Normal Hearing Thresholds Research Articles

The results of high-frequency audiometry in tinnitus patients

Objective: To evaluate high-frequency (HF) audiometry in subjects with unilateral subjective tinnitus and normal pure tone thresholds (≤25 dB HL) at 0.25-8 kHz.Materials and methods: The study group; consisted of 20 patients with unilateral subjective tinnitus (12 women, 8 men) and normal hearing threshold levels. A control group was also selected as 20 subjects (11 women, 9 men) having normal pure tone thresholds below 25 dBHL at 0.25-8 kHz and not complaining of tinnitus. The HF audiometry testing was used. HF hearing threshold measurements were performed in a sound-treated booth using the clinic audiometer (Interacoustics AC 40, Danimarka) with Koss R80 HF headphone at 10, 12.5, 14 and 16 kHz.Results: The pure tone hearing thresholds showed difference between tinnitus ears of study group and control group at 10, 12.5, 14 and 16 kHz (p < .05). Similarly HF hearing thresholds showed difference between tinnitus ears and non-tinnitus ears in the study group at 10, 12.5, 14 and 16 kHz (p < .05).Conclusions: The routinely use of HF audiometry in tinnitus subjects with normal pure tone thresholds with conventional audiometry can provide useful information about the patients’ hearing status.

Association between a High-Potassium Diet and Hearing Thresholds in the Korean Adult Population

The aim of this study was to determine and evaluate the association between potassium intake and hearing thresholds in the Korean adult population. Data from the Korean National Health and Nutrition Examination Survey were analyzed. Participants were divided into tertiles on the basis of their potassium intake as follows: low, middle, and high. Pure-tone audiometry was performed using an automated audiometer. We calculated as the average threshold at the low-frequency pure-tone average (0.5 and 1 kHz), mid-frequency pure-tone average (2 and 3 kHz), and high-frequency pure-tone average (4 and 6 kHz). The average hearing threshold (AHT) was calculated as the pure-tone average of the thresholds at 0.5~3 kHz. Hearing loss (HL) was defined as an AHT of >40 dB in the better ear. There were 1975 participants each in the low, middle, and high tertile groups. The four different average hearing thresholds significantly decreased with an increase in the potassium intake tertile. Multivariate analysis revealed that the four different average hearing thresholds were significantly lower in the high tertile group than in the other two groups. In addition, univariate and multivariate linear regression analyses showed that the potassium intake level was inversely associated with each of the four different average hearing thresholds. Analyses of participants matched based on propensity scores and participants not matched based on propensity scores yielded similar results. The results of this study suggest that high potassium intake levels were associated with a lower prevalence of HL and lower hearing thresholds in the Korean adult population.

Investigating the effect of extended high-frequency hearing loss on duration pattern sequence test

Background and Aim: Temporal processing is affected in people exposed to occupational noi­se. The primary goal of this study was to eva­luate the temporal processing of people exposed to occupational noise of more than 85 dB A but have not experienced clinically significant chan­ges at hearing thresholds at conventional frequ­encies. Methods: A comparison between groups were designed using individuals exposed to occupa­tional noise (n = 15 as the case group) and non-exposed individuals (n = 16 as the control gro­up). Two groups were age-matched (p &lt; 0.05). The extended high-frequency audiometric thre­sholds and temporal processing system were evaluated through a duration pattern sequence test. Finally, the correlation between the exten­ded high-frequency hearing thresholds and the duration pattern test scores was investigated. Results: The case group had significantly high­er hearing thresholds than the control group at 14, 15, and 16 kHz (p &lt; 0.05). Although in other frequencies, the mean hearing thresholds in the case group was higher than the control group, the difference was not significant. Also, the case group had significantly lower duration pattern sequence scores than the control group in the right (p = 0.02) and the left ears (p = 0.03). There was no correlation between extended high-frequency hearing thresholds and duration pattern sequence test scores. Conclusion: In people exposed to occupational noise, both extended high-frequency thresholds and temporal processing in lower frequency ran­ges (with normal hearing thresholds) are inter­rupted.

