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Using "Age" as a Fitness-to-Drive Criterion for Older Adults

I. Introduction

There is no question that a number of medical conditions may have an impact upon the ability of an individual to drive. This is recognized in all provinces, as evidenced by the general requirement for some kind of medical examination of all applicants for driver licenses. As noted in Part 2, some provinces use age as a determinant to trigger medical examinations and re-examinations in the licensing process. Often, the cost of such examinations is borne by the applicant, and in all cases, licenses will be denied or revoked if no examinations occur.

There are a number of reasons for singling out older drivers as high-risk groups. First, in normal aging, there is frequently some psychomotor slowing that may affect driving ability.[60] Second, age-related decreases in reaction time, divided attention (performing two or more simultaneous tasks), and selective attention (filtering out irrelevant information) have been documented.[61] Third, older adults may be at increased risk for medical conditions that may compromise their ability to operate motor vehicles safely.[62]

Even though there is some deterioration of mental, motor, and sensory functions with increasing age (i.e., primary aging), it is not known to what extent this affects driving performance, and elderly persons usually drive safely. Reviews of the research, in fact, show that little data support the assumption that older drivers are, per se, unsafe drivers.[63] According to current statistical trends, the crash rate per miles driven among older adults is not as high as it is among drivers less than 25 years of age.[64] Furthermore, there is some limited research to suggest that healthy older drivers pose less of a threat to others[65] and commit fewer errors on standardized road tests[66] compared to younger drivers. Many older drivers also avoid serious driving problems because they recognize their limitations and limit or adjust their driving by avoiding driving at night, in heavy traffic, and in bad weather.[67] On the other hand, even if self-regulation is a common practice among older drivers, it is not a foolproof method of protecting public safety, especially if one considers that aging drivers with disorders affecting mental functioning (e.g., dementia), for example, may lack insight into their driving difficulties.

Another factor to consider is that older drivers show the greatest variability of any age group, with some older drivers possessing adequate driving skills until a very late age, and others singled out relatively early as being high-risk drivers.[68] However, it is easy to erroneously conclude that there is widespread, gradual age-related deterioration in driving skills when only a few debilitated older adults pose a significant risk to other motorists. Performance is impaired only after considerable loss of function, perhaps because of the onset of a significant medical condition combined with age-associated inefficiencies that interact to significantly impair driving performance. If fitness to drive policies affecting the lives of older adults are to be developed in an equitable and fair fashion, consideration of the complex interplay among all of the variables affecting the driving performance of older adults must be made. The legal requirements for driver licenses may need updating to ensure that only those adults, of any age, who are at high risk for unsafe driving are required to undergo re-evaluation. High risk factors might include the presence of vision, psychological, physical or other medical problems.

Certainly, there is some evidence to suggest that older drivers are at higher risk for crash involvement if they are suffering from certain medical conditions or taking certain prescription medications that affect driving performance. While specific conditions related to each of the factors reviewed might affect driving skills regardless of age, many are more common and prevalent with increasing age. We have not provided an exhaustive listing or complete review of all medical conditions that affect driving. Such documents exist elsewhere.[69] Instead, in the next sections, we have identified areas of particular concern with respect to the older driver and provided general commentary based on available literature: sensory and motor functioning, mental functioning, and frailty. It must be noted that some conditions are easily identified, whereas others are not. Similarly, the criteria for determining the conditions under which a person can no longer drive are clear and easily applied for some disorders, and not for others. Finally, assistive devices (e.g., specialized lenses, mirrors) may be available for facilitating driving under some conditions but not others. As advances are made in medical science and technology, the existing criteria and guidelines are likely to require periodic revisions and clarification.

II. SENSORY and motor CONDITIONS

Several age-related changes in vision can affect driving. For example, peripheral vision declines with age[70], as does depth perception and visual acuity[71]. Furthermore, age-associated visual conditions such as cataracts, glaucoma, and macular degeneration often impact driving performance.

