Risk Of Noise-induced Hearing Loss Research Articles

RELATIONSHIP OF EARPHONE USAGE WITH THE EMERGENCE OF HEARING LOSS AND HEALTH PROBLEMS IN MEDICAL STUDENTS OF SOUTH PUNJAB

Noise induced hearing loss (NIHL) is a rising concern, particularly in the young adult population who frequently use personal listening devices (PLDs) such as earphones. Medical students are at risk of having hearing related problems due to the high usage of PLDs for both academic and recreational purposes. This study aimed to assess the prevalence of hearing loss, symptoms associated with earphone use, and the relationship between earphone usage patterns and hearing thresholds among medical students in South Punjab, Pakistan. Objective: To evaluate the prevalence of hearing loss and associated symptoms (headache, tinnitus, otalgia, fatigue) about earphone usage habits, including daily duration, volume, and frequency of use, among undergraduate medical students. Methods: This cross sectional study was conducted at Nishtar Medical University and CMH Institute of Medical Sciences (CIMS), Multan from October 2023 to August 2024. A total of 267 medical students aged 18 26 years participated in this study. Participants were categorized into two groups: mild users (≤1 hour/day) and Intense users (>1 hour/day) of PLDs. Data were collected using a self administered questionnaire on demographics, earphone usage patterns, and associated symptoms. Audiometric testing was performed using Pure Tone Audiometry (PTA) to assess hearing thresholds at 250 Hz to 8000 Hz. Descriptive statistics, t tests, chi square tests, and Pearson correlation were used to analyze the data. Results: The majority of participants (55.4%) were aged 21 23 years, with a balanced gender distribution (52.4% male, 47.6% female). Intense users (53.2%) had significantly higher hearing thresholds at all frequencies compared to mild users, particularly at higher frequencies (4000 Hz and 8000 Hz). In the right ear, the prevalence of hearing loss is 3.2% for mild users and 13.3% for intense users whereas in the left ear, it is 4.8% and 12.7% for mild and intense users respectively. The most common form of hearing loss was mild sensorineural hearing loss at 4000Hz. Intense users reported higher rates of symptoms, including headache (35.9% vs. 16%), fatigue (47.2% vs. 17.6%), otalgia (46.5% vs. 22.4%), and tinnitus (34.5% vs. 17.6%), with statistically significant associations between symptom prevalence and usage duration and volume. Conclusion: Prolonged earphone usage is significantly associated with the emergence of hearing loss and increased prevalence of auditory symptoms among medical students. Despite being aware of the risks, many students do not follow safe listening practices, underscoring the need for educational initiatives. Promoting the "Rule of 60" and encouraging regular breaks during usage are essential steps to mitigate the risk of NIHL.

Hearing Loss Is Associated With Increased Mortality in a Cohort of Older Construction Trades Workers.

Hearing loss has been associated with increased mortality, and there is evidence that regular use of hearing aids reduces the mortality risk. However, these associations have not been sufficiently studied in worker populations at high risk for noise-induced hearing loss. Medical examination data for 19,379 workers employed in US Department of Energy (DOE) facilities were used. Speech-frequency pure-tone average hearing loss and hearing aid use were ascertained. Mortality status through 2021 was obtained from the National Death Index. Cox regression examined the association between hearing loss and mortality and the impact of hearing aid use. Eight thousand eighty-one workers (41.3%) had speech-frequency hearing loss and 2228 (15.3%) of these workers reported use of hearing aids. A total of 5398 deaths occurred over a median follow-up of 11.1 years. Hearing loss was an independent risk factor for higher mortality with an adjusted hazard ratio (HR) of 1.10 (95% CI = 1.03-1.17). The HR increased with hearing loss severity but the relationship was non-linear. Hearing aid users were at 30% reduced risk of mortality compared to those not using hearing aids (HR = 0.70, 95% CI = 0.63-0.77). Results are consistent with research linking hearing loss with increased mortality and the preventive impact of hearing aid use. These findings should inform workers' compensation programs in favor of: (1) better coverage of hearing loss for noise-exposed workers, and (2) inclusion of hearing aids in medical benefits. Reduction in noise exposures is a priority and workers with hearing loss should be encouraged to use hearing aids.

