Noise and hearing loss: a review

Impact Noise and Vibration Sources Induced by Heavy Gym Activities: Do They in Turn Unnecessarily, Indirectly Affect Our Health?

‘Good health and wellbeing’ is one of the key United Nations sustainable development goals (SDGs). By ensuring healthy lives and promoting positive wellbeing, physical and mental activities have been encouraged for all at all ages. In recent decades, fitness culture and industry has significantly grown in many countries to enhance healthy lives and positive wellbeing. With the vigorous development of the fitness industry, a gym has become one of the common facilities within a neighborhood or on a campus in order to promote more and more people to participate in fitness activities. At the same time, the rapid increase in gym construction also provides more employment opportunities for professional fitness coaches. On the other hand, excessive noises and vibrations stemming from certain heavy gym activities can be observed. Accordingly, the NIHL (noise-induced hearing loss) in a gym should receive more attention. According to critical literature reviews, the high-intensity noise in gyms is mainly caused by the drops of heavy steel bars or dumbbells. Today, most gyms adopt cushioned flooring in specific areas, but the effectiveness of noise suppression still needs to be evaluated. The purpose of this study was to investigate the possibility of hearing loss caused by noise doses in a gym. Noises derived from heavy gym sources (i.e., lifting of heavy weights) were monitored and collected for analyses in order to estimate the risk of NIHL in a traditional gym, as well as to assess the measurements against the authoritative criteria to derive some technical guidelines for fitness and gym managers. The outcome of this study will improve insights into acoustic monitoring techniques and practical management within a gym environment.

Association between exposure to road traffic noise and hearing impairment: a case-control study

PURPOSE

Noise pollution in urban areas is increasing steadily, and the study of road traffic noises and their effects on the auditory system was rare. This study investigated the potential effects of road traffic noise on auditory systems and hearing.

METHODS

A case-control study recruited outpatients from the Otolaryngology department. The case group (n = 41) had binaural hearing loss (HL) of standard pure-tone average(PTA)  ≥ 25 dB or high frequency PTA ≥ 25 dB, while the control group (n = 39) had binaural hearing level of any frequency < 25 dB. Detailed otologic evaluations were performed. Between-group data were evaluated using logistic regression analysis. Case or control group was identified based on the audiogram.

RESULTS

A total of 80 subjects were recruited, including 41 with hearing impairment and 39 as control. The mean exposure level of road traffic noise was significantly higher in the case group than the control group (p = 0.005). A crude OR of 5.78 showed an increased risk of greater than 70 dB of road traffic noise on hearing impairment and tinnitus (p < 0.001). The aOR of 9.24 (p = 0.002) from a multiple variate analysis suggested that road traffic noise levels greater than 70 dB may have a damaging effect on hearing. Damaging effects on hearing persisted even after adjusting for confounders in the full multivariate model (aOR of 9.24 [95% CI: 2.198-38.869]; p = 0.002).

CONCLUSIONS

Exposing to road traffic noise greater than 70 dB showed an increased risk of damage to the auditory system. These results might help public health administrators and physicians to develop programs that address the health dangers of noise.

Diagnostic Accuracy of Smartphone-Based Audiometry for Hearing Loss Detection: Meta-analysis

Background

Hearing loss is one of the most common disabilities worldwide and affects both individual and public health. Pure tone audiometry (PTA) is the gold standard for hearing assessment, but it is often not available in many settings, given its high cost and demand for human resources. Smartphone-based audiometry may be equally effective and can improve access to adequate hearing evaluations.

Objective

The aim of this systematic review is to synthesize the current evidence of the role of smartphone-based audiometry in hearing assessments and further explore the factors that influence its diagnostic accuracy.

Methods

Five databases—PubMed, Embase, Cochrane Library, Web of Science, and Scopus—were queried to identify original studies that examined the diagnostic accuracy of hearing loss measurement using smartphone-based devices with conventional PTA as a reference test. A bivariate random-effects meta-analysis was performed to estimate the pooled sensitivity and specificity. The factors associated with diagnostic accuracy were identified using a bivariate meta-regression model. Study quality was assessed using the Quality Assessment of Diagnostic Accuracy Studies-2 tool.

Results

In all, 25 studies with a total of 4470 patients were included in the meta-analysis. The overall sensitivity, specificity, and area under the receiver operating characteristic curve for smartphone-based audiometry were 89% (95% CI 83%-93%), 93% (95% CI 87%-97%), and 0.96 (95% CI 0.93-0.97), respectively; the corresponding values for the smartphone-based speech recognition test were 91% (95% CI 86%-94%), 88% (95% CI 75%-94%), and 0.93 (95% CI 0.90-0.95), respectively. Meta-regression analysis revealed that patient age, equipment used, and the presence of soundproof booths were significantly related to diagnostic accuracy.

Conclusions

We have presented comprehensive evidence regarding the effectiveness of smartphone-based tests in diagnosing hearing loss. Smartphone-based audiometry may serve as an accurate and accessible approach to hearing evaluations, especially in settings where conventional PTA is unavailable.

Leisure Noise Exposure and Associated Health-Risk Behavior in Adolescents: An Explanatory Study among Two Different Educational Programs in Flanders

Adolescents frequently engage in noisy leisure activities which can result in hearing-related problems. However, the effect of leisure noise exposure is liable to an individual's risk-taking behavior. Identifying leisure noise activities and relevant factors related to risk-taking behavior in adolescents, are important to optimize hearing conservation programs targeting youngsters. The purpose of the study was to explore the presence of hearing-related symptoms, as well as noise exposure during various activities, and the use of hearing protector devices (HPDs) in adolescents in two educational programs in Flanders. In addition, their attitudes and beliefs towards noise, hearing loss, and HPDs were investigated. The final sample consisted of 247 adolescents. The most important hearing-related symptoms after noise exposure were tinnitus and noise sensitivity. With regard to leisure noise exposure, listening to PMPs was most frequently reported. The use of HPDs during most noisy activities was limited, in accordance with the presence of hearing-related symptoms, considering noise as unproblematic, and having worse scores on subscales of the beliefs about hearing protection and hearing loss scale. In the future, hearing conservation programs should target adolescents specifically for a more health-orientated behavior towards noise exposure, hearing loss, and HPDs.

Sleep Characteristics and Hearing Loss in Older Adults: The National Health and Nutrition Examination Survey 2005-2006

BACKGROUND

Sleep characteristics might be associated with hearing loss through disturbed energy metabolism and disrupted cochlear blood flow, but prior evidence is limited. This study aims to investigate cross-sectional associations of sleep duration and signs/symptoms of sleep-disordered breathing with hearing in a nationally representative cohort of U.S. older adults aged 70 and over.

METHODS

We studied 632 older adults aged 70+ years from the 2005-2006 cycle of National Health and Nutrition Examination Survey (NHANES). Hearing thresholds were measured using pure-tone audiometry and were averaged to create speech-frequency (0.5-4 kHz), low-frequency (0.5-2 kHz) and high-frequency (4-8 kHz) pure-tone averages (PTAs) in better-hearing ear, with higher values indicate worse hearing. Sleep duration and signs/symptoms of sleep-disordered breathing (snoring, snorting/stopping breathing, excessive sleepiness) were collected through questionnaire. Multivariable-adjusted spline models with knots at 6 and 8 hours were fitted for associations between sleep duration and PTAs. Multivariable-adjusted linear regression was used for associations between sleep-disordered breathing and PTAs. Primary models adjusted for demographic and lifestyle factors, secondary models additionally adjusted for cardiovascular factors.

RESULTS

When sleep duration exceeded 8 hours, every additional hour of sleep duration was marginally associated with higher(poorer) high-frequency PTA (Primary:2.45 dB HL, 95% CI:-0.34, 5.24; Secondary:2.89 dB HL, 95% CI:0.02, 5.76). No associations were observed between sleep-disordered breathing and hearing.

CONCLUSIONS

Longer sleep duration is marginally associated with poorer high-frequency hearing among older adults sleeping more than 8 hours. However, we cannot infer temporality given the cross-sectional design. Future longitudinal studies are needed to establish temporality and clarify mechanisms.

