,12 Caregiver input can also compliment efforts to determine driver fitness.16

Real-life outcomes. Despite the consistent and unequivocal data about poorer driving performance of PD patients compared to healthy comparisons on experimental road tests and increased crash rates in the simulator,4-15 there are no well established epidemiological data on crash risk in PD.17,18 Although retrospective surveys with a variety of limitations have suggested increased crashes in PD,19,20 increased real-life crash risk in drivers with PD has yet to be shown by community based, prospective, controlled epidemiological studies.17,18 However, compared to healthy comparison drivers, patient with PD are at higher risk for driving cessation. 19,21-23 Driving cessation can lead to social isolation, lower quality of life, and depression. Severity of parkinsonism, in addition to visual and cognitive impairment, is an important predictor of driving cessation.19,21-23

Future directions. "Naturalistic" driving studies, where the driver's own vehicle can be outfitted with sensors, cameras, and tracking technology, can provide with an opportunity to see the real life driving performance of PD patients in their usual environments while living their normal life. "Naturalistic" studies would also help the study the effects of functional fluctuations (e.g., motor, mood, attention) and sleepiness using a more ecologically valid method.

Practical recommendations. PD is a clinically heterogeneous illness. The severity of cognitive, visual, and motor impairments varies between patients. Drivers with PD and neurologists have limited ability to judge driving fitness of the patients.4 Therefore, a diagnosis of PD is not enough to make a decision on driving fitness. A decision about driving fitness in PD should be a joint process including the neurologist, neuropsychologist, the patient, and the family at a minimum. Evaluation by an occupational therapist with expertise on driving can be useful to assess driving abilities.

Opinion from an ophthalmologist or psychiatrist may also be needed. The patient may be asked to take the state road test at periodical intervals. A critical aspect for driving safety in PD is good insight into the cognitive, visual, motor, and driving impairments by the patient and the family. Drivers with PD may need to use compensation strategies to minimize risk by restricting their driving to familiar roads, good weather, light traffic conditions, and avoiding distractions such as cellular phone use during driving. While an occupational therapist with expertise on driving can give potentially valuable individual advice, there are no established driving rehabilitation methods available for drivers with PD at this time.

Supported by R01 NS044930 (Predicting Driver Safety in Parkinson's Disease, PI: Ergun Y. Uc)


    Uc, EY and Rizzo, M. Driving and neurodegenerative diseases. Curr Neurol Neurosci Rep. 2008; 8:377-383.
    Uc, EY, Rizzo, M, Anderson, SW, et al. Visual dysfunction in Parkinson disease without dementia. Neurology. 2005; 65:1907-1913.
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    Stolwyk, RJ, Triggs, TJ, Charlton, JL, et al. Effect of a concurrent task on driving performance in people with Parkinson's disease. Mov Disord. 2006; 21:2096-2100.
    Stolwyk, RJ, Triggs, TJ, Charlton, JL, et al. Impact of internal versus external cueing on driving performance in people with Parkinson's disease. Mov Disord. 2005; 20:846-857.
    Uc, EY, Rizzo, M, Anderson, SW, et al. Driving under low-contrast visibility conditions in Parkinson disease. Neurology. 2009; 73:1103-1110.
    Uc, E, Rizzo, M, Anderson, SW, et al. Impaired navigation in drivers with Parkinson's disease. Brain. 2007; 130:2433-2440.
    Uc, EY, Rizzo, M, Anderson, SW, et al. Impaired visual search in drivers with Parkinson's disease. Ann Neurol. 2006; 60:407-413.
    Uc, EY, Rizzo, M, Anderson, SW, et al. Driving with distraction in Parkinson disease. Neurology. 2006; 67:1774-1780.
    Cordell, R, Lee, HC, Granger, A, et al. Driving assessment in Parkinson's disease-A novel predictor of performance? Mov Disord. 2008.
    Homann, CN, Suppan, K, Homann, B, et al. Driving in Parkinson's disease - a health hazard? J Neurol. 2003; 250:1439-1446.
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    Meindorfner, C, Korner, Y, Moller, JC, et al. Driving in Parkinson's disease: Mobility, accidents, and sudden onset of sleep at the wheel. Mov Disord. 2005; 20:832-842.
    Lafont, S, Laumon, B, Helmer, C, et al. Driving cessation and self-reported car crashes in older drivers: the impact of cognitive impairment and dementia in a population-based study. J Geriatr Psychiatry Neurol. 2008; 21:171-182.
    Singh, R, Pentland, B, Hunter, J, et al. Parkinson's disease and driving ability. J Neurol Neurosurg Psychiatry. 2007; 78:363-366.
    Uc, EY, Rizzo, M, Dastrup, E, et al. Real-life driving outcomes in mild-moderate Parkinson's disease. Neurology. 2010; 74(Suppl 2):A58.

About Ergun Y. Uc, MD

Dr. Ergun Y. Uc is an Associate Professor at the Department of Neurology, Carver College of Medicine, University of Iowa, with a joint appointment at the Veterans Affairs Medical Center of Iowa City. Dr. Uc received his M.D. degree (1988) from University of Istanbul, Turkey, and has completed his Neurology Residency (1994) and Movement Disorders Fellowship (1996) at the University of Iowa. He is the director of the movement disorders fellowship at the University of Iowa and of the movement disorders clinic at the VA Medical Center. He participates in clinical trials by Parkinson and Huntington Study Groups.

Dr. Uc's research focuses on cognitive aspects of Parkinson's disease and he is the co-chair of the Cognition/Behavior Workgroup of the Parkinson Study Group. He serves as an ad hoc reviewer for multiple scientific journals and a grant reviewer for different institutions nationally and internationally. In addition to past research support from private foundations such as American Parkinson Disease Association and Parkinson's Disease Foundation, Dr. Uc is the principal investigator of several federally funded studies including prediction of driver safety in Parkinson's disease (National Institutes of Health-R01), driver rehabilitation in PD (VA-Merit Review), and effect of aerobic exercise on function and cognition in PD (VA-Merit Review).


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