Vertigo, unsteadiness, and other balance-related symptoms are common among older adults. These complaints should be taken seriously because they can lead to falls, injuries, loss of independence, and even death. This chapter provides a review of the underlying causes for the increased prevalence of dizziness with age and discusses how specific test procedures may need to be modified for older individuals. Finally, issues related to the management of these symptoms—including fall prevention—in the aging population are considered.
KeywordsAge-related dizziness, Disequilibrium of aging, Falls in older adults, Vestibular disorders
Dizziness is a broad term used to describe a variety of sensations such as vertigo, unsteadiness, imbalance, light-headedness, and similar symptoms. The prevalence of dizziness increases steadily with age. Although debate is still ongoing regarding the underlying causes of this increase in prevalence, there is universal agreement on the devastating consequences and high physical, cognitive, emotional, and financial toll of dizziness and imbalance on the older population. Taken together, the impact of dizziness on the quality of life in older patients is profound.
It is estimated that one-fourth to one-third of the population older than 65 years has experienced some form of dizziness. This range in the reported prevalence rates reflects differences across the series in the cutoff age of participants, type(s) of symptoms for inclusion, duration and frequency of symptoms, and whether the sample was taken from community-dwelling patients, primary care facilities, or specialty clinics. In the older than 85 years age-group, the number of adults with dizziness increases to about 50%. The prevalence of these symptoms seems to be greater for women.
It is important to recognize that older dizzy patients typically present with a different symptom profile compared to their younger counterparts. Younger patients more often complain of true vertigo, nausea, and emesis, whereas older patients more often report symptoms of unsteadiness, imbalance, and disequilibrium.
Older individuals who suffer from dizziness are at a significantly higher risk of accidental falls and consequent injuries. It is estimated that approximately 30% of adults older than 65 years will fall at least once, and roughly 50% of those will fall again. The consequences of such falls are devastating. Falls are the leading cause of accidental death in people older than 65 years, and non-fatal falls are the main reason for hospital admissions in this age-group. Fall-related injuries can lead to mobility restrictions, loss of independence, and even confinement to nursing facilities. In addition to the physical and emotional cost, these injuries also carry a heavy financial burden, estimated at over $19 billion in direct costs in the year 2000 and rising steadily since.
A number of studies have established that for older adults, a history of dizziness or imbalance is an independent risk factor for falling ; however, the association between the two has not been as strong in other studies. This is not surprising as falls are complex phenomena involving neurologic, biomechanical, and other factors; therefore, fall risk factors can be heavily influenced by study design and patient selection methods. Rubenstein and Josephson used a meta-analysis of 12 large studies and found that balance disorders and dizziness were the second and third leading causes of falls in older persons, respectively. Vertigo, unsteadiness, and related symptoms also have an indirect effect on falls. It is well established that these symptoms in older individuals lead to the fear of falling. In turn, the fear of falling is considered a strong predictor for those who will suffer one or more actual falls.
The general topic of falls is beyond the scope of this chapter. However, the strong association between falls and symptoms of dizziness and imbalance highlights the importance of understanding the causes of these symptoms and devising effective methods for managing them in the older population.
Causes of Dizziness and Disequilibrium in Older Individuals
A substantial body of research demonstrates that the symptom of dizziness stems from a heterogeneous collection of underlying factors and is often multifactorial. In some studies, no specific etiology could be identified to explain the symptoms of a large subset of the subjects. The term presbystasis is used to describe this type of age-related disequilibrium that cannot be attributed to any known pathology. On the other hand, other studies have been able to assign one or more diagnostic categories to the majority of elderly patients suffering from dizziness. These discrepancies have led some investigators to suggest that dizziness in the elderly should be viewed as a multifactorial geriatric syndrome involving many different symptoms and originating from many different systems, such as sensory, motor, vestibular, neurologic, cardiovascular, and other systems.
The underlying causes of dizziness and disequilibrium in older adults can be divided into three broad categories:
Age-related decline of acuity in sensory and motor pathways as well as deterioration of integration mechanisms within the central nervous system (CNS). Loss of hair cells in the labyrinth is an example of an age-related change in the sensory system. These types of losses are considered a normal part of aging because they are so common in older adults. However, they are most likely caused by subtle pathologies accumulated over a lifetime (e.g., ischemia) that are highly prevalent in the elderly.
