Although driving is formally recognized as a privilege, government-directed programs and other social structures suggest that driving is a near universal and essential function in our society. However, our society poorly supports individuals who no longer drive. Patients who forego driving often lose independence, compromise their ability to work and provide for their dependents, and have difficulty maintaining social contacts, continuing involvement in personal interests, and participating in community activities. These losses have profound implications for many patients in terms of emotional and physical well-being, quality of life, and evaluation of self-worth. The physicians' role often is pivotal in determining physical and mental conditions which may impair a patient's ability to drive. In some situations, physicians have an ethical obligation to the safety and welfare of the community to report such disabilities to the authorities. However, this obligation must be in proportion to actual and relative risk and, in order to be just, must cover all disabilities that convey similar public risk. Furthermore, this disclosure must lead to concrete actions in the interest of public safety. Otherwise, the breach of patient confidentiality by physician cannot be justified ethically.
According to the National Highway and Transportation Safety Administration (NHTSA), crash involvement rates per miles driven remain low until age 74 and increase sharply thereafter.5
For drivers over age 85, crash rates are only 1,500 per 100 million miles compared to 2,000 for drivers ages 15 to 19. However, younger drivers drive twice the miles as older ones, and absolute numbers indicate that crashes are primarily a young driver problem. Older drivers are more frail and fatality rates per miles driven among drivers over 85 years are 2.5 times that of the youngest drivers.
Patients who may be considered for revocation or limitation of driving privileges include patients with an ongoing or persistent impairment such as visual defects or dementia, or patients with a propensity for episodic disability such as epilepsy, cardiac dysrhythmias, or substance dependency.
Most conditions that compromise driving safety produce impairment along a continuum, e.g., hearing loss, visual impairment, and cognitive impairment. The presence of a condition in and of itself may not correlate with risk. Particular features of a condition may be a better index of driving risk. For example, mildly demented drivers who have difficulty performing visuospatial skills such as copying a figure, are more likely to have poor driving skill.6,7
Alzheimer dementia is of particular concern for traffic safety given its prevalence and its effect on driving skill. Alzheimer dementia occurs in about 10% of persons over the age of 65 years and in 20% of persons over age 80. A case-controlled study of MVAs among Alzheimer patients suggested an odds ratio of 7.9.8
Interactive driving simulators and performance-based road tests can provide an objective measure of driving ability in demented persons.9,10
A licensing agency assessment using a battery of tests for elderly drivers with dementia or other aging-related medical conditions is currently being field tested.11
Since 1988, California physicians have been required to report older persons with Alzheimer's disease and related disorders to their local health departments. This information is then reported to the Department of Motor Vehicles (DMV).12
Visual impairments are associated with MVAs.13
In a 5-year, case-controlled study, drivers with cataracts were 2.5 times more likely to be in an at-fault MVA.14
Other ophthalmic conditions which may impair driving ability include myopia, glaucoma, and macular degeneration. Screening by the DMV for visual acuity is routine, albeit crude, and when required at license renewal, may be associated with decreased fatal crash risk for older drivers.15
Patients diagnosed with sleep apnea syndrome are 2 to 6 times as likely than healthy control subjects to be involved in a MVA.16,17
Migraine headaches may be associated with a 2-fold risk of MVAs. Benzodiazepine use confers a similar risk of MVAs.18,19
Of note, the use of cellular telephones while driving is associated with a quadrupling of the risk of a collision during the brief time interval involving a call.20
One study found that talking on a cellular telephone more than 50 minutes per month while driving was associated with a 5.59-fold increased risk of a traffic accident.21
Epilepsy is a paradigm disease that involves physicians as both care givers to patient-drivers and consultants to regulatory authorities. Driving restrictions for people with seizure disorders are designed to protect the public safety but may interfere with personal freedom and livelihood.22
As opposed to dementia, epilepsy is more common in younger populations who commonly have family and child-rearing responsibilities. To avoid loss of driving privileges, patients with epilepsy may choose not to report seizures to their physician or to the DMV.11
There is no clear consensus among physicians as to when persons with epilepsy may appropriately resume driving. Data suggest a 93% risk reduction for a MVA after 1 year of being free of seizure.23
Seizure disorders are disproportionately reported compared with other similarly disabling neurologic conditions,24
such as Parkinson's disease, which greatly compromise driving ability early in the disease course.25
Physicians are not well prepared to evaluate for patient suitability to drive.7,26
The NHTSA notes, “Disability is multidimensional and extremely complex …”, and “Disabilities are rarely if ever isolated entities. Rather, they almost always reflect the presence of chronic medical conditions, the positive and adverse aspects of their treatments …” The NHTSA appropriately recognizes the lack of well-validated measures of physical and cognitive disability pertaining to driving and cites this deficiency in their research agenda for older drivers.27
Compounding the difficulty in objectively measuring conditions that potentially affect driving ability, some judgment must be made about the nature of the specific disability, the degree of disability, the incidence of episodic disease, and the likelihood of a driving mishap. Objective assessments of excessive driving risk must be followed by assignment of responsibility to effect cessation of driving.