Occupational noise-induced hearing loss in China: a systematic review and meta-analysis

Comparison of Occupational Noise Exposure Assessment Methods: A Systematic Review

OBJECTIVES

The purpose of this systematic review of publications was to evaluate existing evidence on the accuracy and precision of alternative occupational noise assessment methods, with personal noise dosimetry as the reference.

DESIGN

A structured literature search was performed in Ovid MEDLINE(R) and Embase in July 2021 and 2022. The Covidence software was used for importing articles, screening titles and abstracts, full-text review, and study selection. Two reviewers independently conducted the title, abstract, and full-text screening of eligible studies. The reporting of this systematic review was guided by the recommendations of the Preferred Reporting Items for Systematic Review and Meta-Analysis (PRISMA) statement. The quality of selected articles was assessed using the Joanna Briggs Institute checklist for analytical cross-sectional studies.

RESULTS

In total, 11 studies consistent with the study selection criteria were identified out of 327 articles from the initial search. The noise-measurement methods identified in the selected studies included subjective rating through a questionnaire, expert opinion, smartwatch, sound level meter, sound level meter combined with a radio-frequency identification system, smart devices, workgroup dosimetry sampling, task-based measurement (TBM), and hybrid TBM. The hybrid method (a combination of task-based, subjective rating, and trade mean measurements) was the best alternative to full-shift personal noise-dosimetry with a negligible bias of 0.1 dB, precision of 2.4 dBA, and accuracy of 2.4 dBA.

CONCLUSION

A variety of lower-cost TBM methods had relatively high accuracy and precision levels comparable to personal dosimetry. These findings are particularly relevant for low-income countries where occupational noise measurements should be obtained with minimal work disruptions and costs. However, it should also be noted that TBMs are greatly affected by job variation, multiple tasks, or mobile tasks.

An exploration of biomarkers for noise exposure: mitochondrial DNA copy number and micronucleus frequencies in Chinese workers

Few studies have been conducted that use biomarkers as early warning signals for noise-associated health hazards. To explore potentially effective biomarkers for noise-exposed populations, we recruited 218 noise-exposed male workers in China. We calculated cumulative noise exposure (CNE) through noise intensity and noise-exposed duration. When the model was fully adjusted, ln-transformed relative mitochondrial DNA copy number (mtDNAcn) decreased by 0.014 (95% confidence interval (CI): -0.026, -0.003) units with each 1 dB(A)∙year increase in CNE levels. CNE was further included in the model as a grouping variable, and the results showed a negative dose-effect relationship between relative mtDNAcn and CNE (P-trend = 0.045). However, we did not find a correlation between CNE and micronucleus (MN) frequencies. Our findings suggest that CNE in workers was associated with a decrease in relative mtDNAcn which may provide a potential biomarker for noise and for certain health risk but not with MN frequencies.

Effects of cooking with solid fuel on hearing loss in Chinese adults-Based on two cohort studies

The association between cooking fuel and hearing loss still needs more research to clarify, and two longitudinal cohort studies were explored to find if solid fuel use for cooking affected hearing in Chinese adults. The data from Chinese Health and Retirement Longitudinal Survey (CHARLS) and Chinese Longitudinal Healthy Longevity Survey (CLHLS) were analyzed. Participants (older than 18) without hearing loss at baseline and follow-up visits were included, which were divided into clean fuel and solid fuel groups. Hearing loss rate was from follow-up visits (both in year 2011) until the recent one (year 2018 in CHARLS and 2019 in CLHLS). Cox regressions were applied to examine the associations with adjustment for potential confounders. Fixed-effect meta-analysis was used to pool the results. A total of 9049 participants (average age 8.34 ± 9.12 [mean ± SD] years; 4247 [46.93%] males) were included in CHARLS cohort study and 2265 participants (average age, 78.75 ± 9.23 [mean ± SD] years; 1148 [49.32%] males) in CLHLS cohort study. There were 1518 (16.78%) participants in CHARLS cohort and 451 (19.91%) participants in CLHLS cohort who developed hearing loss. The group of using solid fuel for cooking had a higher risk of hearing loss (CHARLS: HR, 1.16; 95% CI 1.03-1.30; CLHLS: HR, 1.43; 95% CI 1.11-1.84) compared with the one of using clean fuel. Pooled hazard ratio showed the incidence of hearing loss in the solid fuel users was 1.17 (1.03, 1.29) times higher than that of clean fuel users. Hearing loss was associated with solid fuel use and older people were at higher risk. It is advised to replace solid fuel by clean fuel that may promote health equity.

Association between occupational noise exposure level and pure-tone audiometry abnormalities among Metropolitan Manila Development Authority employees: A cross-sectional study

Traffic enforcers are exposed to various occupational health and safety hazards, including noise pollution, which may lead to occupational hearing loss. This cross-sectional study aimed to estimate the prevalence of hearing loss and to assess the relationship between occupational noise exposure level (ONEL) and abnormalities in air conduction thresholds among Metropolitan Manila Development Authority (MMDA) employees along Epifanio delos Santos Avenue, Philippines. Eight-hour ONELs were measured among 108 participants working with greater than 5 years of service. Participants had hearing evaluations using pure tone audiometry (PTA) to calculate the prevalence of hearing loss. Generalized linear models with a Poisson distribution were fitted to estimate the association between ONEL and audiologic abnormalities, controlling for confounding factors. Approximately 16% of employees had hearing loss. The prevalence of hearing loss was higher with ONEL exposures greater than 85 A-weighted decibels (dBA), with traffic enforcers exposed to higher ONELs than office workers. ONELs greater than 85 dBA were related to audiologic abnormalities at different frequencies in PTA. The prevalence of audiologic abnormalities at 4000 Hz and 6000 Hz was 48% higher (adjusted prevalence ratio [aPR], 1.48; 95% CI, 1.12-1.96) and 25% higher (aPR, 1.25; 95% CI, 1.00-1.55), respectively, among participants with ONELs greater than 85 dBA than with ONELs less than or equal to 85 dBA. Participants exposed to ONELs greater than 85 dBA, more likely traffic enforcers, may have increased risk of audiologic abnormalities. Regular ONEL monitoring is warranted for occupational risk assessment of traffic enforcers. A hearing conservation program may need to be considered for this population. Additional studies are needed to determine trends in hearing deterioration among traffic enforcers.

Influence of Different Noise Types on Hearing Function in Patients Treated for Mild Otitis Media

BACKGROUND

Otitis media (OM) refers to a common clinical ear disease. Noise seriously damages human hearing function. This study aimed to investigate the effects of various noise types on the hearing function of patients who have recovered from mild OM.

MATERIALS AND METHODS

A total of 160 patients with mild OM treated at our hospital from May 2020 to May 2023 were retrospectively selected for this study. Based on clinical data, the patients were divided into the non-noise group (n = 80) and the noise (n = 80) group. The hearing thresholds of the two groups were compared across various noise types at 500, 1000, and 2000 Hz. In addition, the hearing thresholds of the noise group were compared under the same conditions.

