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Exposure to loud sound during leisure time is identified as a significant risk factor for hearing by health authorities worldwide. The current standard that defines unsafe exposure rests on the equal-energy hypothesis, according to which the maximum recommended exposure is a tradeoff between level and daily exposure duration, a satisfactory recipe except for strongly non-Gaussian intense sounds such as gunshots. Nowadays, sound broadcast by music and videoconference streaming services makes extensive use of numerical dynamic range compression. By filling in millisecond-long valleys in the signal to prevent competing noise from masking, it pulls sound-level statistics away from a Gaussian distribution, the framework where the equal-energy hypothesis emerged. Auditory effects of a single 4 hour exposure to the same music were compared in two samples of guinea pigs exposed either to its original or overcompressed version played at the same average level of 102 dBA allowed by French regulations. Apart from a temporary shift of otoacoustic emissions at the lowest two frequencies 2 and 3 kHz, music exposure had no detectable cochlear effect, as monitored at 1, 2 and 7 days post-exposure. Conversely, middle-ear muscle strength behaved differentially as the group exposed to original music had fully recovered one day after exposure whereas the group exposed to overcompressed music remained stuck to about 50% of baseline even after 7 days. Subsamples were then re-exposed to the same music as the first time and sacrificed for density measurements of inner-hair-cell synapses. No difference in synaptic density was found compared to unexposed controls with either type of music. The present results show that the same music piece, harmless when played in its original version, induces a protracted deficit of one auditory neural pathway when overcompressed at the same level. The induced disorder does not seem to involve inner-hair cell synapses.

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OBJECTIVE: To evaluate the effectiveness of hearing health education programs aimed at preventing noise-induced hearing loss (NIHL), of recreational and occupational origin, by means of a systematic review and meta-analysis. DESIGN: The search strategy was carried out in on five electronic databases, as well as referrals from experts. The risk of bias was judged, and the random effects meta-analysis was performed. The certainty of the evidence was assessed. STUDY SAMPLE: Effectiveness studies that used educational intervention in hearing health and prevention of NIHL were included. RESULTS: 42 studies were included. The Dangerous Decibels program was the only one that could be quantitatively analysed and showed improvement in the post-intervention period of up to one week [SMD = 0.60; CI95% = 0.38-0.82; I2 = 92.5%) and after eight weeks [SMD = 0.45; CI95% = 0.26-0.63; I2 = 81.6%) compared to the baseline. The certainty of evidence was judged as very low. CONCLUSIONS: The Dangerous Decibels program is effective after eight weeks of intervention. The other programs cannot be quantified. They still present uncertainty about their effectiveness. The level of certainty is still low for this assessment.

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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.

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Abstract Introduction: Noise-induced hearing loss is one of the most common forms of sensorineural hearing loss. Nevertheless, the mechanisms of noise-induced hearing loss are still not fully understood. Objective: To investigate the dynamics of inflammatory responses in the mammalian cochlea following noise trauma at two different times, once during the light cycle and once during the dark. Methods: We challenged C57BL/6J mice with moderate, continuous noise trauma at either 9 a.m. or 9 p.m. Auditory function, histological changes in hair cells, and modifications in gene expression levels of inflammatory mediators were assessed at specific time points. Shifts in auditory brainstem response thresholds were measured at 1, 3, 7 and 14 days after noise exposure to measure potential noise-induced hearing loss. Cochlear basilar-membrane immunofluorescent staining was performed at 3 and 14 days after noise exposure. The mRNA levels of several inflammatory mediators were measured via quantitative real-time polymerase chain reaction before (pre) and after (0, 3, 12, 24 and 72 h) noise exposure. Results: We found that all noise-exposed mice developed a temporary threshold shift and that there were no significant differences between daytime and nighttime noise exposures in terms of inducing hearing-threshold shifts. Similarly, we did not detect significant histological changes in hair cells between these two groups. However, we discovered an interesting phenomenon in that the peak mRNA levels of IL-1β, IL-6, CCL2 and TNF-α were higher in day noise-exposed mice compared to those in night noise-exposed mice, and these mRNA levels subsided more slowly in day noise-exposed mice. Conclusion: Overall, these observations suggest that the circadian timing of noise exposure has a significant effect on noise-induced inflammatory responses in the mouse cochlea and that a greater inflammatory response might occur after daytime exposure.