Histopathologic Characteristics of Internal Auditory Canal Diverticula.

We hypothesize that internal auditory canal (IAC) diverticula occur independent of otosclerosis as demonstrated by temporal bone histopathology. Diverticula at the anterior-inferior aspect of the IAC have been described histologically in the setting of cavitary otosclerosis. Recent radiographic studies show the prevalence of IAC diverticula that is higher than what can be accounted for by cavitary otosclerosis alone. We examined hematoxylin and eosin temporal bone histopathology slides with otosclerosis involving the IAC. We also examined bones from normal hearing subjects with normal histologic findings. Temporal bones were included if donors were more than 18 years of age at time of death and adequate horizontal cuts were available to evaluate the area of interest. IAC diverticula were found in 33 of 47 (70%) temporal bones with IAC otosclerosis and in 5 of 20 (25%) normal temporal bones. The difference in mean pure tone averages (PTA) in the normal temporal bones with (PTA 7.3 ± 7) and without (PTA 8 ± 2) diverticula was not statistically significant (p = 0.86). IAC diverticula which have been previously demonstrated to occur in the setting of cavitary otosclerosis can also occur independent from otosclerosis. Subjects with diverticula but without other temporal bone pathology have normal hearing thresholds.

Scandcleft Project, Trial 1: Comparison of Speech Outcome in Relation to Timing of Hard Palate Closure in 5-Year-Olds With UCLP.

To compare in-depth speech results in Scandcleft Trial 1 as well as reference data from peers without cleft palate (CP). A prospective randomized clinical trial. A Danish and a Swedish CP center. 143 of 148 randomized 5-year-olds with unilateral cleft lip and palate. All received lip and velum closure at 4 months, and hard palate closure at 12 months (arm A) or 36 months (arm B). A composite measure based on velopharyngeal competence (VPC) or velopharyngeal incompetence (VPI), an overall assessment of VPC from connected speech (VPC-Rate), Percentage of Consonants Correct (PCC-score), and consonant errors. Speech therapy visits, average hearing thresholds, and secondary pharyngeal surgeries documented burden of treatment. Across the trial, 61.5% demonstrated VPC and 38.5% VPI. Twenty-two percent of participants achieved age appropriate PCC-scores. There were no statistically significant differences between arms or centers for these measures. In the Danish center, arm B: achieved lower PCC-scores (P = .01); obtained PCC-scores without s-errors below 79% (P = .002); produced ≥3 active oral cleft speech characteristics (P = .004) than arm A. In both centers, arm B attended more speech visits. At age 5, differences between centers and treatment arms were not statistically significant for VPC/VPI, but consonant proficiency differed between treatment arms in the Danish center. Poor speech outcomes were seen for both treatment arms. Variations between centers were observed. As the Swedish center had few participants, intercenter comparisons should be interpreted with caution.

Hearing Loss in Agricultural Workers Exposed to Pesticides and Noise.

Agricultural workers who have concurrent exposure to pesticides and noise are at increased risk of hearing loss. We recruited 163 Thai conventional and 172 organic farmers to answer our questionnaires about personal demographics, agricultural activities, and pesticide and agricultural machinery use. This information was used to calculate the years of conventional (pesticide use) farming and the years of agricultural noise exposure, and to estimate semiquantitative metrics for pesticide exposure (cumulative intensity score-years) and cumulative noise exposure (dB(A)-years) for each conventional farmer. All participants underwent pure tone audiometric testing. The mean hearing threshold in the low-frequency band (0.5-2 kHz) and high-frequency band (3-6 kHz) were used for analysis. Years involved in conventional farming and years using agricultural machinery were associated with an increase in the average hearing threshold for the high-frequency band after controlling for age, ever exposed to industrial noise and cigarette smoking. The highest category of cumulative insecticide exposure (score-years), cumulative organophosphates exposure (score-years) and cumulative noise exposure (dB(A)-years) were also associated with an increased high-frequency band hearing threshold among conventional farmers. Results from the full cohort and the subcohort of conventional farmers support each other and the hypothesis that pesticide and noise have an additive effect on hearing, since no model interactions were significant.

