Association of noise exposure, plasma microRNAs with metabolic syndrome and its components among Chinese adults

AIMS

We aimed to evaluate the association of occupational noise with metabolic syndrome (MetS) and its components, and to assess the potential role of miRNAs in occupational noise-associated MetS.

METHODS

A total of 854 participants were enrolled in our study. Cumulative noise exposure (CNE) was estimated in conjunction with workplace noise test records and research participants' employment histories. Logistic regression models adjusted for potential confounders were used to assess the association of CNE and miRNAs with MetS and its components.

RESULTS

We observed linear positive dose-response associations between occupational noise exposure and the prevalence of MetS (OR: 1.031; 95 % CI: 1.008, 1.055). And linear and nonlinear relationship were also found for the association of occupational noise exposure with high blood pressure (OR: 1.024; 95 % CI: 1.007, 1.041) and reduced high-density lipoprotein (OR: 1.051; 95 % CI: 1.031, 1.072), respectively. MiR-200a-3p, miR-92a-3p and miR-21-5p were inversely associated with CNE, or the prevalence of MetS and its components (all P < 0.05). However, we did not find any statistically significant mediation effect of miRNAs in the associations of CNE with MetS. Furthermore, the prevalence of bilateral hearing loss in high-frequency increased (OR: 1.036; 95 % CI: 1.008, 1.067) with CNE level rising, and participants with bilateral hearing loss in high-frequency had a significantly higher risk of MetS (OR: 1.727; 95 % CI: 1.048, 2.819).

CONCLUSION

Our study suggests that occupational noise exposure is associated with MetS and its components, and the role of miRNAs in noise-induced increasing MetS risk needs to be confirmed in future studies.

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BACKGROUND

Previous studies have linked noise exposure with adverse cardiovascular events. However, evidence remains inconsistent, and most previous studies only focused on traffic noise, excluding other anthropogenic sources like constructions, industrial process and commercial activities. Additionally, few studies have been conducted in the U.S. or evaluated the non-linear exposure-response relationships.

METHODS

We conducted a relative incidence analysis study using all cardiovascular diseases mortality as cases (n = 936,019) and external causes mortality (n = 232,491) as contrast outcomes. Mortality records geocoded at residential addresses were obtained from five U.S. states (Indiana, 2007; Kansas, 2007-2009, Missouri, 2010-2019, Ohio, 2007-2013, Texas, 2007-2016). Time-invariant long-term noise exposure was obtained from a validated model developed based on acoustical measurements across 2000-2014. Noises from both natural sources (natural activities, including animals, insects, winds, water flows, thunder, etc.) and anthropogenic sources (human activities, including transportation, industrial activities, community facilities & infrastructures, commercial activities, entertainments, etc.) were included. We used daytime and nighttime total anthropogenic noise & day-night average sound pressure level combining natural and anthropogenic sources as exposures. Logistic regression models were fit controlling for Census tract-level & individual-level characteristics. We examined potential modification by sex by interaction terms and potential non-linear associations by thin plate spline terms.

RESULTS

We observed positive associations for daytime anthropogenic L50 (sound level exceeded 50% of time) noise (10-dBA OR = 1.047, 95%CI 1.025-1.069), nighttime anthropogenic L50 noise (10-dBA OR = 1.061, 95%CI 1.033-1.091) in a two-exposure-term model, and overall Ldn (day-night average) sound pressure level (10-dBA OR = 1.064, 95%CI 1.040-1.089) in single-exposure-term model. Females were more susceptible to all three exposures. All exposures showed monotonic positive associations with cardiovascular mortality up to certain thresholds around 45-55 dBA, with a generally flattened or decreasing trend beyond those thresholds.

CONCLUSIONS

Both daytime anthropogenic and nighttime anthropogenic noises were associated with cardiovascular disease mortality, and associations were stronger in females.

How 'hidden hearing loss' noise exposure affects neural coding in the inferior colliculus of rats

Exposure to brief, intense sound can produce profound changes in the auditory system, from the internal structure of inner hair cells to reduced synaptic connections between the auditory nerves and the inner hair cells. Moreover, noisy environments can also lead to alterations in the auditory nerve or to processing changes in the auditory midbrain, all without affecting hearing thresholds. This so-called hidden hearing loss (HHL) has been shown in tinnitus patients and has been posited to account for hearing difficulties in noisy environments. However, much of the neuronal research thus far has investigated how HHL affects the response characteristics of individual fibres in the auditory nerve, as opposed to higher stations in the auditory pathway. Human models show that the auditory nerve encodes sound stochastically. Therefore, a sufficient reduction in nerve fibres could result in lowering the sampling of the acoustic scene below the minimum rate necessary to fully encode the scene, thus reducing the efficacy of sound encoding. Here, we examine how HHL affects the responses to frequency and intensity of neurons in the inferior colliculus of rats, and the duration and firing rate of those responses. Finally, we examined how shorter stimuli are encoded less effectively by the auditory midbrain than longer stimuli, and how this could lead to a clinical test for HHL.

Establishing multifactorial risk factors for adult-onset hearing loss: A systematic review with topic modelling and synthesis of epidemiological evidence

BACKGROUND

This systematic review explores the multifaceted nature of risk factors contributing to adult-onset HL. The objective was to synthesise the most recent epidemiological evidence to generate pooled proportional incidences for the identified risk factors.

METHODS

We conducted an extensive search of electronic databases (MEDLINE, EMBASE, and psychINFO) for studies providing epidemiological evidence of risk factors associated with hearing loss. Topic modelling using Latent Dirichlet Allocation (LDA) was first conducted to determine how many risk factor themes were available from the papers. Data were analysed by calculating the pooled proportional incidence using a meta-analysis of proportions.

RESULTS

From the 72 studies reviewed, six key risk factor themes emerged through LDA topic modelling. The review identified ototoxicity, primarily caused by cancer treatments and antibiotics, infectious diseases like COVID-19, occupational noise exposure, lifestyle factors, health conditions, biological responses, and age progression as significant risk factors for HL. The highest proportional incidence was found with cancer-related ototoxicity at 55.4% (95%CI: 39.0-70.7), followed closely by ototoxicity from infectious diseases at 50.0% (95%CI: 28.5-71.5). This high proportional incidence suggests the need to explore less destructive therapies and proactively monitor hearing function during treatments.

CONCLUSIONS

The findings of this review, combined with the synthesis of epidemiological evidence, enhance our understanding of hearing loss (HL) pathogenesis and highlight potential areas for intervention, thereby paving the way for more effective prevention and management of adult-onset hearing loss in our ageing global population.

Cardiometabolic diseases according to the type and degree of hearing loss in noise-exposed workers

Background

This study aimed to determine the association between cardiometabolic diseases, including metabolic syndrome, hypertension, and diabetes, and the type and degree of hearing loss in noise-exposed workers.

Methods

A total of 237,028 workers underwent air conduction pure tone audiometry in 2015 to assess their health and diagnose cardiometabolic diseases. The study defined metabolic syndrome, hypertension, and diabetes using blood pressure, fasting blood sugar, cholesterol, and triglyceride levels. Mid-frequency hearing loss was defined as ≥ 30 dB at 2,000 Hz, whereas high-frequency hearing loss was ≥ 40 dB at 4,000 Hz. The average air conduction hearing thresholds at these frequencies were used to determine hearing loss degrees.

Results

The odds ratio (OR) of combined exposure to noise and night-shift work in all cardiometabolic diseases was higher than that of noise exposure alone. The risk of cardiometabolic diseases was dose-response, with higher hearing loss causing higher ORs. The ORs of hypertension compared with the normal group were 1.147 (1.098-1.198), 1.196 (1.127-1.270), and 1.212 (1.124-1.306), and those of diabetes were 1.177 (1.119-1.239), 1.234 (1.154-1.319), and 1.346 (1.241-1.459) for mild, moderate, and moderate-severe hearing loss, respectively.

Conclusions

Workers who are exposed to noise tend to demonstrate high risks of hearing loss and cardiometabolic diseases; thus, bio-monitoring of cardiometabolic diseases, as well as auditory observation, is necessary.

Heightened OAEs in young adult musicians: Influence of current noise exposure and training recency

Otoacoustic emissions (OAEs) are a non-invasive metric of cochlear function. Studies of OAEs in musicians have yielded mixed results, ranging from evidence of diminished OAEs in musicians-suggesting noise-induced hearing loss-to no difference when compared to non-musicians, or even a trend for stronger OAEs in musicians. The goal of this study was to use a large sample of college students with normal hearing (n = 160) to compare OAE SNRs in musicians and non-musicians and to explore potential effects of training recency and noise exposure on OAEs in these cohorts. The musician cohort included both active musicians (who at the time of enrollment practiced at least weekly) and past musicians (who had at least 6 years of training). All participants completed a questionnaire about recent noise exposure (previous 12 months), and a subset of participants (71 musicians and 15 non-musicians) wore a personal noise dosimeter for one week to obtain a more nuanced and objective measure of exposure to assess how different exposure levels may affect OAEs before the emergence of a clinically significant hearing loss. OAEs were tested using both transient-evoked OAEs (TEOAEs) and distortion-product OAEs (DPOAEs). As predicted from the literature, musicians experienced significantly higher noise levels than non-musicians based on both subjective (self-reported) and objective measures. Yet we found stronger TEOAEs and DPOAEs in musicians compared to non-musicians in the ∼1-5 kHz range. Comparisons between past and active musicians suggest that enhanced cochlear function in young adult musicians does not require active, ongoing musical practice. Although there were no significant relations between OAEs and noise exposure as measured by dosimetry or questionnaire, active musicians had weaker DPOAEs than past musicians when the entire DPOAE frequency range was considered (up to ∼16 kHz), consistent with a subclinical noise-induced hearing loss that only becomes apparent when active musicians are contrasted with a cohort of individuals with comparable training but without the ongoing risks of noise exposure. Our findings suggest, therefore, that separate norms should be developed for musicians for earlier detection of incipient hearing loss. Potential explanations for enhanced cochlear function in musicians include pre-existing (inborn or demographic) differences, training-related enhancements of cochlear function (e.g., upregulation of prestin, stronger efferent feedback mechanisms), or a combination thereof. Further studies are needed to determine if OAE enhancements offer musicians protection against damage caused by noise exposure.