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Abstract 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.

Resumo Introdução: A legislação brasileira atual exige que todos os trabalhadores expostos a ruído recebam um audiograma na admissão, 6 meses após a admissão (primeiro teste periódico), e anualmente após o primeiro teste periódico, mas em outros países as regulamentações dos programas de conservação auditiva não incluem a exigência de teste audiométrico após 6 meses de admissão, mas apenas anualmente. Não há evidências de que a periodicidade adotada pela legislação brasileira seja a mais adequada. Objetivo: Avaliar os três primeiros exames audiométricos ocupacionais de trabalhadores expostos ao ruído. Método: Estudo de coorte histórica com análise transversal. Os participantes eram todos trabalhadores metalúrgicos do sexo masculino com até 40 anos. Os três primeiros audiogramas de cada trabalhador foram analisados: teste audiométrico pré-admissão, teste audiométrico periódico 1 e teste audiométrico periódico 2. Para cada trabalhador, os limiares de frequência médios foram calculados em 3, 4 e 6 kHz nas orelhas esquerda e direita para cada teste. A análise estatística foi feita através do teste não paramétrico de Wilcoxon. Resultados: Foram incluídos 988 trabalhadores. Houve uma diferença significante nos limiares auditivos entre o teste pré-admissão e os 2 testes periódicos subsequentes para as orelhas direita e esquerda. Não houve diferença significante entre o teste 1 e o teste 2 em nenhuma das orelhas. Conclusão: Dada a falta de diferença entre os 2 primeiros testes periódicos, acreditamos que eles poderiam ser combinados em um único teste, ou seja, o primeiro teste audiométrico periódico poderia ser feito após 12 meses de admissão sem comprometer a saúde dos trabalhadores.

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Context: Despite the fact that the new generations of rotary tools emit less noise, some recent studies suggest that dental students are still at risk of hearing impairment. Aims: The aim of the study was to determine a possible association between noise exposure from dental equipment and early signs of noise-induced hearing loss (NIHL) in dental students. Settings and Design: A cross-sectional study was carried out with dental and non-dental students from two universities in Chile. Methods and Material: A group of 102 dental students routinely exposed to noise emitted from dental equipment was selected as the study group. A group of 251 non-dental students was selected as the control group. Pure-tone audiometry was carried out on all participants ensuring that they were not exposed to noise for at least 24 hours prior to testing. The presence of a notch was determined for each participant. Statistical analysis used: Simultaneous-quantile regressions were used to compare percentiles of the hearing threshold between both groups. Then, the notch prevalence ratio adjusted by gender and age was estimated for each group of participants. Finally, the prevalence of an audiometric notch was compared between both groups using logistic regression models and generalized linear methods. Both fixed effect and multilevel hierarchy models were constructed. Results: Significant differences between groups for the 75th percentile of hearing threshold distributions at 4 and 6 kHz in the left ear and at 6 kHz in the right ear were found. In addition, study group participants exhibited a significantly higher prevalence of a notch at 4 kHz in the left ear than control group participants. Conclusions: Exposure to noise derived from learning activities as a dental student is associated with early signs of NIHL. Such signs include poorer hearing thresholds than those of non-dental students at 4 and 6 kHz as well as the presence of a notch at high frequencies.

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Objectives: 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. Methods: 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. Results: 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. Conclusion: 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.

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SUMMARY OBJECTIVE: Noise-induced hearing loss is a preventable form of hearing loss that has serious social and economic impacts. This study aimed to investigate the protective effect of berberine, a potent antioxidant and anti-inflammatory agent, against Noise-induced hearing loss. METHODS: After applying distortion product otoacoustic emission, 28 female Sprague-Dawley rats were randomly divided into four groups. Group 1 was designated as acoustic trauma group, and rats in this group were exposed to white noise for 12 h at an intensity of 4 kHz 110 dB sound pressure level. Group 2 was the control group. Group 3 was designated as the berberine group, and 100 mg/kg of berberine was administered to rats in this group by intragastric lavage for five consecutive days. Group 4 was designated as the acoustic trauma+berberine group. distortion product otoacoustic emission was repeated on the 6th day of the study and cochlear tissues of rats were dissected for histopathological and immunohistochemical analyses after sacrificing rats. RESULTS: The distortion product otoacoustic emission results showed a significant decrease in signal-noise ratio values at higher frequencies in rats of the trauma group compared to those in other groups. Acoustic trauma caused severe histopathological impairment at cochlear structures together with severe 8-hydroxy-2-deoxyguanosine expression. Rats in the acoustic trauma+berberine group showed mild histopathological changes with mild 8-hydroxy-2-deoxyguanosine expression and better signal-noise ratio values. CONCLUSION: The histopathological and audiological findings of this experimental study showed that berberine provides protection in Noise-induced hearing loss and may have the potential for use in acoustic trauma-related hearing losses.

