Asymmetry in Noise-Induced Hearing Loss

Auditory Effects of Acoustic Noise From 3-T Brain MRI in Neonates With Hearing Protection

BACKGROUND

Neonates with immature auditory function (eg, weak/absent middle ear muscle reflex) could conceivably be vulnerable to noise-induced hearing loss; however, it is unclear if neonates show evidence of hearing loss following MRI acoustic noise exposure.

PURPOSE

To explore the auditory effects of MRI acoustic noise in neonates.

STUDY TYPE

Prospective.

SUBJECTS

Two independent cohorts of neonates (N = 19 and N = 18; mean gestational-age, 38.75 ± 2.18 and 39.01 ± 1.83 weeks).

FIELD STRENGTH/SEQUENCE

T1-weighted three-dimensional gradient-echo sequence, T2-weighted fast spin-echo sequence, single-shot echo-planar imaging-based diffusion-tensor imaging, single-shot echo-planar imaging-based diffusion-kurtosis imaging and T2-weighted fluid-attenuated inversion recovery sequence at 3.0 T.

ASSESSMENT

All neonates wore ear protection during scan protocols lasted ~40 minutes. Equivalent sound pressure levels (SPLs) were measured for both cohorts. In cohort1, left- and right-ear auditory brainstem response (ABR) was measured before (baseline) and after (follow-up) MRI, included assessment of ABR threshold, wave I, III and V latencies and interpeak interval to determine the functional status of auditory nerve and brainstem. In cohort2, baseline and follow-up left- and right-ear distortion product otoacoustic emission (DPOAE) amplitudes were assessed at 1.2 to 7.0 kHz to determine cochlear function.

STATISTICAL TEST

Wilcoxon signed-rank or paired t-tests with Bonferroni's correction were used to compare the differences between baseline and follow-up ABR and DPOAE measures.

RESULTS

Equivalent SPLs ranged from 103.5 to 113.6 dBA. No significant differences between baseline and follow-up were detected in left- or right-ear ABR measures (P > 0.999, Bonferroni corrected) in cohort1, or in DPOAE levels at 1.2 to 7.0 kHz in cohort2 (all P > 0.999 Bonferroni corrected except for left-ear levels at 3.5 and 7.0 kHz with corrected P = 0.138 and P = 0.533).

DATA CONCLUSION

A single 40-minute 3-T MRI with equivalent SPLs of 103.5-113.6 dBA did not result in significant transient disruption of auditory function, as measured by ABR and DPOAE, in neonates with adequate hearing protection.

EVIDENCE LEVEL

2.

TECHNICAL EFFICACY

Stage 5.

Laterality and otorhinolaryngology: a review

BACKGROUND

Laterality of paired organs involves the function of the eyes, ears, hands and feet. Whilst most people have a right-handed preference, about 10 per cent are left-handed. Similarly, the right eye is usually preferred to the left. Medicine is both taught and practised for those with right hand and eye preference, and left-handed medical students and doctors must negotiate the right-handed world.

OBJECTIVE

This brief review looks at society's attitudes, medical training and the practice of otolaryngology in the UK towards laterality and handedness.

METHOD

Literature review.

RESULTS

Studies suggest that left-handers are more versatile and so are more ambidextrous. Conversely, this may result in problems when a right-hander tries to undertake a procedure with the non-dominant hand.

CONCLUSION

Cultures and attitudes are changing towards those who are left-handed. Left-handed surgeons may encounter difficulties in the clinical environment throughout their training.

Do Flights Affect Hearing in Hot Air Balloon Pilots?

PURPOSE

This study aimed to reveal occupational effects on the hearing of hot air balloon (HAB) pilots and examine the relationship between the duration of experience and these effects.

METHOD

This study included 31 male HAB pilots and a control group of 32 male participants. Tympanometry, eustachian tube function (ETF) test, pure-tone audiometry, and transient evoked otoacoustic emission (TEOAE) tests were performed.

RESULTS

Pure-tone audiometry results were significantly worse at 125, 500, and 6000 Hz in the right ear and 125, 500, 4000, and 6000 Hz in the left ear in the HAB group than the control group. Although tympanometry evaluation parameters did not differ between the HAB and control groups, ETF test was significantly worse in the HAB group than the controls bilaterally. TEOAE results were significantly worse at 1000, 2000, and 4000 Hz in the right ear and 4000 Hz in the left ear in the HAB group than the controls. There was a significant positive correlation for 125, 4000, 6000, and 8000 Hz between the duration of experience and right ear hearing thresholds. For the left ear, the duration of experience showed a significant positive correlation at 3000, 4000, 6000, and 8000 Hz. When the relationship between the duration of experience and TEOAE results was evaluated, a significant negative correlation was found at 4000 Hz in the left ear.

CONCLUSION

In HAB pilots, in whom eustachian tube dysfunction is quite common, noise and high altitude affected hearing, especially low and high frequencies, and the duration of experience was found to be associated with hearing thresholds.

Evidence for a left ear bias in incidence of Meniere's disease

OBJECTIVE

To explore a side of lesion differences in Meniere's disease (MD).

DESIGN

A retrospective review (2019-2021) was conducted of patients with definite MD, as defined by 2015 Bárány Society diagnostic criteria. Testing information included pure tone audiometry, tympanometry, and extra-tympanic electrocochleography (ECochG). Normative ECochG data from healthy subjects determined the 95% cut-off value for clinical abnormality.

STUDY SAMPLE

107 patients with definite MD were included in the study and 40 healthy controls.

RESULTS

The review identified 75 patients with unilateral MD and 32 patients with bilateral MD according to their clinical histories. 79% of unilateral cases were found to have MD on the L ear. 94% of bilateral MD cases had L ears more affected than R ears. Objective ECochG testing indicated a greater incidence of elevated SP/AP area curve and amplitude ratios in L ears. On binomial testing, all results indicate a highly significant bias of MD to the L side.

CONCLUSIONS

Unilateral MD appears more common on the L side than the R, suggesting that the disease process underlying MD is not symmetrical. MD also appears more common in females than males. It appears that there is a physiological asymmetry in the progression/cause of MD.

Asymmetry of Occupational Noise Induced Hearing Loss: An Electrophysiological Approach

Introduction  The question as to whether occupational noise exposure causes symmetrical or asymmetrical hearing loss is still controversial and incompletely understood. Objective  Two electrophysiological methods (cortical evoked response audiometry: CERA and auditory steady state responses: ASSR) were used to address this issue. Method  156 subjects with a well-documented history of noise exposure, a wide range of noise induced hearing loss (NIHL) and without middle ear pathology underwent both a CERA and an ASSR examination in the context of an exhaustive medicolegal expert assessment intended for possible compensation. Results  Whatever the method (CERA or ASSR), the average electrophysiological hearing thresholds (1-2-3 kHz) are significantly worse in the left ear. The right - left differences in CERA and ASSR thresholds are strongly correlated with each other. No significant effect of frequency is found. No correlation is observed between right - left differences in hearing thresholds and either age or degree of hearing loss. Conclusion  In NIHL, there is an actual average right - left difference of about 2.23 dB, i.e., 3.2%, the left ear being more impaired.