Noise pollution and effectiveness of policy interventions for its control in Kathmandu, Nepal

In Nepal, much emphasis has been given to the pollution of air, water, and solid waste both in terms of research and policymaking. Noise is an ignored pollutant, yet a growing public health concern in Kathmandu. This study is aimed at making an assessment of noise pollution in Kathmandu and study the effectiveness of the enforcement of noise standards and No Horn Regulation to control noise pollution. The study was conducted in 23 locations of four different zones (high traffic, low traffic, commercial, and residential) where 12 sites were considered for evaluating the effectiveness of No Horn Regulations. Noise level was studied at five different times of the day using a sound level meter to compute maximum, minimum, equivalent, and average noise level. This study concludes that (i) there is noise pollution problem in Kathmandu, (ii) No Horn Regulation is in place but it has not been strictly followed by the drivers and riders and monitored adequately by concerned authorities, and (iii) the regulation has been effective in reducing the noise level significantly. The average noise level of Kathmandu was recorded as 66.8 dB(A) with the highest noise level in High traffic zones, followed by commercial, low traffic, and residential zones. In 65.2% of the sampled sites, the noise level was beyond the permissible limit of WHO and National Sound Quality Standard of Nepal, 2012. Of the total honking events, 48.1% were against the provision of the No Horn Regulation. After the enforcement of the regulation, noise level was reduced significantly by 2.1 dB(A) in high traffic, low traffic, and residential zones. A comprehensive noise strategy with more emphasis on compliance monitoring and regular noise assessment should be formulated to address environmental noise as a major public health issue.

Patterns of noise exposure and prevalence of hearing loss amongst Cape Town Minstrel Carnival musicians

Background

Cape Town Minstrel Carnival is one of the oldest and most authentic indigenous New Year’s customs in South Africa. Musicians who perform at this carnival are exposed to excessively loud music and therefore at a risk of acquiring noise-induced hearing loss (NIHL).

Objectives

This study aimed to determine patterns of exposure to loud music and prevalence of hearing loss amongst Cape Town Minstrel Carnival musicians.

Method

A descriptive, observational exploratory survey design was used and 43 participants (21 males and 22 females; mean age, 21 ± 9 years) took part in this study. Sound level measurements were conducted to assess musicians’ sound exposure during rehearsals and performances. All participants underwent the following audiological test battery at least 2 h before music exposure: Case history, otoscopic examination, tympanometry, pure tone audiometry and distortion products otoacoustic emission (DPOAE).

Results

Average noise levels recorded were 86 dBA during rehearsals and 98.7 dBA at performances and average durations of exposure were 240 and 10 min at rehearsals and performances, respectively. One out of 43 (1/43) participants presented with sensorineural hearing loss. Audiometric results of the remaining participants were normal and did not show a pattern suggestive of NIHL. A high proportion of participants (21/43) reported experiencing tinnitus.

Conclusion

Despite being exposed to high levels of noise, there was a low prevalence of hearing loss amongst these musicians. However, a high proportion of them reported tinnitus, which could be an indication that they were at a high risk of NIHL from the music that they played.

Association of occupational noise exposure, bilateral hearing loss with atherosclerotic cardiovascular disease risk in Chinese adults

We aimed to explore the association of occupational noise exposure with atherosclerotic cardiovascular disease (ASCVD) risk in Chinese adults. We included 21,412 participants from the Dongfeng-tongji Cohort Study, occupational noise exposure was evaluated through workplace noise level and/or the job titles, hearing loss was defined as a pure-tone mean of 25 dB or higher at 0.5, 1, 2, and 4 kHz in any ear. Compared with participants without occupational noise exposure, the 10-year ASCVD risk was significantly higher for noise exposure duration ≥20 years (OR = 1.20, 95%CI = 1.05-1.32) after adjusting for potential confounders. In the subgroup analysis, the association was only statistically significant in males (OR = 1.86, 95%CI = 1.12-3.14) and participants aged equal to or over 60 years old (OR = 1.20, 95%CI = 1.05-1.33), but not in females (OR = 1.15, 95%CI = 0.71-1.92) and aged below 60 (OR = 1.51, 95%CI = 0.75-2.85). In the subsample analyses (N = 10,165), bilateral hearing loss was associated with a higher risk of 10-year ASCVD (OR = 1.72, 95%CI = 1.30-2.30), especially for participants who were males (OR = 2.40, 95%CI = 1.61-3.42) and aged equal to or over 60 (OR = 1.85, 95%CI = 1.40-2.44). The present study suggests that occupational noise exposure may be a potential risk factor for ASCVD, especially for males and older participants.

Hearing impairment in military personnel in Eastern Saudi Arabia

BACKGROUND:

Noise exposure is one of the most common occupational hazards worldwide. Studies have shown that the prevalence of hearing loss and tinnitus is higher in military personnel than in other occupations. This study aimed to estimate the prevalence of hearing impairment in military personnel in Eastern Saudi Arabia.

MATERIALS AND METHODS:

A cross-sectional study was conducted among 409 military personnel. A self-administered questionnaire collected data on level of awareness, hearing impairment, and protection of hearing. Pure-tone audiometry (PTA) was conducted on 141 participants to determine the prevalence and pattern of hearing impairment. Multivariate analysis was used to determine the predictors of hearing loss in military personnel.

RESULTS:

More than half of the participants (54.3%) were unaware of the consequences of noise exposure and none used proper hearing protection. A small percentage (5.9%) complied with the annual hearing examination, and only 23% had had a previous hearing evaluation. More than half of the participants (58.4%) had one or more abnormal hearing-related symptoms, with tinnitus as the most common symptom (43.8%). PTA showed hearing impairment in 71.6% of the participants. Multivariate analysis showed older age as only significant factor associated with hearing impairment in military personnel.

CONCLUSION:

Noise-induced hearing loss and tinnitus are common occupational disabilities in military personnel. Hearing conservation programs have to be initiated to ensure the application of hearing protection measures and control the effects of exposure to noise.

The Effect of Parkinson's Disease on Otoacoustic Emissions and Efferent Suppression of Transient Evoked Otoacoustic Emissions

Purpose Several studies have demonstrated increased auditory thresholds in patients with Parkinson's disease (PD) based on subjective tonal audiometry. However, the pathophysiological mechanisms underlying auditory dysfunction in PD remain elusive. The primary aim of this study was to investigate cochlear and olivocochlear function in PD using objective measurements and to assess the effect of dopaminergic medication on auditory function. Method Eighteen patients with PD and 18 gender- and age-matched healthy controls (HCs) were included. Patients with PD participated in medication on and off conditions. Linear mixed models were used to determine the effect of PD on tonal audiometry, transient evoked and distortion product otoacoustic emissions (OAEs), and efferent suppression (ES). Results Tonal audiometry revealed normal auditory thresholds in patients with PD for their age across all frequencies. OAE signal amplitudes demonstrated a significant interaction effect between group (PD vs. HC) and frequency, indicating decreased OAEs at low frequencies and increased OAEs at high frequencies in patients with PD. No significant differences were found between patients with PD and HCs regarding ES. In addition, no significant effect of medication status was found on auditory measurements in patients with PD. Conclusions Altered OAEs support the hypothesis of cochlear alterations in PD. No evidence was found for the involvement of the medial olivocochlear system. Altogether, OAEs may provide an objective early indicator of auditory alterations in PD and should complement subjective tonal audiometry when assessing and monitoring auditory function in PD.

