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Hsu Y, Hu H, Chiu Y, Lee F, Huang H. Association of Sudden Sensorineural Hearing Loss With Vertebrobasilar Insufficiency. JAMA Otolaryngol Head Neck Surg. 2016;142(7):672–675. doi:10.1001/jamaoto.2016.0845
Copyright 2016 American Medical Association. All Rights Reserved. Applicable FARS/DFARS Restrictions Apply to Government Use.
Little is known about the association between sudden sensorineural hearing loss (SSNHL) and vertebrobasilar insufficiency (VBI).
To explore the association between SSNHL and VBI.
Design, Setting, and Participants
This investigation was a population-based, case-control study. Patients from January 1, 2000, to December 31, 2011, were retrospectively identified from the Taiwan National Health Insurance Research Database, which includes claims data on a random sample of 1 million people.
Main Outcomes and Measures
Using propensity score matching on age and sex, patients were stratified at a 1:4 ratio into a study group comprising 5304 patients with a diagnosis of SSNHL and a control group comprising 21 216 patients. Those with a diagnosis of VBI before the index date (the date each patient was diagnosed as having SSNHL) in both groups were then identified. A conditional logistic regression model was used to estimate the adjusted odds ratios (ORs) and 95% CIs as a measure of the association between SSNHL and VBI.
The study cohort comprised 26 520 patients. Their mean (SD) age was 51.3 (17.2) years, and 47.1% (12 500 of 26 520) were female. Vertebrobasilar insufficiency was diagnosed before the index date in 0.5% (26 of 5304) of patients with SSNHL and in 0.2% (38 of 21 216) of controls without SSNHL. After adjusting for comorbid medical disorders, patients with SSNHL were more likely than controls to have had VBI (OR, 1.76; 95% CI, 1.02-3.04). There were no significant differences in the prevalence of VBI among male patients with SSNHL vs male controls (OR, 1.72; 95% CI, 0.87-3.40) or among female patients with SSNHL vs female controls (OR, 1.86; 95% CI, 0.76-4.59).
Conclusions and Relevance
Patients with VBI appear to be at increased risk of developing SSNHL. Further research is needed to investigate the association among the severity of VBI, the risk of SSNHL, and the pattern of the audiometric curve.
Sudden sensorineural hearing loss (SSNHL) is an acute unexplained hearing loss that is often unilateral. The US National Institute for Deafness and Communication Disorders1 defines SSNHL as an idiopathic hearing loss of at least 30 dB over at least 3 test frequencies occurring during a 72-hour period. The annual incidence of SSNHL has been reported to range from as few as 4 cases per 100 000 population to as many as 160 cases per 100 000 population.2-6 The etiology of SSNHL is unclear but is likely multifactorial. Some of the proposed mechanisms include infection, autoimmune conditions, vascular insufficiency, and rupture of the labyrinthine membrane.7-9 Evidence suggests that there is a significant association between vascular events, such as thromboembolism, weak blood circulation, and vasospasm, and the development of SSNHL.10-12
The vertebrobasilar system, which includes the 2 vertebral arteries and the basilar artery, perfuses the medulla, cerebellum, pons, midbrain, thalamus, and occipital cortex. Vertebrobasilar insufficiency (VBI) can lead to a wide variety of symptoms, such as vertigo, visual disturbances (blurring, graying, and diplopia), drop attack, numbness or tingling, slurred or lost speech, confusion, and swallowing disturbance, mainly owing to impaired perfusion of the cerebellum, brainstem, and occipital cortex.13,14 Vertebrobasilar insufficiency is normally caused by insufficient collateral circulation owing to atherosclerotic stenosis of the subclavian, vertebral, or basilar arteries but can also be owing to other causes, such as compression of vertebral arteries by cervical spondylosis or subclavian steal syndrome.14,15
Occlusive diseases of the vertebrobasilar system may lead to cochleovestibular manifestations, such as sudden hearing loss and vertigo, which may be associated with symptoms relating to ischemia of the cerebral trunk.16-22 However, little is known about the association between SSNHL and VBI. In this study, we examined the association between SSNHL and VBI using data from a nationwide, medical insurance claims database in Taiwan.
Question Is there an association between sudden sensorineural hearing loss (SSNHL) and vertebrobasilar insufficiency (VBI)?