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Introduction: Noise-induced hearing loss can be avoided by taking preventive measures. Objective: To assess the effectiveness of the Brazilian version of the Dangerous Decibels® program for noise-exposed workers, using the ecological model as an educational intervention plan. Method: Non-randomized interventional study with a quantitative, experimental trial design, conducted at a meatpacking company. The participants were divided into two groups-the first one (n = 132, divided into 6 subgroups) received the Dangerous Decibels® Brazil educational intervention (DDBEI) adapted to workers while the second group (n = 138, divided into 5 subgroups) received a conventional educational intervention (CEI). The interventions lasted 50 min. The Hearing Protection Assessment Questionnaire (HPA-5) was administered before and after the interventions. The five dimensions (attitude, behavior, knowledge, supports, and barriers) were compared using the Student's t-test for paired data (<0.05). Results: After both the DDBEI and CEI training, workers improved significantly in barriers, supports, knowledge, attitudes, and behavior around noise. By chance, the CEI group scored lower in all measures than the DDBEI group before training, and though both groups improved, the difference was maintained after training. Conclusion: The Brazilian version of the Dangerous Decibels® program for noise-exposed workers was effective, influencing positively the factors at different levels of the ecological model. Though the DDBEI was no more effective than the CEI, the CEI participants began at much lower levels, so the effectiveness of the DDBEI may have been underestimated.

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INTRODUCTION: Noise-induced hearing loss is one of the most common forms of sensorineural hearing loss. Nevertheless, the mechanisms of noise-induced hearing loss are still not fully understood. OBJECTIVE: To investigate the dynamics of inflammatory responses in the mammalian cochlea following noise trauma at two different times, once during the light cycle and once during the dark. METHODS: We challenged C57BL/6J mice with moderate, continuous noise trauma at either 9 a.m. or 9 p.m. Auditory function, histological changes in hair cells, and modifications in gene expression levels of inflammatory mediators were assessed at specific time points. Shifts in auditory brainstem response thresholds were measured at 1, 3, 7 and 14 days after noise exposure to measure potential noise-induced hearing loss. Cochlear basilar-membrane immunofluorescent staining was performed at 3 and 14 days after noise exposure. The mRNA levels of several inflammatory mediators were measured via quantitative real-time polymerase chain reaction before (pre) and after (0, 3, 12, 24 and 72 h) noise exposure. RESULTS: We found that all noise-exposed mice developed a temporary threshold shift and that there were no significant differences between daytime and nighttime noise exposures in terms of inducing hearing-threshold shifts. Similarly, we did not detect significant histological changes in hair cells between these two groups. However, we discovered an interesting phenomenon in that the peak mRNA levels of IL-1ß, IL-6, CCL2 and TNF-α were higher in day noise-exposed mice compared to those in night noise-exposed mice, and these mRNA levels subsided more slowly in day noise-exposed mice. CONCLUSION: Overall, these observations suggest that the circadian timing of noise exposure has a significant effect on noise-induced inflammatory responses in the mouse cochlea and that a greater inflammatory response might occur after daytime exposure.

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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.

