Normal-hearing Workers Research Articles

Evaluation of Subtle Auditory Impairments with Multiple Audiological Assessments in Normal Hearing Workers Exposed to Occupational Noise.

Recent studies involving guinea pigs have shown that noise can damage the synapses between the inner hair cells and spiral ganglion neurons, even with normal hearing thresholds-which makes it important to investigate this kind of impairment in humans. The aim was to investigate, with multiple audiological assessments, the auditory function of normal hearing workers exposed to occupational noise. Altogether, 60 workers were assessed (30 in the noise-exposure group [NEG], who were exposed to occupational noise, and 30 in the control group [CG], who were not exposed to occupational noise); the workers were matched according to age. The following procedures were used: complete audiological assessment; speech recognition threshold in noise (SRTN); speech in noise (SN) in an acoustic field; gaps-in-noise (GIN); transient evoked otoacoustic emissions (TEOAE) and inhibitory effect of the efferent auditory pathway; auditory brainstem response (ABR); and long-latency auditory evoked potentials (LLAEP). No significant difference was found between the groups in SRTN. In SN, the NEG performed worse than the CG in signal-to-noise ratio (SNR) 0 (p-value 0.023). In GIN, the NEG had a significantly lower percentage of correct answers (p-value 0.042). In TEOAE, the NEG had smaller amplitude values bilaterally (RE p-value 0.048; LE p-value 0.045) and a smaller inhibitory effect of the efferent pathway (p-value 0.009). In ABR, the NEG had greater latencies of wave V (p-value 0.017) and interpeak intervals III-V and I-V in the LE (respective p-values: 0.005 and 0.04). In LLAEP, the NEG had a smaller P3 amplitude bilaterally (RE p-value 0.001; LE p-value 0.002). The NEG performed worse than the CG in most of the assessments, suggesting that the auditory function in individuals exposed to occupational noise is impaired, even with normal audiometric thresholds.

Effects of noise on the vestibular system of normal-hearing workers.

Studies in noise-exposed animals have shown changes in vestibular structures. Likewise, studies in humans have been suggesting that noise can damage the vestibular system, even with normal assessment results. To assess the vestibular system of workers exposed to noise and to compare with individuals not exposed. Twenty normal-hearing male adults were divided in the study group (SG), exposed to occupational noise, and control group (CG). We conducted the following procedures: medical history, Dizziness Handicap Inventory (DHI), Dix-Hallpike maneuver, and electronystagmography (eye and caloric tests). The DHI score did not differ between groups. The Dix-Hallpike maneuver was normal for both groups. All individuals had normal responses in the eye tests. 50% of the SG had hyperreflexia in the caloric tests, with a significant difference between the groups. There was a trend towards a statistical significance in the absolute values of angular speed of the slow component in the cold-air test, which were higher in the SG. There was a significant difference between the groups in the relative values of labyrinthine preponderance, which were higher in the SG. Our findings showed that 70% of the workers exposed to occupational noise had vestibular alterations identified with electronystagmography, whereas 100% of the individuals in the CG had normal results in the vestibular assessment. Moreover, only 20% of the sample in both groups had vestibular complaints, indicating the presence of subclinical vestibular changes in 50% of the individuals exposed to occupational noise.

Effects of Noise and Chemical Exposure on Peripheral and Central Auditory Pathways in Normal-hearing Workers.

To assess the effects of noise and chemical exposure on peripheral and central auditory pathways in normal-hearing workers exposed to chemicals or high noise levels and compare the groups with each other and with workers not exposed to either of these agents. A total of 54 normal-hearing workers were divided into three groups (chemical, noise, control) and submitted to the following assessments: conventional and extended high-frequency pure-tone audiometry; transient and distortion-product otoacoustic emissions, the inhibitory effect of the efferent auditory pathway; and Staggered Spondaic Word (SSW) and Pitch Pattern Sequence (PPS) test. There were no significant differences between the groups in extended high-frequency hearing thresholds. Significantly lower amplitudes were observed in the noise group for otoacoustic emissions. There were significantly more absences of the inhibitory effect of the efferent system in the noise group. There was no difference between the groups in the SSW test, while in PPS, the noise group performed worse than the control group. These findings suggest that noise exposure produced deleterious effects on the workers' peripheral and central auditory systems, despite their normal hearing thresholds. The chemical group did not have significantly different results from those of the control group. It is important that individuals exposed to noise or chemicals have their auditory pathways monitored with complementary assessments.

