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 article 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. Issues related to the management of these symptoms in the aging population are also considered.
D.P. is an 82-year-old woman describing gradual onset of lightheadedness and imbalance over the past 2 to 3 years. She denies antecedent illness or injury, and states that these symptoms have been noticeably worse in the last 6 months. She reports one full-fall 2 months ago after getting out of her daughter’s car in the grocery store parking lot and hitting her head, resulting in a laceration on her forehead requiring stitches. She states that she felt somewhat woozy on getting out of the car, tried to grab the car door but missed, and was unable to prevent her fall. She denies loss of consciousness, and afterward reported position-dependent vertigo, which was later diagnosed as benign paroxysmal positional vertigo. This condition was successfully treated by a local otolaryngologist. She reports near-falls daily, and finds that she steadies herself by holding onto walls and furniture while walking around her house. She expresses appropriate concern for falls and fall-related injury, and is worried about maintaining her independence, as she currently lives alone and has a daughter living nearby who assists her. She reports that her medical history is significant for hypertension, congestive heart failure, 2 “mini strokes,” rheumatoid arthritis (affecting her knees, hips, and hands), incontinence, osteoporosis, and bilateral cataracts (scheduled for surgery next month). She indicates long-standing bilateral hearing loss, and denies changes in her hearing with the onset of her balance symptoms.
Dizziness in the elderly
Dizziness is a broad term used to describe a variety of sensations such as vertigo, unsteadiness, lightheadedness, and similar symptoms. The prevalence of dizziness increases steadily with age. Although debate is still ongoing about the underlying causes of this increase in prevalence, there is universal agreement on its devastating consequences and high physical, emotional, and financial toll on the older population.
It is estimated that about one-fourth to one-third of the population older than 65 years has experienced some form of dizziness. The prevalence varies among different studies because of several factors such as the differences in the cutoff age of the participants, the type of symptoms for inclusion in the study, the duration and frequency of symptoms, and whether the sample was taken from community-dwelling seniors, primary care facilities, or from specialty clinics. For those older than 85, the number of adults with dizziness increases to about 50%. Furthermore, the prevalence of these symptoms is greater for women.
Older individuals who suffer from dizziness appear to be at significantly higher risk of accidental falls and consequent injuries. It is estimated that about 30% of adults older than 65 will fall at least once per year, and about 50% of those will fall again. The consequences of such falls are devastating. Falls are the leading cause of accidental death in persons older than 65 years, and are the number one reason for hospital admission for nonfatal falls in this population. Fall-related injuries can lead to mobility restrictions, loss of independence, and even confinement to nursing facilities. In addition to the physical and emotional costs, these injuries also carry a heavy financial burden, estimated at more than $19 billion in direct costs in year 2000 and rising steadily since.
Several studies have established that older adults with a history of dizziness, imbalance, and similar symptoms are at a higher risk of falling. However, the association between the two has not been as strong in other studies, which is not surprising given that falls are complex phenomena involving neurological, biomechanical, and other factors. Therefore, fall risk factors can be greatly influenced by the study design and patient selection methods. In 2006, Rubenstein and Josephson used a meta-analysis of 12 large studies, and determined balance disorders and dizziness as the second and third leading cause 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 fear of falling. In turn, fear of falls is considered a strong predictor for those who will suffer one or more subsequent falls.
The general topic of falls is too broad and is beyond the scope of this article. However, the strong association between falls and symptoms of dizziness and imbalance highlights the importance of understanding the causes of these symptoms and designing effective methods for managing them in the older population.
Causes of dizziness and disequilibrium in older individuals
Although the causes of balance problems in the elderly are seemingly obvious, the substantial body of research in the past 2 or 3 decades suggests that the underlying reasons are far from simple or obvious. 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 the 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 sensory, neurologic, cardiovascular, and other systems.
The underlying causes of dizziness and disequilibrium in older adults can be divided into 3 broad categories:
- 1.
Age-related decline of acuity in the sensory and motor pathways as well as deterioration of integration mechanisms within the central nervous system. Loss of hair cells in the labyrinth is an example of such an age-related change in the sensory systems. 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, such as ischemia, that are highly prevalent in the elderly.
- 2.
Pathologies that cause dizziness in any age group but become more prevalent in older individuals, either because the age-related changes noted above 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), which can occur at any age but is far more common in the elderly because of the ongoing deterioration of the maculae of the otolith organs.
- 3.
An assortment of environmental and lifestyle factors that increase the chance of dizziness and balance problems in the elderly. One such example is increased use of medications in the elderly, with many of the medications having the common side effect of dizziness (see article by Shoair and colleagues in this publication).
A different type of classification is often used to divide the risk factors for falls. This classification involves causes that are intrinsic to the patients versus those that are extrinsic. For dizziness and balance problems, such a classification is more relevant when considering appropriate intervention methods, discussed later in this article. Here, each of the aforementioned 3 categories are discussed in detail.