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RESUMO Objetivo Investigar a associação entre dificuldade auditiva autorreferida e exposição ocupacional à poeira industrial em trabalhadores do sul do Brasil. Método Trata-se de um estudo transversal analítico, realizado com dados do inquérito da Pesquisa Nacional de Saúde (2013). A variável dependente foi a dificuldade auditiva autorreferida e a variável independente principal foi a exposição ocupacional à poeira industrial. As covariáveis foram: sexo, cor da pele, idade em anos completos, exposição a ruído e exposição à substâncias químicas. As variáveis de exposição ocupacional a ruído e substâncias químicas foram utilizadas como variáveis de ajuste (variáveis de confusão) e as análises foram estratificadas por cada estado (Santa Catarina, Paraná e Rio Grande do Sul), com o intuito de verificar a diferença na magnitude dos resultados por região. Tanto para a análise bruta quanto para a ajustada, a razão de chance foi utilizada como medida de associação, estimada por meio da análise de regressão logística. Os dados foram analisados no software Stata, versão 14. Resultados Com relação a exposição principal, 10,1% da amostra (n=490) afirmou estar exposta à poeira industrial em ambiente ocupacional, ao passo que 7,0% afirmou ter dificuldade auditiva. Na análise final, trabalhadores expostos a poeira industrial apresentaram 1,77 vezes mais chance de mencionar dificuldade auditiva, quando comparados a indivíduos não expostos a este agente. Conclusão Houve associação entre dificuldade auditiva e exposição à poeira industrial em trabalhadores da região Sul do Brasil.

ABSTRACT Purpose To investigate the association between self-reported hearing difficulties and occupational exposure to industrial dust in workers in southern Brazil. Methods This is a cross-sectional analytical study conducted with data from the National Health Survey (Pesquisa Nacional de Saúde, 2013). The dependent variable was self-reported hearing impairment, and the primary independent variable was occupational exposure to industrial dust. The covariables were: sex, skin color, age in complete years, exposure to noise, and exposure to chemical substances. The variables of occupational exposure to noise and chemical substances were used as adjustment variables (confounding variables), and the analyses were stratified per state (Santa Catarina, Paraná, and Rio Grande do Sul) to verify the difference in magnitude results per region. For the crude and adjusted analysis, the odds ratio (OR) was used as a measure of association, estimated through the logistic regression analysis. The data were analyzed through the software Stata, version 14. Results Regarding the main exposure, 10.1% of the sample (n = 490) reported being exposed to industrial dust in an occupational environment, while 7.0% reported hearing impairment. In the final analysis, workers exposed to industrial dust were 1.77 times more likely to report hearing impairment when compared to individuals not exposed to this agent. Conclusion There was an association between hearing impairment and exposure to industrial dust in workers in the southern region of Brazil.

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RESUMEN Objetivo Investigar la participación de estudiantes universitarios en actividades de ocio productoras de ruido y la relación entre los niveles de exposición semanal al ruido recreativo y síntomas de hipoacusia auto reportados, en la ciudad de Barranquilla, Colombia. Método Se realizó un estudio transversal mediante encuesta virtual, basada en el Cuestionario de Exposición al Ruido, más 11 preguntas de síntomas auditivos, a una muestra aleatoria de 730 sujetos. El nivel de exposición semanal al ruido recreativo se estimó a partir del tiempo dedicado al total de actividades recreativas reportadas por los participantes y su evaluación subjetiva de la intensidad de ruido producida por cada actividad, transformada en niveles de ruido continuo equivalente. La asociación entre la exposición al ruido recreativo y la presencia de síntomas de hipoacusia se analizó mediante la prueba de Chi-cuadrado. Resultados El 93% de los participantes manifestó al menos un síntoma de hipoacusia y la mitad reportó cuatro o más. El síntoma más frecuente de hipoacusia asociada al ruido fue el tinnitus (72%). El 55% tenía una exposición semanal de ruido por encima de 85 dBA y en éstos la prevalencia de síntomas de hipoacusia fue mayor (p < 0.05). Conclusión Se sugiere la presencia de deterioro auditivo en gran parte la población universitaria, asociado con altas dosis de exposición semanal al ruido recreativo. Es necesario fortalecer los programas de promoción de la salud auditiva en la academia, y desde los servicios de salud, la valoración objetiva y periódica de la audición.