Despite the increased prevalence of visual disturbances with advancing age, the functional relations between driving and a given visual impairment is quite variable.[72] To date, the relations between these visual conditions and risk of accidents in seniors is undetermined, with existing studies showing both positive and negative associations.[73]

Similarly, whether or not hearing loss is associated with an increased risk of car accidents remains questionable. Hearing loss of some sort reportedly affects approximately one-third of all adults between 65 and 74 years of age and about half of those between 75 and 79.[74] Some research indicates that self-reported hearing impairments are associated with adverse driving events;[75] other researchers indicate that hearing loss does not interfere with the ability to drive safely.[76]

Conditions that affect movement such as pain may also affect driving performance. Arthritis, osteoporosis, and debilitating rheumatologic conditions that commonly affect the elderly may restrict an older driver's range of motion, making it difficult to shoulder check and steer, as well as restricting field of view.[77] Drivers who report a diagnosis of many of these conditions often are at increased risk of crash involvement.[78] On the other hand, the severity of the impairment must be taken into account. Obviously, conditions that severely restrict the driver's mobility would be more likely to negatively influence driving performance.[79] However, it is usually possible to adapt the vehicle to accommodate older adults suffering from these conditions.[80]

Other diseases affecting motor functioning, such as neurological conditions such as Multiple Sclerosis, Parkinson's disease, or Amyotrophic Lateral Sclerosis may also impair driving, but the degree of disability varies widely.

Some conditions, more than others, place older adults at increased risk of traffic violations and motor vehicle accidents. Those diseases or disorders that affect mental functioning (e.g., judgment, reasoning) require special consideration: disorders that result in an abrupt change in mental functioning, disorders associated with fluctuations in mental functioning and progressive neurodegenerative disorders.

A. Abrupt change in mental functioning

Seizure disorders, sleep disorders (e.g., narcolepsy, sleep apnea), and coronary heart disease, depending on the frequency and severity of anginal episodes, syncope, arrhythmia, and shortness of breath, are examples of disorders that may result in the sudden loss of consciousness while driving. Most guidelines for determining fitness to drive, such as those proposed by the Canadian Medical Association[81], clearly describe procedures for determining the fitness-to-drive of persons with seizures disorders. Research describing the driving records

of those who suffer from sleep disorders (e.g., narcolepsy, sleep apnea) has shown that sleepiness affects driving performance because it results in decreased vigilance and increased crash risk.[82] Complaints about sleep are common among the elderly, with many older adults suffering from both transient and chronic insomnia as well as specific sleep disorders such as drug-induced sleep disturbances, sleep apnea, sleep complications due to restless leg syndrome, and narcolepsy.[83] Generally, older adults reporting excessive somnolence and a history consistent with an intrinsic sleep disorder may require regular fitness-to-drive evaluations to determine whether or not they pose significant risks to other motorists.

Cardiovascular disorders (e.g., myocardial infarction) can also result in a sudden loss of consciousness while driving. However, research on crash rates for persons with cardiovascular disorders yields mixed results. Some studies focusing on older drivers have reported negligible associations between heart disease and crash involvement.[84] According to McGwin and colleagues, sudden driving incapacitation due to myocardial infarction causes less than 1% of all motor vehicle accidents.[85] Foley and colleagues, for example, found that neither heart disease nor hypertension was associated with risk for crashing.[86] It is possible that older drivers with various types of cardiovascular conditions are at greater risk of motor vehicle crashes, but because they modify their driving habits after receiving their diagnosis, they avoid driving accidents.[87] Nevertheless, other studies have identified heart disease as being associated with automobile crashes[88] and so the quandary for the clinician is estimating the risk in an individual patient.

Considering these mixed findings, the practical advice might be to err on the side of caution and regularly re-evaluate fitness to drive in adults with cardiovascular disease. The Canadian Medical Association has advised refraining from driving for at least four weeks following acute myocardial infarction and coronary bypass surgery.[89]

Cerebral vascular disorders (i.e., vascular disorders affecting the brain) may also affect driving. The incidence rates for transient ischemic attacks are highest among the elderly, and may negatively affect the driving performance of older adults by impairing the cognitive functioning of the driver or via sudden incapacitation.[90] Studies of the driving safety of those who have suffered a cerebral vascular accident (e.g., brain hemorrhage or stroke) have generally reported increased risks.[91] Older stroke patients may be especially prone to unsafe driving because of the combined effects of age-related deficits and focal neurological deficits induced by the stroke. Generally, studies of older stroke patients indicate that the reaction time and steering errors made by stroke patients are worse than that of adults who are aging normally.[92] However, others have observed that those older adults who suffer stroke-related paralysis or weakness are more prone to spontaneously make the decision to stop driving.[93]

B. Fluctuations in mental functioning

There are a variety of circumstances under which mental functioning may fluctuate. These may occur as a function of a specific medical condition that by its nature alters the level of mental functioning of the adult (e.g., psychiatric conditions, diabetes). Treatment for the underlying disorder may reduce or eliminate these fluctuations. Alternatively, a variety of over-the-counter and prescription medications used inappropriately may result in mental fluctuations.