RESULTS

The noise group exhibited significantly higher hearing thresholds at 500, 1000, and 2000 Hz than the non-noise group (P < 0.05). Under traffic, urban construction, and industrial noises, the auditory thresholds at 500, 1000, and 2000 Hz in the noise group were significantly higher than those observed under domestic and speech noises (P < 0.05).

CONCLUSION

Noise shows a close relationship with the hearing function of patients with OM. Traffic, urban construction, and industrial noises greatly influence the hearing function of patients who have recovered from mild OM.

Causal relationship between psychiatric disorders and sensorineural hearing loss: A bidirectional two-sample mendelian randomization analysis

OBJECTIVE

This study employed bidirectional two-sample Mendelian randomization (MR) to investigate the causal links between psychiatric disorders and sensorineural hearing loss (SNHL).

METHODS

Instrumental variables were chosen from genome-wide association studies of schizophrenia (SCH, N = 127,906), bipolar disorder (BD, N = 51,710), major depressive disorder (MDD, N = 500,199), and SNHL (N = 212,544). In the univariable MR analysis, the inverse-variance weighted method (IVW) was conducted as the primary analysis, complemented by various sensitivity analyses to ensure result robustness.

RESULTS

SCH exhibited a decreased the risk of SNHL (OR = 0.949, P = 0.005), whereas BD showed an increased incidence of SNHL (OR = 1.145, P = 0.005). No causal association was found for MDD on SNHL (OR = 1.088, P = 0.246). Multivariable MR validated these results. In the reverse direction, genetically predicted SNHL was linked to a decreased risk of SCH with suggestive significance (OR = 0.912, P = 0.023). No reverse causal relationships were observed for SNHL influencing BD or MDD. These findings remained consistent across various MR methods and sensitivity analyses.

CONCLUSION

This study demonstrated that the causal relationships between diverse psychiatric disorders with SNHL were heterogeneous. Specifically, SCH was inversely associated with SNHL susceptibility, and similarly, a reduced risk of SNHL was observed in schizophrenia patients. In contrast, BD exhibited an increased incidence of SNHL, although SNHL did not influence the prevalence of BD. No causal association between MDD and SNHL was found.

Occupational noise and hypertension in Southern Chinese workers: a large occupational population-based study

INTRODUCTION

An increasing number of original studies suggested that occupational noise exposure might be associated with the risk of hypertension, but the results remain inconsistent and inconclusive. In addition, the attributable fraction (AF) of occupational noise exposure has not been well quantified. We aimed to conduct a large-scale occupational population-based study to comprehensively investigate the relationship between occupational noise exposure and blood pressure and different hypertension subtypes and to estimate the AF for hypertension burden attributable to occupational noise exposure.

METHODS

A total of 715,135 workers aged 18-60 years were included in this study based on the Key Occupational Diseases Surveillance Project of Guangdong in 2020. Multiple linear regression was performed to explore the relationships of occupational noise exposure status, the combination of occupational noise exposure and binaural high frequency threshold on average (BHFTA) with systolic and diastolic blood pressure (SBP, DBP). Multivariable logistic regression was used to examine the relationshipassociation between occupational noise exposure status, occupational noise exposure combined with BHFTA and hypertension. Furthermore, the attributable risk (AR) was calculated to estimate the hypertension burden attributed to occupational exposure to noise.

RESULTS

The prevalence of hypertension among occupational noise-exposed participants was 13·7%. SBP and DBP were both significantly associated with the occupational noise exposure status and classification of occupational noise exposure combined with BHFTA in the crude and adjusted models (all P < 0·0001). Compared with workers without occupational noise exposure, the risk of hypertension was 50% greater among those exposed to occupational noise in the adjusted model (95% CI 1·42-1·58). For participants of occupational noise exposed with BHFTA normal, and occupational noise exposed with BHFTA elevated, the corresponding risks of hypertension were 48% (1·41-1·56) and 56% (1·46-1·63) greater than those of occupational noise non-exposed with BHFTA normal, respectively. A similar association was found in isolated systolic hypertension (ISH) and prehypertension. Subgroup analysis by sex and age showed that the positive associations between occupational noise exposure and hypertension remained statistically significant across all subgroups (all P < 0.001). Significant interactions between occupational noise status, classification of occupational noise exposure combined with BHFTA, and age in relation to hypertension risk were identified (all P for interaction < 0.001). The associations of occupational noise status, classification of occupational noise exposure combined with BHFTA and hypertension were most pronounced in the 18-29 age groups. The AR% of occupational noise exposure for hypertension was 28·05% in the final adjusted model.

CONCLUSIONS

Occupational noise exposure was positively associated with blood pressure levels and the prevalence of hypertension, ISH, and prehypertension in a large occupational population-based study. A significantly increased risk of hypertension was found even in individuals with normal BHFTA exposed to occupational noise, with a further elevated risk observed in those with elevated BHFTA. Our findings provide epidemiological evidence for key groups associated with occupational noise exposure and hypertension, and more than one-fourth of hypertension cases would have been prevented by avoiding occupational noise exposure.

Novel cis compound heterozygous variants in MYO6 causes early onset of non-syndromic hearing loss in a Chinese family

Background: Mutations in the MYO6 gene have been associated with both autosomal dominant non-syndromic hearing loss (ADNSHL) and autosomal recessive non-syndromic hearing loss (ARNSHL), with a cumulative identification of 125 pathogenic variants. To investigate the underlying genetic factor within a Chinese family affected with heriditary hearing loss, prompted the utilization of high-throughput sequencing. Method: A detailed clinical investigation was performed. Genetic testing was performed by using target panel sequencing, and Sanger sequencing. Targeted sequencing identified the variants and Sanger sequencing was employed to validate segregation of the identified variants within family. Additionally, bioinformatics analysis was performed to strengthen our findings. Results: Clinical investigation revealed the family members were affected by progressive and sensorineural hearing loss with an onset around 8-10 years old. Furthermore, genetic testing identified novel MYO6 variants, c.[2377T>G; 2382G>T] p.[Trp793Gly; Lys794Asn], positioned in a cis pattern, as plausible pathogenic contributors to early-onset hearing loss characterized by a severe and progressive course. Moreover, bioinformatics analysis showd disruptin in hydrogen bonding of mutant amino acids with interactive amino acids. Conclusion: Our research uncovered a relationship between mutations in the MYO6 gene and non-syndromic hearing loss. We identified two variants, c.[2377T>G; 2382G>T] p.[Trp793Gly; Lys794Asn] in MYO6 as strong candidates responsible for the observed progressive hereditary hearing loss. This study not only adds to our knowledge about hearing problems related to MYO6 but also reveals the presence of monogenic compound heterozygosity. Our study will provide a new sight for genetic diagnosis in such patients and their management for future use.

