Diabetes, cardiovascular risk factors and idiopathic sudden sensorineural hearing loss: a case-control study

Importance of small vessel disease as a possible cause of sudden sensorineural hearing loss

OBJECTIVE

Vascular disease like small-vessel disease (SVD) is the most likely cause among the potential causes of Sudden sensorineural hearing loss (SSNHL). Understanding the relationship between SVD and SSNHL is crucial for developing effective prevention and treatment strategies. To confirm the relationship between SVD and SSNHL, the effect of SVD is confirmed by focusing on the duration and recurrence of SSNHL.

METHODS

This article reports a retrospective observational study that investigated the relationship between SVD and SSNHL using the South Korea Health Insurance Review and Assessment Service (HIRA) database from 2010 to 2020. This retrospective observational study included 319,569 SSNHL patients between 2010 and 2020.

RESULTS

Participant demographics were controlled using Propensity Score Matching. The hazard ratios (HR) for the effect of SVD on the duration of SSNHL were 1.045 for the group with SVD before the onset of SSNHL and 1.234 for the group with SVD after the onset of SSNHL. SVD was statistically significant for the recurrence of SSNHL, with an odds ratio of 1.312 in the group with SVD compared to the group without SVD. The HR for the period until a recurrence in the group with SVD was 1.062.

CONCLUSIONS

The study identified SVD as a possible cause of SSNHL and found that the duration of SSNHL increased only in the presence of SVD. SVD also affected the recurrence of SSNHL, with the recurrence rate being 1.312 times higher in the group with SVD.

A prognostic value of estimated pulse wave velocity in idiopathic sudden sensorineural hearing loss

PURPOSE

Arterial stiffness, represented by estimated pulse wave velocity (ePWV), is the independent surrogate marker for cardiovascular event. The aim of the study was to investigate the significance of ePWV in the treatment outcome of idiopathic sudden sensorineural hearing loss (SSNHL).

METHODS

One hundred and ten patients with idiopathic SSNHL who hospitalized between April 2019 and March 2022 were evaluated. Arterial stiffness was calculated with formula for ePWV and other cardiovascular parameters of body mass index (BMI), and serum lipid level was determined. All patients received systemic high-dose steroid therapy and intratympanic steroid injections as a salvage management. Treatment outcome was assessed at 6 months after treatment, and classified as recovery and nonrecovery groups according to hearing recovery.

RESULTS

The initial pure-tone hearing threshold was 72.6 ± 23.8 dB and final hearing threshold was 52.63 ± 31.10 dB. After treatment, 60 (54.5%) patients included in recovery group and other 50 (45.5%) were classified as nonrecovery group. Age, days of onset to treatment, BMI, waist circumference, and ePWV were higher in the nonrecovery group compared to recovery group in univariate analysis (p = 0.039, p = 0.049, p = 0.003, p = 0.004, p = 0.007, respectively). In multivariate analysis, days of onset to treatment, BMI, and ePWV were associated with recovery (p = 0.030, p = 0.007, p = 0.022).

CONCLUSION

Higher ePWV, a measure of arterial stiffness, was associated with a poor hearing recovery of SSNHL.

Assessing the Brainstem Auditory Evoked Potentials in Subjects with Family History of Hypertension

Background

Hypertension (HTN) has a genetic predisposition and it also impairs microcirculation, thereby, affecting the well vascularized structures like the brainstem and causing changes in Brainstem Auditory Evoked Potentials (BAEPs).

Purpose

To find out the usefulness of BAEPs as a screening tool in apparently healthy individuals with a family history of HTN.

Methods

One hundred and ten volunteers, aged 17 to 23 years, were enrolled in the study as participants with proper consent. After excluding the subjects with existing diseases or co-morbidities (e.g. diabetes, HTN, schizophrenia, neuropathy, etc.), those on ototoxic or neurotoxic drugs, a preliminary physical examination was performed, following which BAEPs were recorded with a proper device. Statistical analysis is done with SPSS 2016 software using the chi-square test.

Results

A consistent distortion in the inter-peak latency of III-V waves is noted when a family history of HTN is present in either parent or maternal grandparents. Other statistically significant findings are present in V/I% (HTN in mother), wave I (HTN in paternal grandfather), wave III (HTN in maternal grandfather), and inter-peak latency I-V (HTN in maternal grandmother).

Conclusion

BAEP may be used as a screening tool in individuals with a family history of HTN with supportive evidence from further studies in the near future.

Lipids and sudden sensorineural hearing loss: A bidirectional two-sample Mendelian randomization analysis

OBJECTIVE

While numerous observational studies have indicated an association between lipids and Sudden Sensorineural Hearing Loss (SSNHL), it remains uncertain whether dyslipidemia serves as a causal risk factor for SSNHL. Our objective is to elucidate the potential causal relationship between lipid levels and SSNHL through Mendelian randomization analysis.

METHODS

The primary and secondary lipid data used in this study were sourced from the UK Biobank (UKBB) and the Global Lipid Genetics Consortium results (GLGC), respectively. These datasets were obtained from large, publicly available genome-wide association studies (GWAS). The outcome data for sudden sensorineural hearing loss (SSNHL) were acquired from the Finnegan Biobank, consisting of 1491 cases and 196,592 controls. Subsequently, both single-variable Mendelian randomization (SVMR) and multivariate Mendelian randomization (MVMR) methods were employed to evaluate the causal relationship between lipids and the occurrence of SSNHL.

RESULTS

Among the primary lipid data, SVMR analysis showed a significant correlation between high density lipoprotein cholesterol (HDL-C) (OR: 0.822, 95 %CI: 0.694-0.974, p = 0.023) and SSNHL, and triglycerides (TG) (OR: 0.997, 95 %CI: 0.836-1.188, p = 0.975), low density lipoprotein cholesterol (LDL-C) (OR: 1.067, 95 %CI: 0.861-1.322, p = 0.552) did not correlate with SSNHL. In the secondary lipid data, SVMR analysis showed that HDL-C (OR: 0.987, 95 %CI: 0.805-1.210, p = 0.903), TG (OR: 0.991, 95 %CI: 0.787-1.246, p = 0.937) and LDL-C (OR: 1.092, 95 % CI: 0.926-1.287, p = 0.294) did not correlate with SSNHL. MVMR analysis of the primary lipid data showed that HDL-cholesterol (OR: 0.755, 95 % CI: 0.596-0.956, p = 0.019) was significantly associated with SSNHL, while TG (OR: 0.808, 95 %CI: 0.611-1.068, p = 0.134) and LDL-C (OR: 1.146, 95 %CI: 0.869-1.511, p = 0.333) did not correlate with SSNHL, consistent with the results of SVMR. Inverse MR results showed that SSNHL did not correlate with TG (OR: 0.999, 95 %CI: 0.997-1.001, p = 0.835), HDL-C (OR: 1.001, 95 %CI: 0.998-1.003), LDL-C (OR: 0.999, 95 %CI: 0.997-1.002, p = 0.863).

CONCLUSIONS

Mendelian randomization (MR) results suggest that decreased serum HDL-C levels are an independent risk factor for SSNHL. Monitoring and focusing on lipid levels may be of value in the prevention and treatment of SSNHL.

The Impact of Cardiovascular Risk Factors on the Incidence, Severity, and Prognosis of Sudden Sensorineural Hearing Loss (SSHL): A Systematic Review

Sudden sensorineural hearing loss (SSHL) is believed to be mainly idiopathic since the cause is not usually identified. Several recent studies have examined the role of cardiovascular risk factors in this disease. The aim of this systematic literature review is to investigate the possible association between acquired and inherited cardiovascular risk factors and the incidence, severity, and prognosis of SSHL. A systematic review was conducted according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. A search of the PubMed database for the period between February 2010 and January 2023 was performed in order to retrieve eligible articles. The analytic cohort included 24 studies. Overall, this systematic review includes a total of 61,060 patients that were encompassed in these studies. According to most studies, the prevalence of dyslipidaemia, diabetes, and ultrasound indices of atherosclerosis was significantly higher in SSHL patients compared to controls. On the other hand, obesity, hypertension, and smoking did not seem to influence the risk of SSHL. Most studies suggest the presence of a correlation between a high cardiovascular risk profile and the risk of developing SSHL. The theory of microvascular impairment in the development of SSHL is indirectly supported by the findings of this review.

Fibrinogen to HDL-Cholesterol ratio as a predictor of mortality risk in patients with acute myocardial infarction

BACKGROUND

Acute myocardial infarction (AMI) is characterized by inflammation, oxidative stress, and atherosclerosis, contributing to increased mortality risk. High-density lipoprotein (HDL) takes a crucial part in mitigating atherosclerosis and inflammation through its diverse functionalities. Conversely, fibrinogen is implicated in the development of atherosclerotic plaques. However, the mortality risk predictive capacity of fibrinogen to HDL-cholesterol ratio (FHR) in AMI patients remains unexplored. This research aimed to evaluate the effectiveness of FHR for mortality risk prediction in relation to AMI.

METHODS

A retrospective study involving 13,221 AMI patients from the Cardiorenal ImprovemeNt II cohort (NCT05050877) was conducted. Baseline FHR levels were used to categorize patients into quartiles. The assessment of survival disparities among various groups was conducted by employing Kaplan‒Meier diagram. Cox regression was performed for investigating the correlation between FHR and adverse clinical outcomes, while the Fine-Gray model was applied to evaluate the subdistribution hazard ratios for cardiovascular death.