Hidden hearing loss: current perspectives and potential therapies

Abstract Hidden hearing loss (HHL), an auditory dysfunction that has gained much recent attention, has the hallmarks of speech discrimination and intelligibility deficits with normal or near-normal hearing thresholds. The pathological mechanisms of HHL are complicated and are not yet fully understood. HHL can be resulted from disorders of the central nervous system such as auditory cortex, and/or pathological changes of inner ear. Thus far, 2 pathological phenomena, synaptopathy and auditory nerve demyelination, have been reported as underlying causes of otogenic HHL. Here, we review the clinical and physiological characteristics of HHL as well as the molecular pathological mechanisms of otogenic HHL and aim to allude to potential therapy targets for clinical applications in the future.

The impact of intra-operative factors in otosclerosis outcomes: retrospective study in a tertiary centre.

SUMMARYThe aim of the study was to assess results from a large cohort of patients undergoing otosclerosis surgery with respect to the impact of intra-operative variables on post-operative hearing function and complications. We enrolled 384 patients affected by otosclerosis who were subjected to stapes surgery between 2004 and 2013 at a single institution. Surgery was performed in all cases under local anaesthesia, using a manual perforator and/or microdrill. Teflon-piston prosthesis was used in all patients. Audiological data obtained preoperatively and at last follow-up examination (minimum 12 months) were compared. Statistical analysis was performed using the multiple regression model. Peripheral rim otosclerosis and diffuse otosclerosis were associated with better functional results compared to the obliterative pattern (p < 0.05). Mean post-operative Air-Bone Gap was significantly higher in the 0.4 mm, compared to 0.6 mm piston group at 0.5 kHz (p < 0.001) and 1 kHz (p < 0.02); in the stapedotomy group a statistically significant difference was found between 0.4 and 0.6 mm piston groups, in favour of the latter (p < 0.05). No differences were encountered in terms of average hearing threshold and complications. Intra-operative variables cannot be fully predictable and our data could help in stratification of the results and as a landmark for the surgeon’s decisions.

Jet fuel exposure and auditory outcomes in Australian air force personnel

BackgroundAnimal data suggest that jet fuels such as JP-8 are associated with hearing deficits when combined with noise and that the effect is more pronounced than with noise exposure alone. Some studies suggest peripheral dysfunction while others suggest central auditory dysfunction. Human data are limited in this regard. The aim of this study was to investigate the possible chronic adverse effects of JP-8 combined with noise exposure on the peripheral and central auditory systems in humans.MethodsFifty-seven participants who were current personnel from the Royal Australian Air Force were selected. Based on their levels of exposure to jet fuels, participants were divided into three exposure groups (low, moderate, high). Groups were also categorised based on their noise exposure levels (low, moderate, high). All participants were evaluated by tympanometry, pure-tone audiometry (1–12 kHz), distortion product otoacoustic emissions (DPOAEs), auditory brainstem response (ABR), words-in-noise, compressed speech, dichotic digit test, pitch pattern sequence test, duration pattern sequence test and adaptive test of temporal resolution. All auditory tests were carried out after the participants were away from the Air Force base for a minimum of two weeks, thus two weeks without jet fuel and noise exposure.ResultsJet fuel exposure was significantly associated with hearing thresholds at 4 and 8 kHz; average hearing thresholds across frequencies in the better ear; DPOAEs at 2.8, 4 and 6 kHz; ABR wave V latency in the right ear; compressed speech and words-in-noise. Further analyses revealed that participants with low exposure level to jet fuels showed significantly better results for the aforementioned procedures than participants with moderate and high exposure levels. All results were controlled for the covariates of age and noise exposure levels.ConclusionsThe results suggest that jet fuel exposure, when combined with noise exposure, has an adverse effect on audibility in humans. Taking all the test results into consideration, jet fuel exposure combined with noise exposure specifically seems to affect the peripheral hearing system in humans.