Change in gene expression levels of GABA, glutamate and neurosteroid pathways due to acoustic trauma in the cochlea

The characteristic feature of noise-induced hearing loss (NIHL) is the loss or malfunction of the outer hair cells (OHC) and the inner hair cells (IHC) of the cochlea. 90-95% of the spiral ganglion neurons, forming the cell bodies of cochlear nerve, synapse with the IHCs. Glutamate is the most potent excitatory neurotransmitter for IHC-auditory nerve synapses. Excessive release of glutamate in response to acoustic trauma (AT), may cause excitotoxicity by causing damage to the spiral ganglion neurons (SGN) or loss of the spiral ganglion dendrites, post-synaptic to the IHCs. Another neurotransmitter, GABA, plays an important role in the processing of acoustic stimuli and central regulation after peripheral injury, so it is potentially related to the regulation of hearing function and sensitivity after noise. The aim of this study is to evaluate the effect of AT on the expressions of glutamate excitotoxicity, GABA inhibition and neurosteroid synthesis genes.We exposed 24 BALB/c mice to AT. Controls were sacrificed without exposure to noise, Post-AT(1) and Post-AT(15) were sacrificed on the 1st and 15th day, respectively, after noise exposure. The expressions of various genes playing roles in glutamate, GABA and neurosteroid pathways were compared between groups by real-time PCR.Expressions of Cyp11a1, Gls, Gabra1, Grin2b, Sult1a1, Gad1, and Slc1a2 genes in Post-AT(15) mice were significantly decreased in comparison to control and Post-AT(1) mice. No significant differences in the expression of Slc6a1 and Slc17a8 genes was detected.These findings support the possible role of balance between glutamate excitotoxicity and GABA inhibition is disturbed during the post AT days and also the synthesis of some neurosteroids such as pregnenolone sulfate may be important in this balance.

Association of occupational noise exposure, bilateral hearing loss with hypertension among Chinese workers

OBJECTIVE

To evaluate the relationship of occupational noise, bilateral hearing loss with blood pressure and hypertension among a Chinese population.

METHODS

We included 15 422 individuals from a cross-sectional survey of the key occupational diseases in 2017 in Wuhan, Hubei Province, China. Occupational noise exposure was evaluated through workplace noise level and/or the job titles. Hearing loss was defined as a pure-tone average of 25 dB or higher at speech frequency (0.5, 1, 2 kHz) or high frequency (3, 4, 6 kHz) in both ears. Hypertension was defined as blood pressure at least 140/90 mmHg or self-reported current use of antihypertensive medication.

RESULTS

Compared with participants without occupational noise exposure, the prevalence of hypertension was significantly higher for noise exposure duration of 5 to less than 10 years [odds ratio (OR) = 1.13, 95% confidence interval (CI) = 1.04-1.27] and at least 10 years (OR = 1.17, 95% CI = 1.09-1.30). In the sex-specific analysis, the association was significantly pronounced in male (OR = 1.18, 95% CI = 1.06-1.32 for duration of 5 to <10 years; OR = 1.25, 95% CI = 1.12-1.38 for duration ≥10 years), but not in female (OR = 1.01, 95% CI = 0.80-1.11 for duration of 5 to <10 years; OR = 1.06, 95% CI = 0.90-1.20 for duration ≥10 years). In the subsample analyses, bilateral hearing loss was associated with a higher prevalence of hypertension, no matter for speech frequency hearing loss (OR = 1.12, 95% CI = 1.02-1.30 for mild; OR = 1.35, 95% CI = 1.20-1.50 for severe) or for high-frequency hearing loss (OR = 1.24, 95% CI = 1.03-1.50 for mild; OR = 2.40, 95% CI = 1.80-3.17 for severe). The sex-subgroup analysis of hearing loss with hypertension was similar as occupational noise and hypertension.

CONCLUSION

Our study has suggested occupational noise exposure is a potential risk factor for hypertension.

Health study of 11,800 workers under occupational noise in Xinjiang

Background

We investigated the health status of some workers exposed to occupational noise in Xinjiang, and explored the influencing factors of their health level. We aimed to determine the key protection groups of occupational noise hazards, which might provide the basis for the development of targeted noise prevention measures.

Methods

We used descriptive analysis to investigate a total of 11,800 participants who underwent occupational health examination in Xinjiang Occupational Disease Prevention Hospital.

Results

The hearing abnormality rate of noise exposure participants was 8.03%, which was higher in males than females (χ² = 54.507, p < 0.05). The abnormal rate of high-frequency hearing threshold in Xinjiang minorities was lower than in Han nationality (χ² = 11.780, p < 0.05), while the results of the electrocardiogram were reversed (χ² = 9.128, p < 0.05). Differences in abnormal rates of blood pressure (χ² = 149.734, p < 0.05), hearing (χ² = 231.203, p < 0.05), and physical examination (χ² = 360.609, p < 0.05) are statistically significant in different industries. The abnormal rates of blood pressure (χ² = 67.416, p < 0.05) and hearing (χ² = 49.535, p < 0.05) gradually decrease with the expansion of the enterprise scale. Logistic regression analysis showed that gender, nationality, age, enterprise size, and industry were closely related to pure tone audiometry examination abnormal rate.

Conclusion

Workers of male, elder, in mine and small/medium enterprises should be the key populations to prevent occupational noise hazard. It is necessary to standardize occupational health management in enterprises, which helps to improve workers’ self-protection awareness and quality of life.

Associations between adolescents' earphone usage in noisy environments, hearing loss, and self-reported hearing problems in a nationally representative sample of South Korean middle and high school students

Few epidemiological studies have examined the relationship between earphone usage and hearing loss in adolescents. This study identified the prevalence of hearing loss in South Korean adolescents using representative national survey data and evaluated the relationship between earphone usage in a noisy environment and hearing loss. This study analyzed 532 subjects (12-19 years) who participated in a 2012 national survey and completed health and noise environment exposure questionnaires and pure tone audiometry (PTA) test. Hearing loss was defined as an average hearing threshold of 26 Decibel-A (dBA) or higher in PTA. The relationship between earphone usage and hearing loss was analyzed using a hierarchical logistic regression model. Adolescents who were exposed to high noise levels via headphones in a noisy environment had a hearing loss prevalence of 22.6% and adolescents who used earphones 80 minutes or more per day on average had the hearing loss prevalence of 22.3%. The results of the logistic regression analysis revealed that adolescents who used earphones in a noisy environment had a 4.5-fold higher risk of hearing loss and an 8.4 times higher risk of having a subjective hearing problem than those who did not use earphones (prevalence odds ratio (pOR) = 4.54, 95% confidence interval (CI): 1.35-15.24; pOR = 8.39, 95% CI: 1.12-62.83, respectively). Additionally, adolescents who used earphones more than 80 minutes per day in a noisy environment had a 4.7 times higher risk of hearing loss than those who used them less than 80 minutes per day (pOR = 4.68, 95% CI: 1.08-20.22). Longitudinal studies are needed to provide evidence of causality between earphone usage and hearing loss.

Hearing Difficulties and Tinnitus in Construction, Agricultural, Music, and Finance Industries: Contributions of Demographic, Health, and Lifestyle Factors

High levels of occupational noise exposure increase the risk of hearing difficulties and tinnitus. However, differences in demographic, health, and lifestyle factors could also contribute to high levels of hearing difficulties and tinnitus in some industries. Data from a subsample (n = 22,936) of the U.K. Biobank were analyzed to determine to what extent differences in levels of hearing difficulties and tinnitus in high-risk industries (construction, agricultural, and music) compared with low-risk industries (finance) could be attributable to demographic, health, and lifestyle factors, rather than occupational noise exposure. Hearing difficulties were identified using a digits-in-noise speech recognition test. Tinnitus was identified based on self-report. Logistic regression analyses showed that occupational noise exposure partially accounted for higher levels of hearing difficulties in the agricultural industry compared with finance, and occupational noise exposure, older age, low socioeconomic status, and non-White ethnic background partially accounted for higher levels of hearing difficulties in the construction industry. However, the factors assessed in the model did not fully account for the increased likelihood of hearing difficulties in high-risk industries, suggesting that there are additional unknown factors which impact on hearing or that there was insufficient measurement of factors included in the model. The levels of tinnitus were greatest for music and construction industries compared with finance, and these differences were accounted for by occupational and music noise exposure, as well as older age. These findings emphasize the need to promote hearing conservation in occupational and music settings, with a particular focus on high-risk demographic subgroups.