Transcriptome analysis reveals dysfunction of the endoplasmic reticulum protein processing in the sonic muscle of small yellow croaker (Larimichthys polyactis) following noise exposure

Noise pollution is increasingly prevalent in aquatic ecosystems, causing detrimental effects on growth and behavior of marine fishes. The physiological responses of fish to underwater noise are poorly understood. In this study, we used RNA-sequencing (RNA-seq) to study the transcriptome of the sonic muscle in small yellow croaker (Larimichthys polyactis) after exposure to a 120 dB noise for 30 min. The behavioral experiment revealed that noise exposure resulted in accelerated tail swimming behavior at the beginning of the exposure period, followed by loss of balance at the end of experiment. Transcriptomic analysis found that most highly expressed genes in the sonic muscle, including parvalbumin, slc25a4, and troponin C were related with energy metabolism and locomotor function. Further, a total of 1261 differentially expressed genes (DEGs) were identified, including 284 up-regulated and 977 down-regulated genes in the noise exposure group compared with the control group. Gene ontology (GO) analysis indicated that the most enriched categories of DEGs included protein folding and response to unfolding protein. Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis found over-represented pathways including protein processing in the endoplasmic reticulum, chaperones and folding catalysts, as well as arginine and proline metabolism. Specifically, many genes related to fatty acid and collagen metabolism were up-regulated in the noise exposure group. Taken together, our results indicate that exposure to noise stressors alters the swimming behavior of croaker, inducing endoplasmic reticulum stress, disrupting lipid metabolism, and causing collagen degradation in the sonic muscle of L. polyactis.

Effects of 90 dB pure tone exposure on auditory and cardio-cerebral system functions in macaque monkeys

Excessive noise exposure presents significant health risks to humans, affecting not just the auditory system but also the cardiovascular and central nervous systems. This study focused on three male macaque monkeys as subjects. 90 dB sound pressure level (SPL) pure tone exposure (frequency: 500Hz, repetition rate: 40Hz, 1 min per day, continuously exposed for 5 days) was administered. Assessments were performed before exposure, during exposure, immediately after exposure, and at 7-, 14-, and 28-days post-exposure, employing auditory brainstem response (ABR) tests, electrocardiograms (ECG), and electroencephalograms (EEG). The study found that the average threshold for the Ⅴ wave in the right ear increased by around 30 dB SPL right after exposure (P < 0.01) compared to pre-exposure. This elevation returned to normal within 7 days. The ECG results indicated that one of the macaque monkeys exhibited an RS-type QRS wave, and inverted T waves from immediately after exposure to 14 days, which normalized at 28 days. The other two monkeys showed no significant changes in their ECG parameters. Changes in EEG parameters demonstrated that main brain regions exhibited significant activation at 40Hz during noise exposure. After noise exposure, the power spectral density (PSD) in main brain regions, particularly those represented by the temporal lobe, exhibited a decreasing trend across all frequency bands, with no clear recovery over time. In summary, exposure to 90 dB SPL noise results in impaired auditory systems, aberrant brain functionality, and abnormal electrocardiographic indicators, albeit with individual variations. It has implications for establishing noise protection standards, although the precise mechanisms require further exploration by integrating pathological and behavioral indicators.

Effect of chronic noise exposure on glucose and lipid metabolism in mice via modulating gut microbiota and regulating CREB/CRTC2 and SREBP1/SCD pathway

Chronic noise exposure is correlated with gut microbiota dysbiosis and glucose and lipid metabolism disorders. However, evidence on the mechanisms underlying of gut microbiota alterations in chronic noise induced glucose and lipid metabolism disorders is limited, and the potential aftereffects of chronic noise exposure on metabolic disorders remain unclear. In present study, we established chronic daytime and nighttime noise exposure mice models to explore the effects and underlying mechanism of gut microbiota on chronic noise-induced glucose and lipid metabolism disorders. The results showed that exposure to chronic daytime or nighttime noise significantly increased the fasting blood glucose, serum and liver TG levels, impaired glucose tolerance, and decreased serum HDL-C levels and liver TC levels in mice. However, after 4 weeks of recovery, only serum TG of mice in nighttime noise recovery group remained elevated. Besides, exposure to chronic noise reduced the intestinal tight junction protein levels and increased intestinal permeability, while this effect did not completely dissipate even after the recovery period. Moreover, chronic noise exposure changed the gut microbiota and significantly regulated metabolites and metabolic pathways, and further activate hepatic gluconeogenesis CRTC2/CREB-PCK1 signaling pathway and lipid synthesis SREBP1/SCD signaling pathway through intestinal hepatic axis. Together, our findings demonstrated that chronic daytime and nighttime noise exposure could cause the glucose and lipid metabolism disorder by modulating the gut microbiota and serum metabolites, and activating hepatic gluconeogenic CREB/CRTC2-PCK1 signaling and lipid synthesis SREBP1/SCD signaling pathway. The potential aftereffects of noise exposure during wakefulness on metabolic disorders are more significant than that of noise exposure during sleep.

Systemic health effects of noise exposure

Noise, any unwanted sound, is pervasive and impacts large populations worldwide. Investigators suggested that noise exposure not only induces auditory damage but also produces various organ system dysfunctions. Although previous reviews primarily focused on noise-induced cardiovascular and cerebral dysfunctions, this narrow focus has unintentionally led the research community to disregard the importance of other vital organs. Indeed, limited studies revealed that noise exposure impacts other organs including the liver, kidneys, pancreas, lung, and gastrointestinal tract. Therefore, the aim of this review was to examine the effects of noise on both the extensively studied organs, the brain and heart, but also determine noise impact on other vital organs. The goal was to illustrate a comprehensive understanding of the systemic effects of noise. These systemic effects may guide future clinical research and epidemiological endpoints, emphasizing the importance of considering noise exposure history in diagnosing various systemic diseases.

The cochlear matrisome: Importance in hearing and deafness

The extracellular matrix (ECM) consists in a complex meshwork of collagens, glycoproteins, and proteoglycans, which serves a scaffolding function and provides viscoelastic properties to the tissues. ECM acts as a biomechanical support, and actively participates in cell signaling to induce tissular changes in response to environmental forces and soluble cues. Given the remarkable complexity of the inner ear architecture, its exquisite structure-function relationship, and the importance of vibration-induced stimulation of its sensory cells, ECM is instrumental to hearing. Many factors of the matrisome are involved in cochlea development, function and maintenance, as evidenced by the variety of ECM proteins associated with hereditary deafness. This review describes the structural and functional ECM components in the auditory organ and how they are modulated over time and following injury.

Prevalence of tinnitus and hyperacusis in 9-12-year-old children

OBJECTIVES

To estimate the prevalence of tinnitus and hyperacusis in children aged 9-12 years in Flanders, as well as to explore the associations with hearing abilities and listening behaviours.

DESIGN

A cross-sectional survey was undertaken in four different Flemish schools. The questionnaire was distributed among 415 children, with a response rate of 97.3%.

RESULTS

The prevalence of permanent tinnitus was 10.5% and of hyperacusis was 3.3%. The hyperacusis prevalence was higher in girls (p < .05). Some children reported effects of tinnitus in terms of anxiety (20.1%), sleep (36.5%), and concentration (24.8%). When listening to personal listening devices, 33.5% of the children reported to listen for at least 1 h at 60% or higher of the volume range. Moreover, 54.9% of children stated to never wear hearing protection.

CONCLUSIONS

Tinnitus and hyperacusis are prevalent in children aged 9-12 years. Some of these children might be overlooked and, as such, not receiving the required follow-up or counselling. Development of guidelines for the assessment of these auditory symptoms in children would help to determine the prevalence numbers with greater accuracy. Sensibility campaigns for safe listening are warranted, as more than half of the children never use hearing protection.