Easy as 1-2-3: Development and Evaluation of a Simple yet Valid Audiogram-Classification System

Almost since the inception of the modern-day electroacoustic audiometer a century ago the results of pure-tone audiometry have been characterized by an audiogram. For almost as many years, clinicians and researchers have sought ways to distill the volume and complexity of information on the audiogram. Commonly used approaches have made use of pure-tone averages (PTAs) for various frequency ranges with the PTA for 500, 1000, 2000 and 4000 Hz (PTA4) being the most widely used for the categorization of hearing loss severity. Here, a three-digit triad is proposed as a single-number summary of not only the severity, but also the configuration and bilateral symmetry of the hearing loss. Each digit in the triad ranges from 0 to 9, increasing as the level of the pure-tone hearing threshold level (HTL) increases from a range of optimal hearing (< 10 dB Hearing Level; HL) to complete hearing loss (≥ 90 dB HL). Each digit also represents a different frequency region of the audiogram proceeding from left to right as: (Low, L) PTA for 500, 1000, and 2000 Hz; (Center, C) PTA for 3000, 4000 and 6000 Hz; and (High, H) HTL at 8000 Hz. This LCH Triad audiogram-classification system is evaluated using a large United States (U.S.) national dataset (N = 8,795) from adults 20 to 80 + years of age and two large clinical datasets totaling 8,254 adults covering a similar age range. Its ability to capture variations in hearing function was found to be superior to that of the widely used PTA4.

Prevalence and risk factors of hearing loss among the middle-aged and older population in China: a systematic review and meta-analysis

PURPOSE

This paper was aimed at estimating the prevalence and risk factors of hearing loss (HL) among the middle-aged and elderly in China.

METHODS

Databases including the CQVIP (VIP) Database, Chinese National Knowledge Infrastructure (CNKI), China Biology Medicine disc (CBMdisc), Wanfang, PubMed, Web of Science, Excerpta Medica Database (Embase) and the Cochrane Library were comprehensively searched. In this review, random-effect models were used for pooling the prevalence of HL and the odds ratios (ORs) of potential risk factors.

RESULTS

34 studies were included in the meta-analysis. HL among the middle-aged and elderly in China had a pooled prevalence of 45% (95% confidence interval (CI) 40-51%). There were significant differences in the prevalence of HL between males and females (47% vs. 42%), between different screening methods by self-report and pure-tone audiometry (44% vs. 46%), between the middle-aged and the elderly (18% vs. 52%), and between the uneducated and the educated (49% vs. 36%). In urban areas, the prevalence was slightly higher than that in rural areas (50% vs. 48%). The findings suggested that the middle-aged and elderly in the South Central China region (61%, 95% CI 45-78%) and Northwest China (57%, 95% CI 55-58%) were more likely to develop HL. In addition, it was confirmed that advanced age, being male, noise exposure history, hypertension and hyperglycemia were related to a higher prevalence of HL among middle-aged and older adults.

CONCLUSION

The prevalence of HL among the middle-aged and older population in China is 45%, nearly half of the total population. It is urgent to take great efforts to raise people's awareness of HL prevention and early hearing screening.

Comparative transcriptome profiling reveals RNA splicing alterations and biological function in patients exposed to occupational noise

Genetic factors play an important role in susceptibility to noise-induced hearing loss (NIHL). Alternative splicing (AS) is an essential mechanism affecting gene expression associated with disease pathogenesis at the post-transcriptional level, but has rarely been studied in NIHL. To explore the role of AS in the development of NIHL, we performed a comprehensive analysis of RNA splicing alterations by comparing the RNA-seq data from blood samples from NIHL patients and subjects with normal hearing who were exposed to the same noise environment. A total of 356 differentially expressed genes, including 23 transcription factors, were identified between the two groups. Of particular note was the identification of 56 aberrant alternative splicing events generated by 41 differentially expressed genes between the two groups, with exon skipping events accounting for 54% of all the differentially alternative splicing (DAS) events. The results of functional enrichment analysis showed that these intersecting DAS genes and differentially expressed genes were significantly enriched in autophagy and mitochondria-related pathways. Together, our findings provide insights into the role of AS events in susceptibility and pathogenesis of NIHL.

Cardiocerebrovascular risk in sensorineural hearing loss: results from the National Health and Nutrition Examination Survey 2015 to 2018

Objective

This study aims to determine whether the risks of cardiocerebrovascular disease are relevant to sensorineural hearing loss (SNHL) based on a national database.

Methods

A total of 1,321 participants aged from 18 to 69 with complete data including medical history and audiometry from the NHANES database (2015-2018) were analyzed. All included participants had available hearing data and the average thresholds of the hearing data were measured and calculated as low-frequency pure-tone average (LFPTA; 500, 1,000, and 2,000 Hz) and high-frequency pure-tone average (HFPTA; 3,000, 4,000, 6,000, and 8,000 kHz). SNHL was defined as an average pure tone of more than or equal to 20 dB in at least one better ear. Multivariable models to assess the association between cardiocerebrovascular risks and SNHL were used in this study.

Results

The prevalence of stroke was 1.6% in individuals with SNHL and 0.4% in individuals without SNHL (p = 0.023). A higher cardiovascular risk score was observed in SNHL patients compared to participants without SNHL (1.58 vs. 0.90, p < 0.001). Stroke was associated with a 3.67-fold increase in the risk of SNHL (95% CI: 1.12-12.00, p = 0.032) in univariable logistic regression, and the association (OR = 4.22, 95%CI = 1.28-13.93, p = 0.020) remained significant after adjusting for several covariates. Multivariable logistic regression models indicated a positive correlation between cardiovascular risk and SNHL (OR = 1.66, 95% CI = 1.40-1.96, p < 0.001), but no significant relationship was shown with all covariates adjusted. However, significant associations were found between SNHL and both age and sex in both univariable and multivariable logistic regression models.

Conclusion

Our findings suggested that a higher cardiocerebrovascular risk burden was associated with an increased risk of SNHL, and the relationship may be influenced by age and sex. Future longitudinal studies are needed to investigate the mechanistic and pathologic vascular hypothesis of SNHL.

The role of kurtosis and kurtosis-adjusted energy metric in occupational noise-induced hearing loss among metal manufacturing workers

Background

Noise energy has been well-established to increase the risk of occupational noise-induced hearing loss (NIHL). However, the role of noise temporal structure (expressed by kurtosis) or its combination with energy metrics (e.g., kurtosis-adjusted cumulative noise exposure, adj-CNE) in occupational NIHL was still unclear.

Methods

A cross-sectional survey of 867 Chinese workers, including 678 metal manufacturing workers and 189 workers exposed to Gaussian noise, was conducted. Noise energy metrics, including L_Aeq,8h and CNE, kurtosis (β), and adj-CNE were used to quantify noise exposure levels. Noise-induced permanent threshold shift at frequencies 3, 4, and 6 kHz (NIPTS₃₄₆) and the prevalence of high-frequency NIHL (HFNIHL%) were calculated for each participant. The dose-response relationship between kurtosis or adj-CNE and occupational NIHL was observed.