Cochlear involvement in patients with systemic autoimmune rheumatic diseases: a clinical and laboratory comparative study

Inner ear involvement has been reported in systemic rheumatic disease while detection of cochlin-specific antibodies has been reported in patients with idiopatic sensorineural hearing loss, suggesting cochlin's strong link to autoimmune hearing loss. The aim of this cross-sectional study was to calculate the prevalence of sensorineural hearing loss (SNHL) in patients with systemic rheumatic diseases, and to investigate any potential correlation with human antibodies to cochlin. Patients with rheumatoid arthritis (RA), systemic lupus erythematosus (SLE), Sjogren's syndrome (SS) and systemic sclerosis (SSc) according to the criteria of American College of Rheumatology were included in the study. All patients underwent a complete ear-nose-throat physical examination and audiological evaluation with pure tone audiometry and impedance audiometry. Pure tone average was calculated, taking as a starting point the hearing loss in dB according to the recommendation 02/1 of "Bureau International d' Audiophonologie" (BIAP) so as an average hearing threshold value. Sera of all patients were tested for the presence of IgG antibodies to human cochline (COCH-IgG). Sex and age-matched healthy subjects were included as controls to each group. A total of 133 patients were studied; 60 with RA, 41 with SLE, 24 with SS and 8 with SSc. 61.4% of patients reported vertigo, 41% hyperacousis, 39% hearing loss, 38% tinnitus, 37.9% headache and 2.1% sensation of ear pressure with unremarkable otoscopy. The prevalence of SNHL calculated for patients affected by RA, SLE, SS and SSc was 66.6%, 31.71%, 54.17%, and 75% respectively. The calculated average hearing thresholds value in RA was increased in comparison to SLE (p < 0.05). In addition it was also higher in patients with RA and secondary SS, in comparison to RA patients (p > 0.05). There was statistically significant correlation of average hearing threshold with disease activity score 28 (DAS28) in RA, but no correlation observed with disease activity index (SLEDAI) in SLE. COCH-IgG antibodies were detected in only two samples. The results were compared with those of their respective sex and age-matched healthy subjects. Our study revealed increased prevalence of SNHL in patients with systemic autoimmune rheumatic disease but no correlation of hearing loss with COCHIgG antibodies. The mechanism of inner ear damage remains unknown; thus, additional prospective studies will be needed to elucidate its pathogenesis.

Mice heterozygous for the Cdh23/Ahl1 mutation show age-related deficits in auditory temporal processing

A mutation in the Cdh23 gene is implicated in both syndromic and nonsyndromic hearing loss in humans and age-related hearing loss in C57BL/6 mice. It is generally assumed that human patients (as well as mouse models) only have a hearing loss phenotype if the mutation is homozygous. However, a major complaint for patients with a hearing disability is a reduced speech intelligibility that may be related to temporal processing deficits rather than just elevated thresholds. In this study, we used the amplitude modulation following response (AMFR) to test whether mice heterozygous for Cdh23735A > G have an auditory phenotype that includes temporal processing deficits. The hearing of mice heterozygous for the Cdh23735A > G mutation was compared with age-matched mice homozygous for either the mutation or the wild type in 3 cohorts of mice of both sexes at 2-3, 6, and 12 months of age. The AMFR technique was used to generate objective hearing thresholds for all mice across their range of hearing and to test their temporal processing. We found a genotype-dependent hearing loss in mice homozygous for the mutation starting at 5–11 weeks of age, an age when mice on the C57BL/6 background are often presumed to have normal hearing. The heterozygous animals retained normal hearing thresholds up to one year of age. Nevertheless, the heterozygous animals showed a decline in temporal processing abilities at one year of age that was independent of their hearing thresholds. These results suggest that mice heterozygous for the Cdh23 mutation do not have truly normal hearing.