The Post Noise-Exposed Condition of Two Normal Hearing Workers with Tinnitus and Hyperacusis Developed by the Chronic Occupational Noise Exposure

The Post Noise-Exposed Condition of Two Normal Hearing Workers with Tinnitus and Hyperacusis Developed by the Chronic Occupational Noise Exposure

Occupational Performance of Hearing-Impaired and Normal-Hearing Workers in Korea.

Background and ObjectivesThis study aimed to investigate the occupational performance of Korean workers with and without hearing loss and analyze the hearing-related difficulties in the working environment.Subjects and MethodsThe Amsterdam checklist for hearing and work was used for the analyses and the occupational environments of the Korean workers were investigated. Out of 129 total participants, 86 workers experienced severe to profound hearing loss and 43 had the normal hearing ability. The hearing-impaired workers were recruited from two leading vocational centers and normal-hearing workers were their colleagues.ResultsThe hearing-impaired workers were found to take fewer sick leaves and exhibited higher rates of permanent job statuses compared to the normal-hearing workers. Workers with hearing loss rarely detected background sound; however, they could perceive reverberation more frequently. They felt more satisfied with their careers than the normal hearing workers as they received social support and needed to put their effort into hearing for most hearing activities. Furthermore, the effort in hearing increased with the increase in job demand, job control, social support, and career satisfaction. The working hours per week increased with the increase in age, education level, job demand, job control, and social support. Different trends were observed in 9 out of 12 variables while comparing the data from the present study with that obtained from the hearing-impaired workers of the Netherlands, indicating a large difference between countries.ConclusionsAlthough the hearing-impaired Korean workers operate diligently with good job positions, it is necessary to enhance their acoustic environment and provide them social support. Considering the cultural background of the hearing-impaired workers, the development of suitable vocational rehabilitation programs and specific questionnaires is strongly recommended worldwide.

Temporary Threshold Shifts among Iron and Steel Factory Workers in Tanzania: A Pre-Interventional Study.

Background:Workers in iron and steel factories in Tanzania are exposed to noise levels above recommended limit values, without using hearing protection devices. Exposure to noise levels above 85 dB(A) is associated with temporary threshold shifts (TTS) of human hearing. Nevertheless, there are few studies of noise and hearing from African countries.Objective:To determine whether the normal hearing workers in Tanzania experiences TTS after full-shift occupational noise exposure of 85 dB(A) and above.Methods:A total of 55 workers were included. Full-shift personal noise measurements were conducted. Pre- and post-shifts pure-tone audiometry were conducted for each worker. TTS was defined as a 10 dB or greater change at 1000, 2000, 3000 or 4000 Hz in either ear.Results:We found that 85.5% of the workers developed TTS across the work shift. There was significant increase in mean hearing thresholds across shift at 1000, 2000, 3000 and 4000 Hz among the workers exposed to an average personal noise exposure (LAeq,8h) of 90.4 dB(A) (SD = 2.7). The difference in mean hearing thresholds was higher at 4000 Hz [Arithmetic Mean (AM) = 10 dB SD = 4 dB] compared to that of 1000 Hz (AM = 4 dB SD = 3 dB), 2000 Hz (AM = 4 dB SD = 4 dB), and 3000 Hz (AM = 9 dB SD = 6 dB), respectively.Conclusions:Interventions to reduce occupational personal noise exposure are warranted to reduce the high risk of developing a permanent threshold shift with persistent high noise exposure. An intervention study is planned for this group of workers.

Single nucleotide polymorphisms in JNK1 are associated with susceptibility to noise-induced hearing loss in a Chinese population.

