Prevalence and Impact of Bilateral Vestibular Hypofunction: Results From the 2008 US National Health Interview Survey

Importance  Profound bilateral vestibular hypofunction (BVH) causes disabling oscillopsia, chronic disequilibrium, and postural instability, but little is known about its epidemiology and impact.

Objective  To assess prevalence and functional impact of BVH in the US adult population.

Design and Setting  National cross-sectional survey using a national database and corollary validation study.

Patients  Adult respondents to the 2008 Balance and Dizziness Supplement to the US National Health Interview Survey (N = 21 782).

Main Outcomes and Measures  Prevalence of BVH, socioeconomic and quality-of-life impact of BVH, and fall risk. Criteria for the survey-based diagnosis of BVH included all of the following: presence of visual blurring with head movement; unsteadiness; difficulty walking in darkness or unsteady surfaces and in a straight path; and symptoms being at least “a big problem” and present for at least 1 year, in the absence of other neurologic conditions or eye pathologic conditions affecting vision.

Results  Adjusted national estimates from this survey indicate the prevalence of BVH in 2008 was 28 per 100 000 US adults (64 046 Americans). Of the participants with BVH, 44% reported changing their driving habits because of their symptoms, 56% reported reduced participation in social activities, and 58% reported difficulties with activities of daily living. Respondents with BVH had a 31-fold increase in the odds of falling in multivariate analyses compared with all respondents, with 25% reporting a recent fall-related injury.

Conclusions and Relevance  As estimated by the presence of specific symptoms in a nationally representative survey, BVH has considerable socioeconomic and quality-of-life impacts and significantly increases fall risk. These data support the need for new therapeutic strategies for BVH, including vestibular rehabilitation and implantable vestibular prostheses.

Profound bilateral loss of vestibular sensation disables the vestibuloocular and vestibulospinal reflexes that normally maintain stable gaze and posture. Affected individuals experience oscillopsia (illusory movement of the visible world during head movement), chronic disequilibrium, and postural instability that interfere with otherwise routine activities such as walking or driving.^1,2 Although the cause of bilateral vestibular hypofunction (BVH) is frequently unknown, ototoxicity due to gentamicin or other aminoglycosides is the most commonly identified cause of BVH; other causes include Ménière’s disease, labyrinthitis, meningitis, autoimmune disease, and iatrogenic damage due to cochlear implantation or other surgical procedures.^3-5

Incidence and prevalence data are available for a number of conditions affecting vestibular function^6-8; however, few data exist regarding the prevalence of BVH. Accurate estimates have been difficult to generate due to the lack of detailed reporting mechanisms focusing on balance or vestibular dysfunction in large surveys. In 2008, the National Health Interview Survey (NHIS) included supplemental dizziness and balance questions intended to assess the prevalence and associated impairments of vestibular disorders. The objective of this study was to assess the prevalence and impact of severe to profound BVH from the results of this large, nationally representative sample of adults.

The NHIS is an annual nationwide survey of the noninstitutionalized civilian population conducted by household interview.^9,10 Interviews are conducted weekly on an ongoing basis by staff at the US Census Bureau, using stratification, multistage sampling, and a probability cluster sampling technique with oversampling of minorities to improve statistical estimates. In 2008, additional information related to dizziness and balance problems was collected in a subsample of respondents as part of the annual survey. Respondents were asked if during the previous 12 months they had problems with dizziness and balance or associated symptoms. They were then asked a series of questions to characterize the severity, duration, frequency, provoking or mitigating factors, and associated symptoms of their most bothersome problem with dizziness. Additional questions regarding the use of balance aids, health care utilization, use of pharmacologic treatments, and absenteeism from school or work were asked.¹¹ The frequency and severity of falls associated with dizziness or balance problems were also obtained. In 2008, 74 236 individuals were interviewed as part of the NHIS, with a response rate of 84.9%.¹² A subsample of 21 781 adults completed the 2008 NHIS Balance and Dizziness Supplement.