Early-life noise exposure causes cognitive impairment in a sex-dependent manner by disrupting homeostasis of the microbiota-gut-brain axis

Epidemiological investigations show that noise exposure in early life is associated with health and cognitive impairment. The gut microbiome established in early life plays a crucial role in modulating developmental processes that subsequently affect brain function and behavior. Here, we examined the impact of early-life exposure to noise on cognitive function in adolescent rats by analyzing the gut microbiome and metabolome to elucidate the underlying mechanisms. Chronic noise exposure during early life led to cognitive deficits, hippocampal injury, and neuroinflammation. Early-life noise exposure showed significant difference on the composition and function of the gut microbiome throughout adolescence, subsequently causing axis-series changes in fecal short-chain fatty acid (SCFA) metabolism and serum metabolome profiles, as well as dysregulation of endothelial tight junction proteins, in both intestine and brain. We also observed sex-dependent effects of microbiota depletion on SCFA-related beneficial bacteria in adolescence. Experiments on microbiota transplantation and SCFA supplementation further confirmed the role of intestinal bacteria and related SCFAs in early-life noise-exposure-induced impairments in cognition, epithelial integrity, and neuroinflammation. Overall, these results highlight the homeostatic imbalance of microbiota-gut-brain axis as an important physiological response toward environmental noise during early life and reveals subtle differences in molecular signaling processes between male and female rats.

Soundscape of an eastern coastal city of India

The soundscape study of an eastern Indian coastal city (Puri) has been investigated. Acoustic data were collected at 36 sampling locations during two time intervals in and around Puri. A number of noise indices, namely, Lmin, Lmax, and Leq, were calculated to demonstrate the noise level of this city. Noise maps are generated using ARC-GIS to investigate the impact of road traffic noise on the soundscape of the city. The response of the public was appraised by a questionnaire. Due to variable traffic features, the equivalent noise level (Leq) as well as peak (L10) and background noise (L90) levels varied with location and time of the day. It was found that socio-demographic characteristics have no bearing on the amount of annoyance. However, a link was observed between age, hearing condition, and noise perception, as well as between gender and impacts of noise.

Asymmetric hearing thresholds are associated with hyperacusis in a large clinical population

Hyperacusis is a debilitating auditory condition whose characterization is largely qualitative and is typically based on small participant cohorts. Here, we characterize the hearing and demographic profiles of adults who reported hyperacusis upon audiological evaluation at a large medical center. Audiometric data from 626 adults (age 18-80 years) with documented hyperacusis were retrospectively extracted from medical records and compared to an age- and sex-matched reference group of patients from the same clinic who did not report hyperacusis. Patients with hyperacusis had lower (i.e., better) high-frequency hearing thresholds (2000-8000 Hz), but significantly larger interaural threshold asymmetries (250-8000 Hz) relative to the reference group. The probability of reporting hyperacusis was highest for normal, asymmetric, and notched audiometric configurations. Many patients reported unilateral hyperacusis symptoms, a history of noise exposure, and co-morbid tinnitus. The high prevalence of both overt and subclinical hearing asymmetries in the hyperacusis population suggests a central compensatory mechanism that is dominated by input from an intact or minimally damaged ear, and which may lead to perceptual hypersensitivity by overshooting baseline neural activity levels.

Perceiving noise in daily life: How real-time sound characteristics affect personal momentary noise annoyance in various activity microenvironments and times of day

Annoyance is a major health burden induced by environmental noise. However, our understanding of the health impacts of noise is seriously undermined by the fixed contextual unit and limited sound characteristics (e.g., the sound level only) used in noise exposure assessments as well as the stationarity assumption made for exposure-response relationships. To address these limitations, we analyze the complex and dynamic relationships between personal momentary noise annoyance and real-time noise exposure in various activity microenvironments and times of day, taking into account individual mobility, multiple sound characteristics and nonstationary relationships. Using real-time mobile sensing, we collected individual data of momentary noise annoyance, real-time noise exposure as well as daily activities and travels in Hong Kong. A new sound characteristic, namely sound increment, is defined to capture the sudden increase in sound level over time and is used along with the sound level to achieve a multi-faceted assessment of personal real-time noise exposure at the moment of annoyance responses. Further, the complex noise exposure-annoyance relationships are learned using logistic regression and random forest models while controlling the effects of daily activity microenvironments, individual sociodemographic attributes and temporal contexts. The results indicate that the effects of the real-time sound level and sound increment on personal momentary noise annoyance are nonlinear, despite the overall significant and positive impacts, and different sound characteristics can produce a joint effect on annoyance. We also find that the daily activity microenvironments and individual sociodemographic attributes can affect noise annoyance and its relationship with different sound characteristics to varying degrees. Due to the temporal changes in daily activities and travels, the noise exposure-annoyance relationships can also vary over different times of the day. These findings can inform both local governments and residents with scientific evidence to promote the creation of acoustically comfortable living environments.

Association between occupational noise exposure and diabetes: A systematic review and meta-analysis

BACKGROUND

In addition to the well-known risk factors of diabetes, evidence is accumulating on the negative role of environmental and occupational factors such as noise exposure. We conducted a systematic review and meta-analysis on the association between long-term occupational noise exposure and diabetes.

METHODS

We systematically searched evidence in PubMed, Scopus, and Web of Science (until August 2022) according to the PRISMA protocol. Risk of bias was assessed using the Newcastle-Ottawa scale. Random-effects meta-analysis was applied separately for risk ratio (odds ratio, relative risk) and hazard ratio. We evaluated the heterogeneity and publication bias. We applied meta-regressions to identify sources of heterogeneity. The overall body of evidence was assessed using the Grading of Recommendations, Assessment, Development and Evaluations (GRADE) framework.

RESULTS

Of 533 retrieved articles, twelve studies (11 on non-gestational, and one on gestational diabetes) on total 106,045 population (23,996 diabetic cases) met our inclusion criteria; of which eight studies were cross-sectional, three were cohorts, and one was case-control. Only 40% of papers (five out of 12) had fair, good or very good quality, and most of the papers had poor or very poor quality in terms of risk of bias. We observed a non-significant increased risk of diabetes in association with occupational noise exposure (combined risk estimates: 1.16, 95% confidence interval [CI]: 0.97: 1.34; I² = 57.7%). Doing separate meta-analyses on cohort and rest of studies, we found similar findings (cohort studies (n = 3): combined risk estimate: 1.17; 95% CI: 0.84: 1.50; I² = 79%; cross-sectional studies (n = 8): combined risk estimate: 1.26; 95% CI: 0.93: 1.58; I² = 50.4%). We found no indication of publication bias.

CONCLUSIONS

The overall evidence on the association between occupational noise exposure and diabetes is heterogeneous, limited, and mostly with low quality. More robust studies in terms of population selection, exposure and outcome assessment, and adjustment for confounders are necessary.

[Tinnitus]

Tinnitus have different forms and it is possible to identify their origins in many cases. Even if tinnitus is not a kind experience, it is commonly not troublesome. But in some cases, it may become very annoying and lead to psychiatric disorders. Tinnitus is a frequent complaint at the medical office since 10% of the adult population is concerned. Their origin can be defined with different exams. Habituation is the key for therapy.

Investigating sonic injustice: A review of published research

Sound has been researched as either an environmental pollutant (noise) with detrimental health effects or an environmental resource with beneficial outcomes for well-being. We define sonic injustice as unjust inequalities in both noise exposure and access to high-quality, beneficial sound environments. We performed a comparative analysis of 34 peer-reviewed studies on sonic injustice. These studies were from Europe, North America, Accra and Hong Kong. We found suggestive evidence of a social inequality in noise exposure, particularly for low income and racial/ethnic groups. In contrast, children were often associated with an underexposure to noise. We did not find any studies on inequalities in access to beneficial sound environments, except for one study on quiet areas. As well, this review identifies trends in European and North American studies; discusses causal mechanisms for sonic inequalities; and presents avenues for future investigations into sonic injustice.

HMGB1 accumulation in cytoplasm mediates noise-induced cochlear damage

Damage-associated molecular pattern molecules (DAMPs) play a critical role in mediating cochlear cell death, which leads to noise-induced hearing loss (NIHL). High-mobility group box 1 (HMGB1), a prototypical DAMP released from cells, has been extensively studied in the context of various diseases. However, whether extracellular HMGB1 contributes to cochlear pathogenesis in NIHL and the potential signals initiating HMGB1 release from cochlear cells are not well understood. Here, through the transfection of the adeno-associated virus with HMGB1-HA-tag, we first investigated early cytoplasmic accumulation of HMGB1 in cochlear hair cells after noise exposure. We found that the cochlear administration of HMGB1-neutralizing antibody immediately after noise exposure significantly alleviated hearing loss and outer hair cells (OHCs) death induced by noise exposure. In addition, activation of signal transducer and activators of transcription 1 (STAT1) and cellular hyperacetylation were verified as potential canonical initiators of HMGB1 cytoplasmic accumulation. These findings reveal the adverse effects of extracellular HMGB1 on the cochlea and the potential signaling events mediating HMGB1 release in hair cells, indicating multiple potential pharmacotherapeutic targets for NIHL.

Comprehensive study of health effects of plasma technology occupational environment: Exposure to high frequency and intensity noise and toxic gases

OBJECTIVES

To evaluate on animal models the health effects of the combined or separate exposure to main chemical and physical hazards of plasma-based material processing technology environment.

