Differentiating drivers with dementia of the Alzheimer type from healthy older persons with a traffic sign naming test

Background. Dementia may contribute significantly to the driving impairment commonly associated with older adults. A brief, reliable, and sensitive screening method to identify drivers who may have cognitive impairment due to Alzheimer's disease or other dementing illnesses is needed for a variety of settings, including driver's license renewal offices. Methods. Control and demented individuals who participated in the Washington University Alzheimer's Disease Research Center (ADRC) between March 1, 1995, and November 30, 1995, were evaluated for the ability to identify traffic signs correctly. After initially testing 39 traffic signs, 10 signs were selected based on scorer reliability and their ability to discriminate cognitively normal individuals from those with dementia. Results. Sixty-six cognitively normal older people (average age 78 years) and 70 people with dementia (average age 76 years) were tested. Using a cutoff score at or below 9 (out of a possible score of 20), the Traffic Sign Naming test successfully identifies 74% of people with mild or moderate dementia of the Alzheimer type (DAT) from cognitively healthy older persons of comparable age, sex, education, and socioeconomic status; 11% of the healthy drivers were misclassified as demented. Conclusions. A brief, 2-min or less, easily administered naming test of 10 traffic signs differentiated drivers with mild or moderate DAT from cognitively normal controls. This brief test may be useful to identify older drivers in need of further assessment of driving skill.