Questions defining a constellation of symptom characteristics typical of BVH were intentionally incorporated into the 2008 NHIS balance supplement to allow accurate estimation of the prevalence of this disorder. A total of 3411 respondents (14.8%) answered “yes” to 1 of the following questions defining a general problem with dizziness or balance in the past 12 months (excluding times when using alcohol): “problem with dizziness or balance?”; “spinning or vertigo sensation?”; “floating, spacey, or tilting sensation?”; “feeling lightheaded, without a sense of motion?”; “feeling as if you are going to pass out or faint?”; “blurring of your vision when you move your head?”; or “feeling off-balance or unsteady?” Of those who responded “yes,” the prevalence of BVH was estimated based on affirmative responses to all of the following questions: In the absence of alcohol consumption, do you “have blurred or fuzzy vision when moving your head?”; “feel off-balance or unsteady?”; “drift to the side when trying to walk straight?”; or “have difficulty walking in the dark?” or on “uneven ground or surfaces?” Respondents had to additionally report their dizziness problem as at least a “big problem” and with duration of symptoms greater than 1 year. To exclude confounding neurologic or visual conditions with overlapping responses, respondents must have answered “no” to the diagnosis of “spinal cord injury”; “stroke”; “movement disorders such as Parkinson’s”; “muscular dystrophy” or “multiple sclerosis”; or a diagnosis “macular degeneration,” “glaucoma,” “diabetic retinopathy,” or “cataracts” causing visual impairment.

Participants in the NHIS cannot be contacted after completing the interview study; therefore, a corollary study was performed to assess construct validity of our case definition of BVH. We surveyed 3 groups with a sample of questions from the NHIS Balance and Dizziness Supplement: 12 individuals with known BVH, 12 with known chronic unilateral vestibular hypofunction (UVH) of at least 1-year duration, and 13 with no history of dizziness or inner ear pathologic features. For BVH and UVH groups, respondents must have had documented vestibular hypofunction on the basis of history and physical examination findings and confirmed by supine and prone ice water caloric responses with peak slow-phase eye velocity of 5° per second or less bilaterally for patients with BVH or unilaterally for patients with UVH. Causes of BVH included aminoglycoside ototoxicity (n = 5), bilateral Ménière’s disease (n = 1), head and neck trauma (n = 1), and unknown (n = 5). Patients with UVH had a history of unilateral Ménière’s disease that had been treated by intratympanic gentamicin to ablate residual vestibular function. The proposed survey-based case definition of BVH completely differentiated BVH from respondents with chronic UVH (Table 1). One subject with BVH had symptom duration less than 1 year and would not have met the case definition requirement. This requirement of disease duration of at least 1 year was maintained for application to the NHIS data because we wished to exclude temporary vestibular conditions with overlapping symptoms.

Questions regarding activities of daily living and social limitations were asked of all NHIS respondents. Respondents were categorized as having none, 1 to 3, or 4 or more functional limitations by the frequency with which they responded “very difficult” or “can’t do at all” for 9 activities: walk 400 m; walk up 10 steps without resting; stand for 2 hours; sit for 2 hours; stoop, bend, and kneel; reach overhead; grasp small objects; lift and carry up to 4.5 kg; and push and pull large objects. Respondents had at least 1 social limitation if they reported that it was “very difficult” or that they “can’t do at all” for any of the following 3 social or leisure activities: “go out to things like shopping, movies, or sporting events”; “participate in social activities such as visiting friends, attending clubs and meetings, or going to parties”; or “do things to relax at home or for leisure.” Their need for special equipment was determined by the questions “Do you now have any health problem that requires you to use special equipment, such as a cane, a wheelchair, a special bed, or a special telephone?”