Hearing Dysfunction in a Large Family Affected by Dominant Optic Atrophy (OPA8-Related DOA): A Human Model of Hidden Auditory Neuropathy.

Hidden auditory neuropathy is characterized by reduced performances in challenging auditory tasks with the preservation of hearing thresholds, resulting from diffuse loss of cochlear inner hair cell (IHC) synapses following primary degeneration of unmyelinated terminals of auditory fibers. We report the audiological and electrophysiological findings collected from 10 members (4 males, 6 females) of a large Italian family affected by dominant optic atrophy, associated with the OPA8 locus, who complained of difficulties in understanding speech in the presence of noise. The patients were pooled into two groups, one consisting of 4 young adults (19–50 years) with normal hearing thresholds, and the other made up of 6 patients of an older age (55–72 years) showing mild hearing loss. Speech perception scores were normal in the first group and decreased in the second. Otoacoustic emissions (OAEs) and cochlear microphonics (CMs) recordings were consistent with preservation of outer hair cell (OHC) function in all patients, whereas auditory brainstem responses (ABRs) showed attenuated amplitudes in the first group and severe abnormalities in the second. Middle ear acoustic reflexes had delayed peak latencies in all patients in comparison with normally hearing individuals. Transtympanic electrocochleography (ECochG) recordings in response to 0.1 ms clicks at intensities from 120 to 60 dB peak equivalent SPL showed a reduction in amplitude of both summating potential (SP) and compound action potential (CAP) together with delayed CAP peak latencies and prolonged CAP duration in all patients in comparison with a control group of 20 normally hearing individuals. These findings indicate that underlying the hearing impairment in OPA8 patients is hidden AN resulting from diffuse loss of IHCs synapses. At an early stage the functional alterations only consist of abnormalities of ABR and ECochG potentials with increased latencies of acoustic reflexes, whereas reduction in speech perception scores become apparent with progression of the disease. Central mechanisms increasing the cortical gain are likely to compensate for the reduction of cochlear input.

Investigating the Effect of Cochlear Synaptopathy on Envelope Following Responses Using a Model of the Auditory Nerve

The healthy auditory system enables communication in challenging situations with high levels of background noise. Yet, despite normal sensitivity to pure tones, many listeners complain about having difficulties in such situations. Recent animal studies demonstrated that noise overexposure that produces temporary threshold shifts can cause the loss of auditory nerve (AN) fiber synapses (i.e., cochlear synaptopathy, CS), which appears to predominantly affect medium- and low-spontaneous rate (SR) fibers. In the present study, envelope following response (EFR) magnitude-level functions were recorded in normal hearing (NH) threshold and mildly hearing-impaired (HI) listeners with thresholds elevated above 2 kHz. EFRs were elicited by sinusoidally amplitude modulated (SAM) tones presented in quiet with a carrier frequency of 2 kHz, modulated at 93 Hz, and modulation depths of 0.85 (deep) and 0.25 (shallow). While EFR magnitude-level functions for deeply modulated tones were similar for all listeners, EFR magnitudes for shallowly modulated tones were reduced at medium stimulation levels in some NH threshold listeners and saturated in all HI listeners for the whole level range. A phenomenological model of the AN was used to investigate the extent to which hair-cell dysfunction and/or CS could explain the trends observed in the EFR data. Hair-cell dysfunction alone, including postulated elevated hearing thresholds at extended high frequencies (EHF) beyond 8 kHz, could not account for the recorded EFR data. Postulated CS led to simulations generally consistent with the recorded data, but a loss of all types of AN fibers was required within the model framework. The effects of off-frequency contributions (i.e., away from the characteristic place of the stimulus) and the differential loss of different AN fiber types on EFR magnitude-level functions were analyzed. When using SAM tones in quiet as the stimulus, model simulations suggested that (1) EFRs are dominated by the activity of high-SR fibers at all stimulus intensities, and (2) EFRs at medium-to-high stimulus levels are dominated by off-frequency contributions.