Studies of diabetic drivers have indicated that, aside from the effects of visual impairments due to diabetic retinopathy, diabetic individuals may be at risk while driving if the metabolic aspects of the disease are not controlled. For example, people with insulin-dependent (i.e., Type I) diabetes experience cognitive changes at relatively moderate levels of hyperglycemia. Such cognitive changes include visuoperceptual disturbances, disorientation, and decreased attention/concentration; these deficits obviously can impair skills necessary for safe operation of a vehicle. Of the few studies that have been conducted on older diabetic drivers, the risk of accidents among insulin-dependent diabetic seniors was moderate to high.[94] On the other hand, patients with stabilized diabetes with no episodes of altered consciousness are reportedly safe drivers.[95] The majority of these studies, however, are not age-specific, despite the fact that diabetes is fairly common among the elderly with a prevalence of 8.8% among those aged 65-74.[96]

The influence of psychiatric disease and its treatment on seniors' driving performance is an understudied area but is an area that has been identified as worthy of inclusion in some existing guidelines for determining fitness-to-drive.[97] In this section, two questions will be addressed: Are older drivers who are suffering from psychiatric conditions more or less likely to be involved in road traffic accidents? Do medications used to treat these conditions interfere with driving performance?

Psychiatric disorders are common. Research has shown that the lifetime prevalence of psychiatric disorders may be as high as 38%.[98] Persons of all ages are not immune to emotional difficulties. Furthermore, the elderly patient who is suffering from a psychiatric illness is probably at greater risk of involvement in a motor vehicle accident because of changes associated with the psychiatric condition (e.g., reduced attention/concentration, psychomotor slowing) and compounded by the effect of age-related changes.[99]

Some common psychiatric conditions that have been reviewed in the driving literature that are particularly applicable to older adults include: anxiety, depression, manic-depression, psychosis, and personality disorders. With respect to anxiety conditions, the presumption is that anxious drivers are more at risk for unsafe driving because anxiety can cause decreased psychomotor function that in turn can negatively affect driving performance. Indeed, limited research suggests that anxious drivers are at increased risk for motor vehicle accidents.

Little has been written about the effect of mood change, particularly depression, on the driving skills of the elderly. Rubinsztein and Lawton conducted two case studies of older men (ages 77 and 81) admitted to an acute geriatric psychiatry ward with major depressive disorder, and found that both had had motor vehicle accidents prior to admission[100]. Other research demonstrates that patients suffering from mood-induced psychotic episodes and depression demonstrate questionable fitness for driving.[101] With respect to manic-depression, some research demonstrates that adults suffering from this condition have twice the expected accident rate even after correcting for fewer miles driven.[102] Overall, then, a review of the limited research available suggests that the presence of mood disorders places one at a higher risk for unsafe driving.

In addition to the effects of mood disturbances on driving performance, certain personality disorders have been found to be associated with increased accident risk. For example, those suffering from Antisocial Personality Disorder often act in an aggressive and irresponsible manner, character traits that are commonly associated with a propensity to reckless driving and increased risk of being involved in fatal motor vehicle accidents.[103] The personality characteristics that impact driving performance have not specifically been studied in older age cohorts.

Despite the fact that psychiatric patients overall have a higher than expected rate of involvement in motor vehicle accidents, it would be unfairly discriminatory to cancel, deny, or restrict the licenses of all elderly drivers suffering from psychiatric illnesses. On the other hand, a review of the literature suggests that regular fitness to drive re-evaluations of those older adults suffering from psychiatric conditions is most likely warranted.

Medications may also affect the mental functioning of the older adult. The use of medications, like and in response to the number of chronic medical conditions and disabilities, increases with advancing age.[104] Many of these drugs – especially drugs that cause sedation – impair driving. Sedative drugs include antihistamines and alcohol, which used alone or in combination have deleterious effects on driving.

