Meta-analysis of 27 studies showed caregiver reports may be unreliable; visuospatial tests were the best predictors of driving skill
WASHINGTON -- When cognitive skills start fading, how do we know when it's time to stop driving? Although there is some consensus that individuals with moderate to severe dementia should not drive, it has been much harder to screen people with mild dementia, the earliest stage of the mental deterioration typical of Alzheimer's disease. Researchers in Washington state recently reviewed all published reports on the subject and determined that for these people, specific tests of mental status and visuospatial skills predict driving performance. Honing in on specific aspects of an individual's neuropsychological functioning could help clinicians and government agencies develop the right tools to keep drivers – and everyone else on the road – safe. The report appears in the January issue of Neuropsychology, which is published by the American Psychological Association (APA).
On-road and non-road (simulator) tests both proved to be superior to caregiver reports in revealing significant relationships between neuropsychological functioning and driving ability.
"Evidence suggests that participants with dementia have an increased risk for automobile crashes and becoming lost while driving," report the authors, led by Mark Reger, PhD, of the Veterans Affairs Puget Sound Health Care System and University of Washington School of Medicine, where he is a Fellow, Psychiatry and Behavioral Sciences. The progressive course of dementia further complicates screening procedures for those who still have mild symptoms.
Reger and his colleagues observe that practitioners and government agencies face a delicate task, to "consider privacy, encourage independent living and protect the patient's civil liberties while safeguarding the patient and others on the road." As a result, as the pool of people with Alzheimer's disease and other dementias swells, it is increasingly essential to have valid and reliable procedures to accurately assess their driving risk.
The authors conducted a "meta-analysis" – a study of studies -- of 27 primary studies published between 1988 and 2003 that examined the relationship between neuropsychological functioning and driving ability for drivers with dementia. All of the studies looked at participants with Alzheimer's disease, used well-known neuropsychological tests with standard administration, measured driving ability formally (road/non-road) or by caregiver report, and reported sufficient information about results to allow computation of an effect-size estimate. The neuropsychological functions included mental status-general cognition, attention and concentration, visuospatial skills, memory, executive functions and language.
Tests of visuospatial skills generally related best to driving abilities. They may be most helpful in identifying at-risk drivers, especially as visuospatial deficits are common in early Alzheimer's and other dementias.
The authors conclude that, "Although visuospatial deficits alone are not sufficient to recommend driving restrictions, the results indicate that when visuospatial deficits are present, clinicians should complete a careful evaluation of other risk factors." They are a red flag to look for other problems.
Reger et al. were surprised to see that attention and concentration tests may be less helpful than some other tests of functioning. Their effect sizes were significant but not as large as predicted. Also, if clinicians get caregiver reports, they should take into account additional factors to assess risk.
The authors add, "Neuropsychological testing makes a significant contribution to predicting driving ability. However, they do not indicate at what level of impairment a specific patient is unfit to drive." Further research is needed to determine the right cutoffs.
Source: Eurekalert & othersLast reviewed: By John M. Grohol, Psy.D. on 21 Feb 2009
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