Five-Year Longitudinal Cohort Study Determines the Critical Intervals for Periodic Audiometric Testing Based on 5070 Tests of Metallurgical Workers Exposed and Nonexposed to Noise.

OBJECTIVES: To compare the progression of 3-, 4-, and 6-kHz thresholds (pure-tone average) over 5 years and determine the most critical period for occupational risk among workers exposed and nonexposed to noise. DESIGN: Metallurgical workers were divided into 2 groups: noise-exposed and non-noise-exposed groups. The 6 initial audiometric tests of each worker were analyzed as baseline test and annual tests 1 to 5. RESULTS: A total of 845 workers were included, 748 in the noise-exposed group and 97 in the non-noise-exposed group, resulting in 5070 tests analyzed. The nonexposed group showed no significant difference in the mean pure-tone averages between any of the annual tests in either ear. In the exposed group, a significant difference was observed in mean pure-tone averages between baseline and Test1 (p = 0.001 right ear; p = 0.001 left ear), between Test3 and Test4 (p = 0.002 right ear; p = 0.005 left ear), and between Test4 and Test5 (p = 0.003 right ear; p = 0.001 left ear). There was no difference between Test1 and Test2 or between Test2 and Test3 in either ear. CONCLUSIONS: The progression of pure-tone averages at 3, 4, and 6 kHz differed between workers exposed and nonexposed to noise. Noise-exposed workers had a significant progressive worsening of audiometric thresholds after 3 years of employment. This study identified, in an unprecedented way, two critical periods of noise exposure: in the first year and after the third year of employment in a noisy environment.

Large-scale phenotyping of ABR P1-N1 amplitudes before and after exposure to noise in 69 strains of mice.

ABR wave I amplitude represents the synapse of auditory nerve fibers with the inner hair cell and is highly correlated with synapse counts. Cochlear synaptopathy, the loss of synaptic connections between inner hair cells and auditory nerve fibers, has been well-demonstrated in animal models of noise-induced hearing loss. The peak-to-peak wave I amplitude was determined at baseline and 2 weeks after noise exposure. We determined the ABR wave I amplitude at 80 dB SPL at the frequencies of 8, 12, 16, 24, and 32 kHz. A total of 69 strains (1-8 mice/strain) were analyzed. A statistically significant post-noise reduction in wave I amplitude was observed in all the tested frequencies (p < 0.00001). We identify distinct patterns of noise susceptibility and make this complete phenotypic dataset available for general use. This data establishes a new resource for the study of NIHL in mice and we hope this database will be a useful tool to expand the research in this field.

Noise Exposure and Distortion Product Otoacoustic Emission Suprathreshold Amplitudes: A Genome-Wide Association Study.

BACKGROUND: Although several candidate-gene association studies have been conducted to investigate noise-induced hearing loss (NIHL) in humans, most are underpowered, unreplicated, and account for only a fraction of the genetic risk. Mouse genome-wide association studies (GWASs) have revolutionized the field of genetics and have led to the discovery of hundreds of genes involved in complex traits. The hybrid mouse diversity panel (HMDP) is a collection of classic inbred and recombinant inbred strains whose genomes have been either genotyped at high resolution or sequenced. To further investigate the genetics of NIHL, we report the first GWAS based on distortion product otoacoustic emission (DPOAE) measurements and the HMDP. METHODS: A total of 102 strains (n = 635) from the HMDP were evaluated based on DPOAE suprathreshold amplitudes before and after noise exposure. DPOAE amplitude variation was set at 60 and 70 dB SPL of the primary tones for each frequency separately (8, 11.3, 16, 22.6, and 32 kHz). These values provided an indirect assessment of outer hair cell integrity. Six-week-old mice were exposed for 2 h to 10 kHz octave-band noise at 108 dB SPL. To perform local expression quantitative trait locus (eQTL) analysis, gene expression microarray profiles were generated using cochlear RNA from 64 hybrid mouse strains (n = 3 arrays per strain). RESULTS: Several new loci were identified and positional candidate-genes associated with NIHL were prioritized, especially after noise exposure (1 locus at baseline and 5 loci after exposure). A total of 35 candidate genes in these 6 loci were identified with at least 1 probe whose expression was regulated by a significant cis-eQTL in the cochlea. After careful analysis of the candidate genes based on cochlear gene expression, 2 candidate genes were prioritized: Eya1 (baseline) and Efr3a (post-exposure). DISCUSSION AND CONCLUSION: For the first time, an association analysis with correction for population structure was used to map several loci for hearing traits in inbred strains of mice based on DPOAE suprathreshold amplitudes before and after noise exposure. Our results identified a number of novel loci and candidate genes for susceptibility to NIHL, especially the Eya1 and Efr3a genes. Our findings validate the power of the HMDP for detecting NIHL susceptibility genes.