Drugs commonly prescribed to older adults that have been shown to be positively associated with crash involvement include anticoagulants and anti-inflammatory medications. [105] Skeg also identified a significant association between the use of minor tranquilizers among drivers and serious road crashes. [106] Moreover, psychotropic medication may affect driving performance. Psychotropic medications affect driving performance because they decrease psychomotor reaction time.[107] Benzodiazepine use, in particular, is commonly prescribed to older adults, and is known to compromise driving safety.[108] Overall, some researchers report that older adults taking prescription medications for treatment of psychiatric conditions are at increased risk of crashing[109], whereas others report no correlation between medication usage and driving performance.[110]

The impact of antidepressants on road safety is currently unknown. According to some, users of antidepressant drugs are not at increased risk for traffic accidents, [111] perhaps because antidepressants can sharpen a depressed patient's attention and concentration and tracking skills, thereby improving driving performance. On the other hand, in the acute phase of treatment, antidepressant medication usage has been shown to adversely affect driving performance.[112] Certain classes of antidepressant medications have been found to affect

psychomotor abilities to a greater extent than others.[113]

Another important consideration is that polypharmacological treatment has a more severe effect on driving fitness than monotherapeutic interventions.[114]

C. Progressive neurodegenerative disorders

Degenerative disorders affecting the central nervous system occur with increased prevalence at older ages[115]. These disorders may affect specific aspects of the mental functioning of older adults such as perception, memory, judgment, reasoning, planning, early in the disease process with all areas of mental functioning eventually affected. Dementia, a general term indicating impairment of more than one area of mental functioning that interferes with the person’s ability to meet the diverse demands of everyday life, is associated with increased driving problems.[116] Reviews of the literature indicate that dementia patients have 4.7 more accidents than cognitively intact older adults.[117] However available literature suggests that neither the duration since the onset of dementia nor the severity of dementia can predict accurately which patients can drive safely. There are as yet no consistently agreed upon indicators of the point at which persons with neurodegenerative diseases primarily affecting mental functioning (as opposed to physical functioning) may require re-evaluations of the ability to drive. It may be that a diagnosis of a specific neurodegenerative condition may suffice to prompt some specific actions by licensing authorities even though it is not clear that all of these people are unsafe to drive.

IV. FRAILTY

Frailty, in the context of the older adult, is a concept that has emerged to capture the notion that minor impairments or deficits in multiple areas of mental and/or physical functioning increases a person’s vulnerability. Within the context of driving, an older adult may not exhibit any particular specific impairments of sensory, motor, or mental functioning but overall functioning is limited due to a loss of stamina, or a loss of physiologic reserve that increases the risk of disability.[118] There is as yet no agreed upon method for defining frailty although a few studies suggest that physical frailty, either alone or in combination with other conditions, is a factor that impacts driving safety.[119]

V. SUMMARY

In reviewing the literature related to older drivers' fitness-to drive, we found that the presence of sensory or motor deficits or disorders that affect mental functioning may place older adults at increased risk for unsafe driving, traffic violations, and collisions. However, the mere presence of any of these factors does not ubiquitously indicate that driving performance will be affected. On the other hand, we have tried to note that conditions that in isolation are not sufficient to affect driving may, in combination, increase the risk of driving problems. Some of the conditions examined occur more frequently in older adults and older adults are more likely than

younger adults to have multiple medical conditions and be taking medications to treat these conditions. Certain disorders are easier to identify and treat than others. For example, some vision or neurological disorders are quite clear in their presentation and their effects on driving are equally as clear (e.g., uncontrolled seizure disorder). Disorders that result in fluctuating mental functions are less easy to predict but many times can be controlled with appropriate therapeutic regimes. Degenerative conditions change over time and, with respect to neurodegenerative conditions, it may not be clear at what point in a disease process the person is no longer safe to drive. The implication for re-evaluations of the ability to drive is that targeting the presence and severity of certain medical conditions, regardless of age, may identify potential at risk drivers more effectively than age per se.

Despite the fact that detection of high-risk drivers is not foolproof, outlining the variables that increase the risk of crash-involvement is sanctioned when public safety is imperiled. Furthermore, once identified as high risk, a driving re-evaluation may reveal no further functional impediments so that the driver, regardless of age, is deemed fit to drive on a case-by-case basis.