MATERIALS AND METHODS

Male Wistar rats were exposed to actual levels of hazardous factors in plasma technology occupational environment: i.e., ozone and nitrogen oxides (O₃ and NO_x) in respective concentrations of 0.5 mg/m³ and 1.0 mg/m³ and high-frequency (1000-1600 Hz) of 112 dB intensity noise for 3 h/day, 5 days/week for 12 weeks, with a recovery period of 1 month.

RESULTS

Exposure to noise or its combination with chemical factors (ozone, nitrogen oxides) causes non-specific CNS changes testifying for significant excitation dominance, especially in the case of joint exposure. Histological examination of rats' brain in experimental revealed a pronounced increase in blood filling of small vessels on the tenth day of the experiment, with subsequent intensification of vascular alterations and eventually to cerebral edema. The exposure to noise significantly reduced total thymus, bone marrow and spleen cell numbers and these was also more pronounced under the joint impact of noise and toxic gases. Thymus, but not bone marrow or spleen, mitotic activity was as well reduced under the same modes of exposure. Cytological investigation of film preparations of subcutaneous connective tissue revealed that joint exposure led to microcirculatory disorders, increased number of dark mast cells and reduced degranulation processes indicative of increased autoregulatory processes effective at microvasculature level.

CONCLUSIONS

High-frequency and intensity noise is main stressor factor that has negative impact on CNS and immune system, morphology and functioning of hematopoietic organs (spleen, bone marrow, thymus) and connective tissue. Its negative impact is significantly potentiated by concurrent exposure to ozone and nitrogen oxide, while exposure only to these toxic gases has no significant effect on the above targets.

Binaural temporal coding and the middle ear muscle reflex in audiometrically normal young adults

Noise exposure may damage the synapses that connect inner hair cells with auditory nerve fibers, before outer hair cells are lost. In humans, this cochlear synaptopathy (CS) is thought to decrease the fidelity of peripheral auditory temporal coding. In the current study, the primary hypothesis was that higher middle ear muscle reflex (MEMR) thresholds, as a proxy measure of CS, would be associated with smaller values of the binaural intelligibility level difference (BILD). The BILD, which is a measure of binaural temporal coding, is defined here as the difference in thresholds between the diotic and the antiphasic versions of the digits in noise (DIN) test. This DIN BILD may control for factors unrelated to binaural temporal coding such as linguistic, central auditory, and cognitive factors. Fifty-six audiometrically normal adults (34 females) aged 18 - 30 were tested. The test battery included standard pure tone audiometry, tympanometry, MEMR using a 2 kHz elicitor and 226 Hz and 1 kHz probes, the Noise Exposure Structured Interview, forward digit span test, extended high frequency (EHF) audiometry, and diotic and antiphasic DIN tests. The study protocol was pre-registered prior to data collection. MEMR thresholds did not predict the DIN BILD. Secondary analyses showed no association between MEMR thresholds and the individual diotic and antiphasic DIN thresholds. Greater lifetime noise exposure was non-significantly associated with higher MEMR thresholds, larger DIN BILD values, and lower (better) antiphasic DIN thresholds, but not with diotic DIN thresholds, nor with EHF thresholds. EHF thresholds were associated with neither MEMR thresholds nor any of the DIN outcomes, including the DIN BILD. Results provide no evidence that young, audiometrically normal people incur CS with impacts on binaural temporal processing.

Vestibular Hypersensitivity in Patients with Chronic Noise Exposure

It has been demonstrated that high-intensity noise exposure adversely affects the human balance function. The Tullio phenomenon (TP) refers to sound-induced imbalance which is resulted from hypersensitivity of vestibular end organs to normal acoustic stimuli. Although different etiologies have been attributed to TP, evidence on the role of excessive noise exposure in the development of this symptom is limited. The present study aims to assess the vestibular functions in patients manifesting TP symptom who were exposed to long-term excessive noise levels. This was an analytic cross-sectional study conducted on 17 males diagnosed with TP with a history of chronic noise-induced hearing loss (TP group) and 17 healthy individuals. All subjects in both groups underwent complete otological, videonystagmography (VNG), and cervical vestibular myogenic potential (cVEMP) assessments. The most common complaint in TP subjects was vertigo and imbalance. During the VNG assessment, we found abnormal positional nystagmus and caloric irrigation (vestibular hyperfunction) results in 4 (23.53%) and 9 (52.94%) patients, respectively. Seven (41.17%) patients indicated cVEMP thresholds which were abnormally lower than the normal values ( ≤ 70 dB HL). However, when both VNG and cVEMP results were considered together, the abnormal rate reached 70.58% (12 of 17 cases). Our findings showed that both the semicircular canal as well as otolith stuctures could be affected in TP patients with a history of chronic noise exposure.

Establishing Healthy Lifestyle Choices Early: How to Counsel Children and Their Parents

Promoting childhood and adolescent health and long-term well-being requires an emphasis on preventative care and anticipatory guidance. In this review, the authors will focus on pertinent ear, nose, and throat preventative health in children, providing clinicians with relevant and succinct information to counsel children and their parents on the following essential subjects: foreign body aspiration and ingestion, upper respiratory infection prevention, noise exposure risks, aural hygiene, risks of primary and secondhand smoke exposure, and sleep hygiene.

Polycyclic aromatic hydrocarbon exposure and DNA oxidative damage of workers in workshops of a petrochemical group

The petrochemical industry has promoted the development of economy, while polycyclic aromatic hydrocarbons (PAHs) produced by the industry become the threat for environment and humans. Data on human occupational exposure in petrochemical industry are limited. In the present study, urinary hydroxylated PAH metabolites (OH-PAHs) and a biomarker of DNA oxidative damage (8-hydroxy-2'-deoxyguanosine (8-OHdG)) were measured in 546 workers of a petrochemical group in Northeast China, to investigate PAH exposure and related potential health risk. The concentrations of ∑₉OH-PAH in all workers were 0.25-175 μg/g Cre with a median value of 4.41 μg/g Cre. Metabolites of naphthalene were the predominant compounds. The levels of PAH metabolites were significantly different for workers with different jobs, which were the highest for recycling workers (13.7 μg/g Cre) and the lowest for agency managers (5.12 μg/g Cre). Besides, higher levels of OH-PAHs were usually found in males and older workers. There was a dose-response relationship between levels of 8-OHdG and ∑₉OH-PAHs (p < 0.01). No difference was observed in concentrations of 8-OHdG for workers of different gender or ages, work history as well as noise. Furthermore, workers simultaneously exposed to other potential pollutants and higher levels of ∑₉OH-PAH had significantly higher levels of 8-OHdG compared with those in the corresponding subgroups. Our results suggested that exposure to PAHs or co-exposure to PAHs and potential toxics in the petrochemical plant may cause DNA damage. We call for more researches on the associations among noise, chemical pollution and oxidative stress to workers in the real working environment.

A Bayesian network model to predict the role of hospital noise, annoyance, and sensitivity in quality of patient care

Background

Hospital noise can adversely impact nurses’ health, their cognitive function and emotion and in turn, influence the quality of patient care and patient safety. Thus, the aim of this study was to predict the contributing roles of exposure to hospital noise, staff noise-sensitivity and annoyance, on the quality of patient care.

Methods

This descriptive and cross-sectional study was carried out among nurses in an Iranian hospital. To determine nurses’ noise exposure level, the noise was measured in 1510 locations across the hospital in accordance with ISO 9612 standards using KIMO DB 300/2 sound level meter and analyzer. An online survey was used to collect nurses’ individual data. Study questionnaires included demographics, Weinstein noise sensitivity scale, noise annoyance scale, and quality of patient care scale. Finally, to analyze the data, Bayesian Networks (BNs), as probabilistic and graphical models, were used.

Results

For the high noise exposure state, high noise sensitivity, and high annoyance, with the probability of 100%, the probability of delivering a desirable quality of patient care decreased by 21, 14, and 23%, respectively. Moreover, at the concurrently high noise exposure and high noise sensitivity with the probability of 100%, the desirable quality of patient care decreased by 26%. The Bayesian most influence value was related to the association of noise exposure and annoyance (0.636). Moreover, annoyance had the highest association with the physical aspect of quality of care (0.400) and sensitivity had the greatest association with the communication aspect (0.283).

Conclusion

Annoyance induced from environmental noise and personal sensitivity affected the quality of patient care adversely. Moreover, noise and sensitivity had a separate direct adverse effect upon the quality of patient care, and their co-occurrence reduced the potential for delivering quality patient care.