Changes in Plasma Levels of Prestin and Otolin-1 in Dental Students.

Dentists and dental professionals report a high prevalence of noise-induced hearing loss (NIHL) and related symptoms. Chronic exposure to high-frequency dental instrument sounds, which can damage the outer hair cells (OHCs) of the cochlea, is strongly linked to their NIHL. Similarly, dental students in teaching clinics often report symptoms associated with NIHL. In this study, we measured plasma levels of prestin and otolin-1, two biomarkers associated with inner ear health, in first-year (D1) and third-year (D3) dental students. D1 students were selected for their relatively short exposure to dental clinics, while D3 students represented a group with substantial cumulative exposure. First-year (M1) medical students, who have no exposure to dental instruments, served as the negative controls, while dental faculty, many of whom are diagnosed with NIHL or self-report hearing problems, served as the positive controls. Thirty-one students (D1=11, D3=8, M1=12) and 10 dental faculty volunteered for the study. Participating students completed an online survey about their hearing health, exposure to excessive sounds within and outside school, and use of hearing protection. Sound levels of medical Osteopathic Manipulative Medicine (OMM) and dental Simulation (SIM) labs while in session were recorded with a calibrated sound meter. Plasma levels of prestin and otolin-1 were quantitated using commercial ELISA kits. The sound level of in-session OMM lab was significantly higher (72.64 ± 1.69 dBA) than SIM lab (65.37 ± 3.97 dBA). Both medical and dental students experienced similar exposure to outside school noises; however, dental students had significantly longer exposure to high-frequency dental instrument sounds in the SIM lab (12.3 hours/week; 74.93-80.51 dBA). Plasma prestin levels were lowest in D3 students (559.88 ± 24.91 ng/ml), followed by D1 students (576.27 ± 71.44 ng/ml). Negative control M1 students had higher levels (675.73 ± 90.23 ng/ml), while the positive control dental faculty group exhibited the highest prestin levels (727.71 ± 128.65 ng/ml). Prestin levels in D3 students were significantly lower than those in M1 students, and the dental faculty group had significantly higher prestin levels than both D1 and D3 students. No differences in otolin-1 levels were observed among the groups. Our finding that D3 students, with greater experience using dental instruments in the SIM lab, exhibited the lowest plasma prestin levels may indicate a protective mechanism by the OHCs, downregulating its expression to reduce the risk of NIHL. This is in line with the findings in the dental faculty, who self-reported NIHL or hearing problems and exhibited the highest prestin levels. The lack of changes in plasma otolin-1 levels across groups, combined with students self-reporting excellent hearing health, may offer alternate view of subclinical inner ear damage among dental students. Future studies incorporating audiometry and otoacoustic emission tests along with the inner ear biomarkers may provide better understanding of NIHL in dental students.

Occupational Noise Exposure in Foot and Ankle Surgery and the Risk of Noise-Induced Hearing Loss.

Occupational exposure to high levels of noise increases the risk of noise-induced hearing loss (NIHL), resulting in significant long-term quality of life implications. Hearing protection is recommended if occupational noise exposure routinely exceeds 85 decibels (dB). The purpose of this study was to determine if foot and ankle surgeons are exposed to excessive levels of noise, thus putting them at an increased risk for NIHL. A prospective review was conducted of intraoperative recordings during a variety of foot and ankle procedures. Recordings were categorized into 3 subgroups: trauma, deformity correction and degenerative conditions, and soft tissue procedures. Noise levels were reported as maximum dB level (MDL) and time-weighted average (TWA), defined as the average dB level projected over an 8-hour period. Dose was reported as the percentage of allowable daily noise, with projected dose reported as the measured dose projected over an 8-hour period. A total of 147 operative recordings consisting of 64 (44%) deformity correction and degenerative conditions, 40 (27%) soft tissue procedures, and 43 (29%) trauma cases were collected. Maximal and average noise exposures were similar for all procedures (P = .077; P = .090), with an average MDL of 98.9 dB (range, 87.9-109.2) and TWA of 60.5 dB. Procedures also did not significantly differ in dose (P = .273), even when projected over an 8-hour period (P = .362). The average MDL of total ankle arthroplasty (TAA) and hindfoot arthrodesis procedures was 101.5 dB (range, 93.9-109.2), with 52% of all deformity correction and degenerative procedures having an MDL over 100.0 dB. Foot and ankle surgeons are typically not exposed to dangerous levels of occupational noise as per National Institute for Occupational Safety and Health recommendation; however, specific procedures, such as arthrodesis and TAA, routinely achieve noise levels that are above the recommended limits.