Effect of Noise Exposure on 1,382 Metallurgical Workers in Periodic Audiometric Evaluation: A Cohort Study.

INTRODUCTION: Noise-induced hearing loss is the most preventable cause of auditory impairment. Periodic audiometric evaluations are essential to monitor the hearing health of noise-exposed workers. OBJECTIVE: To compare the evolution of audiometric thresholds in the initial three evaluations at frequencies of 3, 4, and 6 kHz in groups of workers exposed or not to noise. METHODS: In this historical cohort study, audiometric evaluations were obtained from male workers between 18 and 40 years of age at six different metallurgical companies in Brazil. The workers were separated into noise-exposed and non-noise-exposed groups. The mean thresholds for 3, 4, and 6 kHz were calculated for both ears at baseline and the first and second periodic evaluations. The non-parametric Wilcoxon test was used for statistical analysis. RESULTS: A total of 1,382 metallurgical workers were evaluated (1,199 noise-exposed and 183 non-noise-exposed). There was a significant difference between baseline and the first periodic evaluation (right ear - effect size = 0.62; p = 0.0030 and left ear - effect size = 0.74; p = 0.0063) and between baseline and the second periodic evaluation (right ear - effect size = 0.85; p = 0.004 and left ear - effect size = 0.96; p = 0.0002). In the non-noise-exposed group, there was no difference between baseline and the first periodic evaluation (right ear - effect size = 0.18; p = 0.2703 and left ear - effect size = 0.12; p = 0.7907) and between baseline and the second periodic evaluation (right ear - effect size = 0.29; p = 0.4475 and left ear - effect size = 0.41; p = 0.6381). CONCLUSION: In noise-exposed workers, there was a significant worsening of audiometric thresholds between baseline and the initial periodic evaluation, but there was no difference between the two post-baseline evaluations. This shows that noise exposure can quickly affect hearing, despite protective measures.

Role of Neuropilin-1/Semaphorin-3A signaling in the functional and morphological integrity of the cochlea.

Neuropilin-1 (Nrp1) encodes the transmembrane cellular receptor neuropilin-1, which is associated with cardiovascular and neuronal development and was within the peak SNP interval on chromosome 8 in our prior GWAS study on age-related hearing loss (ARHL) in mice. In this study, we generated and characterized an inner ear-specific Nrp1 conditional knockout (CKO) mouse line because Nrp1 constitutive knockouts are embryonic lethal. In situ hybridization demonstrated weak Nrp1 mRNA expression late in embryonic cochlear development, but increased expression in early postnatal stages when cochlear hair cell innervation patterns have been shown to mature. At postnatal day 5, Nrp1 CKO mice showed disorganized outer spiral bundles and enlarged microvessels of the stria vascularis (SV) but normal spiral ganglion cell (SGN) density and presynaptic ribbon body counts; however, we observed enlarged SV microvessels, reduced SGN density, and a reduction of presynaptic ribbons in the outer hair cell region of 4-month-old Nrp1 CKO mice. In addition, we demonstrated elevated hearing thresholds of the 2-month-old and 4-month-old Nrp1 CKO mice at frequencies ranging from 4 to 32kHz when compared to 2-month-old mice. These data suggest that conditional loss of Nrp1 in the inner ear leads to progressive hearing loss in mice. We also demonstrated that mice with a truncated variant of Nrp1 show cochlear axon guidance defects and that exogenous semaphorin-3A, a known neuropilin-1 receptor agonist, repels SGN axons in vitro. These data suggest that Neuropilin-1/Semaphorin-3A signaling may also serve a role in neuronal pathfinding in the developing cochlea. In summary, our results here support a model whereby Neuropilin-1/Semaphorin-3A signaling is critical for the functional and morphological integrity of the cochlea and that Nrp1 may play a role in ARHL.

