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Dizziness Demographics and Population Health
Dizziness and imbalance are common conditions affecting people of all ages, and particularly the elderly. This chapter begins by defining dizziness, imbalance, and presbyvestibulopathy , or age-related vestibular loss, which is of particular interest to the otolaryngologist, the neurologist, and the primary care physician. Then the epidemiology of dizziness, imbalance, and presbyvestibulopathy will be reviewed. Finally, the impacts of these conditions on population health from the perspective of the older adult and the healthcare system will be discussed.
Definitions of Dizziness, Imbalance, and Presbyvestibulopathy
Dizziness connotes a subjective perception of disorientation or involuntary motion, which can occur during movement or at rest. Dizziness can be further characterized as vertigo and/or lightheadedness. Vertigo is the false sensation that either the body or the environment is moving (usually spinning) and may be a symptom of vestibular, visual, or neurologic impairment; psychological factors; or the use of multiple medications (“polypharmacy,” see Chapter 18 ). Lightheadedness is the sensation of impending loss of consciousness associated with transient diffuse cerebral hypoperfusion. Causal factors for lightheadedness typically include cardiovascular disease (e.g., aortic stenosis) and orthostatic hypotension (e.g., resulting from excessive medication use or autonomic instability).
Imbalance connotes disequilibrium or postural instability. Imbalance is usually described either while standing or walking and typically does not occur at rest. Imbalance can result from muscle weakness, arthritis, and/or reduced sensory input (e.g., visual, vestibular, proprioceptive) leading to impaired postural reflexes.
Presbyvestibulopathy refers specifically to aging of the vestibular system, akin to presbycusis (age-related hearing loss) and presbyopia (age-related vision loss). Numerous lines of evidence demonstrate a progressive decline in vestibular function associated with aging. Histopathologic studies have shown that hair cell populations throughout the vestibular apparatus (including the three semicircular canals and two otolith organs, the saccule and utricle) decline with age. Moreover, declining cell counts have also been observed for vestibular ganglion cells, primary afferents, and vestibular nucleus cell populations. Studies that have assessed vestibular physiologic responses have also observed declining semicircular canal and otolith responses associated with age.
Presbyvestibulopathy can contribute to symptoms of dizziness and/or imbalance in older individuals. The vestibular system plays an integral role in maintaining the vestibulo-ocular (VOR) and vestibulospinal reflexes (VSR). The VOR is important for stabilizing gaze during head movement, and VOR impairment manifests as dizziness (i.e., abnormal sensation of motion). The VSR is important for trunk and limb stabilization during head movement. VSR dysfunction manifests as imbalance or postural instability. Interestingly, there is increasing recognition of the physiologic importance of vestibulo-autonomic projections (see Chapter 15 ). Vestibulo-autonomic impairment has been associated with orthostatic hypotension. Thus presbyvestibulopathy may also be a causal factor for the symptom of lightheadedness. An effort is ongoing to establish formal diagnostic criteria for presbyvestibulopathy within the International Classification of Vestibular Disorders, a component of the International Classification of Diseases.
The relationship between dizziness, imbalance, and presbyvestibulopathy is depicted in Fig. 1.1 as a set of overlapping conditions. Emerging evidence suggests that a certain amount of presbyvestibulopathy is present in older individuals but may not manifest symptomatically as dizziness or imbalance. This may be because the level of vestibular impairment has not crossed a critical threshold, or because an individual is able to compensate for the presbyvestibulopathy. Presbyvestibulopathy is thus depicted in Fig. 1.1 as asymptomatic or “subclinical” and symptomatic or “clinical.” Moreover, it is evident in Fig. 1.1 that multiple factors in addition to reduced vestibular function have been associated with dizziness and imbalance in the geriatric population. It is well known among researchers who study aging that geriatric conditions often result from numerous factors that coexist at the same time and that may interact to have nonlinear, synergistic effects. Indeed, Tinetti and colleagues have described dizziness as a “geriatric syndrome,” whereby symptoms result not from sole disease entities but from accumulated impairment in multiple systems. As such, presbyvestibulopathy is often not the only contributor to dizziness and imbalance in older adults.