ABSTRACT Purpose The aim of this study was to investigate the total weekly exposure to leisure noise among university students and to assess its association with self-reported symptoms of hypoacusis. Methods This is a cross-sectional survey. An online questionnaire based on the "Noise Exposure Questionnaire", plus 11 questions regarding hearing loss were sent to 730 randomly selected students. Participants self-reported time spent on different leisure noise activities and their subjective evaluation of the loudness of these activities, converted into equivalent noise levels, were used to estimate weekly noise exposure levels that were compared to occupational noise limits (> 85 dBA = hazardous). Inference statistics was applied to relate hearing symptoms and "likely or having some degree of hearing loss" with hazardous weekly leisure noise exposure levels. Results Ninety-three percent of the participants reported at least one hypoacusis symptom. The most frequent sound-related ear symptom was tinnitus (72%). Fifty-five percent of the individuals presented weekly exposure to noise >85 dBA. Symptoms of hearing loss were more prevalent in those exposed to weekly noise levels >85 dBA. Conclusion This study suggests that there may be hearing loss caused by exposure to high levels of leisure noise in a large part of the study population. Health promotion of hearing conservation should be emphasized at university level. Objective repeated measurement of hearing acuity should be part of integral health services for the youth population.

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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.

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BACKGROUND: Musicians and dancers can be considered an at-risk population for developing noise-induced hearing loss. OBJECTIVES: To determine the audiological profile of members of a folklore-related music group and quantify noise exposure at their rehearsal venue. METHODS: This was a quantitative and descriptive study. The musicians and dancers were evaluated in two stages: an interview about their working life, followed by high frequency tonal audiometry. The sound pressure level in the group's rehearsal venue was measured using a BEK 2270 Noise Analyzer. RESULTS: A total of 7.2% of the subjects had noise-induced hearing loss (NIHL) and 39% of the audiometric tests were notch type. During the interview 31.7% of the subjects mentioned discomfort from loud noise, although none of them used ear protection. The environmental assessment showed inadequate humidity and oscillating temperature. Twenty sound pressure level measurements were performed for Leq (equivalent sound pressure levels) and the results ranged from 88 dB (A) to 99 dB (A) with a mean of 97.05. CONCLUSIONS: Exposure to high levels of sound pressure has led to NIHL in some members of the group. Some of those with normal hearing also presented a notch configuration characteristic of NIHL. Tinnitus, indicating that a change in hearing has occurred, was the most frequent auditory symptom.

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ABSTRACT Purpose: to determine the auditory effects of noise exposure from recreational and occupational sources among dentistry students. Methods: forty-two dentistry students, routinely exposed to occupational noise, and 72 students from other health science schools were recruited (control group). Audiometric testing, otoacoustic emissions and questionnaires to assess recreational and occupational noise were applied to the sample. The presence of a notch was determined for each participant audiometry´s test based on the criteria proposed by Coles et al. Differences in notch prevalence were analyzed by applying univariate regression models as well as a multivariate model adjusted by covariates. Results: non-significant differences in auditory thresholds between groups were found. The controls exhibited a significantly higher prevalence of a notch at 4 kHz than the group exposed to noise. However, the differences were not statistically significant in the multivariate model adjusted by recreational noise exposure. Conclusions: the occupational noise exposure was not significantly associated to auditory system dysfunction. In addition, the differences in notch prevalence could be related to recreational noise exposure.

RESUMEN Objetivo: determinar los efectos auditivos producto de la exposición a ruido recreacional y ocupacional en estudiantes de Odontología. Métodos: se reclutó a 42 estudiantes de odontología expuestos rutinariamente a ruido ocupacional, y a 72 estudiantes de otras carreras del área de la salud (grupo control). Se evaluó mediante audiometría, emisiones otoacústicas, junto con aplicar cuestionarios para determinar la exposición a ruido ocupacional y recreacional. A partir de los umbrales audiométricos e determinó la presencia de escotoma usando el criterio de Coles et al. Se analizaron las diferencias en prevalencia de escotomas entre los grupos mediante regresiones logísticas, ajustando por otras variables. Resultados: no existieron diferencias significativas en los umbrales audiométricos entre los grupos estudiados. El grupo control mostró mayor prevalencia de escotoma en 4 kHz al ajustar por sexo y edad, sin embargo, dejó de ser significativa al ajustar adicionalmente por exposición a ruido recreacional. Conclusiones: la exposición a ruido ocupacional no se asoció a alteraciones auditivas. Además, las diferencias en prevalencia de escotomas estarían relacionadas a exposición a ruido recreacional.