This study intended to explore the effect of C-Jun N-terminal kinases 1 (JNK1) polymorphisms on the sensitivity of individual hearing loss. A total of 1333 subjects, including 683 NIHL workers and 650 normal-hearing workers from east China, were included in this cross-sectional study. Genotyping of three JNK1 single nucleotide polymorphisms (rs9284, rs8428, and rs11598320) was performed. The relationship between different genotypes and noise-induced hearing loss was analyzed. Results show that rs11598320 TT genotype was associated with a higher risk of NIHL (OR 1.57, 95% CI 0.91-2.70). Stratified analysis indicated that the rs11598320 AT + AA genotype was associated with a decreased risk of hearing loss in subjects exposed to noise ≤ 16years or a noise level > 92dB (OR 0.68, 95% CI 0.50-0.93 and OR 0.64, 95% CI 0.42-0.96, respectively). The rs8428 TT genotype was associated with an increased risk of noise-induced hearing loss when the noise level was > 92dB (OR 1.73, 95% CI 1.11-2.70). Haplotype TCT (rs9284-rs8424-rs11598320) was associated with an increased risk of noise-induced hearing loss (OR 1.30, 95% CI 1.00-1.68). Single nucleotide polymorphisms (rs11598320 and rs8424) in JNK1 can be used as new biomarkers of susceptibility for noise-induced hearing loss in Chinese workers.

Accuracy of an internet-based speech-in-noise hearing screening test for high-frequency hearing loss: incorporating automatic conditional rescreening

PurposeTo validate the accuracy of an internet-based speech-in-noise hearing screening test for high-frequency hearing loss (HFHL) ‘Occupational Earcheck (OEC)’ incorporating an automatic conditional rescreening, in an occupationally noise-exposed population. Secondary objectives were to assess the effects of age on test accuracy measures, and to assess the test accuracy for different degrees of HFHL.MethodsA study was conducted on cross-sectional data of occupational audiometric examinations, including the index test OEC and reference standard pure-tone air conduction audiometry, of 80 noise-exposed workers. Sensitivity, specificity, and likelihood ratios were calculated for the OEC, after automatic conditional rescreening, for a younger and an older age group, and for two degrees of HFHL (HFHL25: PTA3,4,6 ≥ 25 dB HL, and HFHL35: PTA3,4,6 ≥ 35 dB HL, both for at least one ear).ResultsTest specificity for HFHL25 after a single test was 63%, and improved to 93% after the automatic conditional rescreen. Test sensitivity for HFHL25 decreased from 65% to 59%. Test sensitivity and specificity including automatic conditional rescreening for HFHL35 was 94% and 90%, respectively. The positive likelihood ratio for HFHL25 was 8.4, and for HFHL35 9.4. The negative likelihood ratio for HFHL35 was below 0.1.ConclusionsThe OEC is an appropriate screening test, especially for HFHL35. Normal-hearing workers who obtained a positive test result for the first test for one or two ears, benefit from having an automatic rescreen, resulting in an improvement of the test specificity, and hence prevent unnecessary referral.

Associations of genetic variation in CASP3 gene with noise-induced hearing loss in a Chinese population: a case\u2013control study

BackgroundNoise-induced hearing loss (NIHL) is a complex disease caused by environmental and genetic risk factors. This study explored the relationship between the genetic variations in the CASP gene and the risk of developing NIHL among Chinese workers exposed to occupational noise.MethodsA case–control study of 272 NIHL workers and 272 normal-hearing workers matched for age, sex and years of noise exposure was conducted. Fifteen single-nucleotide polymorphisms (SNP) in the CASP1, CASP3, CASP4, CASP5, CASP6, CASP8, CASP9, CASP10 and CASP14 genes were genotyped using the polymerase chain reaction–ligase detection reaction method. Using conditional logistic regression models, the adjusted odds ratios (ORs) and 95% confidence intervals (CIs) of genetic variations associated with NIHL risk were calculated.ResultsTwo SNPs in the CASP3 gene were associated with NIHL risk. For rs1049216, TT genotype was associated with a decreased risk of NIHL (OR = 0.246, 95% CI = 0.069–0.886) when compared with the CC genotype. For rs6948, the AC and CC genotype were associated with a decreased NIHL risk (OR = 0.568, 95% CI = 0.352–0.916) compared with AA genotype. There were joint effects of working time and CASP3 polymorphisms on NIHL risk (P < 0.05).ConclusionsGenetic variations in the CASP3 gene and the joint effects of working time and CASP3 polymorphisms may modify the risk of developing NIHL.