Artemisinin Loaded mPEG-PCL Nanoparticle Based Photosensitive Gelatin Methacrylate Hydrogels for the Treatment of Gentamicin Induced Hearing Loss

OBJECTIVE

Artemisinin (ART) is a natural anti-malarial sesquiterpene lactone which has the ability to treat and activate the CLRN1 pathway to play a pivotal role in hearing loss and hair cell function. To investigate the therapeutic effect of ART in hearing loss induced by gentamicin (GM), an ART-loaded poly(ethylene glycol)-b-poly(ε-caprolactone) mPEG-PCL nanoparticle-based photosensitive hydrogel was developed and tested in this study.

MATERIALS AND METHODS

Artemisinin-loaded mPEG-PCL nanoparticles (mPEG-PCL-ART-NPs) were prepared by a double emulsion method and the formulation was optimized by an orthogonal experimental design. The particle size, zeta potential, morphology and in vitro dissolution of the mPEG-PCL-ART-NPs were well characterized. Biocompatibility of the mPEG-PCL-ART-NPs were tested on HeLa cells with an MTT assay. The photo-crosslinkable biodegradable gelatin methacrylate (GelMA) hydrogel was prepared and its physicochemical properties (such as substitution, photocrosslinking efficiency, cell viability morphology, mechanical and swelling properties) were evaluated. Finally, mPEG-PCL-ART-FITC-NPs, loaded mPEG-PCL-ART-NPs, and loaded mPEG-PCL-ART-NPs-GelMA hydrogels were fabricated and a GM toxicity-induced guinea pig ear damage model was established to determine the effectiveness of the materials on returning auditory function and cochlea pathomorphology.

RESULTS

The zeta potential of the mPEG-PCL-ART-NPs was about -38.64 ± 0.21 mV and the average size was 167.51 ± 1.87 nm with an encapsulation efficacy of 81.7 ± 1.46%. In vitro release studies showed that the mPEG-PCL-ART-NPs possessed a sustained-release effect and the MTT experiments showed good biocompatibility properties of the drug-loaded nanoparticles. The results indicated that the 5% GelMA with MA-4% hydrogel had a better crosslinking density and 3D structure for drug loading and drug delivery than controls. Skin penetration results showed that the mPEG-PCL-ART-NPs increased adhesive capacity and avoided fast diffusion in the skin. Most importantly, auditory brainstem response results indicated that the mPEG-PCL-ART-NPs-GelMA hydrogel alleviated hearing loss induced by GM.

CONCLUSION

These results suggested that the presently fabricated mPEG-PCL-ART-NPs-GelMA hydrogels are promising formulations for the treatment of hearing loss induced by GM and lay the foundation for further clinical research of inner ear induction therapy.

Use of Personal Listening Devices and Knowledge/Attitude for Greater Hearing Conservation in College Students: Data Analysis and Regression Model Based on 1009 Respondents

Given the concern regarding increased hearing loss in young people who use personal listening devices (PLDs), the present study analyzes the experience of PLDs among college students to identify their knowledge of and attitude toward hearing conservation. It also explains their relationship between knowledge of hearing loss and attitude-related hearing conservation as a questionnaire response using a regression model. A total of 1009 Korean college students responded to an online questionnaire. As a survey tool, the Personal Listening Device and Hearing Questionnaire was adapted as a Korean version with 78 modified items under 9 categories. Using principal component analysis, specific factors were extracted, and their relationships and paths were confirmed using multiple regression analysis. The results of the knowledge category of the questionnaire indicate that most respondents knew how to maintain healthy hearing and understood the signs of hearing loss. Regardless, many college students habitually use PLDs at high levels in noisy environments; they do not recognize how to prevent hearing loss. Even though they continue their current use pattern for PLDs, they also had a positive attitude toward receiving more information about hearing conservation. According to the regression model, the students' self-reported hearing deficits were due to the volume rather than the frequent use. Interestingly, knowledge about hearing loss may encourage students to develop a positive attitude toward reasonable restriction of PLD use. When PLD users have detailed knowledge about the hearing loss provided by professionals, we believe that most will avoid serious hearing problems and its risks and maintain a judicious attitude toward their own conservation.

Feedback-based noise management matrix in action

BACKGROUND

This article presents the details and findings of a practical implementation of a preliminary model for use in hearing conservation programmes (HCPs) in the mining sector in South Africa.

OBJECTIVES

The implementation is based on a previously published model, called feedback-based noise monitoring model (FBNMM), and represents its implementation as a tool of predicting occupational noise-induced hearing loss (ONIHL), as well as monitoring and managing HCPs in the mining sector within the South African context.

METHOD

The article, utilising real miners' data, demonstrates this basic static feedback model with its practical applications such as estimating, monitoring and providing quantitative information to aid miners, mining administrators and policymakers in decision-making around HCPs, as recommended in the previous 2019 publication by Moroe et al. This study was conducted in a South African platinum mine. Evidence on the model's sensitivity and practicability in early identification, intervention and management of ONIHL in the workplace is presented.

RESULTS

Findings show how the use of the model within an HCP viewed as a complex intervention can allow for early prediction of ONIHL, consequently affording more accurate early intervention as part of preventive audiology within the health and safety goals of mines.

CONCLUSION

The feedback-based model should be a useful tool for successful implementation and monitoring of HCPs within South African mines.

Burden of disease: A scoping review of HIV/AIDS and TB in occupational noise-induced hearing loss

BACKGROUND

Occupational noise-induced hearing loss (ONIHL) does not occur in isolation from other influencing factors such as health conditions and illnesses like human immunodeficiency virus and acquired immunodeficiency syndrome (HIV and AIDS), as well as tuberculosis (TB). How the burden of disease influences the occurrence and/or management of ONIHL becomes a key if the goal of hearing conservation programmes (HCPs) is to be achieved within these contexts.

OBJECTIVES

The purpose of this scoping review was to conduct an investigation on how the burden of disease's influence on ONIHL is reported in literature, with a specific focus on the most prevalent diseases in South African mines - HIV and AIDS and TB.

METHOD

A scoping review was conducted using the Arksey and O'Malley's framework. A search was conducted in five electronic bibliographic databases and the grey literature.

RESULTS

The search procured 10 publications, with two specific to ONIHL within the South African context. In addition to the two publications specific to TB and ONIHL, findings revealed a serious gap in the evidence around the scoping review question globally. This obvious lack of investigations into the influence of these two conditions in the South African mining context raises serious implications about the responsiveness, and proactive nature of HCPs within this population.

CONCLUSION

Considering the burden of diseases on otology and audiology is critical as certain diseases cause hearing impairment either as a primary effect, as a secondary/opportunistic effect or as a side effect of treatment options for that disease. An employee suffering from any such disease with concomitant exposure to hazardous noise levels presents an even bigger challenge to HCPs if such is not taken into consideration in the conception, implementation and monitoring of HCPs.

Association between Smoking and Noise-Induced Hearing Loss: A Meta-Analysis of Observational Studies

The purpose of this study was to synthesize the results of previously published observational studies through meta-analysis to clarify the association between smoking and noise-induced hearing loss (NIHL). We searched several databases as of October 2019. Based on the results of heterogeneity analysis (Q statistic and I² statistic), a fixed effect model (for no heterogeneity; Q test P > 0.1 and I² ≤ 50%) or a random effects model (for heterogeneity) was used to calculate the pooled odds ratios (ORs). We explored the potential dose-response relationship between smoking and NIHL as well. In total, 27 studies involving 30,465 participants were included. Compared with non-smokers, the pooled OR of current smokers was 2.05 (95% Confidence interval (CI): 1.71–2.46), and of former smokers was 1.11 (95% CI: 1.05–1.18). We found a curve linear association between an increasing number of pack-years (packages/day × smoking years) and risk of NIHL. The dose-response meta-analysis suggested that when the number of pack-years was less than fifteen, the risk of NIHL was increasing, and the highest combined OR was 5.25 (95% CI: 2.30–11.96) for pack-years of fifteen. After fifteen pack-years, the pooled OR had a slow decline. Our study indicated that smoking is a risk factor for NIHL. Current smokers have a higher risk than former smokers, and there is a positive dose-response relationship between smoking and NIHL.