Results

Among 867 workers, different types of work had specific and independent noise energy and kurtosis values (p > 0.05). HFNIHL% increased with an increase in exposure duration (ED), L_Aeq,8h, CNE, or kurtosis (p < 0.01), and there were strong linear relationships between HFNIHL% and ED (coefficient of determination [R²] = 0.963), CNE (R² = 0.976), or kurtosis (R² = 0.938, when CNE < 100 dB(A)∙year). The "V" shape notching extent in NIPTS became deeper with increasing kurtosis when CNE < 100 dB(A)∙year and reached the notching bottom at the frequency of 4 or 6 kHz. The workers exposed to complex noise (β ≥ 10) had a higher risk of NIHL than those exposed to Gaussian noise (β < 10) at the frequencies of 3, 4, 6, and 8 kHz (OR > 2, p < 0.01). Moreover, HFNIHL% increased with adj-CNE (p < 0.001). There were strong linear relationships between NIHL and adj-CNE or CNE when β ≥ 10 (R²_adj-CNE > R²_CNE). After CNE was adjusted by kurtosis, average differences in NIPTS₃₄₆ or HFNIHL% between the complex and Gaussian noise group were significantly reduced (p < 0.05).

Conclusion

Kurtosis was a key factor influencing occupational NIHL among metal manufacturing workers, and its combination with energy metrics could assess the risk of NIHL more effectively than CNE alone.

The Effect of Noise Exposure on High-Frequency Hearing Loss among Chinese Workers: A Meta-Analysis

The purpose of this study was to determine the burden of high frequency noise-induced hearing loss (HFNIHL) in Chinese workers exposed to hazardous noise through meta-analysis, to evaluate the major risk factors of HFNIHL in Chinese workers, and to provide evidence for reducing the risk of HFNIHL. We searched for relevant studies on HFNIHL published between January 1990 and June 2022. Inclusion and exclusion criteria were established to screen the literature, and the quality of the studies was assessed. Meta-analysis was performed using the software Stata 17.0. A total of 39 studies involving 50,526 workers in different industries were included in this study. The incidence of HFNIHL in the noise-exposed group (36.6%) was higher than that in the control group (12.5%), with a pooled odds ratio (OR) of 5.16 and a 95% confidence interval (CI) of 4.10-6.49. Sensitivity analysis showed that the results of this meta-analysis were stable. Funnel plots and Egger's test showed no publication bias. Subgroup analysis showed heterogeneity among the results of different studies, which was related to gender, publication year, age, length of work, and type of industry. The dose-response analysis showed that cumulative noise exposure (CNE) and length of work were the main risk factors for HFNIHL. This study suggests that the detection rate of HFNIHL is high in Chinese workers, the risk of HFNIHL increases rapidly when CNE reaches 90 dB(A)·year, and the first 15 years of exposure to noise is a period of increasing risk. Therefore, reasonable measures for preventing hearing loss should be taken to reduce the risk of occupational HFNIHL.

Association of polymorphisms in the catalase gene with the susceptibility to noise-induced hearing loss: A meta-analysis

OBJECTIVES

The association between single nucleotide polymorphisms (SNPs) of the Catalase (CAT) gene and noise-induced hearing loss (NIHL) has been reported in several case-control studies. However, their conclusions are conflicting. This study aimed to determine the association between CAT genetic variants and NIHL susceptibility.

METHODS

We searched PubMed, Embase, CNKI, Wanfang, and Web of Science for eligible English and Chinese studies published up to September 26, 2021. Studies reporting primary data that assessed the association between CAT SNPs and NIHL susceptibility were included. The quality of the included studies was assessed using the Newcastle-Ottawa Scale (NOS). The odds ratio (OR), 95 % confidence interval (CI), and P value were calculated to assess the strength of the association. Publication bias was explored using funnel plots and Egger's test.

RESULTS

Our meta-analysis included six articles involving 1428 patients and 2162 healthy controls. For rs208679, a significant association was detected in the allele model (A vs. G: OR = 0.81 [95 % CI, 0.67-0.97], P = 0.02) and the dominant model (AA vs. GG + AG: OR = 0.78 [95 % CI, 0.62-0.98], P = 0.03), but not in the heterozygote model, homozygote model, or the recessive model. For rs769217, rs7943316, and rs769214, no significant association was found in any genetic model. No significant publication bias was observed.

CONCLUSIONS

The rs208679 may be used in the Chinese population as a risk predictor for NIHL. While the rs769217, rs7943316, and rs769214 polymorphisms were not found to be associated with susceptibility to NIHL. Further studies with a larger population and higher quality are required to update the results.

Effectiveness of Kurtosis-Adjusted Cumulative Noise Exposure in Assessing Occupational Hearing Loss Associated With Complex Noise

OBJECTIVES

Occupational noise-induced hearing loss (NIHL) is one of the most prevalent occupational diseases worldwide. Few studies have been reported on applying kurtosis-adjusted noise energy (e.g., kurtosis-adjusted cumulative noise exposure, CNE-K) as a joint indicator for assessing NIHL. This study aimed to analyze the effectiveness of CNE-K in assessing occupational hearing loss associated with complex noise in typical manufacturing industries.

DESIGN

A cross-sectional survey of 1404 Chinese manufacturing workers from typical manufacturing industries was conducted. General demographic characteristics, noise exposure data, and noise-induced permanent threshold shifts (NIPTS) at 3, 4, and 6 kHz (NIPTS 346 ) were collected and analyzed. The role of kurtosis in high-frequency noise-induced hearing loss (HFNIHL) was also analyzed. The degree of overlap of the two logistic curves (i.e., between complex noise CNE-K and HFNIHL%, and between Gaussian noise CNE and HFNIHL%) was used to evaluate the effectiveness of CNE-K, using a stratified analysis based on age, sex, industry, or job type.

RESULTS

The binary logistic regression analysis showed that in addition to age, sex, exposure duration, and Eight-hour Continuous Equivalent A-weighted Sound Pressure Level (L Aeq,8h ), kurtosis was a key factor influencing HFNIHL% in workers (odds ratio = 1.18, p < 0.05), and its odds ratio increased with an increase in kurtosis value. Multiple linear regression analysis demonstrated that the contribution of kurtosis to NIPTS 346 was second to L Aeq,8h . Complex noise led to a higher risk of NIHL than Gaussian noise at frequencies of 3, 4, 6, and 8 kHz after adjusting for age, sex, and CNE ( p < 0.05). As kurtosis increased, the notch in the audiogram became deeper, and the frequency at which the notch began to deepen shifted from 3 to 1 kHz. The logistic curve between complex noise CNE-K and HFNIHL% nearly overlapped with that between Gaussian noise CNE and HFNIHL%, and the average difference in HFNIHL% between the two curves decreased from 8.1 to 0.4%. Moreover, the decrease of average difference in HFNIHL% between the two logistic curves was evident in several subgroups, such as male workers, aged <30 and 30 to 50 years, furniture and woodworking industries and gunning and nailing job types with relatively high kurtosis values.

CONCLUSIONS

Kurtosis, as an indirect metric of noise temporal structure, was an important risk factor for occupational NIHL. Kurtosis-adjusted CNE metric could be more effective than CNE alone in assessing occupational hearing loss risk associated with complex noise.

Noise exposure assessment of non-coal mining workers in four provinces of China

Objective

This study aimed to understand the noise exposure of non-coal mines in China to take appropriate controls to protect workers' health.

