Abstract
BackgroundIn many countries, primary care physicians determine whether or not older drivers are fit to drive. Little, however, is known regarding the effects of cognitive decline on driving performance and the means to detect it. This study explores to what extent the trail making test (TMT) can provide indications to clinicians about their older patients’ on-road driving performance in the context of cognitive decline.MethodsThis translational study was nested within a cohort study and an exploratory psychophysics study. The target population of interest was constituted of older drivers in the absence of important cognitive or physical disorders. We therefore recruited and tested 404 home-dwelling drivers, aged 70 years or more and in possession of valid drivers’ licenses, who volunteered to participate in a driving refresher course. Forty-five drivers also agreed to undergo further testing at our lab. On-road driving performance was evaluated by instructors during a 45 minute validated open-road circuit. Drivers were classified as either being excellent, good, moderate, or poor depending on their score on a standardized evaluation of on-road driving performance.ResultsThe area under the receiver operator curve for detecting poorly performing drivers was 0.668 (CI95% 0.558 to 0.778) for the TMT-A, and 0.662 (CI95% 0.542 to 0.783) for the TMT-B. TMT was related to contrast sensitivity, motion direction, orientation discrimination, working memory, verbal fluency, and literacy. Older patients with a TMT-A ≥ 54 seconds or a TMT-B ≥ 150 seconds have a threefold (CI95% 1.3 to 7.0) increased risk of performing poorly during the on-road evaluation. TMT had a sensitivity of 63.6%, a specificity of 64.9%, a positive predictive value of 9.5%, and a negative predictive value of 96.9%.ConclusionIn screening settings, the TMT would have clinicians uselessly consider driving cessation in nine drivers out of ten. Given the important negative impact this could have on older drivers, this study confirms the TMT not to be specific enough for clinicians to justify driving cessation without complementary investigations on driving behaviors.Electronic supplementary materialThe online version of this article (doi:10.1186/1471-2318-14-123) contains supplementary material, which is available to authorized users.
Highlights
In many countries, primary care physicians determine whether or not older drivers are fit to drive
This study investigated to what extent primary care physicians and geriatricians can transpose screening results using the trail making test (TMT) to their patients’ hypothetical performance in an on-road evaluation
Half of the healthy drivers took less than 42 seconds to perform the TMT-A, and less than 94 seconds to perform the TMT-B (Table 2)
Summary
Primary care physicians determine whether or not older drivers are fit to drive. Studies have so far failed to define appropriate cut-off values for the TMT-B to detect unfitness to drive [11]. These issues are crucial for many of the guidelines [12,13,14], including those of the American Medical Association and the Canadian Medical Association, that recommend the TMT to assess fitness to drive. The TMT is being used by primary care physicians who, in many countries, have assumed the responsibility of detecting unfit older drivers with some relative success [15]. This study investigated to what extent primary care physicians and geriatricians can transpose screening results using the TMT to their patients’ hypothetical performance in an on-road evaluation
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