Epidemiology of Dizziness, Imbalance, and Presbyvestibulopathy
Prevalence
Estimates of the prevalence of dizziness and imbalance in the geriatric population depend largely on the definitions of dizziness and imbalance used and on the populations surveyed. The populations surveyed can vary with respect to their age ranges, whether they are population-based or clinic-based, and what types of clinics are being studied (e.g., primary care vs. specialty). Several large population-based studies report a 20%–30% prevalence of dizziness and imbalance in the elderly population (age ≥ 65 years). The prevalence of dizziness and imbalance is found to increase steeply with age, with levels over 50% in the community-dwelling population over age 80 years. A study in nursing home residents observes a prevalence of dizziness and vertigo of 68%. Among patients aged ≥65 years presenting to a geriatric primary care clinic, 24% report dizziness and 17% identify dizziness as their major presenting complaint. Within the otolaryngology clinic, one study of 131,000 consecutive patients found that 6% of patients over age 65 years presented with vertigo or a presumed vestibular diagnosis. Interestingly, this large-scale survey of otolaryngology practices found that visits from geriatric patients increased from 14.3% in 2004 to 17.9% in 2010. Moreover, this study noted that the five most common geriatric diagnoses were otologic, including hearing loss, external ear disorders, tinnitus, otitis media/Eustachian tube disorders, and vertigo.
A landmark series of studies based in Germany estimated the population prevalence and incidence more specifically of vestibular vertigo, i.e., vertigo resulting from vestibular impairment. Community-dwelling individuals aged ≥18 years were queried in a national telephone survey regarding symptoms of dizziness and vertigo. Those who reported moderate symptoms were administered a detailed neurotologic interview, from which vestibular vertigo was diagnosed based on symptoms of rotational vertigo, positional vertigo, or recurrent dizziness with nausea and oscillopsia or imbalance. The neurotologic interview was found to have good validity based on a gold standard of neurotology clinic-based diagnoses in establishing a vestibular diagnosis. The lifetime prevalence, 1-year prevalence, and incidence of vestibular vertigo were observed to be 7.8%, 4.9% and 1.5%, respectively. The 1-year prevalence of vestibular vertigo increased with age to 7.2% in 60- to 69-year-olds and 8.8% in individuals over age 80 years. This study was among the first to estimate the population prevalence of presbyvestibulopathy.
A more recent study estimated the prevalence of vestibular impairment in the US population using an objective, rather than subjective (self-report based), test. Data were drawn from the 2001–04 National Health and Nutrition Examination Survey (NHANES). Vestibular function was assessed in NHANES using the modified Romberg test, whereby vestibular impairment was inferred from an inability to stand on a foam pad with eyes closed. About 35% of US adults aged 40 years and older had evidence of balance dysfunction based on this postural metric. The frequency of balance dysfunction increased significantly with age, such that 85% of individuals aged 80 years and above had evidence of balance dysfunction. These estimates are considerably higher than the prevalences of vestibular vertigo reported earlier from the German population. It is possible that the symptom of vestibular vertigo represents clinical presbyvestibulopathy, whereas vestibular impairment based on the modified Romberg test encompasses both clinical and subclinical presbyvestibulopathy.
Of the major vestibular diagnoses, benign paroxysmal positional vertigo (BPPV) is particularly common in older adults and bears special mention (see Chapter 9 ). Increased BPPV in the elderly may reflect age-related degeneration of the otoconial membrane, leading to abnormal seeding of otoconia in the endolymph. A study of the German population observed a prevalence of 3.4% in individuals over age 60 years and a cumulative lifetime incidence of almost 10% by age 80 years. BPPV accounted for 39% of cases of vertigo in older patients presenting to neurotology clinics. However, older patients do not always experience the classic presentation of BPPV, short episodes of rotatory vertigo associated with changes in head position. A study of 100 older patients presenting to general geriatric practices for chronic medical conditions found that 9% had unrecognized BPPV. Moreover, patients with BPPV had significantly increased fall risk. Another study found that older patients with BPPV were more likely to experience postural instability. This instability could be improved through canalith repositioning maneuvers.
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