What is noise-induced hearing loss?

Noise-induced hearing loss is sensory deafness caused by long-term exposure of the auditory system to a noisy environment. Auditory fatigue is an early symptom of noise-induced hearing loss, and hearing can gradually recover after people leave a noisy environment. However, if people remain in a noisy environment for a prolonged period of time, their hearing will be permanently impaired. Societal changes mean that people are more likely to be exposed to noise. The hearing loss and tinnitus caused by noise seriously affect people's quality of life and lead to huge economic loss. The pathogenesis of noise-induced hearing loss is complex. Various theories try to explain this, such as the oxidative stress theory, but none perfectly explains the occurrence of noise-induced hearing loss. There is no treatment which can completely reverse the damage. More research is required to explore the pathogenesis and to better guide clinical practice. Preventative strategies, such as educating the public about hearing health, should be adopted to reduce the harm of noise-induced hearing loss.

Challenges of the Use of Sound Emergence for Setting Legal Noise Limits

In the vast majority of legislation on environmental noise, the metric used for expressing limit values is based on sound pressure levels. But some countries have introduced sound emergence limit values where the compliance of a noise-generating activity is defined as a maximum allowable difference between the sound pressure level with and without the regulated activity operating. This paper investigates the foundations and the merits of this kind of differential noise limit values. Our review of literature indicates that there is very little evidence supporting the use of differential noise limits over absolute ones. Moreover, while sound emergence limits seem to originate from consideration about audibility of the regulated noise source, they appear to give little insight into what is audible and what is not. Furthermore, both the definition and the practical measurement of sound emergence raise several challenges that compromise reproducibility. In addition, first, the reference to background noise makes it very difficult first to ascertain the conformity of noisy installations in the long run, second to effectively protect the community from excessive noise and third to evaluate conformity on the basis of simulations. When switching to another metric is not an option the paper makes recommendations toward a more reliable use of sound emergence.

Computational analysis based on audioprofiles: A new possibility for patient stratification in office-based otology

Genetic contribution to progressive hearing loss in adults is underestimated. Established machine learning-based software could offer a rapid supportive tool to stratify patients with progressive hearing loss. A retrospective longitudinal analysis of 141 adult patients presenting with hearing loss was performed. Hearing threshold was measured at least twice 18 months or more apart. Based on the baseline audiogram, hearing thresholds and age were uploaded to AudioGene v4® (Center for Bioinformatics and Computational Biology at The University of Iowa City, IA, USA) to predict the underlying genetic cause of hearing loss and the likely progression of hearing loss. The progression of hearing loss was validated by comparison with the most recent audiogram data of the patients. The most frequently predicted loci were DFNA2B, DFNA9 and DFNA2A. The frequency of loci/genes predicted by AudioGene remains consistent when using the initial or the final audiogram of the patients. In conclusion, machine learning-based software analysis of clinical data might be a useful tool to identify patients at risk for having autosomal dominant hearing loss. With this approach, patients with suspected progressive hearing loss could be subjected to close audiological followup, genetic testing and improved patient counselling.

Occupational noise exposure: A review of its effects, epidemiology, and impact with recommendations for reducing its burden

Exposure to hazardous noise is one of the most common occupational risks, both in the U.S. and worldwide. Repeated overexposure to noise at or above 85 dBA can cause permanent hearing loss, tinnitus, and difficulty understanding speech in noise. It is also associated with cardiovascular disease, depression, balance problems, and lower income. About 22 million U.S. workers are currently exposed to hazardous occupational noise. Approximately 33% of working-age adults with a history of occupational noise exposure have audiometric evidence of noise-induced hearing damage, and 16% of noise-exposed workers have material hearing impairment. While the Mining, Construction, and Manufacturing sectors typically have the highest prevalence of noise exposure and hearing loss, there are noise-exposed workers in every sector and every sector has workers with hearing loss. Noise-induced hearing loss is preventable. Increased understanding of the biological processes underlying noise damage may lead to protective pharmacologic or genetic therapies. For now, an integrated public health approach that (1) emphasizes noise control over reliance on hearing protection, (2) illustrates the full impact of hearing loss on quality of life, and (3) challenges the cultural acceptance of loud noise can substantially reduce the impact of noise on worker health.

Auditory brainstem responses in weaning pigs and three ages of sows

Piglet crushing is a devastating welfare concern on swine farms; however, some sows appear unresponsive to a piglet’s call. Sow hearing ability is rarely considered despite the extensive body of research performed on crushing. In this study, pigs of four age groups (weaning, n = 7; gilts, n = 5; 2nd and 3rd parity, n = 5; 5th parity and up, n = 5) were anesthetized and auditory brainstem responses (ABRs) were performed to measure if pig hearing diminishes with age in a mechanically ventilated barn. Before testing, pigs were placed in a sound dampening box. ABRs were performed on animals using 1,000 clicks at two decibel (dB) levels: 90 and 127 dB sound pressure level. Latencies and amplitudes of waves I–V were measured and interpeak latencies for waves I–III, III–V, and I–V were calculated. Five pigs (three 2nd and 3rd parity, and two 5th parity and above) had no detectable waves at either decibel. Sows in 2nd and 3rd parities had very few distinguishable waves, with only wave I and II present in two sows. Amplitudes of waves I and V increased with increased dB (P < 0.001). Increasing dB decreased the latency of each of the recorded waves (P < 0.01). The vast majority of commercial swine are raised in noisy barn environments; it is possible that these environments directly affect the ability for pigs to hear and normal hearing development in this population of animals. Hearing has a significant effect on swine welfare as hearing is integral to successful animal handing and during moments of animal-to-animal communication. Hearing is a considerable welfare issue on farms and ways to decrease pig hearing loss should be considered.

Psychological Distress in Bullied Deaf and Hard of Hearing Adolescents

Bullying victimization at school is an important concern in terms of mental health, in particular, for deaf and hard of hearing (DHH) adolescents who may be more vulnerable than hearing peers. This study determined the prevalence of bullying victimization among DHH adolescents in Taiwan and ascertained the relation of bullying victimization experiences and family and school variables with their psychological well-being. Data were collected from the 2011 Special Needs Education Longitudinal Study database. Multivariate regression analysis was performed on variables comprising seven items measuring psychological distress; four types of bullying victimizations; and family-, school-, and peer-related factors. Approximately 65% of DHH adolescents experienced at least one type of bullying victimization. Factors such as exclusion bullying, female gender, delayed bedtime, conflicts with parents, unfavorable relationship with parents, inability to get along with friends, dislike for school, and bullying victimization experiences increased psychological distress in the DHH adolescents. Bullying victimization of DHH adolescents is a risk factor for poor mental health. However, a good relationship of these adolescents with their parents and peers could be protective for their psychological well-being. Therefore, parents and teachers should understand the needs of DHH adolescents and establish antibullying strategies to diminish their mental health problems.

Behavioral Hearing Thresholds and Distortion Product Otoacoustic Emissions in Cannabis Smokers

Purpose Cannabis is a widely used drug both medically and recreationally. The aim of this study was to determine if cannabis smoking is associated with changes in auditory function, as measured by behavioral hearing thresholds and/or distortion product otoacoustic emissions (DPOAEs). Method We investigated hearing thresholds and 2f₁-f₂ DPOAEs in 20 cannabis smokers and 20 nonsmokers between 18 and 28 years old. Behavioral thresholds were obtained from 0.25 to 16 kHz. DPOAEs were measured using discrete tones between f₂ of 0.5 and 19.03 kHz using an f₂/f₁ ratio of 1.22 and L₁/L₂ = 65/55 dB SPL. Thresholds and DPOAE amplitudes were compared between groups using linear mixed-effects models with sex and frequency as predictors. Results Behavioral thresholds in smokers did not differ significantly between smokers and nonsmokers (all ps > .05). Although not significant, long-term smokers exhibited poorer thresholds than short-term smokers and nonsmokers. Smokers generally exhibited lower DPOAE amplitudes than nonsmokers, although the differences were not significant. Male smokers had significantly poorer DPOAE amplitudes than male nonsmokers in the low frequencies (f₂ ≤ 2 kHz; p = .0245). Conclusion Results indicate that smoking cannabis may negatively alter the function of outer hair cells in young men. This subtle cochleopathology is evident in the absence of measurable differences in behavioral hearing thresholds between cannabis smokers and nonsmokers.

