Some studies have suggested that patients with Alzheimer's disease should stop driving. Fox and associates examined the correlation between mental status, neuropsychologic testing and open road driving performance in patients diagnosed with Alzheimer's disease.

Patients were included in the study if they had a diagnosis of probable Alzheimer's disease and wished to continue driving. Patients ranged in age from 59 to 84 years. The average length of time since diagnosis of Alzheimer's disease was four years (range: two to eight years). Each patient underwent an assessment by a physician and a clinical neuropsychologist that included a medical and driving history, administration of the Mini Mental Status Examination (MMSE), a physical examination, and a variety of sensory and motor tests. Visual acuity and visual fields were also tested. Each of the 19 participants then underwent an on-road assessment and was rated on 138 predetermined actions at specific locations along the route. The percentage of correct actions was known as the driving score.

Motor and sensory abnormalities were found in only 5.7 percent of patients, and the mean MMSE score was 21.3. The MMSE and the physician's prediction of the driving score were, in fact, associated with the percentage of correct actions on the road test, with significant numbers of patients correctly predicted to pass and to fail the road test (71 percent and 83 percent, respectively). Duration of Alzheimer's disease was not associated with the driving score.

The authors conclude that a diagnosis of Alzheimer's disease alone may not be a good reason to recommend that someone stop driving. However, the progression of this illness mandates frequent reevaluation of driving ability. An objective measure, such as an MMSE, helped physicians predict which patients would not succeed in actual driving situations but was not a sufficient measure in and of itself. An actual standardized driving test provides the best determination of the driving competence of a patient with Alzheimer's disease.