CHAPTER 7 DRIVING
Practice of Geriatrics
CHAPTER 7 DRIVING
David B. Reuben, M.D.
The population of older drivers is rapidly increasing. Between 1984 and 1994, the number of licensed drivers 70 years of age or older increased by 45% to 15.7 million.1 Moreover, the rate of increase will rise dramatically as the “baby boomers” reach age 65 in 2010. Although driving skills appear to be well preserved in healthy older persons,2 the diseases that accompany aging increase the risk of unsafe driving. As a result, older drivers have the highest crash rate per mile driven of any age group except teenagers. Although older drivers represent only 9% of all licensed drivers, they account for 13% of all traffic fatalities.1
Many older drivers, when confronted with the diseases of aging, simply decide to stop driving. Based on several recent studies, the most common factors associated with ceasing to drive include increasing age, female gender, functional impairment, neurologic disease (including dementia, Parkinson’s disease, and stroke), and visual impairment.3,4 and 5 Alternatively, older people may change their driving patterns. For example, older persons concentrate their driving during daylight and off-peak hours (9:00 AM to 4:00 PM) and are more likely than younger persons to rely on public transportation for trips more than 75 miles from home. They also tend to drive on surface streets and they avoid freeways, which are safer on a per-mile basis.6
Older drivers also tend to be involved in particular types of violations and crashes. Failure to yield the right-of-way or disobedience of signs and signals are major contributors to crashes among older persons.7 Compared to younger people, they also have a much higher rate of collisions when making left turns but are much less likely to be intoxicated with alcohol when involved in traffic fatalities.
Because licenses to operate a motor vehicle are conferred by the state, it might be argued that the physician has little responsibility in decisions regarding continued driving by his or her patient. However, other than simple tests for gross sensory impairments (e.g., vision testing), state departments of motor vehicles have little insight into age-related physiologic changes and medical conditions that may impair driving ability. Moreover, the physician’s relationship to the patient as his or her advocate allows the issue of whether to continue driving to be raised in the context of concern about the well-being of the patient rather than in the administrative setting of a licensing station. This relationship can also extend to assistance by the physician in mobilizing family and social service resources to help maintain the older person’s mobility in the community in the absence of driving. Often a frank discussion and careful planning can obviate a stressful and sometimes humiliating experience with state licensing authorities. Thus, the roles of the physician and the state in regard to the older driver are complementary.
The physician can best address the possibility of age-related disabilities that may impair the capacity to drive by knowing the potential risks of physiologic changes and the common diseases that occur with aging, inquiring about the presence or absence of these, and searching for pertinent findings on physical examination. Physicians must also know and follow state guidelines for reporting potentially unsafe drivers.
Age-Related Physiologic Changes that May Affect Driving
There are three general categories of age-related physiologic changes that may affect driving: sensory, cognitive, and psychomotor functioning, including reaction time8 (Table 7-1). Among sensory changes, those affecting visual function are most important. However, with some exceptions, the data linking these changes to violations and collisions are inconclusive. Constriction of horizontal visual fields, alone or combined with measures of visual acuity and contrast sensitivity,9 has been predictive of crashes. Among cognitive changes, impaired visual attention as measured by the useful field of view has been associated with crashes during the previous 5-year period.10
TABLE 7-1 AGE-RELATED PHYSIOLOGIC CHANGES THAT MAY AFFECT DRIVING
Diseases and Disorders Commonly Occurring in Older Persons that May Affect Driving
Far more important than age-related physiologic changes in determining the risks of unsafe driving are diseases that affect older people (Table 7-2). For many of these diseases and disorders, the relationship is only speculative. However, recent epidemiologic studies have clarified the risk for some conditions. The most consistent relationships have been demonstrated for neurologic diseases and diabetes mellitus, and there is lesser support for coronary artery disease, depression, alcohol abuse, falls, and foot disorders.11,12
TABLE 7-2 DISEASES AND DISORDERS THAT COMMONLY OCCUR IN OLDER PERSONS AND MAY AFFECT DRIVING
The cognitive impairments that define dementia—including the hallmark features of memory loss, visual-spatial disturbances, and impaired judgment—place the person with dementia at increased risk for unsafe driving. Other, more subtle impairments that are characteristic of patients with Alzheimer’s disease, such as poor ability to engage in divided attention, poor ability to engage in selective focused attention,13 and visual field limitations,14 may contribute to or aggravate this risk. The potential risk of unsafe driving by drivers with dementia has been substantiated in most15,16,17 and 18 though not all19 retrospective studies that have demonstrated higher rates of motor vehicle crashes and in performance-based studies that have demonstrated poor driving skills on road tests.13,20,21 Although the precise magnitude of risk incurred by the driver who has dementia cannot be estimated from the existing literature, this risk is likely to be substantial. One study reported that 33% of demented persons who were still driving had had motor vehicle crashes or moving violations within the previous 6 months.1
An increased risk of motor vehicle crashes has also been demonstrated for persons with advanced Parkinson’s disease22 and seizures, although the increased risk for the latter is modest.23 Because of the wide variation in deficits that accompany stroke, the risk associated with this disorder has been particularly difficult to assess.
