6.1.1 Relevance to the driving task
Effects of dementia on driving
Dementia is characterised by significant loss of cognitive abilities such as memory capacity, psychomotor abilities, attention, visuospatial functions, insight and executive functions. It may arise due to numerous causes including Alzheimer’s disease, Huntington’s disease, frontotemporal dementia and vascular dementia. Alzheimer’s disease is the most common cause, accounting for 50 to 70 per cent of cases. It mainly affects people over the age of 70.
Dementia may affect driving ability in a number of ways including:
- errors with navigation, including forgetting routes and getting lost in familiar surroundings
- limited concentration or ‘gaps’ in attention, such as failing to see or respond to ‘stop’ signs
- errors in judgement, including misjudging the distance between cars and misjudging the speed of other cars
- confusion when making choices, for example, difficulty choosing between the accelerator or brake pedals in stressful situations
- poor decision making or problem solving, including failure to give way appropriately at intersections and inappropriate stopping in traffic
- poor insight and denial of deficits
- slowed reaction time, including failure to respond in a timely fashion to instructions from passengers
- poor hand–eye coordination.
Evidence of crash risk1
A diagnosis of dementia is associated with a moderately high risk of collision compared with matched controls. However, the evidence does not suggest that all people with a diagnosis of dementia should have their licences revoked or restricted. Throughout all stages of their condition, drivers require regular monitoring regarding progression of the disease. While for some drivers the crash risk is minimised because they choose, or are persuaded by their family, to voluntarily cease driving, others with significant cognitive decline and limited insight may require careful management and support in this regard, as discussed below.