The NHIS Balance and Dizziness Supplement included additional questions specifically pertaining to a problem with dizziness or balance in the prior 12 months. These items further defined symptom character, severity and timing, provoking and mitigating factors, physical and psychological problems as a result of their balance problem, medicine and drug use, health care utilization, diagnoses conferred, treatments offered, outcomes, limitations of activities, days of school or work missed, number of falls in the past 1 and 5 years, and injury sustained due to falls. Respondent answers to these questions were used to assess the impact of BVH relative to all those with dizziness or balance problems within the last 12 months.

Statistical analyses were adjusted for the complex sample design to ensure that estimates accurately represent percentages of the US population. Sample weights were used in all analyses to adjust for the probability of selection for participation. Overall proportions and odds ratios for adults with symptoms consistent with BVH were calculated. Multivariate logistic regression was performed to evaluate for association between BVH and the covariates listed in the previous subsection. Independent variables that have previously demonstrated an association with dizziness were included in the analysis. These included sex, age, and race/ethnicity (Hispanic, non-Hispanic, white, black, native American, and multiple races). Associations were considered statistically significant for 2-sided statistics with a P value of <.05. Stata 12.0 (StataCorp) was used for all prevalence estimates, 95% confidence intervals, and odds ratios.

The 2008 NHIS Balance and Dizziness Supplement revealed that 14.8% of US adults (33.4 million) reported that they had a problem with dizziness or balance during the past year. The prevalence was higher for women (18%; 21.3 million) than for men (11%; 12.1 million) and increased with age up to 27.7% of adults (4.8 million) 75 years and older. Symptoms designated as most bothersome were “unsteadiness” (28%), “feeling lightheaded” (18%), “feeling you are about to pass out” (16%), “vertigo or spinning feeling” (14%), and “blurred vision when moving head” (5%). The least bothersome was a “floating or spacey feeling” (4%), and a few patients (1%) had multiple symptoms but could not choose which was most bothersome. Other respondents (14%) reported a dizziness or balance problem but indicated that their problem was not characterized by one of the specific symptoms listed.

Of 21 782 adults surveyed, 12 respondents reported a history consistent with chronic, disabling, severe to profound BVH (ie, all of the following: dizzy in the past year; visual blurring during head movement; unsteadiness; difficulty walking in darkness, in a straight path, or on uneven surfaces; symptom duration >1 year; and severity of problem “big” or “very big,” in the absence of neurologic or ophthalmic disease causing visual impairment). Table 2 gives the accumulated national prevalence with each “yes” response to the questions that suggest a BVH case. In 2008, the approximate US adult population was 225.2 million people. This yields an estimated adjusted national point prevalence of 28 per 100 000 US adults with BVH, or 64 046 Americans affected.

Baseline demographic characteristics of BVH respondents, all respondents, and those with a dizziness or balance problem in the preceding 12 months are given in Table 3. Compared with all survey respondents taken as a group, respondents with BVH were more likely to be female; to have been diagnosed as having diabetes or depression; and to have functional, social, and physical impairments. They were also more likely to be unemployed and to report being disabled as the reason for their unemployment. Compared with those with dizziness or balance problems in the prior year, respondents with BVH were more likely to be Hispanic, to have functional limitations, and to be on physical disability.

Of the 12 NHIS respondents who met the case definition, 7 were provided a diagnosis for their dizziness or balance problem. Reported diagnoses included benign paroxysmal positional vertigo (n = 1), head and neck trauma (n = 1), inner ear infection (n = 1), Ménière’s disease (n = 1), or other health problems (n = 3). Of the 9 who responded that they had taken or tried treatments to alleviate their symptoms, 5 (56%) had undergone physical therapy, 2 (22%) had tried “head rolling maneuvers,” 1 (11%) had undergone head and neck surgery, 3 (33%) adopted a “low salt diet” or “avoidance of food triggers,” and 6 (66%) attempted alternative therapies including massage therapy (n = 2), herbal remedies (n = 2), chiropractic manipulation (n = 1), or wearable magnets (n = 1). The majority (75%) reported that their balance problem has stayed the same or worsened over the preceding 12 months. Despite seeing a mean (SD) of 5.6 (2.9) health professionals for their dizziness or balance problems, only 25% believed that a health professional had helped with their primary dizziness complaint.