Analysis of Hearing and Tinnitus in Workers Exposed to Occupational Noise.

Noise is one of the harmful agents to health that is present in the various branches of economic activity. Hearing loss and tinnitus are among the most frequently reported complaints by workers exposed to occupational noise. To analyze the hearing and tinnitus in normal-hearing workers exposed to occupational noise. This is a cross-sectional analytical trial in metallurgical industries, in which we evaluated normal-hearing workers through anamnesis, audiometry and otoacoustic emissions. It was observed high prevalence of failure of otoacoustic emissions (40%) and tinnitus (66.6%). Both in the amplitude and in the signal-to-noise ratio, the higher is the frequency of the sound, the worse the results. Despite having audiometry within normal limits, the results indicate that workers are suffering the effects of exposure and reveals association between failure of otoacoustic emissions and tinnitus in this population (X2 = 6,732). It is concluded that failures in DPOAE and tinnitus are predictors of hearing damage in normal-hearing workers.

Genetic variation in APE1 gene promoter is associated with noise-induced hearing loss in a Chinese population.

To investigate whether the apurinic/apyrimidinic endonuclease 1 (APE1) 1349 T>G and -656 T>G polymorphisms were associated with the risk of noise-induced hearing loss (NIHL) in a Chinese population. The two APE1 polymorphisms were analyzed among 613 NIHL workers and 613 normal hearing workers using the minor groove binder TaqMan probe assay. We found that the APE1 -656 TT genotype was associated with a increased risk of NIHL [adjusted odds ratio (OR) 1.46, 95% confidence interval (CI) 1.05-2.06]. This increased risk was more pronounced in the stratification analysis. Furthermore, we found that subjects with two risk genotypes (hOGG1 Cys/Cys, APE1 -656 TT) had a significantly increased risk of NIHL (adjusted OR 1.91, 95% CI 1.27-2.88). Our study identified that the APE1 -656 T>G polymorphism may contribute to the susceptibility of NIHL.

Associations of genetic variations in EYA4, GRHL2 and DFNA5 with noise-induced hearing loss in Chinese population: a case- control study.

BackgroundBoth environmental and genetic factors are attributable to the incidence of noise-induced hearing loss (NIHL). The purpose of this study was to examine the associations between genetic variations in the EYA4, GRHL2 and DFNA5 genes and the risk to noise-induced hearing loss (NIHL) in a Chinese population.MethodsA case–control study was conducted with 476 NIHL workers and 475 normal hearing workers matched with gender, years of noise exposure, and intensity of noise exposure. Twelve tag single-nucleotide polymorphisms (SNP) in the EYA4, GRHL2 and DFNA5 genes were genotyped using nanofluidic dynamic arrays on the Fluidigm platform. Multiple logistic regression was used to analyze the associations of genetic variations with NIHL adjusted by age, smoking/drinking status, and cumulative noise exposure and their interactions with noise exposure.ResultsThe SNPs of rs3777781and rs212769 in the EYA4 gene were significantly associated with NIHL risk. In rs3777781, comparing with the subjects carrying with TT types, the carriers with AT and AA genotypes had the decreased risk of NIHL (OR = 0.721, 95 % CI = 0.522 - 0.996). In rs212769, the AG and AA carriers had increased NIHL risk (OR = 1.430, 95 % CI = 1.014 - 2.016) compared with the subjects with GG genotype. Rs666026 in the associated GRHL2 gene and rs2521758 in the DFNA5 gene were marginally t associated with NIHL (P = 0.065 and 0.052, respectively). Rs2521758 and rs212769 had significantly interacted with noise exposure (P < 0.05).ConclusionsGenetic variations in the EYA4, GRHL2 and DFNA5 genes and their interactions with occupational noise exposure may play an important role in the incidence of NIHL.