Embryonic medial ganglionic eminence cells survive and integrate into the inferior colliculus of adult mice

Acoustic overexposure can lead to decreased inhibition in auditory centers, including the inferior colliculus (IC), and has been implicated in the development of central auditory pathologies. While systemic drugs that increase GABAergic transmission have been shown to provide symptomatic relief, their side effect profiles impose an upper-limit on the dose and duration of use. A treatment that locally increases inhibition in auditory nuclei could mitigate these side effects. One such approach could be transplantation of inhibitory precursor neurons derived from the medial ganglionic eminence (MGE). The present study investigated whether transplanted MGE cells can survive and integrate into the IC of non-noise exposed and noise exposed mice. MGE cells were harvested on embryonic days 12-14 and injected bilaterally into the IC of adult mice, with or without previous noise exposure. At one-week post transplantation, MGE cells possessed small, elongated soma and bipolar processes, characteristic of migrating cells. By 5 weeks, MGE cells exhibited a more mature morphology, with multiple branching processes and axons with boutons that stain positive for the vesicular GABA transporter (VGAT). The MGE survival rate after 14 weeks post transplantation was 1.7% in non-noise exposed subjects. MGE survival rate was not significantly affected by noise exposure (1.2%). In both groups the vast majority of transplanted MGE cells (>97%) expressed the vesicular GABA transporter. Furthermore, electronmicroscopic analysis indicated that transplanted MGE cells formed synapses with and received synaptic endings from host IC neurons. Acoustic stimulation lead to a significant increase in the percentage of endogenous inhibitory cells that express c-fos but had no effect on the percentage of c-fos expressing transplanted MGE cells. MGE cells were observed in the IC up to 22 weeks post transplantation, the longest time point investigated, suggesting long term survival and integration. These data provide the first evidence that transplantation of MGE cells is viable in the IC and provides a new strategy to explore treatment options for central hearing dysfunction following noise exposure.

Noise exposure and risk of myocardial infarction incidence and mortality: a dose-response meta-analysis

The strength and shape of the dose-response relationship between different types of noise and myocardial infarction (MI) remain unclear. Therefore, we aimed to summarize the evidence of the association between various types of noise and MI incidence and mortality through a dose-response meta-analysis. We performed a systematic search of the PubMed, Embase, and Web of Science databases up to December 19, 2021. The generalized least-squares method and restricted cubic splines were used to assess the potential linear and nonlinear dose-response relationships between noise exposure and the risk of MI events. Twenty observational studies with 34 reports met the eligibility criteria. In the linear models, the pooled relative risk and corresponding 95% confidence interval (CI) for MI incidence was 1.04 (95% CI: 1.02 - 1.05), and the MI mortality was 1.02 (95% CI: 1.02 - 1.03) for each 10 dB(A) increase in noise exposure. In addition, we observed an approximately J-shaped dose-response relationship between noise and MI mortality (P_nonlinearity = 0.0037), whereas the threshold for the statistical impact of noise on MI mortality may be 42 dB(A). Our findings support the notion that various types of noise exposure have a positive dose-response relationship with the risk of MI incidence and mortality.

A forskolin-loaded nanodelivery system prevents noise-induced hearing loss

Hearing loss is the most common sensory disorder worldwide and may result from age, drugs, or exposure to excessive noise. Crossing the blood-labyrinth barrier to achieve targeted drug delivery to the inner ear is key to the treatment of hearing loss. We designed a nanoparticle (NP)-based system for targeted drug delivery of forskolin (FSK) to the inner ear, driven by the prestin-targeting peptide LS19 ("ligand-receptor type interaction"). In vivo experiments in developing zebrafish embryos (4-96 h past fertilization) and mice confirmed that LS19-FSK specifically targeted and accumulated in zebrafish lateral line neuromasts and mouse outer hair cells (OHCs). LS19 peptide modification enabled LS19-FSK-NPs to rapidly target OHCs with high specificity. Furthermore, the multifunctional LS19-FSK-NPs were successfully delivered to the OHCs via the round window membrane route and exhibited slow-release properties. The sustained release and intracellular accumulation of FSK inhibited apoptosis of OHCs. Compared with LS19-NPs and FSK-NPs, LS19-FSK-NPs provided significantly stronger protection against noise-induced hearing damage, based on auditory brainstem responses at 4, 8, 16, and 32 kHz. Thus, our specially designed targeted nano-delivery system may serve as a basis for future clinical applications and treatment platforms and has the potential to significantly improve the treatment results of many inner ear diseases.

Annoyance due to residential road traffic and aircraft noise: Empirical evidence from two European cities

Based on a study in two European cities, Mainz in Germany and Zurich in Switzerland, the article investigates both acoustical and non-acoustical factors affecting indoor annoyance due to residential road traffic and aircraft noise. We specifically focus on three factors: (1) the role of windows as a feature of the building where people live; (2) the role of individual environmental concern as a general attitude; and (3) the role of household income as an indicator of socioeconomic resources. Empirical results show that closed windows in general and closed high-quality windows in particular are an important barrier against outdoor road traffic and aircraft noise, as well as a helpful subjective coping tool against corresponding annoyances. Environmental concern, too, proves to be a significant predictor of noise annoyance. Environmentally highly concerned people articulate feelings of annoyance more often than environmentally less concerned ones. As expected income is negatively related to road traffic noise annoyance. However, we find a positive association of income with annoyance from aircraft noise. Although objective exposure to aircraft noise is lower for high-income households, they feel stronger annoyed by noise from airplanes. Income shows various indirect effects on noise annoyance. A comparative analysis of road traffic and aircraft noise annoyance yields similarities, but also remarkable differences in terms of their influence factors.

Association between community noise and children's cognitive and behavioral development: A prospective cohort study

BACKGROUND

Noise exposure has been associated with adverse cognitive and behavioral outcomes in children, but evidence on longitudinal associations between community noise and child development in low- and middle-income countries is rare. We investigated associations between community noise and behavioral and cognitive development in preschool children in São Paulo.

METHODS

We linked child development data from the São Paulo Western Region Birth Cohort with average (Lden) and night-time (Lnight) community noise exposure at children's home, estimated by means of a land use regression model using various predictors (roads, schools, greenness, residential and informal settlements). Outcomes were the Strengths and Difficulties Questionnaire (SDQ) and Regional Project on Child Development Indicators (PRIDI) at 3 years of age and the Child Behavior Checklist (CBCL) and International Development and Early Learning Assessment (IDELA) at 6 years of age. We investigated the relationship between noise exposure and development using cross-sectional and longitudinal regression models.

RESULTS

Data from 3385 children at 3 years of age and 1546 children at 6 years of age were analysed. Mean Lden and Lnight levels were 70.3 dB and 61.2 dB, respectively. In cross-sectional analyses a 10 dB increase of Lden above 70 dB was associated with a 32% increase in the odds of borderline or abnormal SDQ total difficulties score (OR = 1.32, 95% CI: 1.04; 1.68) and 0.72 standard deviation (SD) increase in the CBCL total problems z-score (95% CI: 0.55; 0.88). No cross-sectional association was found for cognitive development. In longitudinal analyses, each 10 dB increase was associated with a 0.52 SD increase in behavioral problems (95% CI: 0.28; 0.77) and a 0.27 SD decrease in cognition (95%-CI: 0.55; 0.00). Results for Lnight above 60 dB were similar.

DISCUSSION

Our findings suggest that community noise exposure above Lden of 70 dB and Lnight of 60 dB may impair behavioral and cognitive development of preschool children.

Strain Comparison in Rats Differentiates Strain-Specific from More General Correlates of Noise-Induced Hearing Loss and Tinnitus

Experiments in rodent animal models help to reveal the characteristics and underlying mechanisms of pathologies related to hearing loss such as tinnitus or hyperacusis. However, a reliable understanding is still lacking. Here, four different rat strains (Sprague Dawley, Wistar, Long Evans, and Lister Hooded) underwent comparative analysis of electrophysiological (auditory brainstem responses, ABRs) and behavioral measures after noise trauma induction to differentiate between strain-dependent trauma effects and more consistent changes across strains, such as frequency dependence or systematic temporal changes. Several hearing- and trauma-related characteristics were clearly strain-dependent. Lister Hooded rats had especially high hearing thresholds and were unable to detect a silent gap in continuous background noise but displayed the highest startle amplitudes. After noise exposure, ABR thresholds revealed a strain-dependent pattern of recovery. ABR waveforms varied in detail among rat strains, and the difference was most prominent at later peaks arising approximately 3.7 ms after stimulus onset. However, changes in ABR waveforms after trauma were small compared to consistent strain-dependent differences between individual waveform components. At the behavioral level, startle-based gap-prepulse inhibition (gap-PPI) was used to evaluate the occurrence and characteristics of tinnitus after noise exposure. A loss of gap-PPI was found in 33% of Wistar, 50% of Sprague Dawley, and 75% of Long Evans rats. Across strains, the most consistent characteristic was a frequency-specific pattern of the loss of gap-PPI, with the highest rates at approximately one octave above trauma. An additional range exhibiting loss of gap-PPI directly below trauma frequency was revealed in Sprague Dawley and Long Evans rats. Further research should focus on these frequency ranges when investigating the underlying mechanisms of tinnitus induction.