Recovery From Sudden Sensorineural Hearing Loss May Be Linked to Chronic Stress Levels and Steroid Treatment Resistance.

Purpose This article investigates the possible connections between the level of chronic stress and success of steroid therapy in patients with sudden sensorineural hearing loss (SSNHL). Method A single-center, retrospective, longitudinal cohort study on 55 patients in a tertiary referral otology center was examined. Patients diagnosed with SSNHL between 2014 and 2017 were asked to complete a Measure of Perceived Stress (Brajac, Tkalcic, Dragojević, & Gruber, 2003 ) questionnaire. Inclusion criteria were patients > 18 years of age, SSNHL diagnosed within 4 previous weeks, completed steroid treatment, and complete documentation. Results There were 30 patients (55%) that showed significant improvement in their pure-tone audiogram (PTA) hearing threshold average (≥ 15 dB) after steroid treatment. Two-step cluster analysis identified 3 clusters based on average PTA hearing threshold recovery and average Measure of Perceived Stress scores. The difference between pretreatment and posttreatment hearing levels was significantly higher in the cluster with moderate stress compared to clusters with mild and high stress levels (Kruskal-Wallis test, Friedman test, p < .001). There were no significant differences in average PTA hearing threshold recovery after steroid therapy between groups of patients with mild and severe stress. Conclusion Patients with moderate stress levels show significantly better results after steroid treatment for SSNHL than patients with low or high stress levels.

Correlation between prognosis and laboratory parameters of complete deafness in patients with sudden deafness

Objective: To study the correlation between the prognosis of sudden deafness and laboratory indicators, and to provide a theoretical basis for clinical evaluation of prognosis and selection of appropriate interventions.Method: A retrospective analysis of 123 cases of total deafness was conducted(all frequencies decreased with 250-8 000 Hz average hearing threshold ≥ 81 dB HL). All patients admitted to the hospital received laboratory test within 24 hours and underwent a unified treatment: alprostadil + mecobalamin + citicoline sodium phosphate + Ginkgo biloba extract + batroxobin + methylprednisolone (patients with hypertension or diabetes were given retro-auricular injection). After 2 weeks of comprehensive treatment, the pure tone audiometry was reviewed and the clinical efficacy was evaluated. According to the prognosis, the patients were divided into the healing group, the marked effective group, the effective group and the ineffective group. The laboratory indicators included: white blood cell count, neutrophil percentage, neutrophil lymphocyte ratio(NHR), erythrocyte sedimentation rate, blood lipid, red blood cell count, hemoglobin(Hb), plasma fibrinogen content(FIB). Result: There were no significant differences in white blood cell count, neutrophil percentage, NHR, erythrocyte sedimentation rate, blood lipid index and red blood cell count between different prognosis groups(all P>0.05). The differences of FIB and Hb were statistically significant(P<0.05). The overall prognosis was negatively correlated with FIB and positively correlated with Hb. Patients with vertigo had a worse prognosis and a higher plasma FIB level than those without vertigo(P<0.05), but there was no significant difference of Hb between patients with and without vertigo(P>0.05). Conclusion: FIB and Hb can be used as correlative indexes to evaluate the prognosis of patients with sudden deafness, and the effects of vertigo and other associated symptoms on the prognosis should be comprehensively analyzed. .

Hearing and Auditory Processing Abilities in Primary School Children with Learning Difficulties