RESULTS

Over a median follow-up of 4.66 years, 2309 patients experienced all-cause death, with 1007 deaths attributed to cardiovascular disease (CVD). The hazard ratio (HR) and its 95% confidence interval (CI) for cardiac and all-cause death among individuals in the top quartile of FHR were 2.70 (1.99-3.65) and 1.48 (1.26-1.75), respectively, in comparison to ones in the first quartile, after covariate adjustment. Restricted cubic spline analysis revealed that FHR was linearly correlated with all-cause mortality, irrespective of whether models were adjusted or unadjusted (all P for nonlinearity > 0.05).

CONCLUSION

AMI patients with increased baseline FHR values had higher all-cause and cardiovascular mortality, regardless of established CVD risk factors. FHR holds promise as a valuable tool for evaluating mortality risk in AMI patients.

TRIAL REGISTRATION

The Cardiorenal ImprovemeNt II registry NCT05050877.

Treatment outcomes for idiopathic sudden sensorineural hearing loss in dialysis patients

Idiopathic sudden sensorineural hearing loss (ISSNHL) is challenging for both nephrologists and otolaryngologists treating patients undergoing dialysis. This single-center, retrospective, observational study investigated the treatment outcomes of patients with ISSNHL undergoing dialysis, enrolling 700 patients (47 undergoing and 653 not undergoing dialysis) diagnosed with ISSNHL between January 2005 and December 2021 at Asan Medical Center, Republic of Korea. To balance pre-existing clinical characteristics, 1:5 propensity score matching (PSM) was performed with the patients who were not undergoing dialysis. Treatment included high-dose systemic steroid therapy or intra-tympanic steroid injections. The pure tone average of the groups was compared before and 2 weeks and 2 months after treatment. The hearing-improvement degree was evaluated using Siegel's criteria. Before PSM, age, prevalence of diabetes or hypertension, initial hearing threshold at each frequency level (0.5, 1, 2, and 4 kHz), and treatment strategies exhibited significant between-group differences. However, in the PS-matched cohort, none of the confounders showed significant between-group differences. Two months after steroid treatment, the non-dialysis patient group demonstrated significantly higher average improvement in pure tone audiometry (P = 0.029) and greater percentage of complete response according to Siegel's criteria. This study suggests that treatment outcomes for ISSNHL are significantly poorer for patients undergoing than for those not undergoing dialysis.

Contemporary Review of Idiopathic Sudden Sensorineural Hearing Loss: Management and Prognosis

Sudden sensorineural hearing loss (SSNHL) is a rapid decline in auditory function that needs urgent medical management. Although etiologic factors, including viral infections, autoimmune diseases, and vascular issues, contribute to the understanding of SSNHL, the condition remains unclear in most cases. Systemic steroids are often used as the first-line treatment because they reduce inner ear inflammation; however, there remains numerous discussions about the effectiveness of alternative treatments. To predict hearing recovery is crucial in patients' counseling with factors, including delayed treatment, vertigo, and other health conditions, which indicate poor prognosis. Herein, we review contemporary research on the treatment approaches and outcome predictions of SSNHL to establish important guidelines for physicians in evaluating and treating patients with SSNHL.

Recovery From Idiopathic Sudden Sensorineural Hearing Loss: Association With Cardiovascular Disease Risk

PURPOSE

The purpose of this study is to investigate the association between cardiovascular disease (CVD) risk factors and idiopathic sudden sensorineural hearing loss (ISSNHL) disease severity and recovery.

METHOD

A retrospective medical chart review was performed on 90 patients (n = 48 men; Mage = 59.8 years, SD = 15.8) evaluated for ISSNHL. Major CVD risk factors (current tobacco smoking, diabetes, total cholesterol ≥ 240 mg/dl or treatment, and hypertension [systolic blood pressure [BP]/diastolic BP ≥ 140/ ≥ 90 mmHg or treatment]) determined two CVD risk groups: lower (no major risk factors) and higher (one or more risk factors). Two pure-tone averages (PTAs) were computed: PTA0.5,1,2 and PTA3,4,6,8. Complete recovery of ISSNHL was defined as PTAinitial - PTAfollow-up ≥ 10 dB. Logistic regression estimated the odds of ISSNHL recovery by CVD risk status adjusting for age, sex, body mass index, noise exposure, and treatment.

RESULTS

Most patients (67.8%) had one or more CVD risk factors. Severity of initial low- and high-frequency hearing loss was similar between CVD risk groups. Recovery was 53.2% for PTA0.5,1,2 and 32.9% for PTA3,4,6,8. With multivariable adjustment, current/former smoking was associated with lower odds of PTA0.5,1,2 recovery (OR = 0.27; 95% CI [0.08, 0.92]). Neither higher CVD risk status nor individual CVD risk factors had a significant association with recovery. For every one-unit increase in Framingham Risk Score, odds of PTA3,4,6,8 recovery were 0.95 times lower (95% CI [0.90, 1.00]) after accounting for age, sex, body mass index, noise exposure, and treatment/time-to-treatment grouping (p = .056).

CONCLUSIONS

The prognosis of low-frequency ISSNHL recovery is worse among current/former smokers than nonsmokers. Other CVD risk factors and aggregate risk are not significantly related to recovery.

Subclinical neural hearing alterations in school children with type 1 diabetes mellitus

BACKGROUND AND OBJECTIVES

Evidence has shown a cause-and-effect relationship between type 1 diabetes mellitus and auditory and cognitive dysfunctions. This study aimed to investigate the effect of type 1 diabetes mellitus (T1DM) on central auditory and cognitive functions in school-age children and adolescents.

METHODS

The study sample consisted of 101 children and adolescents, 50 with T1DM, of both sexes, aged between 7 and 18 years. All participants were selected for a structured interview on hearing, behavioral, and cognitive health and assessment of brainstem auditory evoked potentials (BAEP) and event-related potentials (P300).

RESULTS

Significant differences were observed in memory (p=0.002) and attention (p=0.021) complaints between participants with and without T1DM. In the BAEP responses, there were differences between wave III latencies in the right (p=0.017) and left (p=0.019) ears and in wave V latencies in the left ear (p=0.001) between the evaluated groups. In addition, there was an association between BAEP findings and metabolic control in the T1DM group in the left ear in waves III (p=0.006) and V (p=0.005) and in the right ear in wave V (p=0.026). No differences were observed in the latencies of P300 between the evaluated groups.

CONCLUSION

This study demonstrated the existence of a subclinical finding in the central auditory pathway, offering an increased risk for retrocollear alterations, which may be a consequence of poor metabolic control.

Cardiovascular Risk Factors, Cerebral Small Vessel Disease, and Subsequent Risk of Stroke in Patients with Idiopathic Sudden Sensorineural Hearing Loss: Systematic Review and Meta-Analyses of the Current Literature

Vascular involvement in the pathophysiology of idiopathic sudden sensorineural hearing loss (iSSNHL) has been previously proposed. The objective of this study was to perform a systematic review of the current literature and conduct meta-analyses to evaluate associations between cardiovascular risk factors, cerebral small vessel disease, and subsequent stroke after presentation with iSSNHL. Three systematic literature reviews and meta-analyses were conducted using PubMed, Embase, and CINAHL. All studies investigating associations between iSSNHL and the cardiovascular risk factors: body mass index (BMI), diabetes mellitus, hyperlipidemia, hypertension, medical history of myocardial infarction (MI), smoking, the degree of white matter hyperintensities, and incidence of stroke were included. Adhering to the PRISMA guidelines, two independent reviewers reviewed the articles and assessed risk of bias. The cardiovascular risk factors of abnormal BMI, diabetes, hypertension, total cholesterol, low-density lipoprotein cholesterol, and a medical history of MI were significantly associated with iSSNHL. The adjusted hazard ratio of a higher degree of white matter hyperintensities was 0.70 (95% CI 0.44, 1.12). Patients with iSSNHL showed a higher risk of stroke compared to controls, with hazard ratios ranging from 1.22 up to 4.08. Several cardiovascular risk factors are more frequently present in patients with iSSNHL than in the general population. The degree of white matter hyperintensities does not appear to be increased in patients with iSSNHL, while the risk of stroke following ISSNHL is increased. Prospective studies with larger study populations are needed to confirm the associations between generalized cardiovascular disease and iSSNHL and to assess whether these patients benefit from cardiovascular risk management to prevent future cardiovascular and cerebrovascular disease.

Etiological analysis of patients with sudden sensorineural hearing loss: a prospective case-control study

Sudden sensorineural hearing loss (SSNHL) is a multifactorial emergency disease. Until now, the etiology of SSNHL is still unknown. Previous studies regarding the etiology of SSNHL are clinical studies depending on clinical data collection and analysis. Due to the insufficient sample size or various selective bias in clinical studies, the results of these studies may be inaccurate. This prospective case-control study aimed at exploring the possible etiology and risk factors of SSNHL. We enrolled 255 SSNHL patients and 255 sex-, age- and residence-matched non-SSNHL subjects in the control group. Our study shows that there was no significant difference in the prevalence of comorbidities including hypertension and diabetes, as well as the incidence of smoking and drinking habits between the case and control groups (P > 0.05). In addition, the peripheral blood white blood cell count, neutrophil count, platelet-to-lymphocyte ratio (PLR) and fibrinogen level of the case group were significantly higher than those in the control group (P < 0.05). These findings suggest smoking, drinking, hypertension and diabetes may not be related to the onset of SSNHL. However, hypercoagulable state and inner ear vascular microthrombosis related to an elevated fibrinogen level might be the risk factors of the disease. In addition, inflammation play an important role of SSNHL onset.Trial Registration: Chinese Clinical Trial Registry. Registration number: ChiCTR2100048991.

