Driving performance in persons with mild senile dementia of the Alzheimer type.

OBJECTIVE: To assess the effect of mild senile dementia of the Alzheimer type (SDAT) on driving ability.
DESIGN: Cross-sectional study with correlation analysis.
SETTING: A university-based Alzheimer's Disease Research Center, which evaluates community-living older adult volunteers, and the university's Program in Occupational Therapy. PARTICIPANTS: Healthy elderly controls (n = 13) and subjects with very mild (n = 12) and mild (n = 13) SDAT. Dementia severity was staged by the Washington University Clinical Dementia Rating. MEASUREMENTS: The driving ability of participants on the in-car road test was scored independently by a driving instructor, blinded to the study design and to the dementia status of the subjects, and an unblinded occupational therapist. Interview-based perceptions of driving ability were obtained independently from the subjects and their collateral sources. Attentional and visuospatial performances of the subjects were assessed prior to the road test.
RESULTS: All control and very mild SDAT subjects were judged to be "safe" drivers (ie, passed the in-car road test), but five (40%) of the mild SDAT subjects had driving impairment sufficient to "fail" the road test. Neither subject self-assessment nor caregiver perceptions of driving ability consistently predicted driving performance. Attentional task performance correlated well with road test results.
CONCLUSIONS: Some SDAT subjects retain "safe" driving skills. The greater the dementia severity, the greater the likelihood of poor driving ability. Performance-based (road test) evaluations are necessary to properly determine driving skills at present, but attention and other cognitive screening measures should be developed.