Methods

An assessment of non-coal miners' noise exposures was conducted in four provinces in China. Individual noise exposure levels were measured, and the survey on the hearing protector device (HPD) equipment was administered.

Results

423 noise dosimeter measurements were obtained, including drilling, blasting, ore drawing, transportation, winching, crushing, screening and ball milling, and auxiliary (air pressure, pump, and maintenance). A total of 31.9% of the individual noise levels (L_EX,8h) exceeded 85 dB(A), and the median dosages of non-coal miners with high noise exposure were: excavation workers-89.1 dB(A), mill operators-88.7 dB(A), and crusher operators-87.0 dB(A). The noise dose of underground mine workers is higher than that of surface mine workers (P < 0.001). A total of 53.7% of non-coal mining enterprises are not equipped with HPD for workers, mainly small and micro enterprises.

Conclusions

High levels of hazardous noise exposure are typical in non-coal mines. Noise exposure data can help to develop more feasible noise controls.

Occupation and 20-year hearing decline: findings from The HUNT Study

BACKGROUND

Studies show that certain occupations are associated with an increased risk of hearing loss. However, many studies are cross-sectional, and the few longitudinal studies are mostly small or focus on only one occupation.

AIMS

We aimed to quantify the long-term hearing decline among workers in different occupations and assess whether the change differs between the occupations.

METHODS

The study population was 4525 adults who participated in two population-based health studies in Norway, HUNT2 1996-1998 and HUNT4 2017-2019. Linear regression models assessed the association between occupations (clerks as reference) and 20-year hearing decline (hearing thresholds at 3-6 kHz, averaged over both ears) from HUNT2 to HUNT4. Models were adjusted for age, sex, recurrent ear infections, smoking and ear pathology.

RESULTS

Among the participants (40% men), the mean age at HUNT2 was 31.2 ± 5.4 years (range 20-39) and the average 20-year hearing decline was 11.3 ± 9.8 dB. Occupations that were associated with larger hearing decline included other craft and related trades workers (3.9 dB, 95% confidence interval [CI] 0.2-7.7) and building frame and related trades workers (3.4 dB, 95% CI 1.3-5.4). Among occupations with larger hearing decline, a higher proportion of the workers reported exposure to noise.

CONCLUSIONS

This large longitudinal study shows a larger long-term hearing decline among building frame workers and craft and related trades workers. Differences between occupations were modest, which may indicate successful preventive measures in Norway during the last two decades.

Proposal of Combined Noise and Hand-Arm Vibration Index for Occupational Exposure: Application to a Study Case in the Olive Sector

In many production and industrial sectors, workers are exposed to noise and hand-arm vibrations (HAV). European directives have established the maximum limit values or exposure action values for noise and vibration independently. However, in many cases, workers who endure hand-arm vibration also receive high noise levels. This research suggests a procedure to aid the establishment of precautionary measures for workers with simultaneous exposure to both physical agents. This procedure defines a combined index based on the energy doses for both noise and HAV. From this combined index, the suggested methodology allows a recommended exposure time for workers with simultaneous noise and HAV exposure to be calculated. This methodology can be adapted to tackle the relative importance assigned to both agents according to the safety manager and new knowledge on combined health effects. To test this method, a measurement campaign under real working conditions was conducted with workers from the olive fruit-harvesting sector, where a variety of hand-held machinery is used. The results of the study case show that the suggested procedure can obtain reliable exposure time recommendations for simultaneous noise and HAV exposures and is therefore a useful tool for establishing prevention measures.

Effects of Noise Exposure and Mental Workload on Physiological Responses during Task Execution

Twelve healthy male students were recruited to investigate the physiological response to different noise exposure and mental workload (MW) conditions, while performing multi-attribute task battery (MATB) tasks. The experiments were conducted under three noise exposure conditions, with different sound pressure levels and sharpness. After adaptation to each noise condition, the participants were required to perform the resting test and the MATB task tests with low, medium, and high MW. The electroencephalogram (EEG), electrocardiogram (ECG), and eye movement data were obtained, during the periods when participants were in the resting and task taking state. The results showed that subjects' physiological responses at rest were unaffected by noise exposure conditions. However, during the execution of MATB tasks, the elevated sound pressure level and increased sharpness were significantly correlated with increased mean pupil diameter and heart rate variability (HRV). These responses suggested that the human body defends itself through physiological regulation when noise causes adverse effects. If the negative effects of noise were more severe, this could damage the body's health and result in a significant drop in task performance. The elevated mental demands led to increased stress on the subjects, which was reflected in a considerable increase in theta relative power. Either high or low MW was related with reduced saccade amplitude and a decrease in weighted task performance, indicating an inverted U-shaped relationship between workload level and work performance.

Developing a guideline for measuring workplace non-Gaussian noise exposure based on kurtosis adjustment of noise level in China

Objective

There is no unified standard for measuring workplace non-Gaussian noise (known as complex noise) exposure. This study aimed to develop a draft guideline for measuring workplace non-Gaussian complex noise exposure based on noise temporal structure adjustment.

Methods

Noise exposure level, e.g., the A-weighted sound pressure level normalized to a nominal 8-h working day (L_EX,8h), was adjusted using the temporal structure (expressed by kurtosis) of noise. Noise waveform analysis or the instrument's direct reading was used.

Results

The framework of the draft guideline included measurement metrics, the protocol using kurtosis to adjust L_EX,8h, technical requirements for measuring instruments, measurement steps, data analysis, and measurement recording.

Conclusion

The draft guideline could provide a basis for accurately measuring workers' exposure to non-Gaussian noise.

MicroRNA expression is associated with auditory dysfunction in workers exposed to ototoxic solvents and noise

This study is part of a project on early hearing dysfunction induced by combined exposure to volatile organic compounds (VOCs) and noise in occupational settings. In a previous study, 56 microRNAs were found differentially expressed in exposed workers compared to controls. Here, we analyze the statistical association of microRNA expression with audiometric hearing level (HL) and distortion product otoacoustic emission (DPOAE) level in that subset of differentially expressed microRNAs. The highest negative correlations were found; for HL, with miR-195-5p and miR-122-5p, and, for DPOAEs, with miR-92b-5p and miR-206. The homozygous (mut) and heterozygous (het) variants of the gene hOGG1 were found disadvantaged with respect to the wild-type (wt), as regards the risk of hearing impairment due to exposure to VOCs. An unsupervised artificial neural network (auto contractive map) was also used to detect and show, using graph analysis, the hidden connections between the explored variables. These findings may contribute to the formulation of mechanistic hypotheses about hearing damage due to co-exposure to noise and ototoxic solvents.

Epidemiological characteristics of hearing loss associated with noise temporal structure among manufacturing workers

Objective: This study aimed to investigate the epidemiological characteristics of occupational noise-induced hearing loss (NIHL) among manufacturing workers, and to provide evidence for diagnosing and preventing occupational hearing loss caused by complex noise, which is different from Gaussian noise in temporal structure.