Cardiovascular Risk Factors in Patients With Sudden Sensorineural Hearing Loss: A Systematic Review and Meta-Analysis

OBJECTIVE

The interruption of vascular supply to the inner ear is one of several proposed etiologies of sudden sensorineural hearing loss (SSNHL). The increased presence of cardiovascular risk factors may predispose patients to SSNHL through this pathway. This systematic review and meta-analysis studies the presence of cardiovascular risk factors in patients diagnosed with SSNHL.

DATA SOURCES

Databases included PubMed/Medline, OVID, EMBASE, Cochrane, and Web of Science.

REVIEW METHODS

Inclusion criteria included studies featuring SSNHL patients presenting with 1+ cardiovascular risk factors. Exclusion criteria included case reports and studies without outcome measures. Two investigators independently reviewed all manuscripts and performed quality assessments using validated tools.

RESULTS

Of 532 identified abstracts, 27 studies met inclusion criteria (19 case-control, 4 cohorts, 4 case series). Of these, 24 underwent meta-analysis encompassing a total of 77,566 patients (22,620 SSNHL patients, 54,946 matched controls). The mean age was 50.43 years. SSNHL patients were more likely to have concomitant diabetes (odds ratio [OR] 1.61 [95% confidence interval [CI]: 1.31, 1.99; p < .00001]) and hypertension (OR 1.5 [95% CI: 1.16, 1.94; p = .002]). An increased standard mean difference of total cholesterol of 11.09 mg/dL (95% CI; 3.51, 18.67; p = .004) was noted in the SSNHL group compared with the controls. No significant differences in smoking, high-density lipoprotein, triglycerides, or body mass index were detected.

CONCLUSION

Patients presenting with SSNHL have a significantly higher risk of concomitant diabetes, hypertension, and higher total cholesterol in comparison to matched controls. This may indicate a higher cardiovascular risk profile in this population. More prospective and matched cohort studies are needed to understand the role of cardiovascular risk factors in SSNHL.

Cerebral Small Vessel Disease in Elderly Patients with Sudden Sensorineural Hearing Loss

BACKGROUND

The cause of sudden sensorineural hearing loss (SSNHL) is uncertain in a significant number of patients. A vascular etiology has been proposed because SSNHL increases the risk of developing a stroke. Cardiovascular risk factors can cause cerebral small vessel disease (CSVD). The presence of CSVD in turn raises the risk of stroke.

AIM

The aim of this study was to compare the presence of CSVD and cardiovascular risk factors in elderly patients with idiopathic SSNHL (iSSNHL) to a control cohort.

METHOD

Patients with iSSNHL of 50 years and older were compared with a control cohort with patients suspected of trigeminal neuralgia or vestibular paroxysmia. The primary outcome was the difference in the number of white matter hyperintensities using the ordinal Fazekas scale. Secondary outcomes were the presence of brain infarctions on MRI and the difference in cardiovascular risk factors.

RESULTS

In the SSNHL cohort, Fazekas score 2 was most frequently seen compared with Fazekas 1 in the control cohort. The distribution of Fazekas scores did not differ significantly. The sum of the Fazekas scores were 13,925 and 14,042 for iSSNHL and controls, respectively ( p = 0.908). Brain infarctions were seen in 8 patients with iSSNHL (n = 118) and in 13 patients in the control cohort (n = 118) ( p = 0.361). None of the cardiovascular risk factors were more frequently seen in the iSSNHL cohort.

CONCLUSION

Patients with iSSNHL did not exhibit more CSVD on MRI than controls. This result is in contrast with previous literature demonstrating a higher risk of stroke in patients with iSSNHL than in controls. A prospective analysis with a larger study population is therefore warranted.

Analysis of the vestibular aqueduct development on the risk for suffering from idiopathic sudden sensorineural hearing loss

OBJECTIVE

Large vestibular aqueduct syndrome (LVAS) is one of the etiology of hearing loss. Clinically, we observed that the VA size of patients with idiopathic sudden sensorineural hearing loss (ISSNHL) did not meet the diagnostic criteria of VA enlargement, but there were individual variations. Through this study, we want to understand the VA development and explore its risk for suffering from ISSNHL.

METHODS

74 patients with ISSNHL were retrospectively reviewed in our department from June 2018 to September 2021. Meanwhile, 57 people with no ear diseases were randomly selected as the control group. All their clinical information were systematically collected. The axial thin-slice CT images of temporal bone were used to observe and measure the VA in ISSNHL and controls. ISSNHL were classified as different types and grades according to pure tone audiometry and the degree of hearing loss, respectively. Logistic regression analysis was adopted to evaluate the risk factors of different types and grades of ISSNHL.

RESULTS

The operculum morphology could be funnel-shaped, tubular and invisible, but they had no statistical difference in the morbidity of ISSNHL. The operculum width of the affected sides in the case group was significantly wider than that of the matched sides in the control group (0.84±0.35mm vs 0.68±0.34mm, p=0.009), but the midpoint width had no statistical difference (p=0.447). The operculum width was an independent risk factor for the total hearing loss type (p=0.036, OR=4.49, 95% CI=1.10-18.29), moderate (p=0.013, OR=17.62, 95% CI=1.82-170.95) and profound (p=0.031, OR=4.50, 95% CI=1.14-17.67) grade of ISSNHL. Hypertension was an independent risk factor for the severe grade (p=0.004, OR=12.44, 95% CI=2.19-70.64) of ISSNHL. Both the operculum width (p=0.048, OR=7.14, 95% CI=1.02-50.26) and hypertension (p=0.014, OR=6.73, 95% CI=1.46-30.97) were the risk factors for the flat type of ISSNHL. The midpoint width of the VA, gender, age, diabetes mellitus, hyperlipidemia, and plasma fibrinogen concentration had no significant effect on the risk for suffering from ISSNHL.

CONCLUSION

The development of the VA operculum is a risk factor for some types and grades of ISSNHL. Hypertension remained a risk factor for ISSNHL.

Cardiovascular Risk Factors and Sudden Sensorineural Hearing Loss: A Case-Control Study

OBJECTIVE

To investigate the role of cardiovascular risk factors (specifically hypertension [HTN], hyperlipidemia/dyslipidemia, diabetes mellitus I and II, and body mass index (BMI) on the development of sudden sensorineural hearing loss (SSNHL).

STUDY DESIGN

Case-control retrospective chart review.

SETTING

A tertiary referral center.

PATIENTS

Patients aged 18 to 85 years who presented to the clinic over a 1-year span (September 17, 2020 to September 17, 2021) for evaluation of sudden sensorineural hearing loss.

MAIN OUTCOME MEASURE

Comparing the prevalence of the different cardiovascular risk factors (CVRFs) in patients with sudden sensorineural hearing loss compared with when compared with non-SSNHL patients at a neurotology clinic.

RESULTS

Two hundred twenty-three patients with SSNHL were compared with age- and gender-matched comparison group to investigate the prevalence of cardiovascular risk factors within each group. There are no statistically significant differences (p > 0.05) in the prevalence of HTN, hyperlipidemia/dyslipidemia, diabetes mellitus I and II, and BMI in patients with sudden sensorineural hearing loss when compared with non-SSNHL patients at a neurotology clinic.

CONCLUSIONS

Despite correlation between CVRF and SSNHL found in some other studies, we did not find a significant correlation between CVRF (diabetes, HTN, dyslipidemia, and high BMI) and SSNHL in our retrospective case control study of patients presenting to a nonacademic tertiary neurotology clinic. Although there may be other factors contributing to the pathogenesis of SSNHL, we have not yet identified these factors.

Evaluation of Disturbances in Hearing, Tinnitus, and Dizziness as Signs of COVID-19 Infection

BACKGROUND

There have been reports and studies indicating audiovestibular disturbances in COVID-19 patients with variations in the percentage of sensorineural hearing loss (SNHL). The purpose of this study is to compare the incidence of newly diagnosed SNHL, sudden idiopathic hearing loss (SIHL), tinnitus, and vestibular disturbances between infected and uninfected patients, as well as to identify population groups at risk.

METHODS

This study used TriNetX to obtain statistics on COVID-19 (+) and COVID-19 (-) patients from 61 healthcare organizations. Propensity score with 1:1 matching was used to control confounding variables. This study evaluated the relative risk of developing audiovestibular disturbances up to 1 month after a COVID-19 test and further investigated the incidence in COVID-19 (+) subset groups.

RESULTS

Between COVID-19 (+) and COVID-19 (-) patients who had an audiogram, there was no statistically significant difference in SNHL or SIHL (SNHL: relative risk [RR] = 0.69, 95% confidence interval [CI] = 0.46-1.04; SIHL: RR = 1.00, 95% CI = 0.42-2.40). Race/ethnicity or specified comorbidity did not affect the incidence of SNHL or SIHL. There was a statistically significant difference in tinnitus and vestibular disturbances between the COVID-19 (+) and the COVID-19 (-) groups (RR = 1.29, 95% CI = 1.01-1.66; RR = 2.33, 95% CI = 2.19-2.48).

CONCLUSION

New onset hearing loss is not more common in patients with a positive COVID-19 test than those with a negative COVID-19 test. Audiologic evaluation is needed to verify reported hearing disturbances. Although statistically significant in specific population groups, tinnitus and vestibular disturbances may not be clinically significant due to the low incidence.

Cardiovascular Risk and Sudden Sensorineural Hearing Loss: A Systematic Review and Meta-Analysis

OBJECTIVES/HYPOTHESIS

It was previously suggested that patients with idiopathic sudden sensorineural hearing loss (ISSNHL) have a higher risk of cardiovascular disease. The aim of this study is to determine if ISSNHL patients have an increased cardiovascular risk by means of a systematic review and meta-analysis.

