Prediction of On-Road Driving Performance in Patients with Early Alzheimer's Disease.
Brown LB, Ott BR, Papandonatos GD, Su YMS, Ready RE and Morris JC;
Commented by , 22 Mar 2005
Aims
To validate a simple rating of driving ability in older adults with mild Alzheimer's Disease by the participant, an informant, and their Neurologist.
Methods
Participants were 75 individuals, 25 healthy (family) controls and 50 individuals enrolled in a longitudinal study of driving and dementia. 17 met criteria for possible Alzheimer's Disease (AD), 33 for probable AD, using NINCDS/ADRDA criteria. All scored 0.5 - 1 on the Clinical Dementia Rating Scale (CDR), indicating mild or very mild severity of dementia.
Exclusion criteria included physical, ophthalmic or (other) neurological and psychiatric disorders that might impair driving. Stable treated depression, and being on a variety of anti-dementia drugs (eg., gingko biloba, anticholinesterase inhibitors, Vitamin E) did not preclude entry into the trial.
Procedures
Participants and informants rated driving ability on a 3 point scale:
- "drives alone with good sense of direction and good driving skills"
- "driving, but with some difficulty"
- "unable to drive safely"
A research assistant collected driving history, including accidents and violations over previous 3 years, miles driven per month, and miles driven with informant per month.
The Neurologist, who was blind to participant and informant ratings, assessed ability to drive on the same scale, based on his overall clinical, neurological, and neuropsychological examination, together with test results.
Within two weeks of this clinical assessment, an extensive on-road driving test was administered by a an experienced Driving Instructor, who used an 108-item score on safe driving.
Results
Analysis of variance showed that the on-road driving test score differed significantly between the 3 groups. The normal control group performed significantly better on the road test than either of the AD groups; mildly demented participants did not differ significantly in performance from very mild demented participants. 94 % of AD participants rated their driving as safe.
Analysing the 50 individuals with dementia, the Physician had the highest percentage of correct categorical classification (74 %), followed by informant (64 %), then participant (53 %), as ranked against the expert's driving analysis.
Dr Seymour's comments
A car can be considered a "loaded gun" when in the wrong hands. Whilst older drivers are, in general terms, safe drivers, those with Alzheimer's Disease often (though not inevitably) over-rate their driving ability and often lack insight into the hazards.
Current literature suggests it is difficult to predict through any single neuropsychological test, or battery of tests, an individual's safety and capacity to drive. It is therefore of interest that the Neurologist's assessment was significantly related to the "gold standard" of on-road driving score, and therefore this study is an addition to the literature.
When related to instructor ratings of safety, the Neurologist's ratings were the most sensitive and specific. Even so, he did not get it right on every occasion, which has potential medicolegal implications.
My conclusion is that Governments and driving licensing authorities ought to make more effort to make on-road driving assessments - which is likely to remain the "gold standard" for the forseeable future - more widely available to assess driving capacity of people with mild dementia.