The effect of recreational noise exposure on amplitude-modulation detection, hearing sensitivity at frequencies above 8 kHz, and perception of speech in noise

Psychoacoustic and speech perception measures were compared for a group who were exposed to noise regularly through listening to music via personal music players (PMP) and a control group without such exposure. Lifetime noise exposure, quantified using the NESI questionnaire, averaged ten times higher for the exposed group than for the control group. Audiometric thresholds were similar for the two groups over the conventional frequency range up to 8 kHz, but for higher frequencies, the exposed group had higher thresholds than the control group. Amplitude modulation detection (AMD) thresholds were measured using a 4000-Hz sinusoidal carrier presented in threshold-equalizing noise at 30, 60, and 90 dB sound pressure level (SPL) for modulation frequencies of 8, 16, 32, and 64 Hz. At 90 dB SPL but not at the lower levels, AMD thresholds were significantly higher (worse) for the exposed than for the control group, especially for low modulation frequencies. The exposed group required significantly higher signal-to-noise ratios than the control group to understand sentences in noise. Otoacoustic emissions did not differ for the two groups. It is concluded that listening to music via PMP can have subtle deleterious effects on speech perception, AM detection, and hearing sensitivity over the extended high-frequency range.

Noise Pollution and Associated Hearing Loss in a Metropolitan City-a Preliminary Report

To measure the amount of noise produced in busy parts of a metropolitan and also to assess the audiological status of the civilians exposed to such noise. Cross-sectional study for one year between June 2017 and May 2018 was conducted. Noise was measured in four busy parts of an urban city with a digital sound level meter. People involved in various occupations in the busy parts for more than one year within the age range of 15-45 years were included. Maximum noise level recorded was 106.4 dBA in Koyembedu. Average noise was around 70-85 dBA in Chennai. Totally 100 people were subjected to audiological assessment (69 Males; 31 Females). Among them 93% had hearing loss. Hearing loss was almost equal both in sexes. Sensory hearing loss was the major type (83%). All areas were almost equally affected with maximum (100%) being affected in Annanagar and Koyembedu. The right ear was more affected than the left. All age groups were affected among which the working age group (36-45) years was most affected. The unskilled occupation group was most affected (100%). There was a positive relation between noise levels and hearing loss. Duration of exposure did not have positive correlation with hearing loss. Noise pollution and its induced hearing loss was more prevalent and increased in all four areas. As hearing loss due to noise pollution is predominant as observed in the study, awareness about noise pollution and its effects among the community is a necessity.

Extended high-frequency audiometric analyses of tinnitus patients exhibiting normal hearing on conventional pure-tone audiometry

BACKGROUND

While hearing loss is the greatest risk factor associated with developing tinnitus, some tinnitus patients exhibit no hearing loss on conventional pure-tone audiometry (PTA).

OBJECTIVES

This study was developed to assess whether tinnitus patients with normal hearing as measured via conventional PTA would exhibit differences from normal controls upon extended high-frequency (EHF) audiometric evaluation.

METHODS

In total, 102 tinnitus patients were separated into unilateral and bilateral tinnitus groups. Age- and sex-matched controls without tinnitus were enrolled.

RESULTS

No significant differences were observed when comparing EHF audiometry results in the 9-14 kHz range between controls and tinnitus patients, with only left-sided tinnitus ears exhibiting higher hearing thresholds than contralateral ears at 9, 10, and 14 kHz. Relative to normal controls, the hearing thresholds in the 2-8 kHz range for tinnitus ears were significantly increased.

CONCLUSIONS AND SIGNIFICANCE

Relative to controls, tinnitus patients with normal hearing did not exhibit any significant hearing loss in the EHF range. Unexpectedly, tinnitus patients with normal hearing exhibited significant hidden hearing loss in the conventional frequency range rather than in the EHF range. For patients with normal hearing, it appears to be unnecessary to conduct EHF examinations to detect hearing loss in the EHF range.

Obstructive sleep apnea risk and hearing impairment among occupational noise-exposed male workers

This study aimed to investigate the association between obstructive sleep apnea (OSA) risk and hearing impairment among workers exposed to occupational noise. A cross-sectional study was conducted among 607 healthy male workers at a tire-manufacturing factory. The subjects underwent audiometric testing, and their OSA risk was examined based on the STOP-Bang questionnaire. Hearing impairment was defined as a hearing threshold >25 dB hearing level (HL) in any frequency of 1, 2, 3 and 4 kHz in either ear. High OSA risk was defined as a STOP-bang score of ≥3. Hearing thresholds at 1, 2, 3 and 4 kHz in both ears were significantly higher among workers with high OSA risk than among those with low OSA risk after adjusting for confounders. Multiple logistic regression analysis examining the association of OSA risk and STOP-Bang score with hearing impairment revealed an odds ratio of 1.738 (95% confidence interval [CI] 1.113-2.713, p = 0.015) and 1.256 (95% CI 1.031-1.529, p = 0.023), respectively, after adjusting for confounders. In addition, when the hearing impairment was reclassified into high- and low-frequency hearing impairment, a statistically significant OR was seen for high-frequency hearing impairment. In conclusion, high OSA risk was associated with hearing impairment in occupational noise-exposed workers, especially in the high-frequency range of 3 and 4 kHz. More efforts are required to improve the management of OSA and its risk factors to preserve hearing in occupational noise-exposed workers.

Ear Asymmetry and Contextual Influences on Speech Perception in Hearing-Impaired Patients

The left hemisphere preference for verbal stimuli is well known, with a right ear (RE) advantage obtained when competing verbal stimuli are presented simultaneously, at comfortable intensities, to both ears. Speech perception involves not only the processing of acoustic peripheral information but also top–down contextual influences, filling the gaps in the incoming information that is particularly degraded in hearing-impaired individuals. This study aimed to analyze the potential asymmetry of those contextual influences on a simple speech perception task in hearing-impaired patients in light of hemispheric asymmetry. Contextual influences on disyllabic word perception scores of 60 hearing-impaired patients were compared between left ear (LE) and RE, in a balanced design, involving two repetitions of the same task. Results showed a significantly greater contextual influence on the RE versus the LE and, for the second repetition versus the first one, without any interaction between the two. Furthermore, the difference in contextual influences between RE and LE increased significantly with the RE advantage measured by a dichotic listening test in the absence of any significant correlation with hearing threshold asymmetry. Lastly, the contextual influence asymmetry decreased significantly as age increased, which was mainly due to a greater increase, with age, of contextual influences on the LE versus the RE. Those results agree with the literature reporting a relative right-shift of hemispheric asymmetry observed with age in speech in noise perception tasks in normal hearing subjects and the clinical reports of generally better audiometric speech scores obtained in RE versus LE.