Stress hormone biosynthesis-based genes and lifestyle moderated the association of noise exposure with blood pressure in a cohort of Chinese tobacco factory workers: A cross-sectional analysis

When evaluating noise-related cardiovascular risk, noise is generally solely assessed as the major stressor. However, cardiovascular effect of other simultaneous exposure events, such as unhealthy lifestyle and genetic variation, is easily neglected. The aim of this study is to estimate the combined effect of noise and lifestyle on blood pressure alteration, particularly under different genetic background. This study included 536 workers from a tobacco factory in Wuhan, China, who were divided into high exposure group and low exposure group according to noise measurement in their working area. All participants took annual physical examination and questionnaire survey to provide information on individual systolic and diastolic blood pressure (SBP and DBP) and lifestyle (smoking, drinking and physical activity). Single nucleotide polymorphism at genes related to stress hormone production were determined. Moderated moderation models were constructed to investigate the interaction effect of noise exposure and lifestyle factors on blood pressure with regard to different genetic background. We identified an expected trend in association between noise exposure and SBP among active smokers (P = 0.086). The moderated moderation analysis showed significant three-way interaction effect (COMT rs4680 × smoking status × noise exposure levels) on SBP or DBP (both P < 0.05). For COMT rs4680 GA+AA genotype carriers, active smoking significantly moderated the association between noise exposure and SBP or DBP (both P < 0.05). The results indicated that for COMT rs4680 A allele carriers, tobacco and noise exposure contribute collectively to blood pressure alteration, supporting that stress hormone production may play a certain role in the smoke-and-noise-induced cardiovascular effect.

miR-153/KCNQ4 axis contributes to noise-induced hearing loss in a mouse model

Damage to the cochlear sensory epithelium is a key contributor to noise-induced sensorineural hearing loss (SNHL). KCNQ4 plays an important role in the cochlear potassium circulation and outer hair cells survival. As miR-153 can target and regulate KCNQ4, we sought to study the role of miR-153 in SNHL. 12-week-old male CBA/J mice were exposed to 2-20 kHz broadband noise at 96 dB SPL to induce temporary threshold shifts and 101 dB SPL to induce permanent threshold shifts. Hearing loss was determined by auditory brainstem responses (ABR). Relative expression of miR-153 and KCNQ4 in mice cochlea were determined by Real-Time quantitative PCR. miR-153 mimics were co-transfected with wild type or mutated KCNQ4 into HEK293 cells. Luciferase reporter assay was used to validate the binding between miR-153 and KCNQ4. AAV-sp-153 was constructed and administrated intra-peritoneally 24- and 2-h prior and immediately after noise exposure to knockdown miR-153. The KCNQ4 is mainly expressed in outer hair cells (OHCs). We showed that the expression of KCNQ4 in mice cochlea was reduced and miR-153 expression was significantly increased after noise exposure compared to control. miR-153 bound to 3'UTR of KNCQ4, and the knockdown of miR-153 with the AAV-sp-153 administration restored KCNQ4 mRNA and protein expression. In addition, the knockdown of miR-153 reduced ABR threshold shifts at 8, 16, and 32 kHz after permanent threshold shifts (PTS) noise exposure. Correspondingly, OHC losses were attenuated with inhibition of miR-153. This study demonstrates that miR-153 inhibition significantly restores KNCQ4 in cochlea after noise exposure, which attenuates SNHL. Our study provides a new potential therapeutic target in the prevention and treatment of SNHL.

A neurobiological link between transportation noise exposure and metabolic disease in humans

BACKGROUND

Chronic transportation noise exposure associates with cardiovascular events through a link involving heightened stress-associated neurobiological activity (as amygdalar metabolic activity, AmygA) on ¹⁸F-fluorodeoxyglucose positron emission tomography/computed tomography (¹⁸F-FDG-PET/CT). Increased AmygA also associates with greater visceral adipose tissue (VAT) and type 2 diabetes mellitus (DM). While relationships between noise exposure and VAT and DM have been reported, the underlying mechanisms remain incompletely understood. We tested whether: (1) transportation noise exposure associates with greater (a) baseline and gains in VAT and (b) DM risk, and (2) heightened AmygA partially mediates the link between noise exposure and these metabolic diseases.

METHODS

VAT was measured in a retrospective cohort (N = 403) who underwent clinical ¹⁸F-FDG-PET/CT. AmygA was measured in those with brain imaging (N = 238). Follow-up VAT was remeasured on available imaging (N = 67). Among individuals (N = 224) without baseline DM, incident DM was adjudicated over 2 years from clinical records. Noise (24-h average) was modeled at each individual's home address. Linear regression, survival, and mediation analyses were employed.

RESULTS

Higher noise exposure (upper tertile vs. others) associated with greater: baseline VAT (standardized β [95% confidence interval (CI)]= 0.230 [0.021, 0.438], p = 0.031), gains in VAT (0.686 [0.185, 1.187], p = 0.008 adjusted for baseline VAT), and DM (hazard ratio [95% CI]=2.429 [1.031, 5.719], p = 0.042). The paths of: ↑noise exposure→↑AmygA→↑baseline VAT and ↑noise exposure→↑AmygA→↑subsequent DM were significant (p < 0.05).

CONCLUSIONS

Increased transportation noise exposure associates with greater VAT and DM. This relationship is partially mediated by stress-associated neurobiological activity. These findings suggest altered neurobiology contributes to noise exposure's link to metabolic diseases.

Land use regression modelling of community noise in São Paulo, Brazil

Noise pollution has negative health consequences, which becomes increasingly relevant with rapid urbanization. In low- and middle-income countries research on health effects of noise is hampered by scarce exposure data and noise maps. In this study, we developed land use regression (LUR) models to assess spatial variability of community noise in the Western Region of São Paulo, Brazil.We measured outdoor noise levels continuously at 42 homes once or twice for one week in the summer and the winter season. These measurements were integrated with various geographic information system variables to develop LUR models for predicting average A-weighted (dB(A)) day-evening-night equivalent sound levels (L_den) and night sound levels (L_night). A supervised mixed linear regression analysis was conducted to test potential noise predictors for various buffer sizes and distances between home and noise source. Noise exposure levels in the study area were high with a site average L_den of 69.3 dB(A) ranging from 60.3 to 82.3 dB(A), and a site average L_night of 59.9 dB(A) ranging from 50.7 to 76.6 dB(A). LUR models had a good fit with a R² of 0.56 for L_den and 0.63 for L_night in a leave-one-site-out cross validation. Main predictors of noise were the inverse distance to medium roads, count of educational facilities within a 400 m buffer, mean Normalized Difference Vegetation Index (NDVI) within a 100 m buffer, residential areas within a 50 m (L_den) or 25 m (L_night) buffer and slum areas within a 400 m buffer. Our study suggests that LUR modelling with geographic predictor data is a promising and efficient approach for noise exposure assessment in low- and middle-income countries, where noise maps are not available.

The influence of developmental noise exposure on the temporal processing of acoustical signals in the auditory cortex of rats

Previous experiments have acknowledged that inappropriate or missing auditory inputs during the critical period of development cause permanent changes of the structure and function of the auditory system (Bures et al., 2017). We explore in this study how developmental noise exposure influences the coding of temporally structured stimuli in the neurons of the primary auditory cortex (AC) in Long Evans rats. The animals were exposed on postnatal day 14 (P14) for 12 minutes to a loud (125 dB SPL) broad-band noise. The responses to an amplitude-modulated (AM) noise, frequency-modulated (FM) tones, and click trains, were recorded from the right AC of rats of two age groups: young-adult (ca. 6 months old) and adult (ca. 2 years old), both in the exposed animals and in control unexposed rats. The neonatal exposure resulted in a higher synchronization ability (phase-locking) of the AC neurons for all three stimuli; furthermore, the similarity of neuronal response patterns to repetitive stimulation was higher in the exposed rats. On the other hand, the exposed animals showed a steeper decline of modulation-transfer functions towards higher modulation frequencies/repetition rates. Differences between the two age groups were also apparent; in general, aging had qualitatively the same effect as the developmental exposure. The current results demonstrate that brief noise exposure during the maturation of the auditory system influences both the temporal and the rate coding of periodically modulated sounds in the AC of rats; the changes are permanent and observable up to late adulthood.

Low-sound-level auditory processing in noise-exposed adults

Early signs of noise-induced hearing damage are difficult to identify, as they are often confounded by factors such as age, audiometric thresholds, or even music experience. Much previous research has focused on deficits observed at high intensity levels. In contrast, the present study was designed to test the hypothesis that noise exposure causes a degradation in low-sound-level auditory processing in humans, as a consequence of dysfunction of the inner hair cell pathway. Frequency difference limens (FDLs) and amplitude modulation depth discrimination (MDD) were measured for five center frequencies (0.75, 1, 3, 4 and 6 kHz) at 15 and 25 dB sensation level (SL), as a function of noise exposure, age, audiometric hearing loss, and music experience. Forty participants, aged 33-75 years, with normal hearing up to 1 kHz and mild-to-moderate hearing loss above 2 kHz, were tested. Participants had varying degrees of self-reported noise exposure, and varied in music experience. FDL worsened as a function of age. Participants with music experience outperformed the non-experienced in both the FDL and MDD tasks. MDD thresholds were significantly better for high-noise-exposed, than for low-noise-exposed, participants at 25 dB SL, particularly at 6 kHz. No effects of age or hearing loss were observed in the MDD. It is possible that the association between MDD thresholds and noise exposure was not causal, but instead was mediated by other factors that were not measured in the study. The association is consistent, qualitatively, with a hypothesized loss of compression due to outer hair cell dysfunction.

Hazardous sound outputs of white noise devices intended for infants

OBJECTIVES

To measure the sound intensity of popular infant white noise machines and Apple iPhone applications (apps) as they vary with volume setting and distance, and compare these output levels with current National Institute for Occupational Safety and Health (NIOSH) noise exposure threshold recommendations.

