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The Problem of Driving & Cognitive Impairment
Many common medical conditions are known to be associated with cognitive impairment. This might mean that a person has trouble with their memory, judgement, planning, decision making, attention or other mental functions. Unfortunately, as we age, the incidence of these conditions & cognitive impairment increases. Dementia is the most common cause of cognitive impairment, currently affecting more than 1% of the Australian population and with over 1,300 new cases being diagnosed weekly.
An extensive study showed that 25% of the population over the age of 65 has significant cognitive impairment with approximately 8% being attributed to dementia and 17% due to other causes. This equates to over 700,000 senior Australians currently living with cognitive deficits. Due to the nation’s aging population, this number will escalate rapidly in coming years.
Prevalence of Cognitive Impairment by Age
(Image Source: CSHA 1991) As driving is a complex task requiring the interaction of mental abilities such as perception, memory & decision making it is not surprising that driving competence decreases as the degree of cognitive impairment increases. The graph below shows the increased at fault crash risk that is associated with various medical conditions. Cognitive impairment is associated with the most significant increase in crash risk. Increased Crash Risk by Diagnosis
(Image source: Diller, E et al. Evaluating drivers licensed with medical conditions in Utah DOT HS 809 023 Washington DC National Highway Traffic Safety Administraiton).
Studies have shown that the increase in crash risk for people with cognitive impairment is similar to that for people who are driving over the legal BAC. Unlike alcohol impaired drivers, those with cognitive impairment are impaired 24 hours a day. Sometimes the impairments are difficult to detect, even for medical professionals. One study showed that 90% of cases of cognitive impairment were missed in the primary care setting. It is therefore important that appropriate assessnment tools are used when a patient has a condition that is a "red flag" for driving decline. The issue of driving and cognitive impairment is only going to become more concerning with the aging population. The graph below shows the predicted percentage increase in driver fatalities and injuries between 2001 - 2026, the period during which the baby boomers will be in their senior years.
Projected Increase in Motor Vehicle Accidents (2001-2026) by Age
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