Association of Behavior With Noise-Induced Hearing Loss Among Attendees of an Outdoor Music Festival: A Secondary Analysis of a Randomized Clinical Trial

Importance

To date, factors associated with noise-induced hearing loss at music festivals have not yet been analyzed in a single comprehensive data set. In addition, little is known about the hearing loss-associated behavior of music festival attendees.

Objectives

To assess which factors are associated with the occurrence of a temporary threshold shift (TTS) after music exposure and to investigate the behavior of music festival attendees.

Design, Setting, and Participants

This prospective post hoc analysis gathered data from a randomized, single-blind clinical trial conducted on September 5, 2015, at an outdoor music festival in Amsterdam, the Netherlands. Adult volunteers with normal hearing were recruited via social media from August 26 through September 3, 2015. Intention to use earplugs was an exclusion criterion. Of 86 volunteers assessed, 51 were included. This post hoc analysis was performed from October 3, 2016, through February 27, 2017.

Interventions

Music festival visit for 4.5 hours.

Main Outcomes and Measures

The primary outcome was a TTS on a standard audiogram for the frequencies 3.0- and 4.0-kHz. Multivariable linear regression was performed to determine which factors are associated with a TTS. A questionnaire on behavior, hearing, and tinnitus was distributed to the participants before and after the festival visit.

Results

A total of 51 participants were included (18 men [35%] and 33 women [65%]) with a mean (SD) age of 27 (6) years. Mean (SD) threshold change across 3.0 and 4.0 kHz was 5.4 (5.7) dB for the right ear and 4.0 (6.1) dB for the left ear. Earplug use (absolute difference in the left ear, -6.0 dB [95% CI, -8.7 to -3.2 dB]; in the right ear, -6.4 dB [95% CI, -8.8 to -4.1 dB]), quantity of alcohol use (absolute difference per unit in the left ear, 1.1 dB [95% CI, 0.5 to 1.7 dB]; in the right ear, 0.7 dB [95% CI, 0.1 to 1.4 dB]), drug use (absolute difference in the right ear, 6.0 dB [95% CI, 0.9 to 11.1 dB]), and male sex (absolute difference in the right ear, 4.1 dB [95% CI, 0.3 to 5.9 dB]) were independently associated with hearing loss, with earplug use being the most important factor. Unprotected participants reported significantly worse subjective hearing performance and tinnitus after the festival visit than did participants using earplugs (Cramer V, 0.62 [95% CI, 0.47-0.79] and 0.39 [95% CI, 0.16-0.62], respectively). In the earplug group, the perceived loudness (r = -0.72; 95% CI, -1.00 to -0.43) and appreciation (r = 0.53; 95% CI, 0.29 to 0.78) of music and speech perception (r = 0.21; 95% CI, 0.09 to 0.35) were correlated with the duration of earplug use.

Conclusions and Relevance

The present study identified nonuse of earplugs, use of alcohol and drugs, and male sex as associated with a TTS at an outdoor music festival. Physicians should consider these factors to raise awareness about the combined risk of attending music festivals without using earplugs while consuming alcohol and/or drugs. The intention to use earplugs was correlated with the loudness and appreciation of music with earplugs, which may advocate for the use of personalized earplugs.

Trial Registration

trialregister.nl Identifier: NTR5401.

Bilateral high-frequency hearing loss is associated with elevated blood pressure and increased hypertension risk in occupational noise exposed workers

Objective

To investigate the association of bilateral high-frequency hearing loss (BHFHL) with blood pressure and hypertension among occupational noise exposed workers.

Methods

Occupational noise exposed workers were enrolled in 2017 from the occupational diseases survey of Chengdu. BHFHL was classified as normal, mild, or high by the bilateral high-frequency tone average. Linear regression model was used to assess the effects of occupational noise exposure time and BHFHL on blood pressure. Logistic regression model was performed to estimate hypertension risk odds ratios (ORs) associated to occupational noise exposure time and BHFHL.

Results

Increasing years of occupational noise exposure and BHFHL were significantly associated with systolic and diastolic blood pressure increase (all P<0.001). The lineal trend was only significant in males, with adjusted ORs for hypertension gradually increasing with increasing years of occupational noise exposure (P<0.001). Furthermore, subjects having mild and high BHFHL had a higher hypertension risk of 34% and 281%, respectively (both P<0.001). Dose-response relationship between BHFHL and hypertension was found in both males and females.

Conclusions

Occupational noise exposure was positively associated with blood pressure levels and hypertension risk.

The correlation between hair and eye colour and contralateral suppression of otoacoustic emissions

Genetics and environmental factors frequently influence individual's susceptibility to hearing loss. It is postulated that melanin in the inner ear is related to individual's susceptibility to noise induced hearing loss (NIHL). General pigmentation in turn, suspected to be related to the amount of pigmentation in the inner ear. The amount of melanin in the inner ear is said to modulate the endocochlear potential and provide an otoprotective effect.

AIM

The study aimed to determine the relationship between the contralateral suppression of otoacoustic emissions (CSOAE) in individuals with brown eyes and hair, and blue eyes and blond hair, and temporary emission shift (TES) after short-term noise exposure.

SETTING AND DESIGN

The research was conducted using a quantitative research design with a quasi-experimental repeated within the subject design to compare the CSOAE in subjects with different hair and eyes colour with TES after short-term noise exposure. Quantitative research was used to determine the relationship between the measurable variables to predict occurrence.

MATERIAL AND METHOD

The hearing sensitivity of young adults was determined by using pure tone audiometry followed by CSOAE's and distortion product otoacoustic emissions (DPOAE) before listening to music for one hour individually. Pure tone audiometry and DPOAE's were repeated after music exposure to determine the amount of TES and temporary threshold shift (TTS).

STATISTICAL ANALYSIS USED

One-way ANOVA was used during the analysis of the data obtained during this research study, in addition to, two-tailed Wilcoxon Sign Rank test and Friedman's test. In all analyses, a 95% level of significance (P<0.05) was used.

RESULTS

No statistically significant difference between efferent suppression was measured by CSOAE's between the participant groups. A larger TTS at 4000 Hz and TES at 2000 Hz was evident in the blue eyes and blond hair group after short-term music exposure. Conclusion: CSOAE's were unable to predict which group of individuals were more susceptible to NIHL after short-term noise exposure.

Age-Related Hearing Loss Is Accelerated by Repeated Short-Duration Loud Sound Stimulation

Both age-related hearing loss (ARHL) and noise-induced hearing loss (NIHL) may share pathophysiological mechanisms in that they are associated with excess free radical formation and cochlear blood flow reduction, leading to cochlear damage. Therefore, it is possible that short, but repeated exposures to relatively loud noise during extended time periods, like in leisure (i.e., musical devices and concerts) or occupational noise exposures, may add to cochlear aging mechanisms, having an impact on the onset and/or progression of ARHL. Consequently, the aim of the present study was to determine if repeated short-duration overexposure to a long-term noise could accelerate permanent auditory threshold shifts associated with auditory aging in an animal model of ARHL. Toward this goal, young adult, 3-month-old Wistar rats were divided into two groups: one exposed (E) and the other non-exposed (NE) to noise overstimulation. The stimulation protocol consisted of 1 h continuous white noise at 110 dB sound pressure level (SPL), 5 days a week, allowing 2 days for threshold recovery before initiating another stimulation round, until the animals reached an age of 18 months. Auditory brainstem response (ABR) recordings at 0.5, 1, 2, 4, 8, 16, and 32 kHz were performed at 3, 6, 12, and 18 months of age. The results demonstrate that in the E group there were significant increases in auditory thresholds at all tested frequencies starting already at 6 months of age, which extended at 12 and 18 months. However, in NE animals threshold shifts were not evident until 12 months, extending to 18 months of age. Threshold shifts observed in the E animals at 6 and 12 months were significantly larger than those observed in the NE group at the same ages. Threshold shifts at 6 and 12 months in E animals resembled those at 12 and 18 months in NE animals, respectively. This suggests that repeated noise overstimulation in short-duration episodes accelerates the time-course of hearing loss in this animal model of ARHL.