Despite the presumed risk of crashes due to arrhythmias, sudden death, and ischemia, well-designed studies that substantiate or estimate the magnitude of such risks are lacking. Although a small study demonstrated that persons with severe sleep apnea had higher crash rates than all drivers in Virginia,24 studies assessing crash risk in drivers with chronic obstructive pulmonary disease have not been conducted.
Diabetes can increase the risk of unsafe driving because of the effects of the disease (e.g., blurred vision due to poor metabolic control, retinopathy, neuropathy) or complications associated with treatment (e.g., hypoglycemia). The risk of collisions resulting in injury to older persons with diabetes has become better defined. The risks were substantially increased among all older diabetic drivers, particularly those taking insulin or oral agents, those with disease of more than 5 years’ duration, and those with coexisting coronary heart disease.11 In contrast, those who had had the disease for a short time and those being treated with diet alone had no increased risk. These findings are consistent with a variety of explanations but certainly raise concern about the increased risk that might be associated with increased efforts to achieve tight blood glucose control.
Although arthritis is the most common self-reported condition among older persons, and the accompanying limitations in range of motion (e.g., difficulty in turning and looking to the rear to change lanes) might affect safe driving, the impact of arthritis on adverse driving events (e.g., violations and crashes) has not been systematically studied. However, foot deformities and impairment in functional status (not walking at least a block a day) have been associated with automobile crashes and moving violations.12
Eye diseases, which are common among older persons, probably increase the risk of unsafe driving through the same mechanisms described earlier under age-associated physiologic changes. Although all eye diseases may decrease visual acuity, some produce other characteristic effects (e.g., visual field loss with glaucoma, reduced contrast sensitivity with glaucoma or cataract, decreased resistance to glare with cataract) that may augment the risk beyond that of a simple loss of acuity.
The role of drugs in increasing the risk of unsafe driving may be substantial given the wide use of medications that have psychoactive properties in older persons. Other than alcohol, which remains a contributing factor in fatal crashes among persons 70 years of age or older (albeit less frequently than in younger people), research on the risks associated with prescribed medications has been inconsistent. The most convincing data implicate cyclic antidepressants and benzodiazepines.25 Nevertheless, the systemic effects, particularly those on cognitive and psychomotor function, of many medications commonly used in treating older persons (see Table 7-2) have the potential to compromise driving safety in individual patients.
Few clinicians caring for older persons routinely focus specifically on the patient’s driving capabilities in the course of giving clinical care. Rather, driving problems usually are brought to the physician’s attention by family members or other concerned parties. Nevertheless, the salient points regarding assessment of medical considerations relevant to driving can be integrated into the standard initial and subsequent evaluation and management of the older patient.
For example, the use of a previsit questionnaire that can be completed by patients, family members, or caregivers can identify the medical conditions and medications mentioned earlier26 and can determine whether the patient currently drives. Patients who are still driving should be asked about crashes, “near misses”, or moving violations. If any of these have occurred, the circumstances should be determined. Sometimes simple suggestions may allow the patient to continue to drive safely under designated conditions. For example, if a patient with cataracts and visual acuity that is not severely compromised has had “near misses” at night, such an individual may be able to continue to drive safely by restricting driving to the daytime. Many states have adopted the practice of granting graduated or restricted licenses that permit driving only under specified conditions. If there is a concern about safe driving based on any medical considerations identified, a more detailed history of the person’s driving patterns should be determined. Perhaps most important is a determination of the person’s need to continue to drive. For example, does the patient need to drive to perform essential errands such as shopping and banking? Are other alternatives (e.g., shopping services, family members, neighbors) available to provide these services should the person cease driving?
