Predicting Road Test Performance in Drivers with Dementia

Abstract

Objectives To develop a cognitive and functional screening battery for the on-road performance of older drivers with dementia. Design A prospective observational study. Setting On-road driving evaluation clinic at an academic rehabilitation center Participants Ninety-nine older people with dementia (63% male, mean age = 74.2 years, SD= 9), referred by community physicians to an Occupational Therapy driving clinic. Measurements The outcome variable was pass/fail on the modified Washington University Road Test. Predictor measures were tests of visual, motor and cognitive functioning, selected for their empirical or conceptual relationship to the complex task of driving safely. Results Sixty-five (65%) of participants failed the on-road driving test. The best predictive model, with an overall accuracy of up to 85% when participants were blinded, included AD-8 score, the Clock Drawing Test score, and the time to complete either the Snellgrove Maze Test (SMT) or Trail Making Test A. Visual and motor functioning were not associated with road driving test failure. Conclusion A screening battery that could be performed in less than 10 minutes predicted with good accuracy a failure rating on the on-road driving test in this sample of older drivers with dementia. A “probability of failure” calculator is provided from a logistic regression model that may be useful for clinicians in their decision to refer impaired older adults for further testing. More studies are needed in larger community based samples, along with discussions with patients, families and clinicians, in regards to acceptable levels of test uncertainty.

Evaluating Fitness to Drive in Elderly with Subjective Cognitive Decline

“…No cognitive test was found to be a significant predictor of on-road fitness to drive. These results are unexpected, as previous studies predicting fitness to drive in cognitively impaired elderly did find cognitive tests to be predictive of fitness to drive outcome in elderly with dementia and MCI (Carr et al, 2011.). Our sample does not suffer from cognitive decline in the same order of magnitude as patients with MCI or dementia.…”

“…This decrease in functional abilities can lead to an overall loss of fitness to drive and an increased crash risk (Marshall, 2008). Since decline of functional abilities often occurs with disease, it is not surprising that fitness to drive studies have often focused on elderly with diagnosed diseases such as Alzheimer's or Parkinson's Disease (Carr, Barco, Wallendorf, Snellgrove, & Ott, 2011Snellgrove, & Ott, 2011Grace et al, 2005;Piersma et al, 2016).…”

Prediction of driving ability: Are we building valid models?

“…We focused on studies that primarily included drivers with suspected or confirmed cognitive impairment, including dementia. Eight studies, including three from the current authors, were found (Bowers et al, 2013;Carr et al, 2011;Hoggarth et al, 2013;Innes et al, 2007Innes et al, , 2011Lincoln et al, 2006;Ott et al, 2013;Snellgrove, 2000). These studies are summarized in Table 1.…”

Predicting Road Test Performance in Drivers With Stroke

“…As has been demonstrated in a separate sample of drivers with dementia (Carr et al, 2011), the logistic regression equation and the appropriate coefficients, intercept, and specific scores on a combination of tests can create a probability of road test failure calculator. The concept of a probability statement of a fail rating on a road test could serve as a practical discussion point for clinicians and clients.…”

“…A similar approach by Carr, Barco, Wallendorf, Snellgrove, and Ott (2011) with a sample of older drivers with dementia was recently published. If similar findings are confirmed, these tests might be adopted to determine who is most appropriate for referral for performance-based on-road testing.…”