Genome-wide association study identifies nox3 as a critical gene for susceptibility to noise-induced hearing loss.

In the United States, roughly 10% of the population is exposed daily to hazardous levels of noise in the workplace. Twin studies estimate heritability for noise-induced hearing loss (NIHL) of approximately 36%, and strain specific variation in sensitivity has been demonstrated in mice. Based upon the difficulties inherent to the study of NIHL in humans, we have turned to the study of this complex trait in mice. We exposed 5 week-old mice from the Hybrid Mouse Diversity Panel (HMDP) to a 10 kHz octave band noise at 108 dB for 2 hours and assessed the permanent threshold shift 2 weeks post exposure using frequency specific stimuli. These data were then used in a genome-wide association study (GWAS) using the Efficient Mixed Model Analysis (EMMA) to control for population structure. In this manuscript we describe our GWAS, with an emphasis on a significant peak for susceptibility to NIHL on chromosome 17 within a haplotype block containing NADPH oxidase-3 (Nox3). Our peak was detected after an 8 kHz tone burst stimulus. Nox3 mutants and heterozygotes were then tested to validate our GWAS. The mutants and heterozygotes demonstrated a greater susceptibility to NIHL specifically at 8 kHz both on measures of distortion product otoacoustic emissions (DPOAE) and on auditory brainstem response (ABR). We demonstrate that this sensitivity resides within the synaptic ribbons of the cochlea in the mutant animals specifically at 8 kHz. Our work is the first GWAS for NIHL in mice and elucidates the power of our approach to identify tonotopic genetic susceptibility to NIHL.

The Crista Fenestra and Its Impact on the Surgical Approach to the Scala Tympani during Cochlear Implantation.

OBJECTIVE: The aim of this work was to describe the dimensions of the crista fenestra and determine its presence by means of high-resolution computed tomography (CT) for the purpose of cochlear implantation via the round window approach. METHODS: A series of 10 adult human temporal bones underwent high-resolution CT scanning and were further dissected for microscopic study of the round window niche. RESULTS: In all of the specimens, the round window membrane was fully visualized after the complete removal of bony overhangs. The crista fenestra was identified as a sharp bony crest located in the anterior and inferior borders of the niche; its area ranged from 0.28 to 0.80 mm2 (mean 0.51 ± 0.18). The proportion of the area occupied by the crista fenestra in the whole circumference of the round window ranged from 23 to 50% (mean 36%). We found a moderate positive correlation between the area of the niche and the dimensions of the crista fenestra (Spearman rho: 0.491). In every case, high-resolution CT scanning was unable to determine the presence of the crista fenestra. CONCLUSION: The crista fenestra occupies a variable but expressive area within the bony round window niche. Narrower round window niches tended to house smaller crests. The presence of the crista fenestra is an important obstacle to adequate access to the scala tympani. Nevertheless, a high-resolution CT scan provides no additional preoperative information with regard to its presence for the purpose of surgical access to the scala tympani via the round window niche.

A case report of two different skull base pathologies causing hearing loss in the same ear: vestibular schwannoma and superior semicircular canal dehiscence.

Vestibular schwannoma and superior semicircular canal dehiscence are both uncommon entities, especially when present in the same ear. Here we illustrate how both of these pathologies can be repaired through the same surgical exposure, of the middle cranial fossa, with complete preservation of the cochlear nerve function and relief of symptoms caused by canal dehiscence.

Asymmetry of the anterior ethmoidal artery in relation to the anterior skull base: a population-based study of 500 arteries.