AudioChip: A Deep Phenotyping Approach for Deconstructing and Quantifying Audiological Phenotypes of Self-Reported Speech Perception Difficulties

OBJECTIVES

About 15% of U.S. adults report speech perception difficulties despite showing normal audiograms. Recent research suggests that genetic factors might influence the phenotypic spectrum of speech perception difficulties. The primary objective of the present study was to describe a conceptual framework of a deep phenotyping method, referred to as AudioChipping, for deconstructing and quantifying complex audiometric phenotypes.

DESIGN

In a sample of 70 females 18 to 35 years of age with normal audiograms (from 250 to 8000 Hz), the study measured behavioral hearing thresholds (250 to 16,000 Hz), distortion product otoacoustic emissions (1000 to 16,000 Hz), click-evoked auditory brainstem responses (ABR), complex ABR (cABR), QuickSIN, dichotic digit test score, loudness discomfort level, and noise exposure background. The speech perception difficulties were evaluated using the Speech, Spatial, and Quality of Hearing Scale-12-item version (SSQ). A multiple linear regression model was used to determine the relationship between SSQ scores and audiometric measures. Participants were categorized into three groups (i.e., high, mid, and low) using the SSQ scores before performing the clustering analysis. Audiometric measures were normalized and standardized before performing unsupervised k-means clustering to generate AudioChip.

RESULTS

The results showed that SSQ and noise exposure background exhibited a significant negative correlation. ABR wave I amplitude, cABR offset latency, cABR response morphology, and loudness discomfort level were significant predictors for SSQ scores. These predictors explained about 18% of the variance in the SSQ score. The k-means clustering was used to split the participants into three major groups; one of these clusters revealed 53% of participants with low SSQ.

CONCLUSIONS

Our study highlighted the relationship between SSQ and auditory coding precision in the auditory brainstem in normal-hearing young females. AudioChip was useful in delineating and quantifying internal homogeneity and heterogeneity in audiometric measures among individuals with a range of SSQ scores. AudioChip could help identify the genotype-phenotype relationship, document longitudinal changes in auditory phenotypes, and pair individuals in case-control groups for the genetic association analysis.

Audiometric assessment of hearing loss sustained during military service

An analysis is presented of the audiograms, obtained using Telephonics TDH39 headphones (Huntington, NY), of 80 men claiming compensation for noise-induced hearing loss (NIHL) sustained during military service. A comparison with an independent database of audiograms collected using other headphones suggested that no adjustment was needed to the hearing threshold levels (HTLs) at 6 kHz to allow for the use of TDH39 headphones. The method of Moore [(2020). J. Acoust. Soc. Am. 148, 884-894] for diagnosing military noise-induced hearing loss (M-NIHL) gave a positive diagnosis for 92.5% of right ears and 97.5% of left ears. The mean HTLs were maximal and similar at 4, 6, and 8 kHz but with considerable individual variability. A comparison with age-expected HTLs showed that M-NIHL was typically greatest at 3, 4, 6, or 8 kHz but with considerable individual variability. M-NIHL values were positive from 0.5 to 8 kHz. The HTLs were significantly higher for the left than for the right ears, but the asymmetry varied across individuals and could usually be ascribed to specific features of the noise exposure. The asymmetry existed over the range from 0.5 to 8 kHz, supporting the idea that M-NIHL occurs over a wide frequency range. Tinnitus was reported by 76 of the 80 men.

Genome-wide association study and polygenic risk score analysis for hearing measures in children

An efficient auditory system contributes to cognitive and psychosocial development. A right ear advantage in hearing thresholds (HTs) has been described in adults and atypical patterns of left/right hearing threshold asymmetry (HTA) have been described for psychiatric and neurodevelopmental conditions. Previous genome-wide association studies (GWASs) on HT have mainly been conducted in elderly participants whose hearing is more likely to be affected by external environmental factors. Here, we investigated HT and HTA in a children population cohort (ALSPAC, n = 6,743). Better hearing was associated with better cognitive performance and higher socioeconomic status. At the group level, HTA suggested a left ear advantage (mean = -0.28 dB) that was mainly driven by females. SNP heritability for HT and HTA was 0.13 and 0.02, respectively (n = 4,989). We found a modest negative genetic correlation between HT and reading ability. GWAS for HT (n = 5,344) did not yield significant hits but polygenic risk scores for higher educational attainment (EA, ß = -1,564.72, p = .008) and schizophrenia (ß = -241.14, p = .004) were associated with lower HT, that is, better hearing. In summary, we report new data supporting associations between hearing measures and cognitive abilities at the behavioral level. Genetic analysis suggests shared biological pathways between cognitive and sensory systems and provides evidence for a positive outcome of genetic risk for schizophrenia.

Hearing and Exposure to Music in Adolescents From Four Schools of Córdoba, Argentina

Purposes The aims of this study are (a) to characterize the hearing of adolescents from four schools of Córdoba, Argentina, through the analysis of conventional and extended high-frequency audiometric thresholds and otoacoustic emissions (OAEs) and (b) to analyze the association between the mentioned hearing tests and exposure to music. Method It was a cross-sectional correlational descriptive study. Hearing thresholds (250-16000 Hz), transient evoked OAEs, and distortion product OAEs were evaluated in 225 adolescents (450 ears) aged 14 and 15 years. The ears were split into two groups: Group 1 had thresholds ≤ 21 dB HL in all frequencies, and Group 2 had thresholds > 21 dB HL in at least one. Exposure to music was evaluated through a questionnaire. Results Statistically significant differences were found in both ears between Groups 1 and 2. A notch at 3000-6000 Hz was noted in both groups. Group 2 showed a progressive threshold increase from 9000 Hz. Amplitude decrease, negative values, absent distortion product OAEs, and transient evoked OAEs were noted even in Group 1. A statistically significant association between Groups 1 and 2 and the presence/absence of OAEs was observed in most frequencies. Ears with moderate or high exposure to music had greater hearing thresholds compared to ears with low exposure at most frequencies; this was more evident in Group 1. Regarding exposure to music and OAEs, no significant differences were found between the exposure categories. Conclusions The findings highlight the value of implementing hearing conservation programs in Argentina, analyzing hearing tests correlated with questionnaires about recreational noise exposure in order to detect vulnerable ears early.

Association Analysis of Candidate Gene Polymorphisms and Audiometric Measures of Noise-Induced Hearing Loss in Young Musicians

INTRODUCTION

This study aimed to investigate the association between candidate genetic variants and audiometric measures of noise-induced hearing loss (NIHL) in young musicians.

METHODS

The study analyzed a database by Phillips et al. (Feasibility of a bilateral 4000-6000 Hz notch as a phenotype for genetic association analysis. Int J Audiol 2015;54:645-52.) which included behavioral hearing thresholds, distortion-product otoacoustic emissions (DPOAE), tympanometric, and genetic data of 166 participants meeting the inclusion criteria. Nineteen single nucleotide polymorphisms (SNPs) in 13 cochlear genes previously associated with NIHL in factory workers were included in the present investigation. The average hearing threshold at 3000 and 4000 Hz (AHT) and average DPOAE signal to noise ratio (DPOAE SNR) in both ears were calculated.

