Parkinson's disease and driving
Driving in the elderly
Changes with age
As people become older, there are a number of changes and some of these relate to driving.
Vision changes as people age and it becomes increasingly difficult to sort out the relevant information from a number of competing demands for attention. This is made more difficult if a number of tasks are attempted at once, such as changing radio stations while driving in traffic.
The second major change is in the time it takes to process information. Once the important messages have been sorted out from those that are irrelevant, decisions have to be made based on that information and elderly drivers need more time to make those decisions.
Other relevant age-related changes are slower reaction time and altered depth perception.
Statistics
Studies of elderly drivers have shown that, while elderly drivers seem to have fewer accidents, if accident rates are based on the actual number of miles driven, the only drivers with a higher accident rate are teenagers. Accident rates drop from age 20-30 and are then relatively stable until over 65, when they start to climb, with a sharp increase over the age of 80.
The types of accidents older people are likely to be involved in are making wrong turns, failing to give way, moving out into traffic wrongly and ignoring traffic lights. They are, however less likely to cause drinking related accidents than the rest of the population.
Driving and Parkinson's disease
Driving skills
Although there have been very few studies of driving in people with Parkinson's disease, there are many similarities to the situation with elderly people.
Driving involves a number of activities, including perception, information processing, judgement, decision-making, co-ordinated limb movements, reaction time tasks, continuous tracking and attention. Parkinson's causes a number of abnormalities in these areas. For instance, movement co-ordination, visual perception, information processing, reaction time and maintenance of attention can all be affected.
Drivers with Parkinson's
There have been several studies into the driving ability of people with Parkinson's. One study, using a simulator, lab tests and a driving test, showed that compared with a group of the same age and sex, Parkinson's people had difficulties with accuracy, reaction time and light recognition.
A second study used a simulator and a group of Parkinson's people with a lack of Parkinson's complications, together with controls. The study showed that those with Parkinson's had reduced grip strength, reduced speed of movement, increased reaction times, increased frequency and more serious errors. Of the 28 people in the study, 18 had a driver's license (although 5 of these no longer drove), 5 had given up their licence and 5 had never driven. The results for the whole group were the same as for those with a licence. The average time since diagnosis was 8.75 years and the level of disability was moderate.
In a test of 20 mild to moderately affected Parkinson's men who were regular drivers, compared to a control group, even those with mild Parkinson's were affected. There was an increase in risky faults which could lead to accidents and the most problems were in turning across traffic, driving in traffic and in urban conditions. There were no difficulties in highway driving. Lab tests (including a computer-based 'useful field of view' program), showed that there were difficulties in visual memory, choice reaction time and information processing, even in those with mild Parkinson's, and that these correlated with driving difficulties.
One study showed that people with Parkinson's who were still driving compared with those who had stopped driving were younger (66 v 74 years old) and had been diagnosed for less time (5 v 8 years).
Correlation between severity of Parkinson's and driving ability
There have been a number of studies which have tried to link the severity of Parkinson's with the level of impairment of driving skills but there are no clear links. There is, however, some evidence that there is some increase in the number of accidents in people in the mid stages of Parkinson's.
Accidents
Like the elderly, people with Parkinson's seem to have more accidents per kilometre driven, but overall they have fewer accidents per driver. It would appear that many people with Parkinson's put limits on themselves and choose to restrict their driving.
The social importance of driving
Driving is important in maintaining independence and self esteem. People who are used to driving and are no longer able to may become isolated and dependent, particularly if their partner is unable to drive. There may no longer be easy access to shops, doctors and social activities and, wherever possible, alternatives need to be developed to remain mobile and independent.
As well as the physical aspect of not driving, there are the emotional implications of not driving and giving up something that has always been a symbol of coping independently.
In one study of the 62 patients who still had their licences, only 32 were still driving, indicating that, even though they recognised that they should not be driving, they were unwilling to take the final step of giving up their licence — it is harder to give up a licence than to stop driving.
Driving less or not at all
Insight
An analysis of people who were driving with Parkinson's showed that only 40 per cent were still driving after 5 years and that those who were driving had adopted strategies to drive at times and in conditions that were less dangerous. Of those who had stopped driving (32 out of 150 in one survey), most (18) had stopped because they were concerned about their own safety, and others (10) because of concerns for the safety of their family.
It would seem that people with Parkinson's are aware of the difficulties associated with driving and use strategies to enable them to keep driving safely.
Predicting driving ability
In a study to assess who could best predict the driving ability of a person with Parkinson's, the average score given by driving instructors was 5.8. Neurologists were the worst at predicting driving ability, giving an average score of 8.0. Patients, in spite of their insight into driving difficulties, gave themselves a score of 7.8 and psychologists seemed to be the best predictors with a score of 5.7. There were no scores from family members.
Deciding not to drive
There are a number of unanswered questions relating to driving with Parkinson's and, because of the variability in the disease, there are no simple answers.
- How to decide if a person can still drive is not clear-cut, as the ability to drive is not clearly linked with Parkinson's symptoms.
- The type of testing to use is also difficult, with road testing being the most sensitive and correlating well with simulators (which are not readily available) and clinical tests not correlating well.
- There have not been studies into physiotherapy or occupational therapy assessment as a tool to evaluate driving, but some neurologists are referring to them for testing.
- The best way to assess driving capability seems to be through a driving test, but there has been no consideration given to the possibility of retraining for drivers who are having difficulties.
- The role of family members in assessing driving ability has not been looked at.
- Who decides whether a person should be driving is also difficult, with neurologists and families reluctant to take on the responsibility. (Some neurologists listen to the family and use their assessment as a basis of making a decision about driving.)
- The most straightforward way of deciding is when the person with Parkinson's decides for themselves that it is time to give up driving.
- The possibility of restricted licences is one which also needs to be considered.
Reference:
'Driving and Other Important Activities in Parkinson's Disease.' William J. Weiner, Miami, Florida; Stewart A. Factor, Albany, New York. Seminar presentation at the 5th International Congress of Parkinson's Disease and Movement Disorders, New York 1998.
Last Reviewed: 22 July 2002