The Relationship of Cardiometabolic Risk and Auditory Processing among African Americans: The Jackson Heart Study

Objectives

There is limited research in population-based studies on auditory processing. The purpose of this work is to determine the prevalence of auditory processing impairment in the Jackson Heart Study cohort and to identify potential relationships with cardiometabolic risk factors.

Study Design

Cross-sectional study.

Setting

Jackson Heart Study in Jackson, Mississippi.

Subjects

Participants of an all–African American cardiovascular study cohort (n = 1314).

Methods

The Quick Speech-in-Noise and Dichotic Digits, Double Pairs tests were used to assess auditory processing. Logistic regression and multinomial logistic regression models were used to examine how participants’ cardiometabolic risk factors and audiologic characteristics were associated with speech perception in noise and binaural integration.

Results

Quick Speech-in-Noise and Dichotic Digits, Double Pairs testing showed a prevalence of auditory processing impairment in 69% and 71% of the cohort, respectively, which was significantly related to age, hearing thresholds, sex, and education level. With covariate adjustment in statistical models for age, sex, pure tone average, and education level, waist circumference, systolic blood pressure, and hypertension were statistically predictive of auditory processing impairment ( P < .05).

Conclusion

The results suggest a high prevalence of auditory processing deficits in the Jackson Heart Study cohort. In addition, cardiometabolic and audiologic factors show a statistically significant independent relationship with auditory impairment measures.

Cochlear Synaptopathy Changes Sound-Evoked Activity Without Changing Spontaneous Discharge in the Mouse Inferior Colliculus

Tinnitus and hyperacusis are life-disrupting perceptual abnormalities that are often preceded by acoustic overexposure. Animal models of overexposure have suggested a link between these phenomena and neural hyperactivity, i.e., elevated spontaneous rates (SRs) and sound-evoked responses. Prior work has focused on changes in central auditory responses, with less attention paid to the exact nature of the associated cochlear damage. The demonstration that acoustic overexposure can cause cochlear neuropathy without permanent threshold elevation suggests cochlear neuropathy per se may be a key elicitor of neural hyperactivity. We addressed this hypothesis by recording responses in the mouse inferior colliculus (IC) following a bilateral, neuropathic noise exposure. One to three weeks post-exposure, mean SRs were unchanged in mice recorded while awake, or under anesthesia. SRs were also unaffected by more intense, or unilateral exposures. These results suggest that neither neuropathy nor hair cell loss are sufficient to raise SRs in the IC, at least in 7-week-old mice, 1-3 weeks post exposure. However, it is not clear whether our mice had tinnitus. Tone-evoked rate-level functions at the CF were steeper following exposure, specifically in the region of maximal neuropathy. Furthermore, suppression driven by off-CF tones and by ipsilateral noise were reduced. Both changes were especially pronounced in neurons of awake mice. This neural hypersensitivity may manifest as behavioral hypersensitivity to sound - prior work reports that this same exposure causes elevated acoustic startle. Together, these results indicate that neuropathy may initiate a compensatory response in the central auditory system leading to the genesis of hyperacusis.

Nucleolus vs Nucleus Count for Identifying Spiral Ganglion in Human Temporal Bone

OBJECTIVES

Spiral ganglion (SG) counting is used in experimental studies conducted on age-, noise-, and drug-induced sensorineural hearing loss, as well as in the assessment of cochlear implant performances. Different methods of counting have been reported, but no definite standardization of such procedure has been published. The aim of our study is to identify the best method to count human spiral ganglions (SGs).

MATERIALS AND METHODS

By identification of nuclei or nucleoli as described by Schucknect, seven researchers with different experience levels counted SGs in 123 human temporal bones (TBs). Data on time of post-mortem bone removal post-mortem, methods of specimen's fixation, decalcification, and coloration were collected to test their possible influence on human tissue. Percentage, two-tailed t-test, Spearman's test, and one-way ANOVA were used to analyze the data.

RESULTS

Nucleoli were identified in 61% of cases, whereas nuclei were recognized in 100% of cases (p<0.005). Nucleoli presence in all four segments in the same temporal bone (TB) was observed in 69 cases (92%), whereas nuclei were identified in all four segments in 103 cases (83.7%) (p<0.001). The junior investigators requested a double check by the seniors in 25 (20.3%) cases for identifying and counting nucleoli, whereas the senior researchers showed no doubts in their identification and count. The only parameter positively affecting nucleoli identification in tissue preparation was bone removal for <12 h with respect to longer post-mortem time (p<0.001).

CONCLUSION

We suggest counting nuclei, rather than nucleoli, for spiral ganglion computation because of easier recognition of nuclei, especially in case of investigator's limited experience.

Unilateral Chewing as a Risk Factor for Hearing Loss: Association between Chewing Habits and Hearing Acuity

Hearing loss is a common disease in older adults. In order to lower the prevalence of hearing loss, it is important to identify its risk factors. Although some studies have found a relationship between dental status and hearing acuity, few studies have investigated the relationship between unilateral chewing and hearing acuity. This study aimed to assess the effects of unilateral chewing on hearing acuity, with a focus on the risk of hearing loss. Eighty-one participants (aged 51-87 years) were included in the present study. Their chewing habits were determined by visual inspection. The participants were divided into two groups: the Unilateral Chewing Group (UCG; n = 43) and the Bilateral Chewing Group (BCG; n = 38). The preferred chewing side was identified for the UCG. Hearing acuity was determined using pure tone audiometry in a noise-free chamber, conducted at frequencies of 500, 1,000, 2,000, and 4,000 Hz. Hearing loss was defined as a lower hearing threshold greater than 50 dB in either ear at any frequency. Mean hearing thresholds at frequencies of 2,000 and 4,000 Hz were significantly higher, by 5.12 and 15.75 dB, respectively, for the UCG compared to the BCG (P < 0.05). The UCG had a 3.78-fold higher likelihood of suffering from hearing loss (95% confidence interval [CI]: 1.81-7.88). The results suggest that bilateral chewing could be beneficial for preventing hearing loss. This study may provide evidence to support clinical interventions aimed at reducing the risk of hearing loss in patients with unilateral chewing habits.

Larval Zebrafish Lateral Line as a Model for Acoustic Trauma

Excessive noise exposure damages sensory hair cells, leading to permanent hearing loss. Zebrafish are a highly tractable model that have advanced our understanding of drug-induced hair cell death, yet no comparable model exists for noise exposure research. We demonstrate the utility of zebrafish as model to increase understanding of hair cell damage from acoustic trauma and develop protective therapies. We created an acoustic trauma system using underwater cavitation to stimulate lateral line hair cells. We found that acoustic stimulation resulted in exposure time- and intensity-dependent lateral line and saccular hair cell damage that is maximal at 48–72 h post-trauma. The number of TUNEL+ lateral line hair cells increased 72 h post-exposure, whereas no increase was observed in TUNEL+ supporting cells, demonstrating that acoustic stimulation causes hair cell-specific damage. Lateral line hair cells damaged by acoustic stimulation regenerate within 3 d, consistent with prior regeneration studies utilizing ototoxic drugs. Acoustic stimulation-induced hair cell damage is attenuated by pharmacological inhibition of protein synthesis or caspase activation, suggesting a requirement for translation and activation of apoptotic signaling cascades. Surviving hair cells exposed to acoustic stimulation showed signs of synaptopathy, consistent with mammalian studies. Finally, we demonstrate the feasibility of this platform to identify compounds that prevent acoustic trauma by screening a small redox library for protective compounds. Our data suggest that acoustic stimulation results in lateral line hair cell damage consistent with acoustic trauma research in mammals, providing a highly tractable model for high-throughput genetic and drug discovery studies.