RESULTS

The regression analyses showed that two SNPs- one in KCNE1 (rs2070358) and the other in CAT (rs12273124) revealed a statistically significant relationship with DPOAE SNR in both ears. Two SNPs in MYH14 and one in GJB4 revealed a significant association with DPOAE SNR in the left ear. Two SNPs in HSP70, one in CDH23 and one in KCNJ10 showed significant association with DPOAE SNR in the right ear. None of the included SNPs showed association with AHT in both ears.

CONCLUSIONS

A genetic variant in KCNE1 was associated with the strength of the cochlear amplifier as assessed by DPOAE SNR. Musicians carrying causal genetic variants to NIHL might exhibit changes in their auditory functions early in the lifespan even when most subjects had their hearing thresholds within normal limits. These participants are likely to show the clinical manifestation of NIHL in the future if no preventive measures are applied.

A 4-year follow-up study of hearing acuity in a large population-based cohort of children and adolescents

OBJECTIVES

To describe the prevalence of hearing loss among 13 year old adolescents, and to examine the change in prevalence between ages 9 and 13 years.

METHODS

This study was embedded within Generation R, a population-based prospective cohort study from fetal life onwards in the Netherlands. Pure-tone thresholds were obtained at 0.5 to 8 kHz, and tympanometry was performed. Sensorineural hearing loss (SNHL) was defined as a low-frequency and/or high-frequency pure-tone average of more than 15 dB HL in one of both ears. Audiometric signs suggestive of noise-induced hearing loss (NIHL) included the presence of a notch and/or high-frequency hearing loss. The study was conducted from April 2012 to October 2015, and April 2016 to September 2019.

RESULTS

A total of 4572 adolescents with a mean age of 13 years and 7 months (SD, 5 months) were included, of whom 2334 (51.0%) were girls. Within the cohort, 6.4% (95% CI, 5.7%-7.2%) were estimated to have SNHL, and 12.4% (95% CI, 11.5%-13.4%) met the criteria of NIHL. In total, 3675 participants were included in the longitudinal analysis. The prevalence of SNHL decreased from 8.0% to 5.3% between ages 9 and 13 years (P < .001). The prevalence of NIHL increased from 9.8% to 11.7% (P = .004), due to an increase in number of participants with a notch.

CONCLUSIONS

The prevalence of SNHL significantly decreased by 2.7% (95% CI, 1.6%-3.9%) between ages 9 and 13 years, probably due to a change in alertness during assessment at the age of 13 years. Other possible explanations include the presence of selection bias or a decline in prevalence of conductive hearing loss. The number of participants with audiometric signs suggestive of NIHL increased by 1.9% (95% CI, 0.5%-3.3%).

LEVEL OF EVIDENCE

Level 3.

Is it necessary to perform occupational audiometric testing at 6-months of employment?

Introduction

Current Brazilian legislation requires that all workers exposed to noise are to be given an audiogram upon hiring, after 6 months of employment (first periodic test), and annually after the first periodic test. In other countries, the regulations of hearing conservation programs do not include the requirement for audiometric testing at 6 months of employment, but only annually. There is no evidence that the periodicity adopted by Brazilian legislation is the most appropriate.

Objective

The present study aimed to evaluate the first 3 occupational audiometric tests of workers exposed to noise.

Methods

Historical cohort study with cross-sectional analysis. Participants were all male metallurgy workers aged up to 40 years. The first 3 audiograms of each worker were analyzed: pre-employment audiometric test, periodic audiometric test 1, and periodic audiometric test 2. For each worker, mean frequency thresholds were calculated at 3, 4, and 6 kHz in the left and right ears for each test. Statistical analysis was performed using the nonparametric Wilcoxon test.

Results

A total of 988 workers were included. There was a significant difference in auditory thresholds between the pre-employment test and the 2 subsequent periodic tests for the right and left ears. There was no significant difference between Test1 and Test2 in either ear.

Conclusion

Given the lack of difference between the first 2 periodic tests, we believe that they could be merged into a single test, i.e., first periodic audiometric testing could be performed at 12 months of employment without compromising workers’ health.

The influence of a noisy environment on hearing impairment and tinnitus: The hearing outcomes of 50-year-old male Japan ground self-defense force personnel

OBJECTIVES

Hearing loss is one of the biggest health problems in the world and occupational noise-induced hearing loss is recognized as the most common work-related illness. However, many factors that result in hearing loss make it difficult to define the specific factor that induces noise-induced hearing loss. To access the exact effect of occupational noise exposure on hearing, we conducted a cross-sectional cohort study of the relationship between noise exposure and hearing impairment in 50-year-old male Japanese Self-Defense Force (JSDF) personnel who work in a noisy environment. This population is ideal for the detection of noise-induced hearing impairments due to the homogeneity of genetic and social backgrounds.

METHODS

The data utilized in this study were collected from a "50-year-old milestone health examination" of the JSDF from July 2013 to October 2015. One thousand sixty-seven male personnel were enrolled in the study. Pure-tone audiometry was conducted with an audiometer. A survey questionnaire asked participants to self-report occupational noise exposure.

RESULTS

This cohort revealed that noise-exposed personnel had a higher hearing threshold and a higher odds ratio in 1) the average threshold of 4 frequencies (500 + 1000 + 2000 + 4000 Hz / 4), 2) the average threshold of higher 3 frequencies (2000 + 4000 + 8000 Hz / 3), and 3) the threshold of 4 kHz compared to no noise-exposed control personnel. The prevalence of tinnitus was also significantly higher in the noise-exposed group.

CONCLUSIONS

This study provides specific evidence for the relationship between noise exposure and noise-induced hearing impairments.

Prevalence and clinical aspects of hearing loss among the South Korean adolescent: Data from a population-based study

OBJECTIVES

Slight/mild hearing loss is detrimental to communication and academic achievements. This study aimed to describe the prevalence of hearing loss, and to investigate the factors related to noise-induced hearing loss among South Korean adolescent.

METHODS

As a population-based retrospective study, 1845 South Korean adolescents aged from 12 to 19 years were analyzed using the data from Korea National Health and Nutrition Examination Survey V (KNHANES V, 2010-2012). The prevalence of hearing loss according to the side, severity, and frequency was calculated. For assessing the noise-induced hearing loss in adolescent, the prevalence of hearing loss only in high-frequency (onlyHFHL, defined as 1) thresholds at 0.5 and 1 kHz of ≤15 dB HL, and 2) maximal thresholds at 3, 4, or 6 kHz ≥ 15 dB HL higher than the highest threshold for 0.5 and 1 kHz) was analyzed. Moreover, the relevance of onlyHFHL in context of sociodemographic factors and noise exposure history was evaluated.