Methods: One thousand and fifty manufacturing workers exposed to occupational noise were recruited in a cross-sectional survey. Exposure characteristics and epidemiological distribution of hearing loss and noise exposure metrics (noise energy and kurtosis) were investigated, and the relationship between noise exposure and hearing loss was analyzed. The effects of kurtosis on hearing threshold shift across different frequencies and on NIHL development with exposure duration and noise intensity were also investigated.

Results: Each type of work had specific noise exposure metrics. Noise intensity and kurtosis were independent parameters (r = −0.004, p = 0.885). The prevalence of NIHL and the hearing threshold level had a specific distribution in different types of work. Kurtosis deepened the hearing notch at high frequencies and accelerated the formation of early hearing loss. The effect of exposure duration and noise intensity on the prevalence of high-frequency NIHL (i.e., at 3, 4, 6, and 8 kHz) for manufacturing workers increased with kurtosis in workers with noise exposure duration of less than 10 years and with L_Aeq.8h between 80 and 90 dB(A). Male (OR = 1.557, 95%CI = 1.141–2.124), age (OR = 1.033, 95%CI = 1.014–1.052), exposure duration (OR = 1.072, 95%CI = 1.038–1.107), kurtosis (OR = 1.002, 95%CI = 1.001–1.003), and noise intensity (L_Aeq.8h; OR = 1.064, 95%CI = 1.044–1.084) were risk factors for high-frequency NIHL. The speech-frequency NIHL (i.e., at 0.5, 1, and 2 kHz) risk of workers exposed to manufacturing noise was related to age (OR = 1.071, 95%CI = 1.043–1.100). There were no statistically significant associations between speech-frequency NIHL and sex, noise exposure duration, kurtosis, and noise intensity (L_Aeq.8h).

Conclusion: The high-frequency NIHL prevalence among manufacturing workers is associated with sex, age, exposure duration, noise intensity, and temporal structure of noise, while the speech-frequency NIHL prevalence is associated with age. Kurtosis strengthens the association of noise exposure duration and noise intensity with high-frequency hearing loss. The influence of noise temporal structure should be considered in the diagnosis and early prevention of occupational hearing loss caused by complex noise.

Nurses’ and preschool teachers’ experiences of taking part in a participatory intervention project in communication-intense working environments

BACKGROUND: Noise is a common workplace problem that can affect health and performance. High sound levels have been found in sectors that largely has been overlooked in noise research such as health care and education. In these communication-intense environments the work requires speech communication, thus making it difficult to wear hearing protection. OBJECTIVE: To explore nurses’ and preschool teachers’ experiences of taking part in a participatory intervention project aiming to improve the sound environment and the psychosocial work environment. METHODS: One preschool and one obstetrics ward took part in the study, and a qualitative design was used to evaluate the experience of the participatory intervention approach. RESULTS: Five main themes were found in the analysis: Awareness, Taking control of the sound environment, Influence of the building and interior design, Circumstances influencing the intervention process and Motivation to maintain change. CONCLUSIONS: Despite demanding working situations and lack of financial resources, preschool and obstetrics staff described being creative in planning and implementing several different solutions to improve the sound environment at their workplaces, while interventions specifically improving the psychosocial work environment were fewer. Hence, our study suggest that a participatory intervention approach may facilitate participation and motivation, but resources and support are needed for a comprehensive and effective implementation.

Hearing loss and hypertension among noise-exposed workers: a pilot study based on baseline data

This study aimed to assess the prevalence of noise-induced hearing loss (NIHL) and hypertension, and the association between NIHL and hypertension using occupational physical examination data of 42,588 noise-exposed workers from local enterprises in Yangzhou between 2015 and 2017. The average binaural high-frequency threshold on average (BHFTA), systolic blood pressure (SBP), and diastolic blood pressure (DBP) were 23.09 ± 11.32 dB, 126.85 ± 15.94 mm Hg and 79.94 ± 11.61 mm Hg. The prevalence of NIHL and hypertension were 24.38% and 25.40%. An increased risk of NIHL and hypertension was observed in the groups of males, aged >35 years, noise exposure time >5 years, noise exposure level >85 dB(A) and smoking. 32.25% NIHL workers had hypertension. NIHL workers were at higher risk of hypertension (adjusted OR = 1.07, 95%CI = 1.02-1.13). This study shows that the noise-exposed workers have high risk of developing NIHL and hypertension.

The Impact of Occupational Noise on Hypertension Risk: A Case-Control Study in Automobile Factory Personnel

Background

Many epidemiological studies have investigated the relationship between occupational noise and hypertension, but with conflicting findings. This study aimed to assess the relationship between occupational noise exposure and the risk of hypertension.

Methods

A case-control study was conducted to explore hypertension predictors, and then sensitivity analysis was performed based on propensity score matching (PSM). Data were collected from participants' annual physical examinations and occupational noise exposure measurements. Odds ratios (ORs) and 95% confidence intervals (CIs) were estimated using logistic regression analysis. A restricted cubic spline (RCS) function was used to fit the dose-effect relationship.

Results

500 cases and 4,356 controls were included in the study. Multivariate logistic regression showed that an increase in the level of occupational noise [range 68–102 dB(A)] of 1 dB(A), corresponded to an increase in hypertension risk of 8.3% (OR: 1.083, 95% CI: 1.058–1.109). Compared to the first quartile, the risk of hypertension in the fourth quartile was 1.742 (95% CI: 1.313–2.310). After applying PSM to minimize bias, we obtained a population of 500 cases and 1,000 controls. Noise level was significantly associated with the risk of hypertension. In addition, the RCS curve showed the risk of hypertension was relatively stable until a predicted noise level of around 80 dB(A) and then started to increase rapidly afterward (Pnonlinear = 0.002).

Conclusions

Occupational noise exposure was significantly associated with hypertension risk and there was a positively correlated dose-response relationship.

Effect of ambient noise on indoor environments in a health care facility in Oman

Hospital-noise levels can induce physiological responses and affect sleep quality, which could contribute to cardiovascular-related health problems. Till date, high-resolution hospital noise exposure assessment studies have not received much attention in Oman. This study aims at assessing sound pressure levels across hospital wards and intensive care unit (ICU) rooms to determine annoyance and potential health effects based on perception and risk estimates. An indoor exposure assessment using high precision noise sensors was conducted in a female medical ward (FMW), isolated ward (SLW), emergency ward (EMW), and intensive care unit (ICU) in a public hospital in Muscat city, Oman. Self-administered questionnaire was randomly distributed among respondents using both online and field survey approach to ascertain annoyance, health effects, and potential risks associated with exposure. The study found that 24-h noise levels (L_Aeq) ranged from 55.2 to 61.7 dB(A) in the hospital wards and ICU rooms, which exceeded WHO's hospital indoor rooms critical limit of 35 dB(A) by 58-76%. A total of 150 participants took part in the survey. Among the respondents, 53% reported moderate annoyance at the hospital wards, while 56% felt sensitivity to the noise levels. Noise annoyance was reported by the majority of the patients across the various wards and emergency rooms as causing slight annoyance (50%) and intermittent sleep disturbances (49%). The majority (73%) of the medical staff have complained that the current noise levels affect overall work performance (p = 0.004), while 70% of them have further complained of it as a cause of workplace distraction (p = 0.011). Logistic binary regression analysis has revealed that the complaint of noise sensitivity has a positive association with noise levels in VCW (OR: 1.54; 95% CI: 0.92-2.58), and reported loss of concentration by the medical staff also associated with noise levels at the EMW (OR: 1.61; 95% CI: 0.65-4.01). Quantitative risk estimates showed that both the percentages of highly annoyed (HA) persons (16%), and highly sleep-disturbed (HSD) persons (9%) were very high in FMW, while ICU was found to have the lowest risk. However, the greater number of the respondents (87%) believed that there are possibilities of mitigating (p < 0.001) the current noise levels.