Pathologies that cause dizziness in any age-group, which become more prevalent in older individuals, either because age-related changes noted earlier make the elderly more susceptible to these pathologies or because the cumulative probability of exposure to these pathologies increases with time. An example of such pathology is benign paroxysmal positional vertigo (BPPV) that can occur at any age but is more common in the elderly, likely because of the ongoing deterioration of the maculae of the otolith organs.
An assortment of environmental and lifestyle factors that increases the chance of dizziness and balance problems in the elderly. One such example is polypharmacy in the elderly, with many medications having the common side effect of dizziness (see Chapter 18 ).
A different type of classification is often used to divide risk factors for falls. This classification involves causes that are intrinsic to the patient versus those that are extrinsic. For dizziness and balance problems, such a classification is more relevant when considering appropriate intervention methods, which will be discussed later in this chapter. Here, each of the aforementioned three categories will be discussed in detail.
Age-Related Deterioration of Sensory and Motor Mechanisms
Human balance function depends on coordinated streams of sensory input from the vestibular, proprioceptive, and visual systems as well as proper integration of those inputs in the CNS. Furthermore, movement control requires the motor centers to accurately process sensory information and transmit the necessary commands to the appropriate muscles. Both structural and functional deteriorations in all of the aforementioned systems are known to occur with advancing age.
Age-related loss of hair cells has been documented within the cristae ampullares of the semicircular canals and the maculae of the saccule and utricle. Earlier studies had indicated greater loss of hair cells in the semicircular canals and saccule and a higher proportion of loss for type I versus type II hair cells. More recent studies have used a counting method that is deemed to be less biased. These studies have confirmed the age-related loss of hair cells in the labyrinth, although the affected sites and type of hair cells have differed somewhat from previous studies.
Structural integrity of the vestibular nerve is also affected by age. The number of primary vestibular neurons within Scarpa’s ganglion has been shown to decline by approximately 25% over the life span. Similarly, the study of brainstem specimens in different age-groups has demonstrated a decrease in the number of secondary vestibular neurons within the vestibular nuclei.
Age-related degeneration of peripheral and central vestibular structures is similar to that of the auditory system and is most likely caused by subtle changes of blood flow to the inner ear. Microvascular changes with aging have been reported in both human and animal studies. Any decrease in blood flow to inner ear structures can have profound effects because inner ear arteries lack anastomotic connections.
Age-related changes of vestibular structures have been objectively confirmed by vestibular function tests. For example, both longitudinal and cross-sectional studies have shown an age-related decrease in vestibulo-ocular reflex (VOR) gain during sinusoidal rotation. This finding indicates that, unlike pathologies that usually affect only one labyrinth, age-related changes of vestibular pathways are more likely to mimic bilateral reduction of function. In addition, phase lead for low frequency sinusoidal stimuli and short vestibular time constants for step stimuli have been reported in older subjects. These findings are consistent with deterioration of the velocity storage mechanism within the brainstem. Similar degradation of central vestibular pathways has been demonstrated for otolith-ocular responses during off-vertical axis rotation.
Despite the overwhelming evidence in support of age-related changes of peripheral and central vestibular structures, the relationship between those changes and dizziness or disequilibrium in the elderly is not necessarily linear. Several studies have demonstrated high prevalence of vestibular impairment in elderly individuals. However, once patients with specific vestibular pathologies are removed from the sample, the contribution of age-related vestibular decline to balance impairment in the elderly is not as profound. Clearly, additional research is needed to examine the association of age-related changes in the vestibular pathways in older adults with symptoms of dizziness and disequilibrium.
Proprioceptive sensors reside in the muscles, joints, and tendons and provide information regarding orientation of one body segment with respect to another. Compared with vestibular and visual inputs, these sensors have lower thresholds for motion detection and operate at significantly higher frequencies. Proprioceptive input provides critical information regarding the point of contact with the ground, which can be extrapolated to detect orientation and movement of the body. Proprioceptive cues from the neck also play an important role in detecting head orientation and in providing a stable platform for vestibular and visual receptors.
The proprioceptive system undergoes several age-related changes. Vibration and touch thresholds decline in older individuals, adversely affecting tactile information arising from the feet at their contact point with the ground. Similarly, the ability to detect the position and direction of joint movements declines with age.
A number of studies have demonstrated decreased postural stability when proprioceptive input is altered in such a way that it provides inaccurate information regarding orientation. Horak et al. compared the performance of patients with severe neuropathy with age-matched controls and demonstrated that the performance of the control subjects became similar to that of patients with neuropathy for test conditions in which proprioceptive input was altered. Therefore, it is not surprising that reduction of vibration and tactile sensation at the ankle and knee joints has been associated with an increased risk of falls in the elderly.
