Tactical and strategic adaptation of driving in Parkinson's disease

Individuals with Parkinson’s disease (PD) have been reported to have impairments at both the operational and tactical levels of driving behaviour. Increasingly, studies have further shown associations between impaired driving performance and deficits in frontal-executive functioning in PD. Older driver research suggests that functional impairments, which compromise driving ability, may be compensated for by adaptations to tactical and strategic driving behaviour. However, effective adaptation of tactical and strategic driving behaviour is dependent on a range of frontal-executive functions that are commonly impaired in PD. The aim of this thesis therefore, was to investigate frontal-executive contributions to driving behaviour in PD. A series of three studies were undertaken to investigate: (1) the capacity for tactical adaptation of driving in PD, (2) the capacity for strategic adaptation of driving in PD, and (3) whether a novel dynamic test of frontal-executive functioning, The Subtle Cognitive Impairment Test (SCIT), which measures rapid visuoperceptual processing and decision-making, offers sensitivity as a potential screening tool of cognitive functions thought to be important for safe driving. The overall results from this thesis showed that the capacity for tactical adaptation of driving is significantly limited in individuals with PD and is associated with reduced frontal-executive functioning (i.e., Trail Making Test- Part B scores) but not with disease severity (i.e., duration of diagnosis, Unified Parkinson’s Disease Rating Scale – Motor Scale Score). Tactical driving limitations were ameliorated by the timely provision of valid external cues. In terms of strategic adaptation, individuals with PD were found to self-regulate their driving to a significantly greater extent than healthy controls. Moreover, these self-regulatory practices appropriately targeted areas of self-perceived difficulty, the most prominent being avoidance of in-car distractions, a form of tactical self-regulation. Performance on the SCIT revealed a deficiency in the speed and accuracy of visuoperceptual processing and decision-making in PD, in the context of intact global cognitive functioning (as identified by MMSE). It remains to be determined whether this inefficient visuoperceptual processing is a limiting factor to the ability to adapt tactical driving behaviour in drivers with PD. The SCIT was shown to be sensitive to differences in cognition that fall within the range of normal variation on the MMSE. Future research should therefore investigate its utility as a screening tool for the early detection of mild cognitive impairment and emerging driving difficulties. In summary, these findings indicate that tactical driving ability is impaired in mild to moderate PD and is associated with deficits in frontal-executive functioning that may not be readily apparent to clinicians during examination. Importantly, findings also revealed that individuals with PD had insight into recent decline in their tactical driving ability and self-regulated their driving accordingly. Further research is required to determine whether strategic adaptations can effectively compensate for functional impairment at the operational and tactical levels in drivers with PD. The finding that timely external cues compensated for tactical driving limitations may have the greatest practical and clinical significance for extending safe independent driving in PD. It provides impetus for research into the potential rehabilitative utility of various Advanced Driver Assistance Systems for enabling safe driving in individuals with PD. Such research could lead to the availability of a larger and more varied array of car modifications capable of targeting specific driving difficulties. This could ultimately serve to broaden the application of conditional licensing and maximise participation in safe independent driving in individuals with PD.