Dysexecutive Syndrome, Anosognosia, and Driver and Carer Evaluation of On-road Driving Performance: Results from a Dementia Driving Clinic

Author: Colin Field

Field, Colin, 2017 Dysexecutive Syndrome, Anosognosia, and Driver and Carer Evaluation of On-road Driving Performance: Results from a Dementia Driving Clinic , Flinders University, School of Health Sciences

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This study presents data derived from a specialist dementia driving clinic located in Adelaide, Australia. In Australia, drivers with dementia are not categorically prevented from driving. Licensing authorities typically indicate that, at some stage during the process of a progressive cognitive decline, such as dementia, driving competency will be lost, and individuals with moderate to severe dementia are considered unsafe to hold a licence. The situation is less clear for those with mild dementia or prodromal dementia (mild cognitive impairment), and is further complicated by the likelihood that different subtypes of dementia may be associated with different rates of loss of driving competency. For this reason, it is commonly accepted that the issue of the driver with dementia needs to be considered on a case-by-case basis. It is also recognised that a proportion of individuals suffering from dementia will develop anosognosia (a deficit of self-awareness), which may affect the driver’s ability to self-select a time for driving cessation.

It has been widely accepted that a comprehensive on-road driving assessment represents the gold standard by which the driver diagnosed with dementia may be examined. However, given the cost and complexity of such on-road reviews, there has been interest in the ability to screen drivers with known and suspected dementia using in-office tools, including neuropsychological assessment tools and various in-office questionnaires. Using a comprehensive on-road driving assessment as a gold standard, this project sought to examine selected neuropsychological tools (the Mini Mental State Examination [MMSE] and Trail Making Test Parts A and B [TMT-A and -B]), a self-scoring tool for drivers with dementia (Dementia Driver Questionnaire [DDQ]), tools designed to sample informant/carer opinion (Caregiver Questionnaire, based on a series of previously published informant questionnaires) and tools to measure reduced insight in drivers (the Consortium to Establish a Registry for Alzheimer’s Disease [CERAD] Insight Scale, and the Anosognosia Questionnaire—Dementia [AQ-D]), with and their association with the outcome of on-road assessments in this population. This study also had the opportunity to consider several subtypes of dementia (including mild cognitive impairment) and their effect on on-road outcomes, although it is acknowledged that the available sample size (for at least some subtypes of dementia) was limited.

The results of the current study indicate that selected neuropsychological tools vary in their relationship to on-road outcomes. An initial analysis using analysis of variance indicated no statistically significant difference between the pass–fail groups for MMSE, TMT-A time to completion and errors, and TMT-B time to completion, although there was a highly significant (p = .007) difference for TMT-B errors. However, further analysis using logistic regression indicated that a model incorporating the MMSE score plus driver age was able to distinguish between individuals who passed and failed the test (χ2 = 6.454, p = .04), and explained 10.5% of the variance in pass–fail status (Nagelkerke R2), although a model using the MMSE score alone was unable to distinguish between individuals who passed and failed the test (χ2 = 2.326, p = .127), and explained 3.9% of the variance in pass–fail status. In contrast, a model incorporating the TMT results was statistically significant (χ2 = 13.523, p = .019) and explained 19.7% of the variance. Receiver operating characteristic (ROC) curves were plotted to demonstrate the optimal sensitivity and specificity for each tool under examination.

Logistic regression analyses indicated that a model incorporating the DDQ driver questionnaire was not statistically significant (χ2 = 1.315, p = .252) and explained 2.9% of the variance in pass–fail status; likewise, components of the Caregiver Questionnaire were not statistically significant (χ2 = 4.864, p = .561), yet explained 41% of the variance in pass–fail status. In contrast, logistic regression analysis indicated that a model incorporating the CERAD questionnaire was statistically significant (χ2 = 4.807, p = .000) and explained 29.7% of the variance in pass–fail status, and a model containing components of the AQ-D score was once again statistically significant (χ2 = 9.252, p = .026) explained 28.4% of the variance in pass–fail status. For these measures, ROC curves were once again plotted to demonstrate optimal sensitivity and specificity.

This study concluded that the TMT has some association with pass–fail status, and that in-office tools to measure driver insight also have relationship with on-road outcomes. However, the results also indicate that driver opinion and informant opinion—as measured by selected tools—appear to have limited utility in screening for on-road outcomes. This thesis discusses the implications of these findings, and proposes a trichotomous decision tree for cessation of driving among drivers with dementia. This thesis also makes recommendations with respect to future developments.

Keywords: Dementia, driving, neuropsychology, anosognosia, self-evaluation

Subject: Health Sciences thesis

Thesis type: Masters
Completed: 2017
School: School of Health Sciences
Supervisor: Dr Sam Davis