METHODS

A systematic literature review was performed using PubMed, Embase, Cochrane Libraries and Web of Science. Studies with a clear definition of ISSNHL, investigating an association between traditional vascular risk factors and ISSNHL were included. Adhering to Preferred Reporting Items for Systematic Reviews and Meta-analysis (PRISMA) guidelines, two reviewers extracted the data, assessed the risk of bias and performed the analysis of the collected evidence.

RESULTS

Nineteen case-control studies and two cohort studies were included (102,292 patients). Individual studies argued for higher prevalence of hypercholesterolemia, diabetes mellitus (DM) and higher blood pressure (HBP) in ISSNHL patients with a range of odds ratios (ORs) from 1.03 to 19. Pooled analysis of adjusted ORs revealed a significantly increased risk of ISSNHL for patients with hypertriglyceridemia (OR 1.54; 95% confidence interval [CI] 1.18-2.02) and high levels of total cholesterol (TC) (OR 2.09; 95% CI 1.52-2.87 after sensitivity analysis), but not for HBP, DM, or high levels of low- and high-density lipoproteins.

CONCLUSION

An association between higher vascular risk profile and ISSNHL seems apparent in high levels of triglycerides (TG) and TC, but more studies are needed to confirm this hypothesis due to the high levels of data heterogeneity in the literature.

LEVEL OF EVIDENCE

NA Laryngoscope, 133:15-24, 2023.

Comorbidities and laboratory changes of sudden sensorineural hearing loss: a review

Sudden sensorineural hearing loss (SSNHL) is defined as an abrupt hearing loss of more than 30 dB in three contiguous frequencies within 72 h. It is an emergency disease requiring immediate diagnosis and treatment. The incidence of SSNHL in Western countries' population is estimated between 5 and 20 per 1,00,000 inhabitants. The etiology of SSNHL remains unknown. Due to the uncertainty of the cause of SSNHL, at present, no specific treatment targets the cause of SSNHL, resulting in poor efficacy. Previous studies have reported that some comorbidities are risk factors for SSNHL, and some laboratory results may provide some clues for the etiology of SSNHL. Atherosclerosis, microthrombosis, inflammation, and the immune system may be the main etiological factors for SSNHL. This study confirms that SSNHL is a multifactorial disease. Some comorbidities, such as virus infections, are suggested to be the causes of SSNHL. In summary, by analyzing the etiology of SSNHL, more targeting treatments should be used to achieve a better effect.

Association between atherosclerosis, hearing recovery, and hearing in the healthy ear in idiopathic sudden sensorineural hearing loss: a retrospective chart analysis

Atherosclerosis is reported to be a risk factor for the severity of idiopathic sudden sensorineural hearing loss (ISSNHL). We evaluated the hypothesis that atherosclerosis affects the hearing thresholds of both the affected and healthy sides of ISSNHL patients. We conducted multivariate analyses on retrospectively collected data of patients with ISSNHL (N = 762) to evaluate the relationship between known factors linked to atherosclerosis and hearing thresholds on affected and healthy sides and whether these factors are prognostic for hearing recovery. Older ages, vertigo or dizziness, diabetes mellitus, and congestive heart failure were significantly related to higher hearing thresholds on the affected side. Older ages, male, and vascular disease were significantly related to higher hearing thresholds on the healthy side. Vertigo or dizziness, severe hearing loss and hearing loss at high frequencies on the affected side, higher hearing thresholds on the healthy side, regular anticoagulant medication, and delayed steroid treatment were significantly related to lack of recovery. Since several atherosclerosis-related factors are associated with higher hearing thresholds on both affected and healthy sides in ISSNHL and higher hearing thresholds on the healthy side predict poorer prognosis, diagnosis, and predicting prognosis of ISSNHL may benefit from rigorous evaluation of patients' cardiovascular comorbidities and hearing levels on both the healthy and affected sides.

Astaxanthin protects against hearing impairment in diabetic rats

OBJECTIVE

Diabetes Mellitus (DM) causes an increase in oxidative stress that leads to deterioration in auditory functions. Astaxanthine (AST) is known to have strong antioxidant effects. In this study, the aim is to investigate the effect of AST against hearing loss that is due to DM.

METHODS

This study is an experimental animal study. The study was designed in four groups with 8 animals (n = 8) in each group. The groups were as follows; Control Group (CNT), Diabetic Group (DM), AST applied diabetic group (DM+AST), and AST applied non-diabetic group (AST). Streptozotocin was applied in rats to induce DM. AST was administered by oral gavage. Auditory Brainstem Responses (ABR) and Distortion Product Otoacoustic Emissions (DPOAE) tests were performed on several days of the study. At the end of the study, pro-inflammatory cytokine levels were analyzed in cochlear tissue samples, and Glutathione Peroxidase (GPx), Superoxide Dismutase (SOD), Catalase (CAT) and Malondialdehyde (MDA) levels were measured.

RESULTS

When the findings obtained in the ABR and DPOAE tests in the DM group, it was observed that there was a significant deterioration in the hearing sense. This deterioration was not observed in the DM+AST group. In the DM group, GPx, SOD and CAT levels decreased and MDA levels increased in blood and cochlear tissue. Compared to the DM group, it was noted that antioxidant enzyme levels increased and MDA levels decreased in the DM+AST group. Cochlear tissue pro-inflammatory cytokine levels, which increased with DM, were significantly decreased in the DM+AST group.

CONCLUSION

Even though the effects of AST were investigated in a diabetic experimental animal model, if this molecule is proven to be effective in diabetic humans, it can be considered an adjunct therapeutic option with its antioxidant effects.

LEVEL OF EVIDENCE

The level of evidence of this article is 5. This article is an experimental animal and laboratory study.

Age-Related Hearing Loss: The Link between Inflammaging, Immunosenescence, and Gut Dysbiosis

This article provides a theoretical overview of the association between age-related hearing loss (ARHL), immune system ageing (immunosenescence), and chronic inflammation. ARHL, or presbyacusis, is the most common sensory disability that significantly reduces the quality of life and has a high economic impact. This disorder is linked to genetic risk factors but is also influenced by a lifelong cumulative effect of environmental stressors, such as noise, otological diseases, or ototoxic drugs. Age-related hearing loss and other age-related disorders share common mechanisms which often converge on low-grade chronic inflammation known as “inflammaging”. Various stimuli can sustain inflammaging, including pathogens, cell debris, nutrients, and gut microbiota. As a result of ageing, the immune system can become defective, leading to the accumulation of unresolved inflammatory processes in the body. Gut microbiota plays a central role in inflammaging because it can release inflammatory mediators and crosstalk with other organ systems. A proinflammatory gut environment associated with ageing could result in a leaky gut and the translocation of bacterial metabolites and inflammatory mediators to distant organs via the systemic circulation. Here, we postulate that inflammaging, as a result of immunosenescence and gut dysbiosis, accelerates age-related cochlear degeneration, contributing to the development of ARHL. Age-dependent gut dysbiosis was included as a hypothetical link that should receive more attention in future studies.

Does Metabolic Syndrome Affect the Incidence and Prognosis of Sudden Sensorineural Hearing Loss?

Earlier studies reported that the occurrence of sudden sensorineural hearing loss (SSNHL) is associated with chronic metabolic disorders such as hypertension, diabetes, and hyperlipidemia. Instead of focusing on the relationship between SSNHL and each metabolic disorder, this study aimed to identify the association with metabolic syndrome as a whole, including either prehypertension or prediabetes. As a case-control study, we reviewed 239 patients who experienced SSNHL, and compared them with the same number of healthy subjects (N = 478). Metabolic syndrome-related variables of SSNHL patients were compared to those of healthy control subjects. In addition, patients with SSNHL were classified into two subgroups: the first subgroup showed improvement in hearing (‘response group’), and the second did not present significant improvement (‘non-response group’). Metabolic syndrome was diagnosed according to the US National Heart, Lung, and Blood Institute’s National Cholesterol Education Program Adult Treatment Panel III criteria. The risk for SSNHL was 4.3 times higher in patients with metabolic syndrome compared with patients without the syndrome (95% confidence interval, 1.98 to 9.33), even after adjusting for variables that showed significant between-group differences. The likelihood of being unresponsive to treatment was higher in those with metabolic syndrome (1.21 to 3.93; adjusted odds ratio = 2.18), and when the initial hearing loss pattern on a pure-tone audiometry was high tone or flat. Metabolic syndrome appears to be an independent risk factor for SSNHL and, simultaneously, a predictor of poor prognosis.

Labyrinthine lesions in presumed inner ear hemorrhage-related sudden deafness

PURPOSE

Inner ear hemorrhage (IEH) is a rare cause of sudden sensorineural hearing loss (SSNHL). This study aimed to evaluate the lesional patterns in patients with presumed IEH from morphological and functional aspects.

METHODS

Seventeen patients with SSNHL and presumed IEH who completed audio-vestibular tests were included. The main outcome measures included clinical characteristics, radiology, and functional test results.

RESULTS

The morphological findings and functional tests revealed differences in locations and lesional spectrums. The magnetic resonance imaging (MRI) hyperintensity was likely to involve the vestibule (88.2%), the cochlea (76.5%), and the posterior and lateral semicircular canals (76.5% and 70.6%, respectively). Furthermore, 70.6% of cases showed abnormality in the entire labyrinth, and abnormalities in the vestibule/semicircular canals were observed in 17.6% of cases. Meanwhile, dysfunction was sequentially detected in the cochlea (100%), semicircular canals (94.1%), and vestibule (70.6%); 64.7% of cases showed combined deficit in the entire labyrinth, and 29.4% of cases showed combined deficit in the cochlea/semicircular canals. Although lesions in the labyrinth were frequently detected, the results of the radiological and functional tests did not always match and significantly differed in either cochlear or superior semicircular canal damage detection (p < 0.05 each).