Findings In this population-based case-control study that included 26 520 patients, the prevalence of VBI was 0.5% (26 of 5304) among patients with SSNHL vs 0.2% (38 of 21 216) among controls without SSNHL, a significant difference.
Meaning Patients with VBI appear to be at increased risk of developing SSNHL.
Patients in this population-based, case-control study were retrospectively identified from the Taiwan National Health Insurance Research Database, which consists of standard computerized claims documents submitted by medical institutions seeking reimbursement through the National Health Insurance (NHI) program. The NHI program provides medical services for more than 23 million people, representing more than 99% of the population in Taiwan, and records clinical diagnoses according to International Classification of Diseases, Ninth Revision, Clinical Modification (ICD-9-CM) codes. The NHI sample files, which are constructed and managed by the National Health Research Institute, consist of comprehensive use and enrollment information for a randomly selected sample of 1 million NHI beneficiaries, representing approximately 5% of all enrolled persons in Taiwan in 2000. A multistage stratified systematic sampling design was used to create the sample, and there were no statistically significant differences in sex or age between the sample group and the enrollees.
This well-defined health insurance database has been described in more detail in previous studies.23-25 Confidentiality assurances were addressed by abiding by the data regulations of the bureaus of the NHI.23 This study was approved by the Institutional Review Board of the Taipei City Hospital.
This nested, population-based, case-control study was conducted using ambulatory care and inpatient discharge records from the NHI database for January 1, 2000, to December 31, 2011. All patients with a diagnosis of SSNHL (ICD-9-CM code 388.2) during the study period were included in the study group. These patients (n = 5304) were then matched using propensity score matching at a 1:4 ratio on age and sex to controls without SSNHL (n = 21 216). Individuals with a diagnosis of VBI (ICD-9-CM code 435.3) before the index date of SSNHL diagnosis in both groups were then identified. All diagnoses of VBI were made by neurologists according to clinical symptoms and imaging studies from outpatient departments of hospitals or clinics.
The comorbidities evaluated in this study included hyperlipidemia (ICD-9-CM code 272), diabetes mellitus (ICD-9-CM code 250), and hypertension (ICD-9-CM code 401-405). The comorbidities were identified either in an inpatient setting or from 3 or more ambulatory care claims.
A statistical program (SAS, version 9.3; SAS Institute Inc) was used to link the data in the Taiwan National Health Insurance Research Database. Another statistical program (Stata, version 13; StataCorp LP) was used to perform the statistical analyses. The χ2 test was used for categorical comparisons of data. A conditional logistic regression model was used to estimate the adjusted odds ratios (ORs) and 95% CIs as a measure of the association between SSNHL and VBI. Potential risk factors for the development of sudden deafness included in the model were hyperlipidemia, diabetes mellitus, and hypertension.
After matching for age, sex, and year of the index date, regression analysis revealed that patients with SSNHL had a higher prevalence of hyperlipidemia (22.4% vs 9.7%; difference, 12.7%; 95% CI, 11.5-13.9), diabetes mellitus (17.4% vs 6.5%; difference, 10.9%; 95% CI, 9.8-12.0), and hypertension (34.6% vs 16.6%; difference, 18.0; 95% CI, 16.6-19.4) than controls. These results are summarized in Table 1.
The overall prevalence of VBI before the index date among the study population was 0.2% (64 of 26 520). The prevalence of VBI was 0.5% (26 of 5304) among patients with SSNHL and 0.2% (38 of 21 216) among controls. The proportion of patients with VBI in the SSNHL group was significantly higher than that in the control group (OR, 1.76; 95% CI, 1.02-3.04) (Table 2). The point estimate for the association between SSNHL and VBI was similar among men (OR, 1.72; 95% CI, 0.87-3.40) and women (OR, 1.86; 95% CI, 0.76-4.59) and similar to the point estimate for the entire cohort (OR, 1.76; 95% CI, 1.02-3.04).
To the best of our knowledge, this study is the first to investigate the association between SSNHL and VBI using a nationwide population-based data set. Although the cause of SSNHL is controversial, most studies16-18 indicate that disorders of the circulatory system have an important role. We found that the prevalence of hyperlipidemia, diabetes mellitus, and hypertension was higher among patients with SSNHL, a result consistent with the findings reported in previous studies.26-28 After adjusting for the comorbidities, we found that SSNHL was independently associated with VBI.