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ABSTRACT Purpose: to assess the implementation of hearing conservation programs in two large companies. Methods: an evaluative research that analyzed a type 1b implementation. The study was conducted in three stages, namely: establishing the company's degree of implementation, analyzing the companies' policies and structures, and lastly, analyzing the influence of the companies' policies and structures on their degree of implementation. The following analyses were conducted to collect data: interviews, document analysis, and observation. Results: the hearing conservation program in Company A was classified as implemented (91.1%), while in Company B, it was partially implemented (62.7%). The context in Company A was favorable to implementing the program, whereas in Company B, the context was considered unfavorable, due to disadvantageous categories. Also, the characteristics of the implementation context influenced the placement of the program either positively or negatively. Conclusion: there were satisfactory results regarding the implementation of the hearing conservation program in both companies assessed.

RESUMO Objetivo: avaliar a implantação do programa de conservação auditiva em duas empresas de grande porte. Métodos: trata-se de uma pesquisa avaliativa de análise de implantação do tipo 1b. O estudo foi conduzido em três etapas, sendo: determinação do grau de implantação do Programa de Conservação Auditiva das empresas avaliadas; análise dos contextos políticos e estruturais das empresas avaliadas; e, por fim, uma análise da influência dos contextos políticos e estruturais no grau de implantação nas empresas avaliadas. Foram realizadas as seguintes análises para coleta dos dados: entrevistas, análise documental e observacional. Resultados: o Programa de Conservação Auditiva na 'empresa A' foi classificado como 'implantado' (91,1%) e na 'empresa B' como 'parcialmente implantado' (62,7%). O contexto de implantação da 'empresa A' se apresentou favorável à implantação do programa. Já na 'empresa B' o contexto foi considerado desfavorável, tendo categorias não favoráveis. Foi possível relacionar, também, que as características do contexto de implantação influenciaram positiva ou negativamente na implantação do programa. Conclusão: houve resultados satisfatórios quanto à implantação do Programa de Conservação Auditiva em ambas as empresas avaliadas.

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ABSTRACT Purpose: to validate indicators and parameters to construct an assessment instrument for the Hearing Conservation Program. Methods: methodological research to validate the content and layout of indicators to assess the Hearing Conservation Program, using the Delphi method, as well as the semantic validation of an assessment instrument for the program, in compliance with the procedures used by the European group DISABKIDS. A total of 20 speech-language-hearing therapists participated in the study, answering validation questionnaires. The answers were tabulated and analyzed considering descriptive statistical data, establishing the item content validity index, the scale content validity index, the percentage of absolute agreement, and the content analysis. Results: of the 64 items submitted for validation, two were not considered appropriate. The set of items was considered representative. The validated indicators and parameters provided the means to construct an assessment instrument of the degree of implementation of the Hearing Conservation Program, which proved to be semantically valid. Conclusion: the indicators were validated to meet and represent the functions of quality, control, and follow-up of the Hearing Conservation Program, aiding administrators to carry out their responsibilities and making it possible to construct evaluative instruments.

RESUMO Objetivo: validar indicadores e parâmetros para a construção de um instrumento de avaliação do Programa de Conservação Auditiva. Métodos: pesquisa metodológica de validação de conteúdo e aparência de indicadores para avaliação do Programa de Conservação Auditiva mediante aplicação do método Delphi, bem como a validação semântica de um instrumento de avaliação do programa seguindo os procedimentos adotados pelo grupo europeu DISABKIDS. Participaram do estudo 20 fonoaudiólogos, os quais responderam a questionários de validação. As respostas foram tabuladas e analisadas considerando dados estatísticos descritivos, pelo estabelecimento dos índices de validade de conteúdo por Item (I- IVC), de validade de conteúdo por nível de escala (S-IVC), de nível percentual de concordância absoluta e Análise de Conteúdo. Resultados: dos 64 itens submetidos à validação, dois não foram considerados pertinentes. O conjunto de itens foi considerado representativo. Os indicadores e parâmetros validados subsidiaram a construção de um instrumento para avaliação do grau de implantação do Programa de Conservação Auditiva, o qual se apresentou válido semanticamente. Conclusão: os indicadores foram validados de modo a atender e representar as funções de qualidade, controle e acompanhamento do Programa de Conservação Auditiva, auxiliando os gestores no exercer de suas funções e subsidiando a construção de instrumentos avaliativos.