RESULTS

The prevalence of unilateral and bilateral hearing loss based on the average of six frequencies (0.5, 1, 2, 3, 4, and 6 kHz) in South Korean adolescents were 8.56% and 1.03%, respectively, and most cases were hearing loss with slight/mild degree. The prevalence of unilateral and bilateral onlyHFHL were 32.74% and 5.53%, respectively. Factors found to be associated with onlyHFHL were sex (female) and household income (high).

CONCLUSIONS

According to this population-based study, the prevalence of slight/mild hearing loss and onlyHFHL in the South Korean adolescents were considerably high. With knowledge of the factors related with onlyHFHL, paying more attention to slight/mild hearing loss will be helpful in preventing hearing loss in adolescents.

Effect of vibration on the vestibular system in noisy and noise-free environments in heavy industry

Background: Chronic exposure to whole body vibration can affect the gastrointestinal system, the lumbar spine, the peripheral veins and the vestibulocochlear system. Aims/Objectives: The aim of this study was to evaluate the effects of vibration on the vestibular system in noisy and noise-free environments using the video head impulse test (vHIT). Material and Methods: A total of 138 employees were included in this study. Group 1 were exposed to vibration and noise. Group 2 only exposed to vibration, with no exposure to noise. Group 3 were not exposed to noise or vibration. Results: Canal deficit was observed in 41 of 84 participants in Group 1, 7 of 24 participants in Group 2, and 1 of 30 participants in Group 3. There were more canal deficits in Group 1 and Group 2, than in Group 3 (p < .05). There was no significant difference between Group 1 and Group 2 in terms of canal deficits (p > 0.05). Conclusions and Significance: Semicircular canal deficit can be seen with the synergistic effect of noise and vibration.

Hearing loss in police K9 handlers and non-K9 handlers

Objective: The objective of this study was to assess and compare the hearing of police K9 handlers and non-K9 handlers.Design: Cross-sectional design.Study sample: Hearing was assessed on 30 police officers, 12 K9 handlers and 18 non-K9 handlers, from Northeast Ohio.Results: There were no significant differences in audiologic test results between police K9 handlers and non-K9 handlers. Audiometric results revealed that 66.7% of K9 handlers and 83.3% of non-K9 handlers presented with hearing loss. Noise notches, consistent with noise-induced hearing loss (NIHL), and asymmetric hearing losses were observed for both groups. Subjective questionnaires indicated low awareness regarding the risks and identification of NIHL in this population.Conclusions: This study represents one of the few studies that focus on hearing assessments in police K9 handlers and non-K9 handlers in the United States and internationally. Significant differences between these two groups were not found, suggesting that K9 handlers do not present a higher risk for NIHL than non-K9 handlers. Nonetheless, the high prevalence of hearing loss identified for both groups in this study suggests the need for increased conservation efforts to raise awareness regarding hearing loss prevention and the need for routine audiologic monitoring for this underserved population.

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.

Environmental ototoxicants, a potential new class of chemical stressors

Hearing loss is an injury that can develop over time, and people may not even be aware of it until it becomes a severe disability. Ototoxicants are substances that may damage the inner ear by either affecting the structures in the ear itself or by affecting the nervous system. We have examined the possibility that ototoxicants may present a health hazard in association with environmental exposures, adding to existing knowledge of their proven hazards under medical therapeutic conditions or occupational activities. In addition to the already described human environmental ototoxicants, mainly organochlorines such as polychlorinated biphenyls (PCBs), polychlorinated dibenzo-p-dioxins (PCDDs), dibenzofurans (PCDFs), dichlorodiphenyltrichloroethane (DDT), dichlorodiphenyldichloroethylene (DDE), hexachlorocyclohexane (HCH) and hexachlorobenzene (HCB), we have examined the ubiquitous chemical stressors phthalates, bisphenol A/S/F/, PFCs, flame retardants (FRs) and cadmium for potential ototoxic properties, both as single substances or as chemical mixtures. Our literature review confirmed that these chemicals may disturb thyroid hormones homeostasis, activate aryl hydrocarbon receptor (AhR), and induce oxidative stress, which in turn may initiate a chain of events resulting in impairment of cochlea and hearing loss. With regard to auditory plasticity, diagnostics of a mixture of effects of ototoxicants, potential interactions of chemical and physical agents with effects on hearing, parallel deterioration of hearing due to chemical exposures and ageing, metabolic diseases or obesity, even using specific methods as brainstem auditory evoked potentials (BAEP) or otoacoustic emissions (OAEs) registration, may be difficult, and establishment of concentration-response relationships problematic. This paper suggests the establishment of a class of environmental oxotoxicants next to the established classes of occupational and drug ototoxicants. This will help to properly manage risks associated with human exposure to chemical stressors with ototoxic properties and adequate regulatory measures.

Effects of oral zinc supplementation on patients with noise-induced hearing loss associated tinnitus: A clinical trial

BACKGROUND

Zinc plays a vital antioxidant role in human metabolism. Recent studies have demonstrated a correlation between noise-induced hearing loss (NIHL) and oxidative injury; however, no investigation has focused specifically on the subgroup of NIHL associated tinnitus patients. We aimed to evaluate the effectiveness of zinc supplementation in treating NIHL associated tinnitus.

METHODS

Twenty patients with tinnitus and a typical NIHL audiogram (38 ears) were included in this study. Another 20 healthy subjects were used as the control group. A full medical history assessment was performed, and each subject underwent an otoscopic examination, basic audiologic evaluation, distortion product otoacoustic emissions (DPOAEs), tinnitus-match testing, Tinnitus Handicap Inventory (THI) and serum zinc level analyses. After 2 months of treatment with zinc, all tests were repeated.

RESULTS

There was a significant difference between pretreatment and post-treatment within the tinnitus group (73.6 vs. 84.6 μg/dl). The pre- and post-treatment difference in serum zinc was significantly higher in the young group (≦50 years) compared to the old group (19.4 ± 11.4 vs. 2.6 ± 9.2 μg/dl, respectively; p = 0.002). There were no statistically significant differences in hearing thresholds, speech reception thresholds, or tinnitus frequency and loudness results before and after treatment. In addition, 17 patients (85%) showed statistically significant improvement of THI-total scores post-treatment, from 38.3 to 30 (p = 0.024).

CONCLUSIONS

Zinc oral supplementation elevated serum zinc levels, especially in younger patients. THI scores improved significantly following zinc treatment in patients with NIHL associated tinnitus. However, no improvements in objective hearing parameters were observed.