CONCLUSIONS

In this cohort, IEH preferentially caused sudden audio-vestibular impairment, which was well demonstrated by a combination of MRI and functional tests. The specific lesional configurations revealed in this study may suggest a possible pathomechanism that could be further explored as a therapeutic target.

Influence of Metabolic Syndrome on the Recovery from Idiopathic Sudden Sensorineural Hearing Loss

Introduction  Idiopathic sudden sensorineural hearing loss (ISSHL) is a disabling otologic urgency whose ethiopathogenesis is still controversial. Only in recent years metabolic syndrome (MetS) has been implicated as a possible aggravating factor in the prognosis of recovery from ISSHL.

Objective  To assess whether the preexistence of MetS interferes on hearing recovery levels.

Methods  Retrospective cohort study composed of adult (> 18 years old) ISSHL patients admitted for treatment between January 2015 and December 2019. To diagnose ISSHL, we used pure-tone audiometry, and identified MetS patients based on the criteria of the United States National Cholesterol Education Program Adult Treatment Panel III (NCEP ATP III). The treatment protocol comprised hospitalization for five days for the intravenous administration of dexamethasone, audiometric surveillance, imaging and blood analyses, and, based on recovery, the planning of rescue treatments (intratympanic administration of dexamethasone and/or hyperbaric oxygen). The Siegel criteria were used to evaluate the hearing outcomes.

Results  The final sample was composed of 81 patients, 48 without MetS (nMetS) and 33 with MetS. Regarding the Siegel recovery category, the nMetS group had significantly better results ( p  = 0.001), with 44% of complete recoveries against 6% in the MetS, and 58% of the MetS patients had the worst outcome, contrasting with 27% in the nMetS group. The nMetS group had an overall better evolution in terms of hearing recovery and had a significant improvement in the median hearing gain (20.6 dB versus 8.8 dB; p  = 0.008). Additionally, the multivariate analysis revealed that the presence of MetS is a significant risk factor for a worse outcome (odds ratio [OR] = 0.30; 95% confidence interval [95%CI] = 0.10–0.85).

Conclusion  Regardless of age, gender, the initial audiometry threshold, and autoimmunity, MetS is a clear risk factor for a worse outcome regarding the recovery of hearing after ISSHL.

Clinical Value of 3D-FLAIR MRI in Idiopathic Sudden Sensorineural Hearing Loss

BACKGROUND

Three-dimensional fluid-attenuated inversion recovery sequence magnetic resonance imaging (3D-FLAIR MRI) has been used in the diagnosis of inner ear diseases. However, the relevance of 3D-FLAIR MRI appearances with multiple features and prognosis of patients with idiopathic sudden sensorineural hearing loss (ISSNHL) remains unclear.

METHODS

This study was a retrospective trial. We recruited 1300 patients with unilateral ISSNHL hospitalized from May 2017 to January 2019. They were divided into four groups according to their 3D-FLAIR MRI appearances: normal (n = 739), inner ear hemorrhage (n = 218), increased protein content (n = 288), and blood-labyrinth barrier damage (n = 55). The correlation between 3D-FLAIR MRI appearances and the degree or type of deafness of the participants was analyzed.

RESULTS

There was a statistical difference in the deafness side (p < 0.001) and vestibular dysfunction (p < 0.001) among the four groups. There was a statistical difference in the duration of treatment (p < 0.001) and the incidence of dizziness or vertigo (p < 0.001) for patients among these groups. The degree of deafness in the patients in the inner ear hemorrhage group was significantly more severe than that of the patients in the other three groups (p < 0.001).

CONCLUSION

3D-FLAIR MRI appearances were correlated with the prognosis of patients with ISSNHL.

Severe sudden sensorineural hearing loss related to risk of stroke and atherosclerosis

The cause of idiopathic sudden sensorineural hearing loss (idiopathic SSNHL)—diagnosed after excluding other causes of hearing loss, such as SSNHL associated with vestibular schwannoma (VS)—is unknown. The presumed pathogenesis of idiopathic SSNHL includes circulatory disorders (e.g., cochlear infarction). We tested the hypothesis that patients with SSNHL who are at high stroke risk will have a lower rate of VS compared to those with low stroke risk. The rationale is that the primary cause of SSNHL in patients with high stroke risk might be a circulatory disturbance. We conducted a retrospective study in six hospitals. Our sampling of SSNHL patients included those diagnosed with idiopathic SSNHL and VS-associated SSNHL. SSNHL patients who had a head MRI were stratified by severity of hearing loss and evaluated for differences in the detection rate of VS between the high-scoring CHADS₂ (CHADS₂-H-), an index of stroke risk, and low-scoring CHADS₂ (CHADS₂-L-) groups. We identified 916 patients who met the inclusion criteria. For severe hearing loss, the CHADS₂-H group had a significantly lower rate of VS than the CHADS₂-L group (OR 0 [95% CI 0.00–0.612]; P = 0.007). These results indirectly support the hypothesis that a primary cause of severe idiopathic SSNHL in those at high risk of stroke might be a circulatory disorder.

Long-term exposure to air pollution and the risk of developing sudden sensorineural hearing loss

Background

The association between exposure to air pollution and sudden sensorineural hearing loss (SSNHL) has not been extensively discussed in the literature. Therefore, we conducted this nationwide study to evaluate the risk of SSNHL in Taiwanese residents with exposure to air pollution.

Methods

We enrolled subjects aged older than 20 years with no history of SSNHL from 1998 to 2010, and followed up until developing SSNHL, withdrawn from the National Health Insurance program, and the end of the database (2011/12/31). The air quality data are managed by Taiwan Environmental Protection Administration. The annual concentrations of PM_2.5, SO₂, CO, NO, and NO₂ from 1998 to 2010 were classified into the three levels according to tertiles. We calculated the annual average of pollutants from baseline until the end of the study, and classified into tertiles. The adjusted hazard ratio (aHR) was estimated by using the multivariate Cox proportional hazard model.

Results

When considered continuous air pollutants concentration, subjects who exposed with higher concentration of CO (aHR = 2.16, 95% CI 1.50–3.11), NO (aHR = 1.02, 95% CI 1.01–1.03), and NO₂ (aHR = 1.02, 95% CI 1.01–1.04) developing significant higher risk of SSNHL. When classified air pollutants concentration into low, moderate and high level by tertiles, and selected low level as reference, patients exposed with moderate (aHR = 1.56, 95% CI 1.20–2.04) or high level (aHR = 1.33, 95% CI 1.01–1.75) of PM_2.5 showed significant higher risk of developing SSNHL.

Conclusion

This study indicated an increased risk of SSNHL in residents with long-term exposure to air pollution. Nevertheless, further experimental, and clinical studies are needed to validate the study findings.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12967-021-03095-8.

Sudden Sensorineural Hearing Loss and Metabolic Syndrome: A Systematic Review and Meta-analysis

OBJECTIVE

The objective of this systematic review and meta-analysis is to examine the association between sudden sensorineural hearing loss (SSNHL) and risk of metabolic syndrome (MetS), and the association between MetS and prognosis of SSNHL.

DATABASES REVIEWED

We systematically searched MEDLINE, Embase, and Cochrane Central Register electronic databases from their dates of conception to February 4, 2020.

METHODS

We included observational studies analyzing 1) the prevalence of MetS among SSNHL patients, or 2) the prognosis of SSNHL patients in MetS patients. A standardized form was completed in duplicate extracting data on study characteristics, participant demographics, and SSNHL outcome or recovery measures. Random-effects meta-analyses were performed pooling odds ratios using the generic inverse method. Risk of bias was assessed using the Newcastle Ottawa Scale.

RESULTS

Three studies examining the prevalence of MetS among patients with SSNHL (11,890 total participants; 3,034 SSNHL participants) yielded a significantly increased risk of MetS among SSNHL, with a pooled odds ratio of 1.88 (95% CI, 1.01-3.50). Three studies examining the association of SSNHL prognosis in patients with MetS (608 SSNHL participants, 234 concomitant SSNHL, and MetS participants) demonstrated that SSNHL patients with MetS were significantly more likely to have poorer recovery compared to SSNHL patients without MetS (pooled odds ratio 2.77; 95% CI, 2.33-3.28).

CONCLUSION

Our findings suggest an association between prevalence of MetS and SSNHL, as well as poorer prognosis of SSNHL in patients with concomitant MetS.

Vestibular mapping assessment in idiopathic sudden sensorineural hearing loss

OBJECTIVE

The aim of this study was to investigate patterns of semicircular canal (SCC) and otolith organ dysfunction by vestibular mapping, and to determine the clinical implications of treatment outcomes in idiopathic sudden sensorineural hearing loss (ISSNHL).

METHODS

We retrospectively reviewed 135 consecutive patients diagnosed with ISSNHL from January 2016 to December 2020. Patients underwent video-head impulse tests (vHIT) for each SCC, cervical vestibular-evoked myogenic potential test for the saccules, ocular vestibular-evoked myogenic potential test for the utricles, and hearing tests. Hearing outcomes were evaluated according to the American Academy of Otolaryngology-Head and Neck Surgery criteria and factors associated with prognosis were assessed. We also conducted vestibular mapping assessments and hierarchical cluster analysis.

RESULTS

Overall, utricular impairment (76, 56.3%) was the most frequent diagnosis in the 135 ISSNHL patients, followed by saccular impairment (59, 43.7%) and posterior SCC impairment (30, 22.2%). The mean number of affected end organs was 1.37 ± 1.24, with higher numbers in the complete recovery group than in the partial/no recovery groups. In a multivariate analysis, higher initial hearing level and abnormal vHIT results in the posterior SCC were associated with poor prognosis in ISSNHL. In hierarchical cluster analysis, horizontal SCC and anterior SCC showed the highest similarity but were in different clusters than posterior SCC, and the saccule and utricle were in separate clusters from the three SCCs.