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Abstract Introduction: Previous research has suggested that individuals with different blood groups show varied incidences of noise-induced hearing loss. The reduced otoacoustic emissions amplitudes indicate the higher possibilities of outer hair cell damage for noise exposure. Objective: The objective is to analyze the characteristics of otoacoustic emissions, including the occurrence of spontaneous otoacoustic emission and the amplitudes of distortion product otoacoustic emission at certain frequencies in full term neonates with different ABO blood groups. Methods: A total of 80 selected full-term female neonates who passed the initial newborn hearing screen were enrolled into the study, with equal number of participants in four ABO blood groups (Blood Group A, Blood Group B, Blood Group AB, Blood Group O). Measurements of spontaneous otoacoustic emission and distortion product otoacoustic emission were performed in both ears for all participants. Results: (1) The blood group O participants showed significantly fewer spontaneous otoacoustic emission occurrences than the other three blood groups (A = 70%, B = 80%, AB = 67%, O = 25%, p < 0.05). (2) The blood group O participants showed lower DPOAE amplitudes at 1257 Hz (M = 4.55 dB, SD = 8.36), 1587 Hz (M = 11.60 dB, SD = 6.57), 3174 Hz (M = 7.25 dB, SD = 5.99), 5042 Hz (M = 13.60, SD = 6.70) than participants with the other three blood groups in left ears (p < 0.05). In right ears, the blood group O participants showed reduced amplitudes at 1257 Hz (M = 6.55 dB, SD = 8.36), 1587 Hz (M = 13.60 dB, SD = 6.57), 3174 Hz (M = 7.65 dB, SD = 6.43), 5042 Hz (M = 13.65 dB, SD = 6.50) than participants from non-O blood groups (p < 0.05). Conclusion: Female individuals with blood group O have lower otoacoustic emissions values than individuals with the other three blood groups. We need to further investigate the possible relationships between ABO blood group and cochlear function, including the potential influences of noise damage on cochlear outer hair cells.

Resumo Introdução: Pesquisas anteriores sugeriram que indivíduos de diferentes grupos sanguíneos apresentam incidências distintas de perda auditiva induzida por ruído. As amplitudes reduzidas das emissões otoacústicas indicaram maiores ou menores possibilidades de danos às células ciliadas por exposição a ruídos. Objetivo: Analisar as características das emissões otoacústicas, inclusive a ocorrência de emissões otoacústicas espontâneas e as amplitudes de emissões otoacústicas por produto de distorção em determinadas frequências em neonatos a termo de diferentes grupos sanguíneos do sistema ABO. Método: Foram incluídos 80 neonatos a termo selecionados na triagem auditiva neonatal inicial para participar do estudo, com número igual de participantes de grupos sanguíneos do sistema ABO (grupo sanguíneo A, grupo sanguíneo B, grupo sanguíneo AB e grupo sanguíneo O). As emissões otoacústicas espontâneas e emissões otoacústicas por produto de distorção foram medidas em ambas as orelhas de todos os participantes. Resultados: (1) Os participantes do grupo sanguíneo O apresentaram ocorrências de emissões otoacústicas espontâneas significantemente menores do que os dos outros três grupos sanguíneos (A = 70%, B = 80%, AB = 67%, O = 25%, p < 0,05). (2) Os participantes do grupo sanguíneo O apresentaram amplitudes de emissões otoacústicas por produto de distorção mais baixas a 1257 Hz (M = 4,55 dB, DP = 8,36), 1587 Hz (M = 11,60 dB, DP = 6,57), 3174 Hz (M = 7,25 dB, DP = 5,99), 5042 Hz (M = 13,0, DP = 6,70) do que os participantes dos outros três grupos sanguíneos nas orelhas esquerdas (p < 0,05). Nas orelhas direitas, os participantes do grupo sanguíneo O apresentaram amplitudes reduzidas em 1257 Hz (M = 6,55 dB, DP = 8,36), 1587 Hz (M = 13,60 dB, DP = 6,57), 3174 Hz (M = 7,65 dB, DP = 6,43), 5042 Hz (M = 13,65 dB, DP = 6,50) em comparação aos participantes de grupos sanguíneos não O (p < 0,05). Conclusão: Os indivíduos do sexo feminino do grupo sanguíneo O apresentaram valores menores de emissões otoacústicas do que os indivíduos dos outros três grupos sanguíneos. É necessário continuar a investigar as possíveis relações entre o grupo sanguíneo ABO e a função coclear, inclusive as possíveis influências do dano por ruídos às células ciliadas externas da cóclea.