OBJECTIVE: To analyze variability in the distance between the Anterior Ethmoidal Artery (AEA) and the anterior Skull Base (SB), as well as the frequency of lateral asymmetry in a Latin American population using computed tomography. METHODS: A total of 250 computed tomography scans of paranasal sinuses in coronal reconstruction (500 AEAs) were analyzed. After determining the image with the best anatomical view of the artery, the distance between its midpoint and the ethmoidal roof was measured, and the images were independently interpreted by 2 physicians. RESULTS: Of the 500 AEAs, 279 (55.8%) adhered to or passed through the SB at a distance of 0mm. A total of 221 AEAs (44.2%) were at some distance from the SB, of which 107 (48.4%) were on the right side, ranging from 1.18 to 6.75mm, and 114 (51.5%) were on the left side, ranging from 1.15 to 6.04mm. The overall mean distance between the AEA and SB was 1.22 (SD=1.57) mm, increasing to 2.77 (SD=1.14) when the arteries adhered to the SB were excluded. Seventy-six individuals (30.4%) had a lateral distance variation > 1mm. CONCLUSION: Our study includes the largest sample of AEA analyzed with computed tomography scans of paranasal sinuses. There was some distance between the AEA and SB in almost half the patients, and we found a high rate of lateral variability >1mm. LEVEL OF EVIDENCE: Level 3.

Anteromedial Petrous (Gardner's) Triangle: Surgical Anatomy and Relevance for Endoscopic Endonasal Approach to the Petrous Apex and Petroclival Region.

BACKGROUND AND OBJECTIVES: Triangular corridors have been used as reliable surgical entry points for open transcranial approaches to the petrous apex (PA) and petroclival region (PCR). The endoscopic endonasal approaches have grown rapidly in the last decade, and the indications have advanced. The knowledge of accurate and reliable anatomic landmarks through endoscopic endonasal route is essential and remain to be established. The purpose of this study was to describe the feasibility and surgical exposure of the anteromedial petrous (Gardner's) triangle as a novel corridor to the PA and PCR. METHODS: Five anatomic specimens were dissected. The PA and PCR were accessed through endoscopic endonasal approaches and contralateral transmaxillary approach. The limits of the anteromedial petrous (Gardner's) triangle were identified and dissected and associated measurements performed. RESULTS: The dissection was divided into 6 steps. The limits of the anteromedial petrous (Gardner's) triangle were identified and defined by the paraclival internal carotid artery anterolaterally, the abducens nerve posteromedially, and the petroclival synchondrosis inferiorly. Three lines were established following the limits of the triangle. The mean distance of the anterolateral limit was 10.03 mm (SD = 0.94), of the posteromedial limit was 20.06 mm (SD = 2.90), and of the inferior limit was 17.99 mm (SD = 2.99). The mean area was 87.56 mm 2 (SD = 20.06). The 3 anatomic landmarks with a critical role to safely define the triangle were the pterygosphenoidal fissure, the petrosal process of the sphenoid bone, and the petroclival synchondrosis. CONCLUSION: The anteromedial (Gardner's) triangle is a well-defined bone corridor which provides access to the entire petrous bone and petroclival junction through endoscopic endonasal route. Regardless of the anatomic variations or tumor location, the landmarks of the abducens nerve, paraclival internal carotid artery, and petroclival synchondrosis are key for understanding lateral access to tumors extending from the clivus.

Effectiveness of Hypoglossal-Facial Anastomosis in the Rehabilitation of Facial Paralysis Following Vestibular Schwannoma Surgery: A Systematic Review.

The facial nerve plays a crucial role in facial expression and sensory functions, with irreversible injuries often demanding rehabilitation therapies, with hypoglossal-facial nerve anastomosis (HFA) being one of the treatment options. This systematic review assessed different HFA techniques for facial paralysis, particularly post vestibular schwannoma resection, focusing on effectiveness and associated morbidities. Fifteen studies, comprising a case series and a retrospective cohort, were analyzed. Techniques included end-to-end, split, side-to-side, end-to-side, and jump interpositional graft hypoglossal-facial anastomosis (JIGHFA). Positive outcomes were observed with end-to-end and side-to-side techniques, while the split technique and JIGHFA showed promise. Comparative analyses favored the 'end-to-side' approach. Shorter intervals between surgery and HFA correlated with improved outcomes. Methodological variations highlight the need for prospective studies with standardized methodologies for robust evidence and informed decision-making on optimal HFA techniques.

Task force of the Brazilian Society of Otology - evaluation and management of peripheral facial palsy.