This study aimed to investigate hearing and auditory processing ability in primary school children with learning difficulties (LD). A nonrandomized, cross-sectional single measure research design was used. A total of 486 children, aged 7.7 to 10.8 years and attending years 3 and 4 in six primary schools, were classified as having an LD (n = 67) or being typically developing (TD, n = 419). This classification was based on a Learning Score generated from their school report results and National Assessment Program - Literacy and Numeracy scores. All children attempted a conventional hearing assessment (CHA) involving pure-tone audiometry, tympanometry, acoustic reflexes (AR), and otoacoustic emissions (OAEs). Children returning pure-tone audiometry results within normal limits also attempted an auditory processing assessment (APA) including dichotic digits (DD) and low-pass filtered speech (LPFS) tests. In children with LD, 21/67 (31.4%) failed the CHA, 20/58 (34.5%) failed the APA, and 32/58 (55.2%) failed the overall hearing assessment (OHA) if they failed either or both CHA and APA. In comparison, in TD children, 55/413 (13.3%) failed the CHA, 52/314 (16.6%) failed the APA, and 86/313 (27.5%) failed the OHA. Proportionally, children with LD were 2.4 times more likely than TD children to fail the CHA, 2.1 times more likely to fail the APA, and 2.0 times more likely to fail the OHA. In children who had completed the OHA, multiple linear regressions showed average AR thresholds, DD scores, and LPFS scores explained 13 to 18% of the variance in the Learning Score. The potential for hearing impairment should be investigated in children with LD. These investigations should begin with CHA, and for children returning normal-hearing thresholds, should continue with measures of AR, DD, and LPFS, to ensure these children receive the appropriate auditory support needed to enhance their learning.

Hearing as an Independent Predictor of Postural Balance in 1075 Patients Evaluated for Dizziness

To evaluate the association between hearing and postural balance. Retrospective cross-sectional study. Tertiary care otolaryngology clinic. Patients examined for suspected vestibular disorder were included in this study. The outcome variable was postural sway measured by static posturography during quiet standing with eyes closed. The predictor variable was pure-tone average hearing threshold on the best hearing ear at 0.5, 1, 2, and 3 kHz. Covariates were age, sex, and vestibular disease or vestibular asymmetry assessed by bithermal caloric irrigation. In total, 1075 patients were included. Increased hearing threshold was a strong predictor of increased postural sway (path length) after correcting for age and sex. A 10-dB increase in hearing loss on the best hearing ear predicted a mean 6.0% increase in path length (confidence interval, 2.9%-9.3%, P < .001). Of the covariates, increasing age (P < .001) and male sex (P = .009) were significant predictors of increased postural sway. The effect of increased hearing threshold was also significant after adjusting for vestibular disease. Increased hearing threshold was an independent predictor of increased postural instability, and this effect was strongest for the best hearing ear. Unilateral vestibular disease did not seem to explain this association between hearing and postural balance. Reduced hearing is associated with impaired balance, and interventions to prevent falls should be considered for patients at risk.

Effects of occupational noise exposure on asymmetric hearing loss in automobile manufacturing workers

Objective: To investigate the characteristics of asymmetric hearing loss in automobile manufacturing workers and the effect of occupational noise exposure on asymmetric hearing loss. Methods: A cross-sectional approach was used in this study. From March 2017 to February 2018, Subjects (7066) from four complete vehicle factories were given a pure tone audiometry (Hearing thresholds were measured at frequencies of 0.5, 1, 2, 3, 4 and 6 kHz in each ear) and were required to complete a health-related information questionnaire. According to the inclusion criteria, a total of 6339 workers were selected. The mean hearing thresholds for the left and right ears at overall frequencies were compared using the repeated means analysis of variance (ANOVA) test. The threshold differences at each frequency were compared using paired t tests. Results: The overall mean left minus right threshold difference across all frequencies was determined to be 0.58 dB, which met statistical significance (P<0.01) . Hearing threshold in the left ear was statistically significantly higher compared with the right ear at each frequency. The differences between binaural threshold shifts at each frequency among subjects with a asymmetry in terms of worse left ear and worse right ear were at the range of 6.17-9.87 dB and 6.39-10.92 dB, respectively. Hearing threshold in the left ear was statistically significantly higher compared with the right ear at only 2, 3 kHz of subjects with high-frequency hearing threshold shifts (HFHTs) more than 25 dB. Hearing threshold in the left ear was statistically significantly higher compared with the right ear at only 3 kHz of subjects with high-frequency hearing threshold shifts (HFHTs) more than 30 dB. With the increase of HFHTs, the proportion of subjects with a asymmetry at 2 and 3 kHz of more than 10 dB in terms of worse left ear and worse right ear increased. Conclusion: The average hearing threshold of the left ear across overall frequencies is higher compared with the right ear, the proportion of the cases with a higher left ear hearing threshold is higher that that of the cases with a higher right ear hearing threshold. As hearing loss caused by occupational noise exposure getting worse, the proportion of the cases with a higher left ear hearing threshold and the cases with a higher right ear hearing threshold may tent to be the same.