CONCLUSIONS

The vestibular end organ showed various patterns of dysfunction in patients with ISSNHL. Of the five vestibular end organs, only abnormal posterior SCC was associated with poor prognosis for hearing recovery.

Hearing Impairment in a Mouse Model of Diabetes Is Associated with Mitochondrial Dysfunction, Synaptopathy, and Activation of the Intrinsic Apoptosis Pathway

Although previous studies continuously report an increased risk of hearing loss in diabetes patients, the impact of the disease on the inner ear remains unexplored. Herein, we examine the pathophysiology of diabetes-associated hearing impairment and cochlear synaptopathy in a mouse model of diabetes. Male B6.BKS(D)-Lepr^db/J (db/db, diabetes) and heterozygote (db/+, control) mice were assigned into each experimental group (control vs. diabetes) based on the genotype and tested for hearing sensitivity every week from 6 weeks of age. Each cochlea was collected for histological and biological assays at 14 weeks of age. The diabetic mice exerted impaired hearing and a reduction in cochlear blood flow and C-terminal-binding protein 2 (CtBP2, a presynaptic ribbon marker) expression. Ultrastructural images revealed severely damaged mitochondria from diabetic cochlea accompanied by a reduction in Cytochrome c oxidase subunit 4 (COX4) and CR6-interacting factor 1 (CRIF1). The diabetic mice presented significantly decreased levels of platelet endothelial cell adhesion molecule (PECAM-1), B-cell lymphoma 2 (BCL-2), and procaspase-9, but not procaspase-8. Importantly, significant changes were not found in necroptotic programmed cell death markers (receptor-interacting serine/threonine-protein kinase 1, RIPK1; RIPK3; and mixed lineage kinase domain-like pseudokinase, MLKL) between the groups. Taken together, diabetic hearing loss is accompanied by synaptopathy, microangiopathy, damage to the mitochondrial structure/function, and activation of the intrinsic apoptosis pathway. Our results imply that mitochondrial dysfunction is deeply involved in diabetic hearing loss, and further suggests the potential benefits of therapeutic strategies targeting mitochondria.

Autonomic Nervous Function in Patients with Sudden Sensorineural Hearing Loss and Its Association with Prognosis and Disease Severity

INTRODUCTION

Vascular disorder is considered one of the main mechanisms of sudden sensorineural hearing loss (SSNHL) due to the anatomy of the inner ear. One factor that can contribute to vascular disorder is impairment in the autonomic nervous system. This study aims to investigate autonomic function in patients with SSNHL and its association with prognosis and disease severity from January 2018 to October 2019.

METHODS

We conducted a cross-sectional study involving 40 healthy controls and 55 subjects with SSNHL. We compared the autonomic function of controls and patients using heart rate variability (HRV). SSNHL patients were divided into improvement and no-improvement groups and into mild and severe groups according to pure-tone audiometry results.

RESULTS

The SSNHL group had significantly decreased total power (TP), low frequency (LF), and high frequency (HF) compared to the control group. However, there were no significant differences between the mild and severe groups. In the no-improvement group, LF was significantly higher and normalized HF was significantly lower than in the improvement group. According to a multiple logistic regression analysis, age and LF were significantly correlated with improvement.

CONCLUSION

This is the first study to evaluate the significance of HRV in patients with SSNHL, according to prognosis and disease severity. Further studies about the relationship between autonomic nervous system and SSNHL with larger sample size and prospective design are needed.

The prognostic and predictive value of platelet parameters in diabetic and nondiabetic patients with sudden sensorineural hearing loss

BACKGROUND

We aimed to evaluate the association between mean platelet volume, platelet distribution width (PDW), platelet count (PC) and plateletcrit (PCT), and the presence of sudden sensorineural hearing loss (SSNHL) and treatment response. In the literature, there is no study that investigates the platelet functions in diabetic patients with SSNHL.

METHODS

The patients were retrospectively assigned into Group 1 (68 diabetic patients with SSNHL), Group 2 (63 nondiabetic patients with SSNHL) and Group 3 (64 healthy controls).

RESULTS

PC was not significantly different between the groups (p > 0.05). MPV, PDW and PCT values were significantly higher in Group 1 as compared to Groups 2 and 3 (p < 0.05). Platelet parameters were not significantly different between the patients who were responsive and nonresponsive to the treatment. Therefore, the platelet parameters did not affect prognosis significantly in this study samples (p > 0.05).

CONCLUSIONS

This study showed that platelet parameters did not have a significant effect as a prognostic and predictive value in diabetic and nondiabetic patients with SSNHL. Further studies with more homogenous and larger study groups investigating the platelet parameters are needed to demonstrate microvascular damage and vascular alterations induced by diabetes mellitus.

Is the risk of idiopathic sudden sensorineural hearing loss higher in nasopharyngeal carcinoma than in hypopharyngeal cancer? A population-based study

BACKGROUND

The aim of this study was to compare the risk of developing sudden sensorineural hearing loss (SSHL) in patients with hypopharyngeal cancer with that in patients with nasopharyngeal carcinoma (NPC).

METHODS

A population-based, retrospective cohort study was performed using the Taiwan National Health Research Database databank. Patients selected for this study were diagnosed with hypopharyngeal cancer or NPC and treated with radiotherapy in the period from 2001 to 2004. Routine follow-up was conducted for 8 years (2004-2012), and the incidence of SSHL was calculated at the final follow-up.

RESULTS

There was no significant difference in the risk of developing SSHL between the hypopharyngeal cancer group and its control group (p = 1.000). In hypopharyngeal cancer and NPC groups, the rates of SSHL were 0.12% and 1.00%, respectively (p < 0.001). The cumulative hazard of SSHL during the follow-up period was significantly higher in the NPC group than in the control group (p < 0.001).

CONCLUSION

Radiotherapy in patients with hypopharyngeal cancer did not increase the risk of developing SSHL, but postirradiation NPC was significantly associated with an increased incidence of SSHL.

The Role of Anti-Endothelial Cell Autoantibodies and Immune Response in Acute Low-Tone Hearing Loss

OBJECTIVE

Immunity is associated with acute low tone hearing loss. However, the exact pathophysiology of immunity-mediated acute low tone hearing loss remains unknown. In this study, we evaluated the presence, therapeutic effectiveness, and immunopathological mechanisms of anti-endothelial cell autoantibodies (AECEs) in patients with acute low-frequency hearing loss.

MATERIAL AND METHODS

Forty-nine patients who were treated as inpatients having acute low-frequency hearing loss and additional symptoms, such as ear fullness, tinnitus, dizziness, or hyperacusis, were enrolled in this study. Serum samples from these patients were collected for laboratory serum autoimmunity detection, including AECAs, antinuclear antibodies, immunoglobulin, and circular immune complex. Therapeutic responses to combination therapy in short-term outcome and serum cytokine levels were compared between AECA-positive and AECA-negative patients.

RESULTS

Anti-endothelial cell autoantibodies-positive patients tended to show significantly less response to standard therapy compared with AECAs controls (P < .05). Moreover, some serum cytokine levels elevated in both AECAs- and AECAs+ groups. Positive ratio of interleukin-8 and concentrations of macrophage inflammatory protein-1α were found higher in AECAs+ groups (P < .05).

CONCLUSION

The results supported that AECAs might wield influence on the short-term outcome of acute low-tone hearing loss (ALHL) treatment. Furthermore, AECA-mediated acute low-frequency hearing loss possibly involved dysregulation of inflammation process and release of cytokines.

Pterostilbene protects cochlea from ototoxicity in streptozotocin-induced diabetic rats by inhibiting apoptosis

Diabetes mellitus (DM) causes ototoxicity by inducing oxidative stress, microangiopathy, and apoptosis in the cochlear sensory hair cells. The natural anti-oxidant pterostilbene (PTS) (trans-3,5-dimethoxy-4-hydroxystylbene) has been reported to relieve oxidative stress and apoptosis in DM, but its role in diabetic-induced ototoxicity is unclear. This study aimed to investigate the effects of dose-dependent PTS on the cochlear cells of streptozotocin (STZ)-induced diabetic rats. The study included 30 albino male Wistar rats that were randomized into five groups: non-diabetic control (Control), diabetic control (DM), and diabetic rats treated with intraperitoneal PTS at 10, 20, or 40 mg/kg/day during the four-week experimental period (DM + PTS10, DM + PTS20, and DM + PTS40). Distortion product otoacoustic emission (DPOAE) tests were performed at the beginning and end of the study. At the end of the experimental period, apoptosis in the rat cochlea was investigated using caspase-8, cytochrome-c, and terminal deoxyribonucleotidyl transferase-mediated dUTP-biotin end labeling (TUNEL). Quantitative real-time polymerase chain reaction was used to assess the mRNA expression levels of the following genes: CASP-3, BCL-associated X protein (BAX), and BCL-2. Body weight, blood glucose, serum insulin, and malondialdehyde (MDA) levels in the rat groups were evaluated. The mean DPOAE amplitude in the DM group was significantly lower than the means of the other groups (0.9–8 kHz; P < 0.001 for all). A dose-dependent increase of the mean DPOAE amplitudes was observed with PTS treatment (P < 0.05 for all). The Caspase-8 and Cytochrome-c protein expressions and the number of TUNEL-positive cells in the hair cells of the Corti organs of the DM rat group were significantly higher than those of the PTS treatment and control groups (DM > DM + PTS10 > DM + PTS20 > DM + PTS40 > Control; P < 0.05 for all). PTS treatment also reduced cell apoptosis in a dose-dependent manner by increasing the mRNA expression of the anti-apoptosis BCL2 gene and by decreasing the mRNA expressions of both the pro-apoptosis BAX gene and its effector CASP-3 and the ratio of BAX/BCL-2 in a dose-dependent manner (P < 0.05 compared to DM for all). PTS treatment significantly improved the metabolic parameters of the diabetic rats, such as body weight, blood glucose, serum insulin, and MDA levels, consistent with our other findings (P < 0.05 compared to DM for all). PTS decreased the cochlear damage caused by diabetes, as confirmed by DPOAE, biochemical, histopathological, immunohistochemical, and molecular findings. This study reports the first in vivo findings to suggest that PTS may be a protective therapeutic agent against diabetes-induced ototoxicity.