Increased medial olivocochlear reflex strength in normal-hearing, noise-exposed humans

Research suggests that college-aged adults are vulnerable to tinnitus and hearing loss due to exposure to traumatic levels of noise on a regular basis. Recent human studies have associated exposure to high noise exposure background (NEB, i.e., routine noise exposure) with the reduced cochlear output and impaired speech processing ability in subjects with clinically normal hearing sensitivity. While the relationship between NEB and the functions of the auditory afferent neurons are studied in the literature, little is known about the effects of NEB on functioning of the auditory efferent system. The objective of the present study was to investigate the relationship between medial olivocochlear reflex (MOCR) strength and NEB in subjects with clinically normal hearing sensitivity. It was hypothesized that subjects with high NEB would exhibit reduced afferent input to the MOCR circuit which would subsequently lead to reduced strength of the MOCR. In normal-hearing listeners, the study examined (1) the association between NEB and baseline click-evoked otoacoustic emissions (CEOAEs) and (2) the association between NEB and MOCR strength. The MOCR was measured using CEOAEs evoked by 60 dB pSPL linear clicks in a contralateral acoustic stimulation (CAS)-off and CAS-on (a broadband noise at 60 dB SPL) condition. Participants with at least 6 dB signal-to-noise ratio (SNR) in the CAS-off and CAS-on conditions were included for analysis. A normalized CEOAE inhibition index was calculated to express MOCR strength in a percentage value. NEB was estimated using a validated questionnaire. The results showed that NEB was not associated with the baseline CEOAE amplitude (r = -0.112, p = 0.586). Contrary to the hypothesis, MOCR strength was positively correlated with NEB (r = 0.557, p = 0.003). NEB remained a significant predictor of MOCR strength (β = 2.98, t(19) = 3.474, p = 0.003) after the unstandardized coefficient was adjusted to control for effects of smoking, sound level tolerance (SLT) and tinnitus. These data provide evidence that MOCR strength is associated with NEB. The functional significance of increased MOCR strength is discussed.

Hearing threshold shifts among military pilots of the Israeli Air Force

Background

Military aviators are potentially at risk for developing noise-induced hearing loss. Whether ambient aircraft noise exposure causes hearing deficit beyond the changes attributed to natural ageing is debated. The aim of this research was to assess changes in hearing thresholds of Israeli Air Force (IAF) pilots over 20 years of military service and identify potential risk factors for hearing loss.

Methods

A retrospective cohort analysis was conducted of pure-tone air conduction audiograms of pilots, from their recruitment at 18 years of age until the last documented medical check-up. Mean hearing thresholds were analysed in relation to age, total flight hours and aircraft platform. Comparisons were made to the hearing thresholds of air traffic controllers (ATCs) who were not exposed to the noise generated by aircraft while on duty.

Results

One hundred and sixty-three pilots were included, with flying platforms ranging from fighter jets (n=54), combat helicopters (n=27), transport helicopters (n=52) and transport aircraft (n=30). These were compared with the results from 17 ATCs. A marked notch in the frequency range of 4–6 kHz was demonstrated in the mean audiograms of all platforms pilots, progressing with ageing. Hearing threshold shifts in relation to measurements at recruitment were first noted at the age of 30 years, particularly at 4 kHz (mean shift of 2.97 dB, p=0.001). There was no statistical association between flying variables and hearing thresholds adjusted for age by logistic regression analysis.

Conclusions

The audiometric profile of IAF pilots has a pattern compatible with noise exposure, as reflected by characteristic noise notch. However, no flight variable was associated with deterioration of hearing thresholds, and no significant difference from non-flying controls (ATCs) was seen.

Work-Related Noise Exposure in a Cohort of Patients with Chronic Tinnitus: Analysis of Demographic and Audiological Characteristics

Work-related noise exposure is one of the major factors contributing to the development of adult-onset hearing loss and tinnitus. The aim of this study was to analyze, in patients with chronic tinnitus and long-term occupational noise exposure, (A) characteristics of hearing loss, tinnitus, comorbidities, demographic characteristics and a history of work-related noise exposure and (B) differences among individuals employed in occupations with high and low risk of developing work-related noise-induced hearing loss (NIHL). One hundred thirty six patients with chronic tinnitus and at least a 10 year-long working history were divided into two groups based on the risk of their profession to induce NIHL. Individuals employed in jobs at high risk for NIHL were mostly males and exhibited a poorer hearing threshold, more evident in the left ear. Tinnitus was mostly bilateral; the next largest presentation was left-sided; patients described their tinnitus as buzzing or high-pitched. Correlation between age, length of tinnitus and worse hearing was found. Patients with a higher degree of hearing impairment were mostly males and were more likely to have a family history of hearing loss and at least one cardiovascular comorbidity. Our study shows some differences in individuals with tinnitus and a history of a profession associated with increased exposure to NIHL compared to those without such a history.

Current insights in noise-induced hearing loss: a literature review of the underlying mechanism, pathophysiology, asymmetry, and management options

BACKGROUND

Noise-induced hearing loss is one of the most common forms of sensorineural hearing loss, is a major health problem, is largely preventable and is probably more widespread than revealed by conventional pure tone threshold testing. Noise-induced damage to the cochlea is traditionally considered to be associated with symmetrical mild to moderate hearing loss with associated tinnitus; however, there is a significant number of patients with asymmetrical thresholds and, depending on the exposure, severe to profound hearing loss as well.

MAIN BODY

Recent epidemiology and animal studies have provided further insight into the pathophysiology, clinical findings, social and economic impacts of noise-induced hearing loss. Furthermore, it is recently shown that acoustic trauma is associated with vestibular dysfunction, with associated dizziness that is not always measurable with current techniques. Deliberation of the prevalence, treatment and prevention of noise-induced hearing loss is important and timely. Currently, prevention and protection are the first lines of defence, although promising protective effects are emerging from multiple different pharmaceutical agents, such as steroids, antioxidants and neurotrophins.

CONCLUSION

This review provides a comprehensive update on the pathophysiology, investigations, prevalence of asymmetry, associated symptoms, and current strategies on the prevention and treatment of noise-induced hearing loss.

Asymmetric Hearing Loss in Chinese Workers Exposed to Complex Noise

OBJECTIVES

Evaluate the audiometric asymmetry in Chinese industrial workers and investigate the effects of noise exposure, sex, and binaural average thresholds on audiometric asymmetry.

DESIGN

Data collected from Chinese industrial workers during a cross-sectional study were reanalyzed. Of the 1388 workers, 266 met the inclusion criteria for this study. Each subject underwent a physical examination and an otologic examination and completed a health-related questionnaire. χ and t tests were used to examine the differences between the asymmetric and symmetric hearing loss groups.

RESULTS

One hundred thirty-one subjects (49.2%) had a binaural hearing threshold difference of 15 dB or more for at least one frequency, and there was no statistically significant difference between the left and right ears. The asymmetric hearing loss group was not exposed to higher cumulative noise levels (t = 0.522, p = 0.602), and there was no dose-response relation between asymmetry and cumulative noise levels (χ = 6.502, p = 0.165). Men were 1.849 times more likely to have asymmetry than women were (95% confidence interval, 1.051 to 3.253). Among the workers with higher high-frequency hearing thresholds, audiometric asymmetry was 1.024 times more prevalent than that among those with lower high-frequency hearing thresholds (95% confidence interval, 1.004 to 1.044).