Association between genetic polymorphisms of cadherin 23 and noise-induced hearing loss: a meta-analysis

BACKGROUND

NIHL is one of the most common occupational diseases induced by gene-environment interaction. The CDH23 gene is a candidate gene related to NIHL susceptibility. However, the relationship between CDH23 gene and NIHL is still inconclusive.

AIM

To clarify the association between CDH23 gene and NIHL, a meta-analysis was performed.

SUBJECTS AND METHODS

A search in MEDLINE, PubMed, Web of Science, EBSCO, China National Knowledge Infrastructure (CNKI), and Wanfang Data was implemented to collect data.

RESULTS AND CONCLUSIONS

Six studies were eventually included and all the subjects were Chinese. The results showed that rs1227051, rs1227049, and rs3752752 were not associated with NIHL susceptibility under five genetic models. But rs3802711 reduced the risk of NIHL under the recessive model, and the BB genotype and B allele of rs3802711 were significantly linked to NIHL under recessive, super-dominant, homozygote, and allele genetic models when stratified by the HWE result. Moreover, when not conform to HWE, the BB + AB genotypes and B allele of Exon7 in dominant, super-dominant, homozygote, and allele genetic model increased the risk of NIHL. CDH23 may be a potential gene marker for the prevention and early screening of NIHL in Chinese. Further large and well-designed studies are needed to confirm this association.

Applying Kurtosis as an Indirect Metric of Noise Temporal Structure in the Assessment of Hearing Loss Associated With Occupational Complex Noise Exposure

OBJECTIVE

The association of occupational noise-induced hearing loss (NIHL) with noise energy was well documented, but the relationship between occupational noise and noise temporal structure is rarely reported. The objective of this study was to investigate the principal characteristics of the relationship between occupational NIHL and the temporal structure of noise.

METHODS

Audiometric and shift-long noise exposure data were collected from 3102 Chinese manufacturing workers from six typical industries through a cross-sectional survey. In data analysis, A-weighted 8-h equivalent SPL (LAeq.8h), peak SPL, and cumulative noise exposure (CNE) were used as noise energy indicators, while kurtosis (β) was used as the indicator of noise temporal structure. Two NIHL were defined: (1) high-frequency noise-induced hearing loss (HFNIHL) and (2) noise-induced permanent threshold shift at test frequencies of 3, 4, and 6 kHz (noise-induced permanent threshold shift [NIPTS346]). The noise characteristics of different types of work and the relationship between these characteristics and the prevalence of NIHL were analyzed.

RESULTS

The noise waveform shape, with a specific noise kurtosis, was unique to each type of work. Approximately 27.92% of manufacturing workers suffered from HFNIHL, with a mean NIPTS346 of 24.16 ± 14.13 dB HL. The Spearman correlation analysis showed that the kurtosis value was significantly correlated with the difference of peak SPL minus its LAeq.8h across different types of work (p < 0.01). For a kurtosis-adjusted CNE, the linear regression equation between HFNIHL% and CNE for complex noise almost overlapped with Gaussian noise. Binary logistic regression analysis showed that LAeq.8h, kurtosis, and exposure duration were the key factors influencing HFNIHL% (p < 0.01). The notching extent in NIPTS at 4 kHz became deeper with the increase in LAeq.8h and kurtosis. HFNIHL% increased most rapidly during the first 10 years of exposure. HFNIHL% with β ≥ 10 was significantly higher than that with β < 10 (p < 0.05), and it increased with increasing kurtosis across different CNE or LAeq.8h levels. When LAeq.8h was 80 to 85 dB(A), the HFNIHL% at β ≥ 100 was significantly higher than that at 10 ≤ β < 100 or β < 10 (p < 0.05 and p < 0.01, respectively).

CONCLUSIONS

In the evaluation of hearing loss caused by complex noise, not only noise energy but also the temporal structure of noise must be considered. Kurtosis of noise is an indirect metric that is sensitive to the presence of impulsive components in complex noise exposure, and thus, it could be useful for quantifying the risk for NIHL. It is necessary to re-evaluate the safety of permissible exposure limit of 85 dB(A) as noise with a high kurtosis value can aggravate or accelerate early NIHL.

Surveillance of Noise Exposure Level in the Manufacturing Industry - China, 2020

Introduction

Occupational noise exposure is a widespread issue in the manufacturing industry in China. Since 2019, the National Surveillance System for Occupational Hazards in the workplace was established to understand different occupational hazards, especially occupational noise, in workplaces in China.

Methods

Both environmental and individual noise exposure levels were measured for 19,378 enterprises according to the Work Plan for Surveillance of Occupational Hazards in the Workplace (2020) issued by National Health Commission of the People's Republic of China. Median and interquartile range (IQR) were calculated to describe the distribution of the noise exposure level by industry classification, enterprise-scale, and ownership type of the enterprise.

Results

Overall, 25.14% of the individual noise exposure samples exceeded the Chinese national standard among the selected enterprises. The overall median of environmental noise exposure level was 82.8 dB(A) in selected enterprises, while the median of individual noise exposure level was 81.3 dB(A). The individual noise exposure level in the manufacture of metal products, manufacture of motor vehicles, mini-sized enterprises, collective enterprises and private enterprises was relatively high.

Conclusion

Occupational noise is still one of the occupational hazards that cannot be ignored in the manufacturing industry, especially in mini-sized and private enterprises. The risk of noise exposure in the target industry is still high and will pose a threat to the health of workers.

The Benefits of Curcuminoid to Expression Nuclear Factor Erythroid 2 Related Factor 2 (NRF2) and Signal to Noise Ratio (SNR) Value in the Noise Exposed Organ of Corti of Rattus Norvegicus

BACKGROUND

Noise-induced hearing loss (NIHL) can cause damage to the cochlea. Curcumin and nuclear factor erythroid 2-related factor 2 (NRF2) are transcription activators that play a crucial role in defence mechanisms against oxidative stress. The aim of this study was to determine the effect of curcuminoid administration on NRF2 expression, in the organ of Corti of cochlea of Rattus norvegicus that were exposed to noise, from the results of the distortion product otoacoustic emission (DPOAE) examination.

METHODS

We divided 36 rats into six groups including Group 1 (control); Group 2 (noise exposure without curcuminoid administration); Group 3 (noise exposure+curcuminoid dose 100 mg/day for four days); Group 4 (noise exposure+curcuminoid dose 200 mg/day for four days); Group 5 (curcuminoid dose of 100 mg/day for 14 days followed by two days of noise exposure); Group 6 (curcuminoid dose 200 mg/day for 14 days followed by two days of noise exposure).