Don't forget ototoxicity during the SARS-CoV-2 (Covid-19) pandemic!

Aim of this communication is to remind clinical professionals to be aware of ototoxic side effects of several specific drugs proposed for the treatment of the new virus SARS-CoV-2 (Covid-19). In particular, chloroquine and hydroxychloroquine, azithromycin, as well as antiviral drugs such as remdesivir, favipiravir and lopinavir can all present potential ototoxic side effects. The data in the literature do not offer specific information on their potential synergetic effects nor on their interactions.

Nimodipine and Steroid Combination Therapy for Idiopathic Sudden Sensorineural Hearing Loss

OBJECTIVE

To evaluate the treatment outcomes of nimodipine and steroid combination therapy for idiopathic sudden sensorineural hearing loss (ISSNHL).

STUDY DESIGN

Retrospective case review.

SETTING

Tertiary referral center.

PATIENTS

Seventy-eight patients who were diagnosed with ISSNHL were divided into two group based on the treatment strategies used: steroid+nimodipine (SN, n = 36) and steroid only (SO, n = 42) groups. Based on the level of hearing loss before treatment, subgroup analysis (<90 dB HL, SN-S versus SO-S groups; ≥90 dB HL, SN-P versus SO-P groups) was performed.

INTERVENTIONS

Nimodipine+dexamethasone versus dexamethasone alone.

MAIN OUTCOME MEASURES

Hearing thresholds and complete/partial recovery rate after treatment.

RESULTS

Hearing thresholds after treatment were not significantly different between the SN and SO groups (46.8 ± 29.4 versus 54.8 ± 27.6 dB HL, p = 0.218). However, the complete recovery rate was significantly higher in the SN group than in the SO group (41.7% versus 16.8%, p = 0.014). In subgroup analysis, the complete recovery rate was significantly higher in the SN-S group than in the SO-S group (60.9% versus 19.2%, p = 0.003), whereas the difference between the SN-P and SO-P groups was not significant (7.7% versus 12.5%, p = 0.672). The cumulative incidence of complete recovery was significantly higher in SN-S group than in the SO-S group (p = 0.005); the mean recovery time was 4.4 weeks (95% confidence interval [CI], 2.8-6.1) in the SN-S group and 8.8 weeks (95% CI, 7.0-10.5) in the SO-S group.

CONCLUSIONS

The results of this study suggest that nimodipine and steroid combination therapy for ISSNHL results in a higher complete recovery rate than steroid alone in patients with moderate to severe hearing loss.

Trajectories of recall memory as predictive of hearing impairment: A longitudinal cohort study

Objectives

Accumulating evidence points to a relationship between hearing function and cognitive ability in later life. However, the exact mechanisms of this relationship are still unclear. This study aimed to characterise latent cognitive trajectories in recall memory and identify their association with subsequent risk of hearing impairment.

Methods

We analysed data from the English Longitudinal Study of Ageing Wave 1 (2002/03) until Wave 7 (2014/15). The study population consisted of 3,615 adults aged 50+ who participated in the first wave of the English Longitudinal Study of Ageing, who had no self-reported hearing impairment in Wave 1, and who underwent a hearing test in Wave 7. Respondents were classified as having hearing impairment if they failed to hear tones quieter than 35 dB HL in the better ear.

Results

The trajectories of recall memory scores were grouped using latent class growth mixture modelling and were related to the presence of hearing impairment in Wave 7. Models estimating 1-class through 5-class recall memory trajectories were compared and the best-fitting models were 4-class trajectories. The different recall memory trajectories represent different starting points and mean of the memory scores. Compared to respondents with the highest recall memory trajectory, other trajectories were increasingly likely to develop later hearing impairment.

Conclusions

Long-term changes in cognitive ability predict hearing impairment. Further research is required to identify the mechanisms explaining the association between cognitive trajectories and hearing impairment, as well as to determine whether intervention for maintenance of cognitive function also give benefit on hearing function among older adults.

Association of carotid intima-media thickness with the risk of sudden sensorineural hearing loss

Cardiovascular factors are associated with the pathophysiological features and risk of sudden sensorineural hearing loss (SSNHL). However, little is known about the link between carotid intima-media thickness (IMT), SSNHL risk, and their respective treatment outcomes. In this study, we retrospectively reviewed 47 SSNHL cases and 33 control subjects from a single medical center and compared their demographic data and clinical characteristics, including their carotid IMT and audiological data. Of the 80 enrolled subjects, the proportion of those with high carotid IMT was greater in the SSNHL group (53.2%) than in the control group (21.2%), with an odds ratio (OR) of 4.22 (95% confidence interval (CI) [1.53–11.61], P = 0.004). Notably, high carotid IMT was more common in female SSNHL patients than females in the control group (54.2% vs. 12.5%; OR, 8.27 (95% CI [1.53–44.62]), P = 0.008), particularly in female patients ≥50 years of age (75% vs. 25%; OR, 9.0 (95% CI [1.27–63.9]), P = 0.032). The multivariate regression analyses showed the association between high carotid IMT and SSNHL with an adjusted OR of 4.655 (95% CI [1.348–16.076], P = 0.015), particularly in female SSNHL patients (adjusted OR, 9.818 (95% CI [1.064–90.587], P = 0.044). The carotid IMT was not associated with the treatment outcomes of SSNHL. Our results indicate that early-stage atherosclerosis may be associated with SSNHL, particularly in female patients more than 50 years old.

[New progress of IGF-1 and allosteroid injection in the treatment of sudden deafness complicated with type 2 diabetes]

Glucocorticoids are a recognized treatment for sudden deafness, and there has always been a contradiction between the control of blood glucose levels and the use of glucocorticoids. The systemic use of hormones may lead to a series of adverse events, which are dose-dependent. High doses can induce an increase in blood sugar, especially for patients with type 2 diabetes, which can aggravate their condition or cause complications. The systemic application of glucocorticoids has been largely replaced by local glucocorticoids treatment. Topical insulin-like growth factor （IGF-1） is used without increasing blood sugar, thus avoiding the possible complications. The author intends to compare the local IGF-1 treatment and local glucocorticoid treatment to systemic therapy. The efficacy of local IGF-1 therapy in treating corticosteroid-refractory sudden sensorineural hearing loss combined with type 2 diabetes is reviewed.

The Influence of Metabolic Syndrome on the Prognosis of Idiopathic Sudden Sensorineural Hearing Loss

OBJECTIVES

We aimed to verify the hypothesis that metabolic syndrome (MetS) and its components affect the prognosis of idiopathic sudden sensorineural hearing loss (ISNNHL).

STUDY DESIGN

A retrospective cohort study.

SETTING

Tertiary otology referral center.

PATIENTS

We divided patients who were diagnosed with ISSNHL between January 2015 and January 2018 into a MetS group and a Non-MetS group according to the diagnostic criteria of MetS.

INTERVENTIONS

We diagnosed ISSNHL patients by using pure-tone audiometry and treated them with oral steroids, blood flow promoting agents, and hyperbaric oxygen therapy.

MAIN OUTCOME MEASURES

We used multivariate logistic analysis to identify prognostic factors of ISSNHL.

RESULTS

The MetS group comprised 94 patients, and the Non-MetS group comprised 162 subjects. Despite the rate of hypertension, diabetes mellitus, hyperlipidemia, and BMI, no significant difference was observed between the two groups (p > 0.05). The rates of complete recovery and partial recovery of the MetS group were significantly lower than those of the Non-MetS group (p < 0.05). According to the multivariate analysis, MetS was significantly correlated with a poor prognosis (OR = 2.912, p = 0.008), and the OR increased with an increase in the number of MetS components. Late onset of treatment, high initial hearing threshold, and presence of diabetes mellitus and hyperlipidemia were associated with a poor prognosis (p < 0.05).

CONCLUSIONS

The presence of MetS may negatively affect the recovery of Chinese patients with ISSNHL, and the prognosis was poorer with an increase in the number of MetS components. Early onset of treatment, low initial hearing threshold and absence of diabetes mellitus, and hyperlipidemia are associated with favorable hearing recovery.

Framingham risk score is associated with hearing outcomes in patients with idiopathic sudden sensorineural hearing loss

Objective

To assess the Framingham risk score as a prognostic tool for idiopathic sudden sensorineural hearing loss patients.

Methods

Medical records were reviewed for unilateral idiopathic sudden sensorineural hearing loss patients between January 2010 and October 2017. The 10-year risk of developing cardiovascular disease was calculated. Patients were subdivided into groups: group 1 – Framingham risk score of less than 10 per cent (n = 28); group 2 – score of 10 to less than 20 per cent (n = 6); and group 3 – score of 20 per cent or higher (n = 5).