Specific functional limitations of NHIS respondents who meet the case definition of BVH compared with those with dizziness or balance problems are demonstrated in Table 4. As a result of their balance problem, the majority of BVH respondents reported limitations in social activities and employment, at higher rates than those with dizziness or balance problems alone. Of those respondents reporting a symptom complex consistent with BVH, 44% reported that they had either changed or limited their driving habits because of their symptoms, while the majority had motion discomfort, particularly when traversing tunnels; navigating stairs, escalators, or moving walkways; or riding as a passenger in car, bus, train, or plane. In addition, 88% of respondents reported falling within the past 5 years. This equates to an age-adjusted 9.9 (95% CI, 1.8-53.6)-fold increase in fall risk among those with BVH compared with those with dizziness or imbalance but not BVH, and a 31 (95% CI, 6.1-165.0)-fold increase in fall risk compared with the nationwide average. In the 12 months prior to the survey, 67% reported falling, with a mean (SD) count of 1.75 (1.8) falls. One-quarter (n = 3) reported bodily injury from a fall in the last 12 months, and 1 respondent missed 3 months of work as a result of the injury.

The results of this study indicate that a constellation of symptoms and historical features consistent with severe to profound BVH affects approximately 28 of every 100 000 US adults. This equates to a prevalence of 64 046 cases of severe to profound BVH in the United States, and 1.8 million worldwide (by extrapolation of US estimates to the 2008 world population). Prior studies on the prevalence of BVH have been restricted to subspecialty practices and to the etiology or prognosis of the condition.^3-5,13

In applying the broad series of balance-related questions in the NHIS Balance and Dizziness Supplement to patients with known BVH by examination in our validation study, we identified a series of items to which patients with BVH consistently respond, distinguishing them from patients with chronic UVH. Some items such as presence of “unsteadiness,” “blurred vision with head motion,” and “difficulty walking in darkness” have been reported previously^4,14; however, others such as difficulty walking on uneven surfaces, or difficulty walking in a straight path, may provide additional diagnostic power to clinicians and researchers attempting to distinguish BVH from chronic UVH. While all the patients with known BVH responded affirmative to the questions of the case definition, some questions better discriminated BVH from UVH. All patients with BVH ranked their problem with dizziness or balance as a “big” or “very big” problem, whereas this was found in only 1 of the 12 patients with chronic UVH (8%). The presence of symptoms “1 or more times a day” or “almost always” was found in no patients with chronic UVH and in all patients with chronic BVH. The least discriminating questions included “feeling off-balance or unsteady” (92% of patients with UVH), having “difficulty walking in the dark” (67%), “drifting to the side when trying to walk straight” (58%), having “difficulty walking on uneven ground” (42%), and experiencing “blurred vision during head movements” (42%). A combination of these questions may aid clinicians and researchers in establishing a history-based case definition of BVH.

Although the ages of patients with BVH found in this study are consistent with prior reports,^3,5,14 the present study found a higher proportion of female respondents who met the case definition for BVH. The distribution of BVH by sex has varied across prior studies, with a recent study by Kim et al¹⁴ reporting a slight female preponderance; however, these studies investigated patients in subspecialty clinics. A higher prevalence of dizziness and balance symptoms among female patients has been noted more generally in a nationally representative sample.⁶ Whether the higher proportion of women with BVH in this study represents selection bias or altered referral patterns to dizziness specialists warrants additional study.

