Despite requests to determine a patient's driving safety, many physicians do not feel competent to make such a decision because of the time required for assessment and lack of expertise and because they often do not understand their role in driver reporting. They rely on expertise from other health care providers who use road tests and/or office-based predictive tests.17 Office-based driving tests sample multiple domains, such as processing speed, visual attention, and executive function.
The Trail Making Test (TMT) is a commonly used predictive driving assessment. Data suggest that the TMT is useful in the identification of impaired drivers in a clinical driving competency program, as is a less culturally biased TMT analog, the Color Trails Test.18,19 The AMA recommends the TMT as a screening tool in predictive driving evaluations.20 The TMT Part B has been shown to predict at-fault motor vehicle collisions (MVCs) at the 90th percentile.21 The National Highway Traffic Safety Administration and American Association of Motor Vehicle Administrators support the use of the TMT and the Mini-Mental Status Exam (MMSE) as predictive tests of driving ability and as tools to identify persons who warrant further evaluation, but they note that these tests cannot be used to preclude licensure.22
The Useful Field of View (UFOV) test has also been shown to have predictive validity for driving ability.23 The UFOV measures the amount of information that a driver can attend to on a computer screen. A 40% UFOV reduction is considered “unsafe to drive” because of the loss of peripheral information. Those who struggle on the UFOV are about twice as likely to have an at-fault MVC.21 In a study of about 2000 participants older than 55, high-risk drivers were identified through cognitive testing. The combination of UFOV and TMT results predicted at-fault MVCs. In addition, slower TMT and slower UFOV performance were associated with a 2-fold increase in MVCs.21 However, Langford24 cautioned that predictive tests, such as the UFOV, are not accurate enough to be the sole factor in license revocation.
The MMSE is a predictive measure of driving. A cutoff score of 24 on the 30-point test indicates that a road test is warranted. A score of 24/30 on the MMSE indicates a 70% chance of failure on the road test while a score of 19/30 indicates a 95% chance of failure. But the DMV notes that even a score of 30/30 on the MMSE does not preclude the possibility of road test failure.22
Office-based testing is helpful, but it is no substitute for a road test. The road test is the gold standard of driving assessment. Multiple driving tasks are assessed (eg, starting the car, following road signs, using signals, maneuvering, controlling speed, solving problems). A number of studies have shown that individuals with mild dementia are capable of normal performance on road tests. For instance, Ott and colleagues9 found that the majority of subjects with early AD passed road tests. Similarly, Classen and colleagues25 showed that nearly 44% of patients with mild to moderate PD were able to pass road tests.
Considerations in driving cessation
Driving is a highly valued and socially important activity that is tied to one's sense of self-esteem and personal efficacy. Studies have shown that individuals who do not drive are more prone to social isolation, depression, early nursing home admission, increased health care costs, and decreased quality of life.26-28 Given the pragmatic and social ramifications of driving cessation, decisions about each person's driving fitness must be carefully considered. As noted, research studies indicate that decisions about driving cessation should not be made solely on the basis of advanced age or medical diagnosis. Instead, an evidenced-based approach is recommended.
When mild dementia is detected on office-based testing, a road test should be conducted. Individuals who have moderate or severe dementia should be counseled not to drive. The possibility of future driving cessation should be discussed before the onset of a medical condition that might impair driving. A number of steps can be taken to encourage the at-risk driver to stop driving. Some health providers advocate the use of a contract to provide guidelines regarding circumstances that should prompt driving cessation. Discussions should focus on risk to others and frame potential problems in medical terms. Potential legal and insurance issues should be reviewed. Loss of driving privileges will likely lead to reduced mobility and a lack of access to important work and leisure pursuits; thus, it is critical to identify transportation resources or to initiate a move to a place with adequate transportation resources. Family members can help identify resources and reinforce the need for driving cessation.
While a diagnosis of mild to moderate dementia does not necessarily preclude driving, physicians must glean information by screening for possible safety issues, initiate conversations about driving with every patient older than 70, and document the discussion in the medical record. They should also inquire about driving history, including recent accidents and near misses; confidence in driving skills; nervousness when driving; use of medications; and getting lost on familiar routes. In addition, they should probe for psychiatric issues (eg, anxiety, depression, psychosis), adverse effects of medications, and physical limitations that might affect driving.
Family concerns and cognitive function are significantly associated with road test performance and family members should be included in an assessment.29 If there is concern about unsafe driving, the patient can be referred to a hospital-based occupational therapy program for a road test.
Medical professionals may be reluctant to initiate a discussion about driving with older patients in anticipation of a negative impact on the physician-patient relationship. However, they should consider this a part of medical care that is important to ensure personal and public safety.