RESULTS

Following noise exposure in rats, there was an effect/correlation between NRF2 expression, the SNR values obtained from DPOAE and curcuminoid administration.

CONCLUSION

There was a correlation between curcuminoid administration, NRF2 expression and DPOAE treatment. Following noise exposure in rats (Rattus norvegicus), SNR values obtained from DPOAE showed improved cochlear function.

Sex Differences in the Triad of Acquired Sensorineural Hearing Loss

The triad of noise-generated, drug-induced, and age-related hearing loss is the major cause of acquired sensorineural hearing loss (ASNHL) in modern society. Although these three forms of hearing loss display similar underlying mechanisms, detailed studies have revealed the presence of sex differences in the auditory system both in human and animal models of ASNHL. However, the sexual dimorphism of hearing varies among noise-induced hearing loss (NIHL), ototoxicity, and age-related hearing loss (ARHL). Importantly, estrogen may play an essential role in modulating the pathophysiological mechanisms in the cochlea and several reports have shown that the effects of hormone replacement therapy on hearing loss are complex. This review will summarize the clinical features of sex differences in ASNHL, compare the animal investigations of cochlear sexual dimorphism in response to the three insults, and address how estrogen affects the auditory organ at molecular levels.

Modeling individual noise-induced hearing loss risk with proxy measurements of external-ear amplification

Significant variability in noise-induced hearing loss (NIHL) susceptibility suggests there are factors beyond sound level and duration of exposure that contribute to individual susceptibility. External-ear amplification (EEA) from external-ear structures varies significantly due to ear size and shape, potentially influencing NIHL susceptibility. This study tested the hypothesis that EEA can be predicted using non-technical proxy measurements including pinna height (cm), body height (m), and earcanal volume (cm³). 158 participants (4-78 years) completed otoscopy, tympanometry, pinna measurements, body height measurements, and two EEA measurements: (1) total real-ear unaided gain (REUG) of the open ear and (2) real-ear to coupler difference (RECD), representing unaided gain from the earcanal. Participants' individual noise doses were compared in hypothetical exposures. REUG ranged from 5 to 19 dBA and was correlated with pinna height. High-REUG participants were estimated to accrue noise doses at least 5 times higher than low-REUG participants. RECD ranged from 7 to 24 dBA and was correlated with earcanal volume and body height. The results support the hypothesis that EEA measurement could significantly improve estimation of an individual's position along the NIHL risk spectrum. Non-technical proxy measurements of EEA (pinna height, body height, earcanal volume) were statistically significant but yielded high variability in individual EEA prediction.

Occupational Hearing Loss Associated With Non-Gaussian Noise: A Systematic Review and Meta-analysis

OBJECTIVES

Epidemiological characteristics of occupational noise-induced hearing loss (NIHL) associated with non-Gaussian noise are still unclear and have been rarely reported in the literature.

METHODS

The relationships between non-Gaussian noise exposure and occupational NIHL were analyzed based on the published papers. Systematic review and meta-analysis of epidemiological studies were performed.

RESULTS

Of 78 epidemiological studies (47,814 workers) selected, there were seven cohort studies and 71 cross-sectional studies. The incidence of high-frequency NIHL (HFNIHL) and speech-frequency NIHL (SFNIHL) in the seven cohort studies was 10.9 and 2.9%, respectively. In 71 cross-sectional studies, the prevalence of HFNIHL and SFNIHL was 34.2 and 18.9%, respectively. The average hearing threshold level at the high frequencies was 42.1 ± 17.4 dB HL. Workers exposed to non-Gaussian noise had a higher risk of developing HFNIHL than those not exposed to noise (overall-weighted odds ratio [OR] = 4.46) or those exposed to Gaussian noise (overall-weighted OR = 2.20). The Chi-square trend test demonstrated that the prevalence of HFNIHL was positively correlated with age, cumulative noise exposure, and exposure duration (p < 0.001).

CONCLUSIONS

Workers exposed to non-Gaussian noise suffered from greater NIHL than those exposed to Gaussian noise or not exposed to noise. Age, exposure duration, noise level, and noise temporal structure were the main risk factors for occupational NIHL. The A-weighted equivalent continuous sound pressure level (LAeq) is not a sufficient measurement metric for quantifying non-Gaussian noise exposure, and a combination of kurtosis and noise energy metrics (e.g., LAeq) should be used. It is necessary to reduce the exposure of non-Gaussian noise to protect the hearing health of workers.

The Role of the Kurtosis Metric in Evaluating the Risk of Occupational Hearing Loss Associated with Complex Noise - Zhejiang Province, China, 2010-2019

What is already known about this topic?

Occupational noise-induced hearing loss (NIHL) has been the second most common occupational disease in China. Noise energy is the main risk factor for occupational NIHL. Evidence shows the temporal structure of noise (as indicated by kurtosis metric) contribute to the development of NIHL. However, the role of the kurtosis metric in evaluating the risk of occupational NIHL associated with complex noise has been rarely reported.

What is added by this report?

Noise temporal structure (as indicated by kurtosis) is an important risk factor for occupational NIHL in addition to noise energy. Kurtosis can be used to quantify complex noise exposure. A combination of noise kurtosis and noise energy can effectively evaluate the risk of occupational hearing loss associated with complex noise.

What are the implications for public health practice?

Considering the effect of noise temporal structure on occupational NIHL, the existing international noise exposure standards (e.g. measurement method and noise exposure limit) for complex noise should be modified based on noise temporal structure. More effort is needed to reduce noise exposure, improve health screening, and monitor occupational NIHL.

The Immediate and Long-Term Impact of Military Aircraft Noise on Hearing: A Cross-Sectional Comparison of Fighter Pilots and Ground Staff

We examined the immediate and long-term impacts of military aircraft noise exposure on noise-induced hearing loss (NIHL) in fighter pilots and ground staff. We recruited 40 pilots, 40 ground staff, and 136 age-matched controls; all participants underwent hearing tests, including conventional pure-tone audiometry (PTA) (0.25–8.0 kHz), extended high-frequency (EHF) audiometry (9.0–18.0 kHz), and distortion-product otoacoustic emission (DPOAE) as a recent reference. A subsequent hearing test immediately after flight-mission noise exposure was requested. The results revealed higher recent hearing thresholds in pilots and ground staff than in controls. Threshold shifts at many octave band frequencies were also significantly elevated in ground staff. The grouped frequency threshold was significantly elevated in the 4–8 kHz high-frequency range. After a single flight-mission noise exposure, both ground staff and pilots showed decreased signal-to-noise ratios for DPOAE (1–8 kHz), whereas only ground staff showed significantly elevated left-ear hearing thresholds at 3, 11.2, and 12.5 kHz by conventional and EHF PTA. Fighter pilots and ground staff serve in hazardous noise-exposed environments that cause hearing damage and subsequent NIHL, but ground staff may be more vulnerable. A comprehensive hearing conservation program should be implemented to protect high-risk service members, and especially ground staff, from high-intensity noise exposure.