OBJECTIVE: To review key evidence-based recommendations for the diagnosis and treatment of peripheral facial palsy in children and adults. METHODS: Task force members were educated on knowledge synthesis methods, including electronic database search, review and selection of relevant citations, and critical appraisal of selected studies. Articles written in English or Portuguese on peripheral facial palsy were eligible for inclusion. The American College of Physicians' guideline grading system and the American Thyroid Association's guideline criteria were used for critical appraisal of evidence and recommendations for therapeutic interventions. RESULTS: The topics were divided into 2 main parts: (1) Evaluation and diagnosis of facial palsy: electrophysiologic tests, idiopathic facial palsy, Ramsay Hunt syndrome, traumatic peripheral facial palsy, recurrent peripheral facial palsy, facial nerve tumors, and peripheral facial palsy in children; and (2) Rehabilitation procedures: surgical decompression of the facial nerve, facial nerve grafting, surgical treatment of long-term peripheral facial palsy, and non-surgical rehabilitation of the facial nerve. CONCLUSIONS: Peripheral facial palsy is a condition of diverse etiology. Treatment should be individualized according to the cause of facial nerve dysfunction, but the literature presents better evidence-based recommendations for systemic corticosteroid therapy.

Non-Hodgkin Lymphoma Mimicking Vestibular Schwannoma.

Progressive unilateral hearing loss and an MRI are usually enough to diagnose vestibular schwannoma (VS). We were consulted by a 45-year-old man with otalgia and left-sided hearing loss as well as ipsilateral facial paralysis that had begun two weeks prior. Due to a possible atypical presentation of VS, an MRI was ordered, which revealed an intracanalicular lesion occupying the left cerebellopontine angle cistern. With no signs of systemic disease and considering the total left ear deafness, the patient underwent retrolabyrinthine mastoidectomy. During the procedure, a mass incompatible with VS was found and a biopsy was performed, which led to a diagnosis of non-Hodgkin's lymphoma (NHL). The patient was referred to an oncologist for treatment and, in time, achieved complete remission of the lesion. This case shows us that symptoms of VS may vary in tumor size and location and that atypical presentations warrant investigation. Non-Hodgkin's lymphoma (NHL), although not among the most common differential diagnoses, should be remembered due to its varied clinical presentation broadly dependent on its subtype and dissemination.

Are hearing protection devices used in the workplace really efficient? A systematic review.

BACKGROUND: The most common current hearing protection devices (HPDs) on the market include earplugs and earmuffs. A variety of materials can be used to manufacture these devices, and each offers a level of noise attenuation that is informed by the manufacturer although it does not always correspond to the attenuation observed in real-world use. OBJECTIVE: To evaluate the noise attenuation of HPDs available to workers exposed to noise. METHODS: The most relevant studies originally published in English, Portuguese, or Spanish that investigated the noise attenuation effectiveness of HPDs used by workers exposed to noise were analyzed. The following electronic databases were searched by 2 independent reviewers for studies published from 1999 to 2019: MEDLINE (PubMed), Scopus, Web of Science, EMBASE, Cochrane Library (OVID), ProQuest, and BVS-Bireme. Different combinations of the following search terms (MeSH terms) were used for all databases: "Hearing Loss, Noise-Induced", "Ear Protective Devices" (Efficacy OR Effectiveness)", "Noise, Occupational". RESULTS: The search strategy yielded a total of 326 potentially relevant studies. After the removal of duplicates, 156 remained for the screening of titles and abstracts. After reviewing titles and abstracts, 46 studies were selected for full-text reading. Of these, six were included in this systematic review. CONCLUSION: Hearing protection devices reduced the noise exposure and were effective in all included studies in different countries, types of activity, and sound pressure exposure.

Task force Guideline of Brazilian Society of Otology - hearing loss in children - Part II - Treatment.