Causes of dizziness and disequilibrium in older individuals
Although the causes of balance problems in the elderly are seemingly obvious, the substantial body of research in the past 2 or 3 decades suggests that the underlying reasons are far from simple or obvious. 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 the 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 sensory, neurologic, cardiovascular, and other systems.
The underlying causes of dizziness and disequilibrium in older adults can be divided into 3 broad categories:
- 1.
Age-related decline of acuity in the sensory and motor pathways as well as deterioration of integration mechanisms within the central nervous system. Loss of hair cells in the labyrinth is an example of such an age-related change in the sensory systems. 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, such as ischemia, that are highly prevalent in the elderly.
- 2.
Pathologies that cause dizziness in any age group but become more prevalent in older individuals, either because the age-related changes noted above 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), which can occur at any age but is far more common in the elderly because of the ongoing deterioration of the maculae of the otolith organs.
- 3.
An assortment of environmental and lifestyle factors that increase the chance of dizziness and balance problems in the elderly. One such example is increased use of medications in the elderly, with many of the medications having the common side effect of dizziness (see article by Shoair and colleagues in this publication).
A different type of classification is often used to divide the risk factors for falls. This classification involves causes that are intrinsic to the patients versus those that are extrinsic. For dizziness and balance problems, such a classification is more relevant when considering appropriate intervention methods, discussed later in this article. Here, each of the aforementioned 3 categories are discussed in detail.
Age-Related Deterioration of Sensory and Motor Mechanisms
Human balance function depends on sensory inputs from the vestibular, proprioceptive, and visual systems as well as proper integration of those inputs in the central nervous system (CNS). Furthermore, control of movements requires the motor centers to accurately process the sensory information and transmit the necessary commands to the appropriate muscles. Both structural and functional deteriorations in all of these systems have been reported with increasing age.
Vestibular System
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 saccules, 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 age-related loss of hair cells in the labyrinth, but the affected sites and types 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 one’s 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 can have profound effects because inner ear arteries lack anastomotic connections.
Age-related changes of the vestibular structures have been confirmed by vestibular function tests. For example, both longitudinal and cross-sectional studies have shown decrease in vestibulo-ocular reflex (VOR) gain during sinusoidal rotations. This finding indicates that unlike pathologies that usually affect only one labyrinth, age-related changes of the vestibular pathways are more likely to mimic bilateral reduction of function. In addition, increase in the low-frequency phase for sinusoidal stimuli and decrease in the time constant for step velocity stimuli have been reported in older subjects. These findings are consistent with deterioration of the velocity storage mechanism within the brainstem. A similar degradation of central vestibular pathways has been demonstrated for otolith-ocular responses during off-vertical axis rotations.
Despite overwhelming evidence in support of age-related changes of peripheral and central vestibular structures, the relationship between those changes and complaints of dizziness and disequilibrium in the elderly is still uncertain. Several studies have demonstrated high prevalence of vestibular impairments 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. It is clear that additional studies are needed to examine the association of age-related changes in the vestibular pathways with symptoms of dizziness and disequilibrium in older adults.
Proprioceptive System
The proprioceptive sensors residing in muscles, joints, and tendons provide information regarding orientation of one body segment with respect to the others. Compared with the vestibular and visual inputs, these sensors have lower thresholds for motion detection and operate at significantly higher frequencies. These sensors provide 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 the 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.
Several studies have demonstrated a decrease in postural stability when proprioceptive input is altered in such a way that it provides inaccurate information regarding orientation. Horak and colleagues compared the performance of patients with severe neuropathy with age-matched controls, and demonstrated that the performance of 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 increased risk of falls in the elderly.
The role of neck proprioception on postural control has been studied using vibration of neck muscles. 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 observation is an important one because as noted before, age-related decline of the vestibular system usually involves bilateral reduction of function. In younger patients who suffer from bilateral vestibular loss, the 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 the reduced neck proprioception.
Visual System
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. Depth perception and contrast sensitivity have been shown to be the most important visual impairments that contribute to 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. Of interest, 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, when subjects were exposed to moving visual surrounds, older subjects were affected more and produced greater postural sway. While both older and younger subjects were able to adapt to moving visual stimuli, this adaptation required significantly more time for older individuals. In addition, postural sway of older subjects who were presented with spatially inaccurate visual stimuli was significantly greater than the sway response of younger subjects.
Motor System
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 the characteristics of muscle. Muscle strength has been shown to be 20% to 40% lower in the 70- to 80-year-old age group compared with that of young adults. This reduction in muscle strength is related to decreases in the number and size of muscle fibers as well as changes in the central motor command centers. Similarly, the speed by which the 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 occur in the eye 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 are not significantly affected. The gain of slow tracking eye movements or smooth pursuit also declines substantially with age, especially for higher velocity target movements. The ability to suppress vestibular nystagmus by fixation accordingly declines, as the tracking and fixation mechanisms share many neural pathways. Finally, the gain of reflexive optokinetic responses is also reduced in older individuals, mainly for high-velocity surround movements.