Bone conduction hearing in the Guinea pig and the effect of artificially induced middle ear lesions

Although human bone conduction (BC) hearing is well investigated, there is a lack of information about BC hearing in most other species. In humans, the amount of conductive loss is estimated as the difference between the air conduction (AC) and BC thresholds. Similar estimations for animals are difficult since in most species, the normal BC hearing thresholds have not been established. In the current study, the normal BC thresholds in the frequency range between 2 kHz and 20 kHz are investigated for the Guinea pig. Also, the effect of a middle ear lesion, here modelled by severing the ossicles (ossicular discontinuity) and gluing the ossicles to the bone (otosclerosis), is investigated for both AC and BC.The hearing thresholds in the Guinea pigs were estimated by a regression of the amplitude of the compound action potential (CAP) with stimulation level and was found robust and gave a high resolution of the threshold level. The reference for the BC thresholds was the cochlear promontory bone velocity. This reference enables comparison of BC hearing in animals, both intra and inter species, which is independent on the vibrator and stimulation position. The vibration was measured in three orthogonal directions where the dominating vibration directions was in line with the stimulation direction, here the ventral direction. The BC thresholds lay between −10 and 3 dB re 1 μm/s.The slopes of CAP growth function were similar for AC and BC at low and high frequencies, but slightly lower for BC than AC at frequencies between 8 and 16 kHz. This was attributed to differences in the stimulus levels used for the slope estimation and not a real difference in CAP slopes between the stimulation modalities. Two kinds of middle ear lesions, ossicular discontinuity and stapes glued to the surrounding bone, gave threshold shifts of between 23 and 53 dB for AC while it was below 16 dB when the stimulation was by BC. Statistically different threshold shifts between the two types of lesions were found where the AC threshold shifts for a glued stapes at 2 and 4 kHz were 9–18 dB greater than for a severed ossicular chain, and the BC threshold shifts for a glued stapes at 4 and 12 kHz were 8–9 dB greater than for a severed ossicular chain.

Association between cadmium exposure and hearing impairment: a population-based study in Korean adults

BackgroundThe present study aimed to evaluate the clinical association between cadmium exposure and hearing impairment among the Korean population.MethodsThis retrospective cross-sectional study used the data obtained from the Korean National Health and Nutrition Examination Survey were used for our study. Finally, 3,228 participants were included in our study, which were then divided into quartiles based on their blood cadmium levels: first quartile (1Q), second quartile (2Q), third quartile (3Q), and fourth quartile (4Q) groups. The hearing thresholds were measured using an automatic audiometer at 0.5, 1, 2, 3, 4, and 6 kHz. Hearing loss (HL) was defined as >25 dB average hearing threshold (AHT).ResultsAll the groups had 807 participants each. The area under the receiver operating characteristic curves of cadmium level for HL were 0.634 (95% confidence interval [CI], 0.621–0.646). The participants in the 4Q group had higher Low/Mid-Freq, High-Freq, and AHT values than those in the other groups in the multivariate analysis after adjusting for confounding factors. The logistic regression showed that the OR for HL per 1 µg/L increase in cadmium was 1.25 (95% CI, 1.09–1.44; p=0.002) on the multivariate analysis. Moreover, the multivariate logistic regression analyses revealed that the participants in the 4Q group exhibited a 1.59-, 1.38-, and 1.41-fold higher odds for HL than those in the 1Q, 2Q, and 3Q groups, respectively. ConclusionHigh cadmium level quartile was associated with increased hearing thresholds and HL among the Korean adult population.