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Abstract Introduction: The 72 kDa heat shock protein, HSP72, located intracellularly provides cochlear cytoprotective and anti-inflammatory roles in the inner ear during stressful noise challenges. The expression of intracellular HSP72 (iHSP72) can be potentiated by alanyl-glutamine dipeptide supplementation. Conversely, these proteins act as pro-inflammatory signals in the extracellular milieu (eHSP72). Objective: We explore whether noise-induced hearing loss promotes both intracellular and extracellular HSP72 heat shock response alterations, and if alanyl-glutamine dipeptide supplementation could modify heat shock response and prevent hearing loss. Methods: Female 90 day-old Wistar rats (n = 32) were randomly divided into four groups: control, noise-induced hearing loss, treated with alanyl-glutamine dipeptide and noise-induced hearing loss plus alanyl-glutamine dipeptide. Auditory brainstem responses were evaluated before noise exposure (124 dB SPL for 2 h) and 14 days after. Cochlea, nuclear cochlear complex and plasma samples were collected for the measurement of intracellular HSP72 and extracellular HSP72 by a high-sensitivity ELISA kit. Results: We found an increase in both iHSP72 and eHSP72 levels in the noise-induced hearing loss group, which was alleviated by alanyl-glutamine dipeptide treatment. Furthermore, H-index of HSP72 (plasma/cochlea eHSP72/iHSP72 ratio) was increased in the noise-induced hearing loss group, but prevented by alanyl-glutamine dipeptide treatment, although alanyl-glutamine dipeptide had no effect on auditory threshold. Conclusions: Our data indicates that cochlear damage induced by noise exposure is accompanied by local and systemic heat shock response markers. Also, alanyl-glutamine reduced stress markers even though it had no effect on noise-induced hearing loss. Finally, plasma levels of 72 kDa heat shock proteins can be used as a biomarker of auditory stress after noise exposure.

Resumo Introdução: A proteína de choque térmico de 72 kDa, HSP72 localizada intracelularmente, tem papéis citoprotetores e anti-inflamatórios cocleares na orelha interna durante situações de ruído estressantes. A expressão dessa proteína pode ser potencializada pela suplementação com dipeptídeo de alanil-glutamina. Por outro lado, essas proteínas atuam como sinais pró-inflamatórios no meio extracelular. Objetivo: Investigar se a perda auditiva induzida por ruído promove alterações tanto das proteínas HSP72 intracelulares quanto extracelulares na resposta de choque térmico e se a suplementação com alanil-glutamina pode modificar a resposta de choque térmico e evitar a perda auditiva. Método: Ratos Wistar fêmeas, com 90 dias de idade (n = 32), foram divididos aleatoriamente em quatro grupos: controle, perda auditiva induzida por ruído, tratados com alanil-glutamina e perda auditiva induzida por ruído mais alanil-glutamina. Os potenciais evocados auditivos do tronco encefálico foram avaliados antes da exposição ao ruído (124 dB NPS por 2 h) e 14 dias após. A cóclea, o complexo nuclear coclear e amostras de plasma foram coletadas para mensuração de HSP72 intra e extracelular com um kit Elisa de alta sensibilidade. Resultados: Houve um aumento nos níveis de HSP72 intra e extracelular no grupo perda auditiva induzida por ruído, que foi minimizado pelo tratamento com alanil-glutamina. Além disso, o índice H das HSP72 (razão HSP72 extracelular/HSP72intracelular plasma/cóclea) aumentou no grupo perda auditiva induzida por ruído, mas foi limitado pelo tratamento com alanil-glutamina, embora o alanil-glutamina não tenha efeito no limiar auditivo. Conclusões: Nossos dados indicam que o dano coclear induzido pela exposição ao ruído é acompanhado por marcadores da resposta de choque térmico locais e sistêmicos. Além disso, alanil-glutamina reduziu os marcadores de estresse, mesmo não tendo efeito sobre a perda auditiva induzida por ruído. Finalmente, os níveis plasmáticos de proteínas de choque térmico de 72 kDa podem ser usados como biomarcador do estresse auditivo, após a exposição ao ruído.

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