CONCLUSIONS

The results indicated that occupational noise exposure contributed minimally to asymmetry, whereas sex and binaural average thresholds significantly affected audiometric asymmetry. There was no evidence that the left ears were worse than the right ears.

DPOAEs in infants developmentally exposed to PCBs show two differently time spaced exposure sensitive windows

The study aim was to identify the timing of sensitive windows for ototoxicity related to perinatal exposure to PCBs. A total of 351 and 214 children from a birth cohort in eastern Slovakia underwent otoacoustic testing at 45 and 72 months, respectively, and distortion product otoacoustic emissions (DPOAEs) at 11 frequencies were recorded. Cord and child 6-, 16-, 45-, and 72- month blood samples were analyzed for PCB 153 concentration. The PCB 153 concentration-time profiles were approximated with a system model to calculate area under the PCB*time curves (AUCs) for specific time intervals (3 and 6 months for 45 and 72 months data, respectively). DPOAE amplitudes were correlated (Spearman) with cord serum PCB and AUCs, markers of prenatal and postnatal exposure, respectively. Two exposure critical windows were identified in infants, the first related to prenatal and early postnatal and the second to postnatal exposure to PCBs. Our data have shown tonotopicity, sexual dimorphism, and asymmetry in ototoxicity of PCBs.

Tinnitus and normal hearing: a study on contralateral acoustic reflex

PURPOSE

The aim of this study was to evaluate the difference of the contralateral acoustic reflex (AR) threshold between adult subjects with hearing within clinically normal limits, with and without tinnitus.

METHOD

The study sample in this exploratory, descriptive, and comparative study comprised 40 female subjects who were evaluated: 20 had tinnitus and 20 formed the control group. The contralateral AR threshold was evaluated at the frequencies of 500, 1000, and 2000 Hz.

RESULTS

Elevated or absent AR thresholds were found only in subjects with complaints of tinnitus. At all frequencies and in either ear, the median AR threshold was higher in the group that complained of tinnitus (100.0 dB; range = 95.0–100.0 dB) compared with the control group (90.0 dB; range = 86.3–95.0 dB; p < .01). There was a statistically significant difference ( p < .05) in the group with tinnitus, in each of the frequencies studied and in both the right and left ear.

CONCLUSION

The results suggest that evaluation of the efferent system, through AR, could be an important tool for the differential diagnosis of tinnitus in patients whose hearing was within clinically normal limits.

Audiogram comparison of workers from five professional categories

INTRODUCTION

Noise is a major cause of health disorders in workers and has unique importance in the auditory analysis of people exposed to it. The purpose of this study is to evaluate the arithmetic mean of the auditory thresholds at frequencies of 3, 4, and 6 kHz of workers from five professional categories exposed to occupational noise.

METHODS

We propose a retrospective cross-sectional cohort study to analyze 2.140 audiograms from seven companies having five sectors of activity: one footwear company, one beverage company, two ceramics companies, two metallurgical companies, and two transport companies.

RESULTS

When we compared two categories, we noticed a significant difference only for cargo carriers in comparison to the remaining categories. In all activity sectors, the left ear presented the worst values, except for the footwear professionals (P > 0.05). We observed an association between the noise exposure time and the reduction of audiometric values for both ears. Significant differences existed for cargo carriers in relation to other groups. This evidence may be attributed to different forms of exposure. A slow and progressive deterioration appeared as the exposure time increased.

The relationship between distortion product otoacoustic emissions and extended high-frequency audiometry in tinnitus patients. Part 1: normally hearing patients with unilateral tinnitus

BACKGROUND

The aim of this study was to evaluate distortion product otoacoustic emissions (DPOAEs) and extended high-frequency (EHF) thresholds in a control group and in patients with normal hearing sensitivity in the conventional frequency range and reporting unilateral tinnitus.

MATERIAL/METHODS

Seventy patients were enrolled in the study: 47 patients with tinnitus in the left ear (Group 1) and 23 patients with tinnitus in the right ear (Group 2). The control group included 60 otologically normal subjects with no history of pathological tinnitus. Pure-tone thresholds were measured at all standard frequencies from 0.25 to 8 kHz, and at 10, 12.5, 14, and 16 kHz. The DPOAEs were measured in the frequency range from approximately 0.5 to 9 kHz using the primary tones presented at 65/55 dB SPL.

RESULTS

The left ears of patients in Group 1 had higher median hearing thresholds than those in the control subjects at all 4 EHFs, and lower mean DPOAE levels than those in the controls for almost all primary frequencies, but significantly lower only in the 2-kHz region. Median hearing thresholds in the right ears of patients in Group 2 were higher than those in the right ears of the control subjects in the EHF range at 12.5, 14, and 16 kHz. The mean DPOAE levels in the right ears were lower in patients from Group 2 than those in the controls for the majority of primary frequencies, but only reached statistical significance in the 8-kHz region.

CONCLUSIONS

Hearing thresholds in tinnitus ears with normal hearing sensitivity in the conventional range were higher in the EHF region than those in non-tinnitus control subjects, implying that cochlear damage in the basal region may result in the perception of tinnitus. In general, DPOAE levels in tinnitus ears were lower than those in ears of non-tinnitus subjects, suggesting that subclinical cochlear impairment in limited areas, which can be revealed by DPOAEs but not by conventional audiometry, may exist in tinnitus ears. For patients with tinnitus, DPOAE measures combined with behavioral EHF hearing thresholds may provide additional clinical information about the status of the peripheral hearing.

Prevalence of Noise Induced Hearing Loss in Indian Air Force Personnel

BACKGROUND

Noise exposure is an inherent part of duty of the aircrew and maintenance staff in the Indian Air Force (IAF). An audiometric survey of IAF personnel was carried out to analyze the prevalence and severity of noise induced hearing loss (NIHL).

METHODS

An audiometric study of 1000 IAF personnel of various trades, age and exposure groups were carried out at an operational base. Age related correction of 5 dB per decade was applied for personnel above SO years of age. Personal factors like smoking, blood group and use of ear defenders were analysed for their effect on the prevalence of NIHL.

RESULT

The study revealed an overall incidence of NIHL of 22.9 % in the personnel with a higher prevalence among the technical trades (26.18 %) as compared to non technical trades (12.5 %). There was a significant increase in prevalence of hearing loss with duration of exposure with 50.8% of personnel above 30 years of exposure having hearing loss. A higher incidence of hearing loss was observed in personnel of blood group O and smokers whereas use of ear defenders was protective.

CONCLUSION

The study reveals a significantly increased prevalence of NIHL among the technical trades of the IAF personnel. The deleterious effects of smoking and protective effect of regular use of ear defenders are emphasized.

