Evidence-Based Reviews

Driving with dementia: How to assess safety behind the wheel

Current Psychiatry. 2008 December;7(12):37-48

References

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3. Marottoli RA, Mendes de Leon CF, Glass TA, et al. Driving cessation and increased depressive symptoms: prospective evidence from the New Haven EPESE. Established Populations for Epidemiologic Studies of the Elderly. J Am Geriatr Soc 1997;45(2):202-6.

4. Hebert LE, Scherr PA, Bienias JL, et al. Alzheimer disease in the US population: prevalence estimates using the 2000 census. Arch Neurol 2003;60(8):1119-22.

5. Jang RW, Man-Son-Hing M, Molnar FJ, et al. Family physicians’ attitudes and practices regarding assessments of medical fitness to drive in older persons. J Gen Intern Med 2007;22(4):531-43.

6. Herrmann N, Rapoport MJ, Sambrook R, et al. Predictors of driving cessation in mild-to-moderate dementia. CMAJ 2006;175(6):591-5.

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9. Li G, Braver ER, Chen LH. Fragility versus excessive crash involvement as determinants of high death rates per vehicle-mile of travel among older drivers. Accid Anal Prev 2003;35(2):227-35.

10. Physician’s guide to assessing and counseling older drivers. Washington, DC: National Highway Traffic Safety Administration; 2003. Available at: http://www.nhtsa.dot.gov/people/injury/olddrive/OlderDriversBook. Accessed September 29, 2008.

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16. Molnar FJ, Patel A, Marshall SC, et al. Clinical utility of office-based cognitive predictors of fitness to drive in persons with dementia: a systematic review. J Am Geriatr Soc 2006;54(12):1809-24.

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Mr. D and his wife live in a rural area, 5 miles from the nearest grocery store. His wife never drove, and she relies on him for weekly shopping trips and to drive her to her bridge club. She denies any problems with his driving but states, “Other drivers have become so aggressive; they’re always honking at him.” Their daughter denies that Mr. D has driving problems but admits that for the last 2 years she has refused to allow her child to ride in his car.

Focused in-office assessment

Information to assess driving ability can come from the patient, family caregiver/informant, and clinical judgment. Patients with dementia are notoriously inaccurate in self-reported driving ability, either for lack of insight or as a testament to the importance of driving to their autonomy. Caregivers often are more accurate in describing a patient’s driving, but other agendas may color their responses.

In a study of patients with very mild or mild AD, 94% reported themselves as safe drivers, whereas on-road driving instructors rated <50% of drivers in these groups as safe. Caregivers were better able to classify driving performance, but 36% of their ratings were incorrect.¹²

Cognitive assessment. To assess older drivers’ cognition, AMA/NHTSA’s Guide to Assessing and Counseling Older Drivers recommends the Trail-Making Test, Part B and the clock-drawing test.¹⁰ The Canadian Medical Association suggests the MMSE.¹³ Both guides say that abnormalities in these tests indicate a need for more detailed testing, including referral to specialized driving assessment and retesting at regular intervals (Algorithm). Retest patients with mild dementia at least every 6 months or sooner when dementia severity increases noticeably¹⁴ (Box 1).^6,15

Clinical Point

Consider all aspects of the patient’s clinical status; anything could change a safe driver with mild dementia into an unsafe driver

The MMSE is widely used to screen for cognitive impairment and identify dementia or delirium, but it is not a diagnostic tool or proxy driving test. A patient with dementia may produce a high MMSE score and yet be an unsafe driver. For example, well-educated patients or those with vascular or frontotemporal dementia may retain cognitive abilities as measured by the MMSE until later in the disease.

Considerable effort has been put into developing tools to help clinicians quickly and accurately differentiate safe from unsafe drivers by assessing cognition. Unfortunately, no consistent link has been found between cognitive test results and driving outcome measures. A systematic review of office-based predictors of fitness to drive in dementia found 5 studies showing an association between MMSE scores and driving and 5 studies showing no such association.¹⁶ Thus, although the AMA/NHTSA guide recommends the MMSE, Trails B, and clock-drawing tests, cognitive tests—including these—are not sufficient to assess driving ability.

Severity of dementia. International consensus groups have attempted to create guidelines for patients with dementia who drive. American, Canadian, and Australian groups suggest that a diagnosis of moderate to severe dementia precludes driving, and the driver’s licenses of persons with these conditions should be revoked.¹⁷

In general, AD is considered severe when the MMSE score is <10 or the patient becomes dependent on a caregiver for survival.¹⁸ AD of moderate severity is more difficult to define, but a Canadian consensus conference suggested a practical approach: Patients with AD would be considered to have moderate to severe dementia and should not drive when they cannot independently perform multiple instrumental activities of daily living or any of the basic activities of daily living.¹⁹

Some dementias may impair driving more quickly than AD does. For example, hallucinations may occur early in Lewy body dementia, as may impulsivity in frontotemporal dementia and motor impairment in vascular dementia.

Box 1

Case report: AD-related behavioral symptoms

Mrs. Y visits your office for a follow-up regarding mild Alzheimer’s disease (AD), which was diagnosed 2 years ago. She passed an on-road test 3 months ago and has an Mini-Mental State Examination score of 24/30. Over the last month she has become depressed, with insomnia and mild psychomotor retardation. She occasionally has hallucinations.

Behavioral and psychological symptoms such as agitation, aggression, hallucinations, apathy, depression, and anxiety are common neuropsychiatric sequelae of AD. Little is known about the risks these symptoms pose to road safety, but we recommend that clinicians strongly consider the potential for impaired driving.

In a longitudinal study, cognitive impairment and behavioral disturbances—especially agitation, apathy, and hallucinations—were strong predictors of driving cessation among patients with dementia.⁶ Furthermore, a case crossover study of patients with dementia found a 54% increase in risk of motor vehicle collisions associated with the use of psychotropic medications.¹⁵

Consider all aspects of the patient’s clinical status, including neuropsychiatric symptoms, psychotropic medications, comorbid medical conditions (including hearing and vision impairment), and concomitant therapy for medical conditions. Any could change a safe driver with mild dementia into an unsafe driver.