The physical examination should focus on vision, mental status, mobility, and possible neurologic conditions. For most older persons, there is no need for a separate “driving-specific” examination. For example, copying a pentagon, which is a component of the commonly employed Mini-Mental State Examination, has been found to be an independent predictor of adverse driving events.12 Visual acuity, which can be tested by office staff using a Snellen eye chart, is only one component of the visual function necessary for safe driving. More detailed visual testing (e.g., visual field testing) is usually conducted by an optometrist or ophthalmologist, and these records should be requested if there is a question about visual impairment. Gait, balance, and mobility evaluations, including cervical neck motion, are components of the initial physical examination of most older persons. In conducting these examinations the clinician must be aware that impairments discovered on the standard examination may contribute to unsafe driving, and he or she must synthesize the relevant information accordingly.
The physician’s ability to assess driving capability adequately is quite limited but can be supplemented by appropriate referral to rehabilitation therapists, particularly occupational therapists, who have developed expertise in assessing and treating physically impaired drivers. Frequently, these assessments include simulators and on-road evaluations. Unfortunately, the quality of driver assessment programs varies widely, and physicians must often learn by word-of-mouth about the availability of reliable programs in their geographic area.
A variety of formal tests of skills and function have been developed in an attempt to identify older drivers who are at increased risk for motor vehicle accidents. Although some of these have shown promise in correctly identifying those at risk, they are still best regarded as research tools that may eventually be incorporated into clinical practice or, more likely, into driver licensing procedures.
Management of the older patient who is at risk for driving unsafely consists of appropriate treatment for any medical conditions and age-associated physiologic changes, careful consideration of the ethical issues involved, and compliance with state laws. In addition, sometimes vehicle modifications and assistive devices can attenuate some of the risk associated with medical impairments.
Once a medical condition has been identified, optimal treatment should be initiated in an attempt to reduce its potential risk. This treatment may be as simple as providing the appropriate refraction to improve visual acuity or discontinuing an inappropriate medication. Unfortunately, in many cases medical management is more complicated with respect to its impact on driving. For example, the goal of treatment of diabetes may be excellent metabolic control to forestall the vascular complications of the disease. Such control may result in hypoglycemic episodes that substantially increase the risk of accidents. Other disorders, such as dementia, are resistant to medical therapy.
With many patients, the physician is faced with the decision of whether to recommend that the patient cease driving. Such decisions are usually difficult, particularly if no alternative methods are available to meet the patient’s transportation needs. Some patients may be willing to take the risk of a fatal crash if it means that they can continue to maintain their independence. The physician may feel torn between preserving the independence and autonomy of the patient and protecting society against an unsafe driver. In these cases, the physician must depart from the traditional role of patient advocate in recommending that the patient cease driving. Such decisions are particularly difficult in states that have mandatory reporting requirements (e.g., in California, physicians must report patients who have Alzheimer’s disease and related disorders) and are likely to have a negative impact on the physician-patient relationship. Nevertheless, physicians must comply with such regulations or they may be subject to loss of their medical license as well as legal liability should one of their patients who should have been reported be involved in a collision.
State-initiated policies may be effective in reducing fatal accidents. A recent analysis of license renewal policies and fatal crashes involving drivers aged 70 years or older demonstrated that state-mandated tests of visual acuity were associated with lower fatal crash rates.27 Several states are developing and testing performance-based methods of assessing risk for adverse driving events among older drivers. Such methods will probably be used as screening tests that can be administered quickly to identify those who need more extensive testing, such as on-road driving tests. The National Highway Traffic Safety Administration has also become interested in promoting increased reporting of potentially unsafe driving by family members. As these methods are refined further, the physician will be increasingly relied on to optimize medical treatment and provide information on the severity and prognosis of medical conditions.
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