Concomitant conditions such as diabetes mellitus or other causes of peripheral neuropathy that can be more common in older patients may have a synergistic effect with age-related decline in lower extremity proprioceptive function. Peripheral neuropathy itself is predictive of falls in patients with bilateral vestibulopathy.
The role of neck proprioception on postural control has been studied using neck muscle vibration. Prolonged unilateral vibration of neck muscles during in-place stepping caused subjects to rotate about a vertical axis away from the side of vibration. Using a similar type of neck vibration during locomotion, Deshpande and Patla demonstrated reduced sensitivity of neck proprioception in older adults. This is an important observation because as noted before, age-related decline of the vestibular system usually involves bilateral reduction of function. In younger patients with bilateral vestibular loss, neck receptors play an important role as substitutes for the vestibular system. This mode of compensation may not be available in the elderly because of reduced neck proprioception.
The visual system undergoes significant age-related changes. In addition to visual acuity, several other visual functions, such as depth perception, accommodation, contrast sensitivity, and dark adaptation, decline with age. Deficits in depth perception and contrast sensitivity have been shown to have the largest contributory influence on falls. These impairments affect the ability of older adults to accurately judge distances and to avoid obstacles.
Age-related changes in static visual acuity as measured with stationary subjects and stationary targets have been studied extensively. The association between reduced static visual acuity and balance problems in the elderly is still in dispute. Deterioration of dynamic visual acuity, in which either the target or the subject is moving, has also been documented in older individuals. Interestingly, patients with acute unilateral and bilateral vestibular lesions also exhibit impaired dynamic visual acuity and complain of blurred vision during head movements. The coexistence of this impairment in the elderly and in patients with known balance disorders may explain some of the symptoms in older adults.
It has been shown that reliance on visual input increases with age. For example, older subjects exposed to moving visual surrounds were affected more and demonstrated greater postural sway than younger subjects. Although both older and younger subjects were able to adapt to moving visual stimuli, older individuals required significantly more time for adaptation to occur. In addition, postural sway of older subjects who were presented with spatially inaccurate visual stimuli was significantly greater than the response of younger subjects.
Sensory information regarding orientation and movement of the body is processed by the motor centers, and appropriate commands are transmitted to a select group of skeletal muscles to preserve balance and maintain upright postural stability. The most notable effect of aging on the motor system relates to changes in anatomic and physiologic characteristics of the muscles. Muscle strength has been shown to be lowered by 20%–40% in the 70–80 age-group compared to that of young adults. Reduction in muscle strength is related to a decrease in the number and size of muscle fibers as well as changes in the central motor command centers. Similarly, the speed with which muscles can be contracted declines with age. These and other similar age-related changes in skeletal muscles may prevent older individuals from exerting adequate force and reacting quickly to postural disturbances.
Similar changes are observed in extraocular muscles, which can lead to age-related decline of oculomotor function. Fast eye movements or saccades are only modestly affected by aging. Saccade latency has been shown to increase with age, but other saccade parameters, such as peak velocity or accuracy, were not significantly affected. Gain of slow tracking eye movements or smooth pursuit also declined substantially with age, especially for higher-velocity target movements. The ability to suppress vestibular nystagmus by visual fixation accordingly declines, as tracking and fixation mechanisms share many neural pathways. Finally, optokinetic reflex gain is also reduced in older individuals, mainly for high-velocity full-field visual target movement.
Although changes in eye muscles may have an effect on the decline of oculomotor responses, aging of central structures discussed in the next section seems to have a substantially greater role in age-related control of eye movements. These changes have profound effects on the perception of orientation and balance because they influence the sensory input from the visual system.
Central integration mechanisms
The brainstem, cerebellum, and higher cortical structures within the CNS all suffer from age-related degenerative changes. These changes include decrease in the number of neurons, loss of myelination, decrease in the number of Purkinje cells, and other neuronal changes. Age-related degeneration of central structures is likely to affect the integration of information from different sensory inputs and interfere with accurate perception of orientation and motion.
A few examples of impaired sensory integration have been mentioned previously. Over-reliance on the visual system even when it is providing erroneous spatial information is an example of how prioritization of inputs from different sensory mechanisms can be affected in older individuals. Another example is the faulty integration of optokinetic and vestibular inputs that can lead to deterioration of dynamic visual acuity. Fig. 17.1 shows how subtle age-related reduction in the gain of both the VOR and optokinetic reflex can result in images not remaining stationary on the retina, thereby causing blurred vision during head movement. This type of deterioration in visual-vestibular interaction has been documented in older individuals.