Symptoms of VBI vary depending on the severity of the condition. Common symptoms of VBI include vertigo, transient loss of vision, tinnitus, and numbness. Some patients with SSNHL (but not all) experience vertigo and tinnitus, in addition to loss of hearing. In those patients, vertigo and tinnitus can persist for months or years after their hearing condition improves following treatment. The arterial circulation of the inner ear is completely supplied by the labyrinthine artery, which in most people is a branch of the anterior inferior cerebellar artery, although in some individuals it is a direct branch of the basilar artery. As it enters the inner ear, the labyrinthine artery bifurcates into the anterior vestibular artery and the common cochlear artery. These 2 arteries are responsible for the perfusion of the peripheral vestibular system. In some cases, it is hypothesized that SSNHL is a “minimal ischemic event” caused by decreasing vertebrobasilar blood supply.10-12
Sudden sensorineural hearing loss has been shown to be associated with several circulatory system diseases, such as stroke and myocardial infarction. Lin et al10 reported that 12.7% of 1423 patients with SSNHL had a stroke within 5 years of receiving the diagnosis. In addition, Lee et al18 and Lee and Baloh19 found that sudden deafness with cochlear audiometric features can be the initial presentation of VBI and noted that it was an important sign for the diagnosis of anterior inferior cerebellar artery infarction. In another study using the Taiwan National Health Insurance Research Database, Lin et al12 found that SSNHL was an independent risk factor for the development of myocardial infarction. The aforementioned studies indicate that SSNHL is a circulation system disorder. The results from our study support those findings in a more direct way because the vertebrobasilar system provides the main blood supply to the cochlear nerve.
The most common causes of VBI are atherosclerosis, embolism, penetrating artery disease, and arterial dissection. Symptoms depend on the arteries involved and include vertigo, headache, loss of vision, numbness, and weakness. Cases of VBI-related SSNHL have been reported. In a retrospective analysis of 333 patients treated for SSNHL in a tertiary care center during 1999 to 2002, Sauvaget et al17 found that vertebrobasilar occlusive disorders were the cause of SSHL in 4 patients (1.2%). Ohinata et al21 used Doppler ultrasound to measure blood flow in the common carotid artery and the vertebral artery in 14 male patients with sudden deafness and 70 healthy adults and found that blood flow on the affected side in patients was slower than that on the normal side and was slower than the blood flow in the control group.
The key strength of this study is its large sample size, based on data from a national medical insurance database. The National Health Insurance Administration in Taiwan examines the medical records and routinely makes detailed assessments of the accuracy of medical coding. In addition, the Taiwan National Health Insurance Research Database has been reported to be a valid source for population-based research.23 Nevertheless, our study has some limitations. First, the incidence of VBI could be underestimated because it was based on claims data. Second, the degree of VBI is not indicated in the database, thereby precluding us from determining whether the severity of VBI influences the likelihood of developing SSNHL.
Patients with VBI appear to be at increased risk of developing SSNHL. Further research is needed to investigate the associations among the severity of VBI, the risk of SSNHL, and the pattern of the audiometric curve.
Accepted for Publication: March 19, 2016.
Corresponding Author: Hung-Meng Huang, MD, Department of Otolaryngology, School of Medicine, College of Medicine, Taipei Medical University, 250 Wu-Shing St, Taipei, Taiwan 11031 (firstname.lastname@example.org).
Published Online: May 19, 2016. doi:10.1001/jamaoto.2016.0845.
Author Contributions: Drs Hsu and Huang 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: Hsu, Chiu, Lee, Huang.
Acquisition, analysis, or interpretation of data: Hu, Chiu, Huang.
Drafting of the manuscript: Hsu, Chiu, Huang.
Critical revision of the manuscript for important intellectual content: Hsu, Hu, Lee, Huang.
Statistical analysis: Hsu, Hu, Chiu, Huang.
Administrative, technical, or material support: Hsu, Huang.
Study supervision: Lee, Huang.
Conflict of Interest Disclosures: All authors have completed and submitted the ICMJE Form for Disclosure of Potential Conflicts of Interest, and none were reported.