Although changes of the eye muscles may have an effect on the decline of oculomotor responses, aging of central structures (discussed in the next section) appears 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 undergo age-related degenerative changes. These 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 integration of information from different sensory mechanisms and to 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. 1 illustrates that subtle age-related reduction in both the VOR and optokinetic gains can result in an image not remaining stationary on the retina, thereby causing blurred vision during head movements. 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 following changes to the 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 failed to adapt to the reintroduction of accurate proprioceptive cues as quickly as did younger subjects. Similar age-related differences in adaptation time were noted previously when subjects were exposed to moving visual stimuli. These observations have profound and troubling implications for older individuals with regard to recovery and compensation after diseases that involve the balance system.
Pathologic Causes of Dizziness
Although age-related changes in the 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, most of the studies in the past two decades have been able to identify one or more specific pathologies as the underlying cause of symptoms. None of these pathologies was unique to the elderly. That is, the same diseases are responsible for causing dizziness in both younger and older individuals. These pathologies become more prevalent in older individuals either because the age-related changes already noted make the elderly more susceptible to them or because the cumulative probability of exposure to them increases with time.
In a recent study of elderly patients seen in primary care settings, the major cause of dizziness in more than 80% of the patients was ascribed to 1 of 3 categories :
- 1.
Cardiovascular (including cerebrovascular)
- 2.
Peripheral vestibular
- 3.
Psychiatric diseases.
In 8% of patients no clear cause was identified, and “all other causes” were attributed to 11% of the patients. Two or more contributing causes were identified in 70% of the patients. Adverse medication effects were the leading secondary cause. The results of this study were similar to those of previous studies with respect to the disease categories, but the prevalence of peripheral vestibular diseases was significantly lower than for other studies. This study was based on the patient population seen in primary care facilities, and did not include formal assessment of vestibular function.
Dizziness is one of the primary symptoms in more than 60 diseases. All of them should be considered in the differential diagnosis of older dizzy patients; however, the prevalence of some of the diseases is far greater in the elderly.
Among the peripheral vestibular disorders, BPPV is by far the most common finding. In one study, almost 40% of patients older than 70 years were diagnosed with BPPV. In some cases, BPPV was secondary to other diseases such as a previous peripheral vestibular disorder or diabetes. Late-onset Ménière’s disease, vestibular neuritis, and other otologic diseases do occur in the elderly but they are not as common. The authors’ own clinical experience suggests that some older patients who present with a sudden onset of symptoms are experiencing decompensation rather than a new vestibular lesion. These patients usually have a history of long-standing previously compensated peripheral vestibular disease.
Among the non-vestibular causes of dizziness, cardiovascular and cerebrovascular diseases are common in the elderly. Atherosclerotic narrowing of the 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 (VBI), which is a common cause of dizziness in the elderly, is an example of this type of disorder (see article by Ishiyama and Ishiyama in this publication). Other diseases in this category include those that reduce cardiac output such as arrhythmia, heart valve failure, and congestive heart failure.
Some neurologic disorders such as Parkinson disease are also more prevalent in the elderly, but are not considered a major cause of isolated dizziness. Similarly, metabolic and endocrine disorders can cause dizziness with about the same frequency in younger and older adults.
Finally, the impact of psychiatric disorders, including cognitive impairments, should be considered in the elderly. Sloane and colleagues compared the prevalence and characteristics of psychiatric diseases between older patients having chronic dizziness with age-matched and sex-matched controls. More than 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 findings, 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 falls. It has been shown that fear of falling is an important risk factor for actual falls.
Environmental and Lifestyle Causes of Dizziness
In addition to age-related changes and pathological factors that affect balance mechanisms, several lifestyle and environmental factors can contribute to disorientation and sense of imbalance. The most prominent of these factors is the adverse effects of medications. Several studies have linked 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. However, there is considerable debate about the methodological efficacy of studying drug effects in risk populations. Nonetheless, ototoxic and vestibulotoxic effects of some medications such as aminoglycosides or chemotherapeutic agents are well known. The use of medication is usually unavoidable. However, careful review of the necessity, dosage, drug interactions, and possible alternatives can greatly reduce the dizziness side effects of these medications.
Another factor in this category relates to vision correction. In general, poor vision contributes to disorientation. Regular eye examinations and using correct prescription glasses can greatly improve this deficit. As the visual acuity for both distance 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 greatly reduce the chance of falling.
The aforementioned is a partial list of environmental and lifestyle factors that can influence a patient’s sense of balance. Careful attention to these and other similar factors combined with patient education and simple corrective measures may alleviate the symptoms without extensive medical intervention.
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