Dementia and driving: a cognitive test approach

The deleterious effect of dementia on driving performance has been well established. Whilst all individuals with this disease will eventually need to cease driving, simply having a diagnosis of dementia is not sufficient for preclusion from driving. Instead, determinations regarding fitness to drive are left to medical practitioners. Whilst there are medical fitness to drive guidelines to support practitioners in their decision-making, there is currently no standardised objective in-office assessment which can be used to reliably make judgements regarding driving capacity for individuals with dementia. Due to the relationship between dementia and declining cognitive function, and cognitive function and driving, cognitive tests have been proposed as an appropriate tool to fill this gap.This thesis aimed to examine the current method of determining fitness to drive in Australia, and develop an evidence based alternative form of assessment that could be utilisedin-office by front line clinicians. These aims were achieved through four studies, which examined 1) practitioners'perspectives on the current system, 2) a systematic review of the literature into cognitive testing and driving in dementia, 3) a meta-analysis to provide empirical evidence for the formation of a potential composite cognitive test battery and, 4) a pilot experimental study investigating the validity of the proposed assessment. The results of the survey study suggested that front line practitioners did not find the current guidelines adequate, with the majority calling for a more objective assessment to assist with making decisions on driving capacity for individuals with dementia. The systematic review demonstrated that there is insufficient evidence to support the clinical use of either a single cognitive test or tests from a single cognitive domain. The review did, however, provide evidence for the use of composite batteries which combine multiple cognitive tests from the various domains important to driving. To date there has been little consensus on which tests should be included in this battery. Building on the results of the systematic review, the meta- xviii analysis provided empirical support for a proposed fitness to drive battery for individuals specifically with Alzheimer's Disease which included:the Mini Mental Status Examination, all conditions of the Rey Complex FigureTest, and the Trail Making Test Part A and Part B. This proposed battery also aimed to take into account practical considerations relevant to front line clinical practice. Finally, the results from the pilot study provided promising preliminary evidence that the battery proposed by the meta-analysis is able to differentiate between safe and unsafe drivers with Alzheimer's. Significant differences between safe and unsafe drivers were found in scores on four of the eight of recommended tests, with a potential pattern of scores that differentiate these drivers emerging. The research reported in the current thesis achieved its aim of exploring the current system for assessing fitness to drive, and determined that the guidelines and resultant subjective approach taken by medical practitioners is not sufficient for making reliable determinations of fitness to drive. Building from this, determining driving capacity needs to be in the form of a composite battery, and an evidence based practical, composite battery for clinical use has been proposed. Finally, preliminary empirical results support the use of this battery in making decisions regarding driving capacity for individuals with Alzheimer's disease. Overall the findings from this thesis provide a strong evidence base for future large scale, multi-site, on-road studies to validate the findings presented herein.