Results

Initial pure tone average and Framingham risk score were not significantly associated (p = 0.32). Thirteen patients in group 1 recovered completely (46.4 per cent), but none in groups 2 and 3 showed complete recovery. Initial pure tone average and Framingham risk score were significantly associated in multivariable linear regression analysis (R2 = 0.36). The regression coefficient was 0.33 (p = 0.003) for initial pure tone average and −0.67 (p = 0.005) for Framingham risk score.

Conclusion

Framingham risk score may be useful in predicting outcomes for idiopathic sudden sensorineural hearing loss patients, as those with a higher score showed poorer hearing recovery.

Serum non-high-density lipoprotein cholesterol is associated with the risk of sudden sensorineural hearing loss

The aim of this study was to investigate the association between the non-high-density lipoprotein cholesterol (non-HDL-C) with sudden sensorineural hearing loss (SSHL) and the predictive value of non-HDL-C for SSHL.A total of 324 patients with SSHL and 972 well-matched controls were enrolled from 2009 to 2012 in Korea. The association of serum non-HDL-C with the risk of SSHL was evaluated using multivariate regression analysis, smooth curve fitting after adjusting for potential confounders. The discrimination ability of non-HDL-C in predicting SSHL was determined by calculating the area under the curve (AUC), and its clinical usefulness was evaluated by decision curve analysis. This was a secondary analysis of a case-control study.There was a non-linear relationship between the serum non-HDL-C and the incidence of SSHL. After adjustment for potential confounders, the incidence of SSHL rose significantly with ascending quartiles of serum non-HDL-C (using Q1 as the reference group, the OR [95% CI] of Q2, Q3, and Q4 were 4.34 [2.43-7.74], 7.08 [3.99-12.56], and 20.88 [11.86-36.75], respectively [P for trend <.0001]). The discrimination ability of serum non-HDL-C in predicting SSHL was 0.747 (95% CI, 0.717-0.776), and the AUC was 0.733 (95% CI, 0.705-0.777) in the internal validation.Elevated serum non-HDL-C was strongly associated with increased risk of SSHL, and it may play a role as a useful biomarker in predicting the risk of SSHL.

Bidirectional relation between depression and sudden sensorineural hearing loss: Two longitudinal follow-up studies using a national sample cohort

A few studies have explored the association between depression and sudden sensorineural hearing loss (SSNHL). This study was aimed to investigate the reciprocal relations between SSNHL and depression using a nationwide cohort of the Korean population. Subjects aged > 20 years from the Korean National Health Insurance Service-National Sample Cohort were enrolled from 2002 to 2013. In study I, a total of 60,178 depressed patients were matched 1:4 with 242,872 control I subjects. In study II, a total of 4,328 SSNHL patients were 1:4 matched with 17,312 control II subjects. They were matched for age, sex, income, and region of residence. The Charlson comorbidity index (CCI) was adjusted. Subgroup analysis was performed according to age and sex. The crude and adjusted CCI hazard ratios (HRs) of SSNHL in depressed patients (study I) and depression in SSNHL patients (study II) were analyzed using the stratified Cox proportional-hazard model. In study I, the depression group exhibited an elevated adjusted HR of SSNHL 1.16 times that of the control group (confidence interval [95% CI] = 1.02–1.31, P < 0.023). The middle-aged women subgroup demonstrated an increased risk of SSNHL within the depression group. In study II, the SSNHL group showed a higher adjusted HR of depression 1.29 times that of control II group (95% CI = 1.06–1.57, P = 0.010). The middle-aged women subgroup showed an elevated risk of depression in the SSNHL group. The risk of SSNHL was elevated in the depressed patients and the risk of depression was increased in the SSNHL patients.

Metabolic syndrome components and sudden sensorineural hearing loss: a case-control study

PURPOSE

Cardiovascular risk factors, including metabolic syndrome (MetS) components, were reported as possible risk factors of sudden sensorineural hearing loss (SSNHL). The objective of this study was to evaluate the relationship between MetS (and its components) and SSNHL.

METHODS

Eighty-one SSNHL patients and 243 sex-, aged-matched controls participated from January 2018 to July 2019. The participants included 176 (54.3%) men and 148 (45.7%) women. The correlation between Mets components, total cholesterol, low-density lipoprotein-cholesterol, and the onset of SSNHL was analyzed using used multivariate conditional logistic regression analysis.

RESULTS

A total 12 patients (14.8%) with SSNHL and 27 subjects (11.1%) in control group had MetS (p > 0.05). The rate of low levels of high-density lipoprotein-cholesterol (HDL-C), hypertriglyceridemia, and hypertension was significantly higher in the SSNHL group than those in the control group (p < 0.05). A trend of odds SSNHL was observed with increasing the number of MetS components (p < 0.001). The multivariable analysis revealed that the rate of hypertriglyceridemia and low HDL-C concentration was significantly higher in the SSNHL groups compared to the controls.

CONCLUSIONS

Hypertriglyceridemia and low levels of HDL-C may be important factors in the pathogenesis of SSNHL, and should be assessed during the investigation of patients with this condition.

Effect of Diabetes on the Prognosis of Sudden Sensorineural Hearing Loss: Propensity Score Matching Analysis

Objective

The aim of this study was to investigate the clinical implications of diabetes for the management of idiopathic sudden sensorineural hearing loss (ISSNHL).

Study Design

Retrospective study.

Setting

Tertiary referral center.

Subjects and Methods

ISSNHL patients (N = 403) who received inpatient management between January 2015 and December 2018 were analyzed. All were managed by a uniform treatment protocol of high-dose steroid therapy and salvage intratympanic steroid injections. Treatment results were evaluated according to the American Academy of Otolaryngology—Head and Neck Surgery’s criteria 3 months after the start of treatment. We compared the clinical parameters and treatment outcomes of ISSNHL with and without diabetes. We also evaluated the influence of diabetes on the prognosis of ISSNHL by propensity score matching.

Results

Overall, of the 403 ISSNHL patients, 94 (23.3%) had diabetes, and 11 were newly diagnosed with diabetes. The patients with diabetes were older than those without diabetes ( P < .001), and their initial hearing threshold was significantly higher ( P < .001). The diabetic patients were hospitalized for a longer period, and their hearing recovery rate was lower. However, when age, sex, and initial hearing level were adjusted by propensity score matching, the diabetic patients and matched controls yielded similar treatment results.

Conclusions

ISSNHL with diabetes usually presents with severe hearing loss and requires longer hospitalization. However, diabetes itself may not influence the prognosis of ISSNHL. Proper management must be provided in ISSNHL with diabetes.

Association of Metabolic Syndrome With Sudden Sensorineural Hearing Loss

Importance

Each of the 5 diagnostic criteria or factors of metabolic syndrome-hyperglycemia or type 2 diabetes, hypertension, obesity, elevated triglyceride levels, and decreased high-density lipoprotein cholesterol level-is associated with the pathophysiologic features of sudden sensorineural hearing loss (SSNHL). Little is known, however, about the association of metabolic syndrome, defined as the presence of at least 3 of these factors, with the prognosis of SSNHL.

Objective

To evaluate the association of metabolic syndrome with the rate of recovery from SSNHL.

Design, Setting, and Participants

This retrospective medical record review of 124 patients treated for SSNHL at a single tertiary university hospital was performed from June 1, 2014, through May 31, 2016. Medical records were reviewed for demographic and clinical characteristics and audiologic variables.

Exposure

Sudden sensorineural hearing loss.

Main Outcomes and Measures

Correlation among demographic and clinical characteristics, audiologic results, and prognosis.

Results

Of the total 124 patients (52 men [41.9%]; 72 women [58.1%]; mean [SD] age, 56.0 [14.6] years), 70 had metabolic syndrome and 54 did not. Rates of type 2 diabetes (36 [51.4%] vs 6 [11.1%]; mean difference [MD], 40.3%; 95% CI, 24.4%-53.1%), hypertension (46 [65.7%] vs 9 [16.7%]; MD, 49.1%; 95% CI, 32.3%-61.7%), and obesity (47 [67.1%] vs 6 [11.1%]; MD%, 56.0; 95% CI, 40.0%-67.5%) and mean (SD) concentrations of triglycerides (192.9 [159.7] vs 133.4 [116.6] mg/dL; MD, 59.4 mg/dL; 95% CI, 53.0-65.9 mg/dL) were significantly higher and mean (SD) concentrations of high-density lipoprotein cholesterol (45.8 [9.4] vs 62.6 [17.7] mg/dL; MD, 16.8 mg/dL; 95% CI, 16.1-17.4 mg/dL) were significantly lower in the group with metabolic syndrome than in the group without metabolic syndrome. Mean (SD) pure-tone audiometry thresholds were similar at baseline in the groups with and without metabolic syndrome (65.0 [24.2] vs 60.8 [24.2] dB; MD, 4.3 dB; 95% CI, 3.2-5.4 dB), but recovery rates after treatment were significantly lower in the group with metabolic syndrome (16 [22.9%] vs 23 [42.6%]; MD, -19.7%; 95% CI, -35.4% to -3.2%). No differences were found in the 5 factors among patients with metabolic syndrome who did and did not recover. Level of hearing loss was higher in patients with than without metabolic syndrome, but the difference was not statistically significant. Audiogram patterns also differed but not significantly. Hearing recovery rates were similar in patients with 3 factors of metabolic syndrome and those with none but differed significantly between patients with 4 or more factors and those without metabolic syndrome (4 [19.0%] vs 27 [50.0%]; MD, -31.0%; 95% CI, -48.1% to -6.4%).

Conclusions and Relevance

The rate of recovery from SSNHL was lower among patients with metabolic syndrome than among those without metabolic syndrome, and prognosis was poorer in patients with 4 or more diagnostic factors of the metabolic syndrome.