Consistent with the perceived severity of their balance problem, many BVH respondents reported a negative impact of their dizziness or balance problem on daily activities: approximately 44% either stopped driving because of these symptoms or changed driving habits as a result of their dizziness, and 55% reported missed work or school. Cohen et al¹⁵ note a negative impact of vestibular deficiencies on driving habits, particularly in situations with limited visual feedback such as driving at night or in the rain. While that study found no decrease in total distance driven between vestibular patients and controls, no patient with BVH was included. Other studies also demonstrate the influence of dizziness symptoms on daily activities, including increased sick leave from work and lost productivity.^6,16 The present study found that three-quarters of BVH respondents were unemployed, with a significantly greater percentage on disability, compared with those with a dizziness and/or balance problem but not BVH by our case definition.

Data on the influence of BVH on quality of life have been limited, but recent evidence suggests social and physical limitations of patients with this condition.¹⁷ In this study, 39% of BVH respondents reported at least 1 social activity as “very difficult” or “unable to do,” and 58% reported severe limitations in at least 4 of 9 activities of daily living. However, 42% of those who met the case definition reported no functional limitations. This supports wide variation in reported disability due to bilateral vestibular deficiency and may depend on the degree of vestibular loss and age at onset. Those with congenital BVH or those who acquire it at a young age may experience delays in reaching developmental milestones for sitting, standing, and walking, delays that may depend on the degree of remaining otolith organ function.¹⁸ Long-term data on functional impairments of congenital BVH are lacking. Patients who acquire acute BVH as adults, however, may be dramatically affected by relentless disequilibrium, chronic oscillopsia, and cognitive dysfunction due to the need for constant attention to normally automatic functions like walking.¹ Dizziness Handicap Inventory scores have recently been shown to vary in patients with bilateral vestibulopathy depending on residual otolith function.¹⁹ While patients with BVH as a group report profound impairments in quality of life, functional impairment may vary depending on age of onset and degree of vestibular loss.

Bilateral vestibular hypofunction may impart additional risks of fall-related injury. An analysis of the National Health and Nutrition Examination Survey demonstrated that 35.4% of adults 40 years or older fail a modified Romberg test and that this finding increases the odds of falling by as much as 12 times in those who also self-report dizziness or balance problems.²⁰ In the present study, the age-adjusted fall risk of those respondents who answered according to the case definition of BVH was more than 9 times greater than that of other respondents reporting problems with dizziness and/or balance and 31 times the national average. Furthermore, one-quarter of those who met the case definition reported a fall-related injury within the last 12 months. Results from this study and others support a need for effective treatments of patients with BVH.

Currently, the only widely available treatment of BVH is vestibular rehabilitation, which can enlist visual and proprioceptive cues to partly supplant missing vestibular sensation.^21,22 Although rehabilitation is helpful for active or predictable head movements, the benefits are modest for rapid and unpredictable movements.²³ Furthermore, some patients with BVH never adequately recover performance, as can be demonstrated in the functional impairments seen in many respondents in this and other studies.¹⁷ Attempts to replace vestibular sensation with tactile stimulation of the torso, sound, and electrical stimulation of the tongue have identified postural effects but are unlikely to improve vestibuloocular reflex function.²⁴ In contrast, implantable vestibular prostheses may help patients with BVH recover vestibuloocular reflex function.^24,25

This study describes 12 respondents with symptoms consistent with BVH, but without confirmatory clinical examination or laboratory testing. The case definition for BVH used in this study was developed to include symptoms most commonly seen in patients with this condition who present to a dizziness clinic. We further excluded respondents who reported symptom duration less than 1 year, in addition to neurologic diagnosis with overlapping symptoms or ophthalmic disease causing vision loss. Though these restrictions may exclude individuals who also had BVH, we intended to provide a more conservative estimate, given the limitations of being unable to contact survey respondents. The prevalence estimate in this study may therefore underestimate the true disease prevalence. By using a less restrictive case definition that also distinguished BVH from patients with UVH in the corollary validity study (ie, presence of dizziness or balance problem in the last 12 months, feeling off-balance or unsteady, difficulty walking in the dark, and blurred vision with head motion, defined as at least a big problem and present for >1 year) the projected prevalence of BVH could extend to 85 per 100 000 or 193 369 US adults.