One manifestation of impaired sensory integration in the elderly is related to the time required for adaptation after natural changes affect balance control mechanisms. For example, when proprioceptive input was modulated by vibration of different muscles in the lower leg, there were no significant age-related differences in lower-level reflexes; however, older individuals did not adapt to reintroduction of accurate proprioceptive cues as quickly as the younger subjects did. Similar age-related differences in adaptation time were noted when subjects were exposed to moving visual stimuli. These observations have profound and troubling implications for older individuals with regard to recovery and compensation following impairment of the balance system.
Pathologic Causes of Dizziness
Although age-related changes in sensory and motor systems do play a role in the high prevalence of dizziness among the elderly, they are no longer considered the most prominent contributors. In contrast to earlier research, recent studies have identified one or more specific pathologies as the underlying cause(s) of symptoms. None of these pathologies was unique to the elderly: the same diseases are responsible for causing dizziness in both younger and older individuals. These pathologies become more prevalent in older individuals, either because age-related changes detailed earlier make the elderly more susceptible to them, or because the cumulative probability of exposure to them increases with time.
Major causes of dizziness based on primary care encounters (and not including formal assessment of vestibular function) in more than 80% of elderly patients fall into one of the three categories: cardiovascular (including cerebrovascular), peripheral vestibular, and psychiatric diseases. In 8% of patients, no clear cause is identified, and all other causes constitute 11% of patients. Two or more contributing causes are identified in 70% of patients. Adverse medication effects are the leading secondary cause. Dizziness is one of the primary symptoms in over 60 diseases. Thus, a broader differential diagnosis must be maintained when examining an older dizzy patient. Referrals to internal medicine, neurology, and other colleagues must be made, as appropriate, for additional evaluation and definitive management.
Among peripheral vestibular disorders, BPPV is by far the most common. In one study, almost 40% of patients above the age of 70 years were diagnosed with BPPV. While some earlier studies suggest that older patients with BPPV experience a more protracted course and higher rates of recurrence, other more recent prospective reviews show outcomes equivalent to those of younger counterparts. Late-onset Meniere’s disease, vestibular neuritis, and other otologic diseases do occur in the elderly but are not as common. Our own clinical experience suggests that some older patients who present with sudden onset of symptoms are experiencing decompensation related to an existing, and sometimes long-standing, condition rather than a new vestibular lesion. These patients may have a history of a previously compensated peripheral vestibular disease, which may have been undiagnosed.
Among non-vestibular causes of dizziness, cardiovascular and cerebrovascular diseases are common in the elderly. Atherosclerotic narrowing of blood vessels can lead to ischemic events and produce symptoms similar to either peripheral vestibular or central lesions depending on the affected sites. Vertebrobasilar insufficiency, which is a common cause of dizziness in the elderly (see Chapter 16 ), is an example of this type of disorder. Other diseases in this category include those that reduce cardiac output such as arrhythmia and heart valve failure. Orthostatic hypotension is extremely common in the elderly, often associated with dizziness or disequilibrium (see Chapter 15 ). Vertigo and nystagmus may be present as well.
Some neurologic disorders such Parkinson’s disease and Alzheimer’s disease are also more prevalent in the elderly, but evidence supporting vestibular dysfunction as a predictor or as a direct result of either condition is limited at this point in time. Unsteady gait associated with Parkinsonism, however, is a strong predictor of falls. Metabolic and endocrine disorders can cause dizziness with similar frequency in both younger and older adults.
Finally, the impact of psychiatric disorders, including cognitive impairment, should be considered in the elderly. Sloane et al. compared the prevalence and characteristics of psychiatric diseases between older patients with chronic dizziness with age- and sex-matched controls. Over 37% in the chronic dizziness group had a psychiatric diagnosis. Although psychiatric diseases rarely were considered the primary cause of dizziness, they were common as a contributing factor to dizziness in the elderly. In this study, anxiety and depression were the most common conditions. This finding is similar to results from other studies that have examined psychogenic aspects of chronic dizziness in patients of all age groups. One psychogenic factor that is specific to the elderly is increased fear of falling. It has been shown that the fear of falling is a risk factor for actual falls.