An investigation into the use of recorded music as a surgical intervention: A systematic, critical review of methodologies used in recent adult controlled trials

CONTEXT

While music is being increasingly used as a surgical intervention, the types of music used and the reasons underlying their selection remain inconsistent. Empirical research into the efficacy of such musical interventions is therefore problematic.

OBJECTIVE

To provide clear guidelines for musical selection and employment in surgical interventions, created through a synthesis of the literature. The aim is to examine how music is implemented in surgical situations, and to provide guidance for the selection and composition of music for future interventions.

METHODS

English language quantitative surgical intervention studies from Science Direct, ProQuest, and Sage Journals Online, all published within the last 10 years and featuring recorded music, were systematically reviewed. Variables investigated included: the time the intervention was performed, the intervention length, the outcomes targeted, music description (general and specific), theoretical frameworks underlying the selection of the music, whether or not a musical expert was involved, participant music history, and the participants' feedback on the chosen music.

RESULTS

Several aspects contribute to the lack of scientific rigour regarding music selection in this field, including the lack of a theoretical framework or frameworks, no involvement of musical experts, failure to list the music tracks used, and the use of vague and subjective terms in general music descriptions. Patients are frequently allowed to select music (risking both choosing music that has an adverse effect and making study replication difficult), and patient music history and listening habits are rarely considered. Crucially, five primary theoretical frameworks underlying the effectiveness of music arose in the literature (distraction, relaxation, emotional shift, entrainment, and endogenous analgesia), however music was rarely selected to enhance any of these mechanisms.

CONCLUSIONS

Further research needs to be conducted to ensure that music is selected according to a theoretical framework and more rigorous and replicable methodology. Music interventions can be made more effective at improving psychological states and reducing physiological arousal by selecting music conducive to specific mechanisms, and also by considering at what point during the surgical experience the music would be most effective. Greater involvement of music experts in interventions would help to ensure that the most appropriate music was chosen, and that it is clearly and precisely described.

Regular Exposure to Cowbells Affects the Behavioral Reactivity to a Noise Stimulus in Dairy Cows

In alpine regions, cows are often equipped with bells during pasture season to ensure that farmers can locate them. Constant exposure to the chime of a bell may affect cows' acoustic perception in general. The aim of this study is to test whether routine bell exposure affects the reactivity to a noise stimulus and might be associated with hearing impairment in cows. For the assessment, behavioral and cardiac indicators were used as indirect measures of hearing capacity. Cows that were either used to wearing a bell or not were exposed to a playback of low and high amplitude (=varying loudness). In addition, we tested whether wearing earplugs, mimicking hearing impairment, reduced the cows' reactivity toward the playback. On 24 farms, half of them routinely using cowbells, 96 Brown Swiss cows were tested in a 2 × 2 factorial cross-over design (65 or 85 dB, without or with earplugs) in a balanced order. The effects of bell experience, amplitude, and earplugs on the latency to the first behavioral and cardiac response to a 5-s playback were analyzed using linear mixed-effects models, considering dependencies within the data set. Cows reacted faster without earplugs and when they were exposed to 85 dB compared with 65 dB. The proportion of cows leaving the feeding rack after onset of the playback was reduced by bell experience and earplugs and was increased when exposed to 85 dB compared with 65 dB. Exposure without earplugs to 85 dB but not to 65 dB increased heart rate. Heart rate and heart rate variability indicated increased sympathetic activation during the exposure to 85 dB compared with 65 dB. In general, behavioral and cardiac indicators did not indicate severe hearing impairment due to routine bell exposure. The 85-dB stimulus increased arousal and avoidance compared with the 65-dB stimulus, with bell experience and earplugs leading to a general decrease in avoidance of the stimulus. This may reflect an altered acoustic perception of the playback stimulus in dairy cows that are routinely exposed to bells.

Knowledge and attitude of mothers regarding infant hearing loss in Changsha, Hunan province, China

OBJECTIVE

The objective of this study was to explore the knowledge and attitude among mothers of newborns regarding infant hearing loss (HL) in Changsha, Hunan province, China.

DESIGN

A questionnaire including 18 items was given to mothers.

STUDY SAMPLE

A total of 115 mothers participated in the study.

RESULTS

Seven risk factors for hearing loss were identified correctly by above 60% of respondents and the top three were prolonged noise (88.7%), high fever (82.6%) and ear discharge (82.6%). Poor knowledge was demonstrated on risk factors jaundice (20.0%), measles (22.6%), convulsion (33.0%) and traditional Chinese medicine (39.1%). Maternal knowledge scores in identification and intervention (2.68 ± 0.31) was slightly higher than the score in risk factors (2.47 ± 0.34). Ninety-nine per cent of the mothers expressed the willingness to test baby's hearing soon after birth and concern about hearing.

CONCLUSIONS

Mothers were concerned about baby's hearing and the attitude was positive. However, the correct recognition rate towards some risk factors for HL was low. Action needs to be taken to raise awareness about ear and hearing care, prevent HL caused by preventable causes and prompt early identification, early diagnosis and intervention of HL.

Personal Listening Devices in Australia: Patterns of Use and Levels of Risk

Personal listening devices (PLDs) have the potential to increase the risk of noise-induced hearing loss (NIHL) for users. The present study aimed to investigate the nature and extent of the risk posed, by describing the user profile of a PLD population, identifying listening habits of that population, and examining whether PLD risk status is associated with hearing damage. A sample of 4,185 Australian PLD users completed an online survey about listening behaviors and hearing health. Listeners were characterized as low, high, or very high-risk based on daily noise dose estimates calculated from self-reported listening volume and durations. Listening patterns and hearing difficulties were examined in relation to risk status. Results indicated differences in listening volumes and durations with respect to age, with higher listening volumes reported for environments with greater background noise. Fifteen percent of participants' usage was classified as posing a potential risk to hearing, with a significantly greater proportion of younger people in higher-risk categories. Forty-one percent of participants reported feeling they have a hearing loss, with ∼20% reporting difficulties with speech in noise. For 18- to 35-year-olds, higher-risk status was associated with a greater proportion of self-reported hearing difficulties, including perceived poorer speech perception. These results have implications for hearing health promotion activities and suggest that messages should focus on either volume levels or durations depending on the particular activity in which the PLD is used. In addition, the results underline the importance of placing PLD exposure in the context of individuals' wider noise exposure. Although PLD use alone is not placing the majority of users at risk, it may be increasing the likelihood that individuals' cumulative noise exposure will exceed safe levels.

The combined effect of cigarette smoking and occupational noise exposure on hearing loss: evidence from the Dongfeng-Tongji Cohort Study

Combined effect of cigarette smoking and occupational noise exposure on hearing loss has rarely been evaluated among Chinese population, especially among females. This cross-sectional study was conducted in 11196 participants of Dongfeng-Tongji cohort study. Smoking status was self-reported through questionnaire and occupational noise exposure was evaluated through workplace noise level and/or the job titles. Hearing loss was defined as a pure-tone mean of 25 dB or higher at 0.5, 1, 2, and 4 kHz in both ears. Compared with participants without occupational noise exposure, the risk of hearing loss was significantly higher for noise exposure duration ≥20 (OR = 1.45, 95%CI = 1.28–1.65). The association was particularly evident among individuals who were males (OR = 1.74, 95%CI = 1.45–2.08) and aged ≥ 70 (OR = 1.74, 95%CI = 1.30–2.33). Similarly, the risks increased with the increasing of pack-years in males and all age groups except for those aged <60. As to the combined effect, the hearing loss risk was highest for noise exposure duration ≥20 and pack-years ≥25 (OR = 2.41, 95%CI = 1.78–3.28), especially among males (OR = 2.42, 95%CI = 1.74–3.37) and those aged ≥70 (OR = 2.76, 95%CI = 1.36–5.60). Smoking may be an independent risk factor for hearing loss. And it may synergistically affect hearing when combined with occupational noise exposure, especially among males and older participants.

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

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