The more the worse: the grade of noise-induced hearing loss associates with the severity of tinnitus

Tinnitus disturbs lives and negatively affects the quality of life of about 2% of the adult world population. Research has shown that the main cause of tinnitus is hearing loss. To analyze a possible association of the degree of hearing loss with the severity of tinnitus, we have performed a retrospective study using admission data on 531 patients suffering from chronic tinnitus. We have found that 83% of our tinnitus patients had a high frequency hearing loss corresponding to a noise-induced hearing loss (NIHL). There was a significant correlation between the mean hearing loss and the tinnitus loudness (p < 0.0001). Interestingly, patients suffering from decompensated chronic tinnitus had a greater degree of hearing loss than the patients with compensated form of tinnitus. In addition, we demonstrate that the degree of hearing loss positively correlates with the two subscales ("intrusiveness" and "auditory perceptional difficulties") of the Tinnitus Questionnaire. Our retrospective study provides indirect evidence supporting the hypothesis that the degree of noise-induced hearing loss influences the severity of tinnitus.

Test-retest tinnitus characteristics in patients with noise-induced hearing loss

PURPOSE

The purpose of the study was to examine the test-retest value of tinnitus pitch and loudness in patients with tinnitus and noise-induced hearing loss (NIHL).

MATERIALS AND METHODS

The study sample consisted of 30 patients of mean age 35 +/- 6.7 years with long-standing tinnitus and hearing loss due to exposure to noise during military service. Ten patients had unilateral tinnitus, and 20 had bilateral tinnitus. All presented with a typical NIHL audiogram on the affected side(s). None of the patients was receiving drug therapy.

RESULTS

There was no statistically significant difference in tinnitus pitch or loudness between the 2 tests for the whole group and separately in patients with unilateral or bilateral tinnitus.

CONCLUSION

Subjective testing of pitch and loudness of tinnitus secondary to NIHL is accurate and reproducible, making it a valuable tool for diagnosis and follow-up. The lack of differences between patients with unilateral or bilateral tinnitus indicates that both types may be managed in a similar manner.

Serum PCB concentrations and cochlear function in 12-year-old children

Experimental evidence from animals indicates that exposure to polychlorinated biphenyls (PCBs) causes deterioration of the outer hair cells (OHCs) of the cochlea. To test this hypothesis in humans, we measured serum PCB concentrations in 574 12-year-old children residing in three districts in the Slovak Republic using high-resolution gas chromatography with microelectron capture detection. As a marker of cochlear status, we measured transient evoked (TE) and distortion product (DP) otoacoustic emissions (OAEs), and assessed the cross-sectional association between serum PCBs and OAEs. Median total PCB concentrations were 352.8, 150.5, and 134.9 ng/g lipid in Michalovce, Svidnik, and Bratislava, respectively. In multivariate regression models where otoacoustic measures were modeled as a function of log (base 10) PCB concentrations with adjustment for gender, age, and site of examination, dioxin-like PCBs, nondioxin-like PCBs and a PCB grouping targeting upregulation of hepatic uridine 5'-diphospho-glucuronosyltransferase were significantly associated with lower TEOAE powers at 1000 and 1500 Hz. At 1500 Hz, we observed a strong association with sum of PCBs and DL-PCBs, in the left ear only. The DPOAEs at 1000 Hz were associated with all four PCB groupings. The results of this study show that PCBs may affect the OHCs of the cochlea, a result consistent with findings from animal studies published to date.

A normative study of otoacoustic emissions, ear asymmetry, and gender effect in healthy schoolchildren in Slovakia

OBJECTIVE

The aim of this normative study was to examine cochlear status and possible ear asymmetry and gender effect in transient evoked and distortion product otoacoustic emissions in a group of healthy 12-year-old children in Slovakia.

METHODS

Two hundred and twenty-nine 12-year-old children from Slovakia with normal hearing were included in this study. Adolescents with acute infection, abnormal otoscopic findings and abnormal tympanometry were excluded. Pure tone audiometry was performed in standard conditions in a sound proof room. Recordings of transient evoked (TE) and distortion product otoacoustic emissions (DPOAEs) were performed using an ILO 292 USB Echoport. Parameters of hearing thresholds and OAEs were compared using correlation analysis and Wilcoxon test.

RESULTS

We found highly statistically significant associations between the hearing thresholds for the left and right ears. When comparing pure tone audiometry with OAEs no significant correlation was found. In TEOAE a significant gender effect and side effect in TEOAE SNR were found. On the other hand there was no side effect in TEOAE response level. In DPOAE neither gender nor side effects were determined.

CONCLUSIONS

This is the first comprehensive information on cochlear status among Slovak adolescents. The TEOAEs were significantly higher in girls than boys, but the ear asymmetry in TEOAE was not significant. For DPOAE responses ear asymmetry and gender did not play a role. The data obtained are a basis for population hearing screening, especially for hearing screening programs in infants and children in Slovakia. Moreover data from particular age group represent a link between data from infants and adults.

The effect of tightened hearing protection regulations on military noise-induced tinnitus

The objective of this study was to investigate the effect of tightened hearing protection regulations on tinnitus in the Finnish Defence Forces. The initial study group comprised 252 officers and non-commissioned officers (NCOs), of which 229 were included in the final study group. Subjective symptoms of tinnitus and audiometric test results for these officers and NCOs examined before retirement, from 1984 to 1986 (Period I), and 2003 to 2005 (Period II), were reviewed. Changes in tinnitus reports between the two time periods, during which regulations had been revised, were investigated. Prevalence of tinnitus showed a decline both in officers (from 68% to 63%) and in NCOs (from 76% to 72%) between the two study periods, in accordance with tightened hearing protection regulations. The Cox regression analysis showed a significantly decreased hazard ratio for constant or disturbing tinnitus for Period II. Tinnitus prevalence, especially constant or disturbing tinnitus, in the Finnish Defence Forces was diminished by tightened hearing protection regulations. Tinnitus might be more persistent than hearing loss and does not necessarily improve in direct relation to hearing loss after protective measures.

Hearing conservation program for agricultural students: short-term outcomes from a cluster-randomized trial with planned long-term follow-up

OBJECTIVES

(1) To conduct a contemporary analysis of historical data on short-term efficacy of a 3-year hearing conservation program conducted from 1992 to 1996 in Wisconsin, USA, with 753 high school students actively involved in farm work; (2) to establish procedures for assessment of hearing loss for use in a recently funded follow-up of this same hearing conservation program cohort.

METHODS

We analyzed a pragmatic cluster-randomized controlled trial, with schools as the unit of randomization. Thirty-four rural schools were recruited and randomized to intervention or control. The intervention included classroom instruction, distribution of hearing protection devices, direct mailings, noise level assessments, and yearly audiometric testing. The control group received the audiometric testing.

RESULTS

Students exposed to the hearing conservation program reported more frequent use of hearing protection devices, but there was no evidence of reduced levels of noise-induced hearing loss (NIHL).

CONCLUSION

Our analysis suggests that, since NIHL is cumulative, a 3-year study was likely not long enough to evaluate the efficacy of this intervention. While improvements in reported use of hearing protection devices were noted, the lasting impact of these behaviors is unknown and the finding merits corroboration by longer term objective hearing tests. A follow-up study of the cohort has recently been started.