Environmental and Lifestyle Causes of Dizziness
In addition to age-related changes and pathologies that affect balance mechanisms discussed earlier, several lifestyle and environmental factors can contribute to disorientation and the sense of imbalance. The most prominent of these factors is adverse effects of medications. Several studies have linked the use of CNS-acting medications to increased risk of falls in the elderly. Furthermore, adverse medication effects have been considered the leading secondary cause of dizziness. Benzodiazepines, antidepressants, and anticonvulsants have been the most commonly implicated classes of medication. Unlike the well-known ototoxic and vestibulotoxic effects of aminoglycosides or chemotherapeutic agents, adverse drug effects of other classes of medication and their association with dizziness are less clear. There is considerable debate about the methodological efficacy of studying drug effects in at-risk populations. The use of implicated medications may be unavoidable; however, careful review of the necessity, dosage, drug interactions, and possible alternatives can greatly reduce dizziness due to these medications (see Chapter 18 ).
Another potentially modifiable lifestyle factor relates to vision correction. In general, poor vision contributes to spatial disorientation. Regular eye examinations and use of corrective prescription eyeglasses can greatly improve this deficit. As visual acuity for both distant and near vision decreases with age, more adults are required to wear multifocal lenses for vision correction. The use of these lenses has been associated with disorientation and increased chance of contact with surrounding objects, especially when performing a secondary task. Advising patients to wear single focal lenses during outdoor activities may reduce the chance of falling.
The aforementioned is a partial list of environmental and lifestyle factors that can influence patients’ sense of balance. Careful attention to these and other similar factors combined with patient education and simple corrective measures may alleviate or lessen the symptoms and prevent falls, without extensive medical intervention.
Diagnosis of Dizziness in Older Individuals
As noted, dizziness in younger and older individuals is generally caused by the same diseases. Therefore, the diagnostic path is essentially the same regardless of age, and includes a careful and detailed history, a thorough physical examination, and targeted laboratory tests, when indicated, all of which are discussed in detail elsewhere in this book. In this section, we will focus only on issues that are specific or particularly relevant to the elderly.
As is the case with dizziness in any age group, a case history should include a thorough description of the patient’s current and previous medical conditions, medication use, social environment, and fall risk factors. An accurate description of symptoms, their time course, and precipitating events is essential in identifying the underlying cause. These symptoms include vertigo, unsteadiness, imbalance, presyncope, and other less well-defined sensations such as light-headedness. Table 17.1 is a summary of the most common causes of dizziness in the elderly.
|Vertigo||Position-induced||BPPV||If nystagmus does not match BPPV, consider central pathologies. If induced by neck rotation, consider cervical vertigo|
|Acute-onset, persistent with neurologic signs||Stroke||Acute ischemia involving vestibular structures can mimic vestibular neuritis|
|Acute-onset, persistent without neurologic signs||Labyrinthitis||Differential diagnosis is based on the presence of hearing loss|
|Recurrent with no neurologic signs||Ménière’s disease||Late-onset Ménière’s is possible but not common. Migraines lack progressive auditory symptoms. Transient ischemic attacks should be considered in patients with vascular risk factors|
|Disequilibrium||Acute or rapidly progressive||Stroke||Autoimmune or post-infectious diseases should also be considered. May include severe oculomotor abnormalities|
|Worse in the absence of other sensory inputs||Bilateral vestibular loss||Usually includes history of ototoxicity. Hearing loss or oscillopsia may be present|
|Worse in the absence of vision with numbness/weakness||Proprioception and somatosensory loss||Often associated with peripheral neuropathy related to metabolic disorders, diabetes, or renal failure|
|With bradykinesia, rigidity, tremor||Parkinson’s disease||Frontal lobe or other basal ganglia disorders|
|With speech disorder, lack of coordination, intention tremor||Cerebellar lesions||The imbalance is usually the same with or without vision|
|Isolated disequilibrium, gait difficulty, light-headedness||Disequilibrium of aging||Often accompanied by borderline diffuse central findings but no other specific complaints|
|Presyncope||With blood pressure drop on standing||Postural hypotension||Associated with reduced blood volume, autonomic disorders, or chronic use of anti-hypertensive medications|
|Abnormal cardiac examination||Heart valve disease||When 24-hour electrocardiogram is abnormal, indicates transient arrhythmia|
|Induced by fear or anxiety||Vasovagal attacks||Decline in heart rate and blood pressure leads to decrease in cerebral blood flow|
|Light-headedness, non-specific||Associated with fear, anxiety, and depression||Psychogenic||Often accompanied by autonomic symptoms|