Genetic Variation in GSTM1 Is Associated With Susceptibility to Noise-Induced Hearing Loss in a Chinese Population

To investigate whether glutathione S-transferases (GST) genetic polymorphisms (GSTT1 rs1049055, GSTM1 rs10712361, and GSTP1 rs1695) are associated with susceptibility to noise-induced hearing loss (NIHL). These polymorphisms were analyzed in 444 NIHL and 445 normal hearing workers. In addition, total plasma GST activity was measured in all subjects. Individuals with the GSTM1 null genotype had a statistically significantly increased risk of NIHL (odds ratio [OR] = 1.64, 95% confidence interval [CI] = 1.26 to 2.13) compared with those carrying a wild-type GSTM1 genotype. This effect was more pronounced among the workers exposed to 86 to 91 dB(A) (OR = 3.35, 95% CI = 1.54 to 7.31). Glutathione S-transferase activity of the NIHL workers was also lower than that of normal hearing workers (14.5 ± 5.1 U/ml vs 15.9 ± 6.3 U/ml, P = 0.010). Our results suggest that GSTM1 polymorphism is associated with susceptibility to NIHL.

Otoacoustic Emission in Noise‐Exposed Normal Hearing Workers

Objective: Otoacoustic emission test is useful in monitoring hearing changes and cochlear damage by noise still not detectable in pure-tone audiometry.The aim was to evaluate amplitude of the signal and signal/noise ratio of distortion product otoacoustic emissions (DPOAE) in normal hearing workers exposed to different noise doses. Method: This is a cohort prospective study performed in metalworking industries, in 3 groups of normal hearing workers, GI not exposed (n = 50), GII sporadically exposed (n = 50), and GIII often exposed to occupational noise (n = 50). DPOAE were performed after 14 hours of hearing rest. “Pass-fail” criterion was employed for analyses. Results: Six hundred eight workers underwent hearing thresholds, and 150 of them matched the inclusion criteria and had DPOAE recorded. DPOAE alterations in amplitude of signal and signal to noise ratio were found in groups II and III bilaterally, and the higher the frequency tested the lower were the results in GII and GIII ( P &lt; .05). The greater the exposure to noise dose the lower the results ( P &lt; .05). GI showed better results according to pass and fail criterion and higher amplitude of the signal and signal/noise ratio than GII and GIII ( P &lt; .05). Conclusion: DPOAE results are worse in the exposed groups according to occupational noise dose. It is important to search for undetectable hearing changes in all workers exposed to occupational noise even sporadically, and to encourage the use of hearing protectors, in order to prevent possible irreversible damage.

Noise dosimetry for telephone users

Due to recent F.C.C. regulations, all telephones in North America will be required to have at least 12 dB of amplification. While this is a definite asset to the hard of hearing community, there are fears that normal hearing workers who use the telephone most of the day could suffer noise-induced hearing loss. Theoretical calculations validate this hypothesis. Measurements of actual levels in a call center were taken. Finally, a method of providing noise dosimetry within a digital telephone set is presented. Simultaneous measurements show good correlation.

Psychosocial Disadvantages Associated with Occupational Hearing Loss as Experienced in the Family: Les désavantages psycho-sociaux associés à la surdité professionnells tells que vécus dans la famille

A questionnaire has been developed to investigate the psycho-social disadvantages resulting from occupational hearing loss (OHL). It was designed to measure the awareness of the hearing disability, the coping strategies and the family response to the consequences of OHL. Answers to the questionnaire were obtained from 54 workers with various degrees of presumed OHL and from 44 normal-hearing workers employed in the same noisy plant. The results show (a) that the family bears several consequences of the noise exposure and of the hearing loss of the worker and (b) that its spontaneous reaction to OHL appears as one source of the psycho-social disadvantages experienced by the worker. The implications of these results for rehabilitative intervention are discussed.Un questionnaire a ete mis au point pour etudier les desavantages psychosociaux associes a la surdite professionnelle. Il a ete concu de maniere a mesurer principalement la conscience de la perte auditive, les strategies d'adaptation et la reponse de...