METHODS

A total of eight infant white noise machines and six iPhone applications were included in the study based on product rating, number of ratings, and cost. The NIOSH Sound Level Meter application through the Apple App Store was used to measure output levels in A-weighted decibels (dBA). Each device was tested at its lowest and highest volume setting and at speaker-to-microphone distances simulating placement within a crib (10 cm), just outside of a crib rail (30 cm), and on a nightstand across the room (100 cm).

RESULTS

At the minimum volume setting, no device exceeded the NIOSH recommended noise exposure threshold of 85 dBA at any distance tested. At maximum volume setting, nine out of fourteen (64.3%) devices exceeded output levels of 85 dBA at a speaker-to-microphone distance of 10 cm. No device exceeded the recommended threshold at its maximal volume when placed 30 cm or 100 cm away.

CONCLUSION

Excessive white noise exposure has the potential to lead to noise-induced hearing loss and other adverse health effects in the neonatal and infant population. We recommend conservative use of white noise machines and apps by avoiding maximal volume setting and placing any device well outside of the crib or at least 30 cm away from the child. To promote safe use of white noise devices, future studies are needed to fully understand the association between early noise exposure and hearing loss in infants.

A community noise survey in Southwest Detroit and the value of supplemental metrics for truck noise

Noise exposure can affect sleep, health and cognitive performance, and it disproportionately affects communities of color. This study has the objective of evaluating both conventional and supplemental noise metrics in a community noise survey examining Southwest Detroit, Michigan, a densely populated and industrialized area with extensive truck traffic on residential streets. Sound pressure level (SPL) monitors were deployed at 21 residential sites within 900 m of a major interstate highway. With assistance from youth volunteers, continuous SPL measurements were obtained for 1.5-7 days at each site, and short-term vehicle counts on local roads were recorded. We calculated conventional noise metrics, including the day-evening-night average sound level L_DEN and the 90th percentile 1-hr maximum L₁₀(h), and evaluated the effect of distance from highways, traffic volume, time-of-day, and other factors. Supplemental metrics potentially appropriate for intermittent traffic noise were calculated, including fraction of time over specific SPL thresholds using a new metric called F_DEN, which is the fraction of time over 60, 65 and 70 dB during night, evening and daytime periods, respectively, and a peak noise metric called L_2P(h), which utilizes the 98th percentile SPL within time blocks to increase robustness. The conventional metrics indicated five sites that exceeded 70 dB, and the highest noise levels were found within ~50 m of truck routes, arterials and freeway ramps. The estimated impact of truck traffic ranged up to 17 dB for hourly averages and to 33 dB for 1-s peaks. The conventional metrics did not always capture short-term noise exposures, which may be especially important to annoyance and sleep issues. In addition to showing widespread exposure to traffic noise in the study community that warrants consideration of noise abatement strategies, the study demonstrates the benefits of supplemental noise metrics and community engagement in noise assessment.

Correlations between cochlear pathophysiology and behavioral measures of temporal and spatial processing in noise exposed macaques

Noise-induced hearing loss (NIHL) is known to have significant consequences for temporal, spectral, and spatial resolution. However, much remains to be discovered about their underlying pathophysiology. This report extends the recent development of a nonhuman primate model of NIHL to explore its consequences for hearing in noisy environments, and its correlations with the underlying cochlear pathology. Ten macaques (seven with normal-hearing, three with NIHL) were used in studies of masked tone detection in which the temporal or spatial properties of the masker were varied to assess metrics of temporal and spatial processing. Normal-hearing (NH) macaques showed lower tone detection thresholds for sinusoidally amplitude modulated (SAM) broadband noise maskers relative to unmodulated maskers (modulation masking release, MMR). Tone detection thresholds were lowest at low noise modulation frequencies, and increased as modulation frequency increased, until they matched threshold in unmodulated noise. NH macaques also showed lower tone detection thresholds for spatially separated tone and noise relative to co-localized tone and noise (spatial release from masking, SRM). Noise exposure caused permanent threshold shifts that were verified behaviorally and audiologically. In hearing-impaired (HI) macaques, MMR was reduced at tone frequencies above that of the noise exposure. HI macaques also showed degraded SRM, with no SRM observed across all tested tone frequencies. Deficits in MMR correlated with audiometric threshold changes, outer hair cell loss, and synapse loss, while the differences in SRM did not correlate with audiometric changes, or any measure of cochlear pathophysiology. This difference in anatomical-behavioral correlations suggests that while many behavioral deficits may arise from cochlear pathology, only some are predictable from the frequency place of damage in the cochlea.

Tinnitus characteristics at high-and low-risk occupations from occupational noise exposure standpoint

INTRODUCTION

The aim of the present study was to compare tinnitus characteristics in high- and low-risk occupations from the occupational noise exposure standpoint, considering demographic data, hearing loss and concomitant diseases.

METHODS

Demographic data, characteristics of tinnitus, hearing and concomitant diseases were recorded in the questionnaires. Their pure tone air conduction thresholds were determined using a double-channel diagnostic Audiometer and the Bone Conduction was assessed using a B-71 bone vibrator.

RESULTS

Totally, 6.3% subjects (6.8% high-risk group and 5.6% low-risk group) had subjective tinnitus, mainly as whistling sound. In the high-risk group, tinnitus was mainly left-sided (41.18%) and hearing loss was mild. Bilateral tinnitus (52.63%) and slight hearing loss were observed predominantly in the low-risk group.

CONCLUSIONS

The study showed higher incidence of tinnitus in high-risk professions regarding with occupational noise exposure.

Impact of a visual indicator on the noise level in an emergency medical dispatch centre - a pilot study

BACKGROUND

Noise levels are monitored in call centres. A maximum of 52 to 55 dB(A) is recommended in order to prevent adverse events. We aimed at assessing the noise level and the impact of a visual noise indicator on the ambient noise level in a French Regional Emergency Medical Dispatch Centre (EMDC).

METHODS

We conducted an observational study in the EMDC of the SAMU25 (University Hospital of Besancon). We measured the noise level using a SoundEarII® noise indicator (Dräger Medical SAS, France). The measurement took place in two phases on three consecutive days from 00:00 to 11:59 PM. At baseline, phase 1, the device recorded the average ambient noise for each minute without visual indication. Secondly, phase 2 included a sensor mounted with a light that would turn on green if noise was below 65 dB(A), orange if noise ever exceeded 65 and red if it exceeded 75 dB(A).

RESULTS

In the presence of the visual noise indicator, the L_Aeq was significantly lower than in the absence of visual noise indicator (a mean difference of - 4.19 dB; P < 10^-3). It was higher than 55 dB(A) in 84.9 and 43.9% of the time in phases 1 and 2, respectively.

CONCLUSIONS

The noise levels were frequently higher than the standards, and sometimes close to recommended limits, requiring preventive measures. The noise indicator had a positive effect on the ambient noise level. This work will allow the implementation of effective prevention solutions and, based on future assessments, could improve operators' well-being and better care for patient.

Age-related and noise-induced hearing loss alters grasshopper mouse (Onychomys) vocalizations

Age-related and noise-induced hearing loss disorders are among the most common pathologies affecting Americans across their lifespans. Loss of auditory feedback due to hearing disorders is correlated with changes in voice and speech-motor control in humans. Although rodents are increasingly used to model human age- and noise-induced hearing loss, few studies have assessed vocal changes after acoustic trauma. Northern grasshopper mice (Onychomys leucogaster) represent a candidate model because their hearing sensitivity is matched to the frequencies of long-distance vocalizations that are produced using vocal fold vibrations similar to human speech. In this study, we quantified changes in auditory brainstem responses (ABRs) and vocalizations related to aging and noise-induced acoustic trauma. Mice showed a progressive decrease in hearing sensitivity across 4-32 kHz, with males losing hearing more rapidly than females. In addition, noise-exposed mice had a 61.55 dB SPL decrease in ABR sensitivity following a noise exposure, with some individuals exhibiting a 21.25 dB recovery 300-330 days after noise exposure. We also found that older grasshopper mice produced calls with lower fundamental frequency. Sex differences were measured in duration of calls with females producing longer calls with age. Our findings indicate that grasshopper mice experience age- and noise- induced hearing loss and concomitant changes in vocal output, making them a promising model for hearing and communication disorders.

Long-term exposure to traffic noise and mortality: A systematic review and meta-analysis of epidemiological evidence between 2000 and 2020

We aimed to update the evidence-base of long-term noise exposures from road, rail, and aircraft traffic on both non-accidental and cardiovascular mortality. A systematic review and meta-analysis were conducted following PRISMA guidelines. The literature was searched using PubMed, Scopus, Web of Science, and EMBASE for the period between January 01, 2000 and October 05, 2020. 13 studies were selected for final review. The risk of bias and overall quality of evidence was evaluated using a pre-defined list of criteria. Risk estimates from each study were converted into per 10 dB higher of L_den for each traffic source. Inverse-Variance heterogeneity (I-Vhet) meta-analysis was used to pool these individual risk estimates, along with assessment of heterogeneity and publication bias. Sensitivity analyses include using random-effect model and leave-one-out meta-analysis. Subgroup analyses by study design and noise exposure assessment were conducted to explore potential sources of heterogeneity. For road traffic, the pooled relative risk (RR) per 10 dB higher L_den for mortality from non-accidental causes was 1.01 (95% CI: 0.98, 1.05) (5 studies, I² = 78%), CVD was 1.01 (95% CI: 0.98, 1.05) (5 studies, I² = 41%), ischemic heart disease (IHD) was 1.03 (95% CI: 0.99, 1.08) (7 studies, I² = 46%), and stroke was 1.05 (95% CI: 0.97, 1.14) (5 studies, I² = 62%). The overall quality of evidence for most meta-analyses was rated as very low to low, except for CVD or IHD mortality, for which the quality of evidence was rated as moderate. A possible threshold of 53 dB was visually suggested for CVD-related mortality from road traffic noise in the trend analysis. For aircraft noise, pooled estimates were based on fewer studies and varied by mortality outcomes. Evidence of long-term exposure to traffic noise on mortality remains weak except the association between road traffic noise and IHD mortality. High-quality longitudinal studies are required to better characterise mortality effects of traffic noise.