OBJECTIVES: To provide an overview of the main evidence-based recommendations for the diagnosis of hearing loss in children and adolescents aged 0-18 years. METHODS: Task force members were educated on knowledge synthesis methods, including electronic database search, review and selection of relevant citations, and critical appraisal of selected studies. Articles written in English or Portuguese on childhood hearing loss were eligible for inclusion. The American College of Physicians' guideline grading system and the American Thyroid Association's guideline criteria were used for critical appraisal of evidence and recommendations for therapeutic interventions. RESULTS: The topics were divided into 2 parts: (1) treatment of sensorineural hearing loss: individual hearing aids, bilateral cochlear implants, cochlear implants in young children, unilateral hearing loss, and auditory neuropathy spectrum disorder; and (2) treatment of conductive/mixed hearing loss: external/middle ear malformations, ventilation tube insertion, and tympanoplasty in children. CONCLUSIONS: In children with hearing loss, in addition to speech therapy, Hearing AIDS (HAs) or implantable systems may be indicated. Even in children with profound hearing loss, both the use of HAs and behavioral assessments while using the device are important.

Task force Guideline of Brazilian Society of Otology ‒ hearing loss in children - Part I ‒ Evaluation.

OBJECTIVES: To provide an overview of the main evidence-based recommendations for the diagnosis of hearing loss in children and adolescents aged 0 to 18 years. METHODS: Task force members were educated on knowledge synthesis methods, including electronic database search, review and selection of relevant citations, and critical appraisal of selected studies. Articles written in English or Portuguese on childhood hearing loss were eligible for inclusion. The American College of Physicians' guideline grading system and the American Thyroid Association's guideline criteria were used for critical appraisal of evidence and recommendations for therapeutic interventions. RESULTS: The evaluation and diagnosis of hearing loss: universal newborn hearing screening, laboratory testing, congenital infections (especially cytomegalovirus), genetic testing and main syndromes, radiologic imaging studies, vestibular assessment of children with hearing loss, auditory neuropathy spectrum disorder, autism spectrum disorder, and noise-induced hearing loss. CONCLUSIONS: Every child with suspected hearing loss has the right to diagnosis and appropriate treatment if necessary. This task force considers 5 essential rights: (1) Otolaryngologist consultation; (2) Speech assessment and therapy; (3) Diagnostic tests; (4) Treatment; (5) Ophthalmologist consultation.

Brazilian Society of Otology task force - Vestibular Schwannoma ‒ evaluation and treatment.

OBJECTIVE: To review the literature on the diagnosis and treatment of vestibular schwannoma. METHODS: Task force members were educated on knowledge synthesis methods, including electronic database search, review and selection of relevant citations, and critical appraisal of selected studies. Articles written in English or Portuguese on vestibular schwannoma were eligible for inclusion. The American College of Physicians' guideline grading system and the American Thyroid Association's guideline criteria were used for critical appraisal of evidence and recommendations for therapeutic interventions. RESULTS: The topics were divided into 2 parts: (1) Diagnosis - audiologic, electrophysiologic tests, and imaging; (2) Treatment - wait and scan protocols, surgery, radiosurgery/radiotherapy, and systemic therapy. CONCLUSIONS: Decision making in VS treatment has become more challenging. MRI can diagnose increasingly smaller tumors, which has disastrous consequences for the patients and their families. It is important to develop an individualized approach for each case, which highly depends on the experience of each surgical team.

Brazilian Society of Otology task force - Otosclerosis: evaluation and treatment.

OBJECTIVES: To review and provide evidence-based recommendations for the diagnosis and treatment of otosclerosis. METHODS: Task force members were educated on knowledge synthesis methods, including electronic database search, review and selection of relevant citations, and critical appraisal of selected studies. Articles written in English or Portuguese on otosclerosis were eligible for inclusion. The American College of Physicians' guideline grading system and the American Thyroid Association's guideline criteria were used for critical appraisal of evidence and recommendations for therapeutic interventions. RESULTS: The topics were divided into 2 parts: 1) Diagnosis - audiologic and radiologic; 2) Treatment - hearing AIDS, pharmacological therapy, stapes surgery, and implantable devices - bone-anchored devices, active middle ear implants, and Cochlear Implants (CI). CONCLUSIONS: The pathophysiology of otosclerosis has not yet been fully elucidated, but environmental factors and unidentified genes are likely to play a significant role in it. Women with otosclerosis are not at increased risk of worsening clinical condition due to the use of contraceptives or during pregnancy. Drug treatment has shown little benefit. If the patient does not want to undergo stapedotomy, the use of hearing aids is well indicated. Implantable systems should be indicated only in rare cases, and the CI should be indicated in cases of profound deafness.

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.