There are several additional limitations associated with the use of cross-sectional survey data such as in the NHIS. Conclusions regarding causation for the associations with functional impairments noted in this study cannot be determined; however, respondents attributed functional limitations (given in Table 4) to their most troublesome problem with dizziness or balance. Because the data are also self-reported, recall bias or observational bias could lead to either an overestimation or underestimation of the true prevalence of BVH. Though we tried to exclude individuals who may have symptoms that confound our definition of BVH, we may also potentially include respondents with other causes of chronic, severely symptomatic disequilibrium and visual blurring during head movement. Of the 12 cases, however, the conferred etiology and treatments were consistent with what has previously been reported in the literature for patients with BVH.⁴ Alternatively, patients with BVH may be affected by a misclassification bias by underreporting the severity of their disability, therefore leading to underestimation of prevalence. Finally, there are limitations in generalizing these results, as aminoglycoside use is more common outside of the United States, and therefore the prevalence of BVH may vary geographically.

Future studies assessing BVH prevalence would benefit from physical examination and quantitative testing such as static and dynamic visual acuity assessments, which could be administered during a future round of the NHIS. Similar studies in countries outside the United States may additionally add greater insight into the global prevalence of this morbid condition. In addition, a universal consensus regarding a case definition of BVH is needed.

In conclusion, as estimated from self-reported symptoms obtained during a comprehensive interview about balance and vestibular dysfunction in a nationally representative survey of US adults, chronically symptomatic severe to profound bilateral loss of vestibular sensation affects many US adults, at prevalence estimates comparable to Ménière’s disease.⁸ Individuals reporting a constellation of symptoms consistent with BVH are at increased risk for falls and functional impairments.

Submitted for Publication: March 6, 2013; final revision received April 10, 2013; accepted April 25, 2013.

Corresponding Author: Bryan K. Ward, MD, Johns Hopkins Outpatient Center, Department of Otolaryngology–Head and Neck Surgery, 601 N Caroline St, Sixth Floor, Baltimore, MD 21287 (bward15@jhmi.edu).

Author Contributions: Dr Ward and Mr Hoffman had full access to all the data in the study and take responsibility for the integrity of the data and the accuracy of the data analysis.

Study concept and design: Ward, Hoffman, Carey, Della Santina.

Acquisition of data: Hoffman.

Analysis and interpretation of data: Ward, Agrawal, Hoffman, Carey, Della Santina.

Drafting of the manuscript: Ward, Hoffman.

Critical revision of the manuscript for important intellectual content: Ward, Agrawal, Hoffman, Carey, Della Santina.

Statistical analysis: Ward, Hoffman.

Obtained funding: Hoffman.

Administrative, technical, and material support: Hoffman, Carey.

Study supervision: Hoffman, Carey, Della Santina.

Conflict of Interest Disclosures: Dr Della Santina holds an equity interest in Labyrinth Devices LLC. The terms of this arrangement are being managed by the Johns Hopkins Office of Policy Coordination in accordance with Johns Hopkins University policies on potential conflicts of interest.

Funding/Support: During their work on this project, Dr Ward was supported by grant T32DC000027 from the National Institute on Deafness and Other Communication Disorders (NIDCD), and Dr Della Santina was supported by grants R01DC9255 and R01DC2390 from the NIDCD.

Disclaimer: Any analyses, interpretations, or conclusions reached by the authors are credited to the authors and not to the National Center for Health Statistics, which is responsible only for the initial data.

Additional Contributions: We appreciate the efforts of the staff at the National Center for Health Statistics with collaboration and funding from the NIDCD for completing the 2008 National Health Interview Survey Balance and Dizziness Supplement. Katalin Losonczy, NIDCD, assisted in verifying the results in Tables 3 and 4.