Noise exposure assessment of occupational health and safety (OHS) consultants: A preliminary study

No published noise exposure assessment of occupational health and safety (OHS) consultants exists. An assessment was performed to quantify the noise level of OHS consultants while they were on site at a client's facility. OHS consultants wore a dosimeter set to A-weighting, slow response, 60 s log interval and a criterion level of 85dBA with a 3 dB exchange rate. Both the projected time-weighted average (TWA) and projected dose were recorded. Of the 32 noise assessments collected, three had projected TWAs that exceeded the occupational exposure limit of 85 dBA. Nearly 75% of the projected TWA measurements were equal or greater than the Action Level of 80 dBA. According to best practices, occupational noise levels greater than 80 dBA present a risk for noise-induced hearing loss and, therefore, a hearing loss prevention program should be implemented.

Changes in audiometric threshold and frequency selectivity correlate with cochlear histopathology in macaque monkeys with permanent noise-induced hearing loss

Exposure to loud noise causes damage to the inner ear, including but not limited to outer and inner hair cells (OHCs and IHCs) and IHC ribbon synapses. This cochlear damage impairs auditory processing and increases audiometric thresholds (noise-induced hearing loss, NIHL). However, the exact relationship between the perceptual consequences of NIHL and its underlying cochlear pathology are poorly understood. This study used a nonhuman primate model of NIHL to relate changes in frequency selectivity and audiometric thresholds to indices of cochlear histopathology. Three macaques (one Macaca mulatta and two Macaca radiata) were trained to detect tones in quiet and in noises that were spectrally notched around the tone frequency. Audiograms were derived from tone thresholds in quiet; perceptual auditory filters were derived from tone thresholds in notched-noise maskers using the rounded-exponential fit. Data were obtained before and after a four-hour exposure to a 50-Hz noise centered at 2 kHz at 141 or 146 dB SPL. Noise exposure caused permanent audiometric threshold shifts and broadening of auditory filters at and above 2 kHz, with greater changes observed for the 146-dB-exposed monkeys. The normalized bandwidth of the perceptual auditory filters was strongly correlated with audiometric threshold at each tone frequency. While changes in audiometric threshold and perceptual auditory filter widths were primarily determined by the extent of OHC survival, additional variability was explained by including interactions among OHC, IHC, and ribbon synapse survival. This is the first study to provide within-subject comparisons of auditory filter bandwidths in an animal model of NIHL and correlate these NIHL-related perceptual changes with cochlear histopathology. These results expand the foundations for ongoing investigations of the neural correlates of NIHL-related perceptual changes.

Assessment of low-frequency noise from wind turbines under different weather conditions

BACKGROUND

Low-frequency (20-200 Hz) noise (LFN) from wind turbines has received much public attention due to potential health concerns. This work tries to estimate the sound power level of wind turbines (L _W,A (dB)) at 20-200 Hz, which are not provided by manufacturers but essential for estimating LFN exposure (L _Aeq) of nearby residents.

METHODS

L _W,A at 20-200 Hz at three wind farms, each with a different brand of wind turbine (Brands A, B and C, respectively) were estimated using propagation model ISO 9613-2 under different weather conditions (rain, wind speed and wind direction) and validated with LFN monitoring data. The feasibility of using validated L _W,A as inputs for ISO 9613-2 to simulate residents' exposure (L _Aeq) to LFN were assessed considering interferences from rain, wind speed and wind directions.

RESULTS

The average L _W,A at 20-200 Hz ranged between 93.2 and 100.4 dB, 97.8 and 107.2 dB, and 96.5 and 110.4 dB for turbines of Brands A, B, and C, respectively, operating under wind speeds from 2 to 12 m/s. The L _W,A at wind speed of 2-8 m/s increased on average by 1.4, 1.9 and 1.7 dB per 1 m/s increase for Brands A, B and C, respectively. The differences in modeled L_eq obtained through the input of L _W,A into the ISO 9613-2 model and the measured L _Aeq for the three studied wind farms all fall within 1.5 dB.

CONCLUSION

This study successfully determined and validated the L _W,A of wind turbines of three brands, and subsequent residents' LFN exposure (with 1.5 dB difference) at three wind farms. Accurately obtaining LFN exposure will serve as the basis for assessing LFN exposure-health relationship. As wind power widely use worldwide, health impact should be assessed based on validated LFN exposure assessment.

Association between noise exposure and diabetes: meta-analysis

Diabetes is one of the typical chronic diseases, and its incidence is related to many environmental factors. At present, there is no radical cure for diabetes, so the prevention of diabetes is particularly important. In order to effectively prevent the occurrence of diabetes, it is necessary to understand the conditions leading to the occurrence of diabetes. Current studies have shown that long-term exposure to noise will increase the risk of diabetes. Literature was retrieved from Pubmed and Web of Science. The relationship between noise exposure and diabetes published in the past 10 years was retrieved from the literature. Two researchers screened the literatures and extracted the data according to the inclusion and exclusion criteria. Endnote software was used to manage the literature, and NOS (Newcastle-Ottawa Scale) scale was used to evaluate the quality of the included literatures. Random effects meta-analysis was used to comprehensively evaluate the noise exposure of diabetic patients, and stata13.1 was used for data analysis. After adherence to strict inclusion and exclusion criteria, eight studies on the association between noise and diabetes were selected, including five cohort studies and three cross-sectional studies, with a total of 514,570 participants and 23,708 diabetics. The results showed that exposure to noise increased the risk of developing diabetes (OR = 1.08; 95% CI = 1.03 ~ 1.12). From the analysis of these selected articles, it can be seen that there is a positive correlation between noise and the occurrence of diabetes. As a result, it is necessary to strengthen routine blood tests for people who have been exposed to noise for a long time, especially those who have to be exposed to noise due to their occupations.

An intracochlear DP-gram: Proof of principle in noise-damaged rabbits

Distortion-product otoacoustic emissions (DPOAEs) can be used to assess cochlear damage and are often evaluated by generating a DP-gram in which 2f₁-f₂ DPOAE levels are plotted as a function of the higher-frequency primary at f₂. DPOAEs are derived from the reverse propagation of distortion-product (DP) wavelets from their intracochlear sites of generation to emerge as measurable acoustic signals in the outer ear canal. However, at least, some of these same wavelets also propagate within the cochlea in the normal forward direction to the DP-frequency (f_dp) place, where they appear as intracochlear distortion products (iDPs). Depending on several factors, especially, the extent to which DP wavelets add or cancel with each other in phase, one might expect iDPs to differ from DPOAEs in their ability to map the frequency pattern of cochlear damage. In the present study, the behavior of 2f₁-f₂ iDPs was inferred by interacting a probe tone (f₃) with the iDP of interest to produce a 'secondary' DPOAE (i.e., DPOAE^2ry), which was then used to infer the level of 2f₁-f₂ iDPs as a function of the f₂-test frequency, thus, constituting a newly developed iDP-gram. To determine the feasibility of and potential applications for the iDP-gram procedure, noise-induced cochlear damage was assessed in two 'test' rabbits, one of which exhibited a well-defined punctate loss in their DP-gram, while the other exhibited a broader V-shaped loss. To validate the iDP-gram procedure, standard DP-grams were simultaneously collected and compared to their iDP-gram counterparts. Cochlear damage was independently assessed using auditory brainstem responses (ABRs) describing threshold-shift patterns to which both DP-gram types could be compared. Each DP-gram variety, to some extent, was able to detect a punctate loss in one rabbit and a broader V-shaped loss in the other. For the punctate-loss subject, the standard DP-gram showed a more generalized loss across test frequencies, while iDP-grams showed several localized notches superimposed on the generalized-loss pattern. In general, for the V-shaped loss pattern, both DP-gram types performed very well at detecting the large loss, with the lower primary-tone levels being most sensitive. At the narrow primary-tone ratios of f₂/f₁=1.05, standard DP-grams were unable to detect either loss pattern, while for the punctate loss, they paradoxically showed enhancement. Notably, the simultaneously collected iDP-grams performed favorably at the narrow-ratio setting, which is consistent with the notion that DPs travelling toward the 2f₁-f₂ f_dp place are not subject to the cancellation of wavelets typical for narrow primary-ratio conditions that can confound measures of DPs moving towards the ear canal to emerge as DPOAEs.