Changes in Auditory Performance Following a Virtual Reality Music Concert.

The purpose of this study was to evaluate threshold and suprathreshold auditory risk from a newly popular platform of music concert entertainment; virtual reality (VR) headsets. Recreational noise exposure to music is the primary source of hearing hazard in young-adults, with noise doses of in-person concert venues and music festivals well in excess of the recommended daily exposure recommendation from the National Institute for Occupational Safety and Health. While research on the relationship between personal music players and noise-induced hearing loss risk is abundant, no study has yet evaluated noise-induced hearing loss risk from VR headsets, which are newest to the commercial market at this time. Thirty-one young-adult participants (18 to 25 years) with normal-hearing sensitivity (0 to 16 dB HL) experienced a VR music concert and participated in three data collection timepoints: Session A preexposure, Session A post-exposure, and Session B post-exposure. Participants underwent baseline testing for audiometry (0.25 to 20 kHz), distortion product otoacoustic emission testing (1 to 10 kHz), and Words-in-Noise testing. Participants then wore a commercially available VR headset (Meta Quest 2) and experienced a freely available online VR music concert (via the video-sharing website "YouTube"). The VR music concert duration was 90 min set to maximum volume, which yielded an average sound level equivalent of 78.7 dBA, max sound level of 88.2 dBA, and LC peak sound level of 98.6 dBA. Post-exposure testing was conducted immediately at the conclusion of the VR concert, and again within 24 hr to 1 week after the exposure. Participants also answered a questionnaire that estimated noise exposure history (National Acoustics Laboratory "Noise Calculator"). Post-exposure deficit was not observed in DPOAEs or Words-in-Noise score (p's > 0.05). However, statistically significant temporary post-exposure deficit was observed in audiometry at 4, 8, and 12.5 kHz (p's < 0.05) (mean differences: 2 to 3 dB HL). Twenty-four hours and 1-week post-exposure measurements revealed no permanent changes from baseline measurements (p's > 0.05) aside from one spurious difference at 12.5 kHz. Males tended to exhibit a significantly higher noise history score on average than females. The primary, secondary, and tertiary sources of noise hazard history in this young-adult cohort included amplified music. These preliminary data suggest that VR music concerts-which are likely to produce a substantially lower noise dose than in-person music concerts-may still be capable of producing at least slight, temporary threshold shifts on the order of 2 to 3 dB HL. Future research should include VR headsets in personal music player risk assessment, as the VR music concert platform is increasing rapidly in popularity among young-adults.

Comparison of the risk of noise-induced hearing loss between male police officers and male non-police officers: a nationwide cohort study using propensity score matching in South Korea

BackgroundPolice officers are at a high risk of noise-induced hearing loss (NIHL) owing to the nature of their work. Therefore, this study aimed to compare the risk of NIHL in police officers and controls.MethodsThis study used the National Health Insurance claims data of workers aged 25–65 years obtained from 2005 to 2015. The case group comprised police officers, while the control group comprised general workers and public officers. The study followed a three-phase cohort design. The standardized incidence ratio (SIR) was calculated using an indirect standardization method based on age. Propensity score matching was performed using the greedy matching method, with a police officer-to-control group ratio of 1:3. Cox regression analysis was performed for each matched control group. Statistical significance was determined by a lower limit of greater than 1, based on the 95% confidence interval (CI).ResultsThe SIR values for police officers were 1.62 (95% CI: 1.44–1.82) compared with general workers and 1.78 (95% CI: 1.66–1.73) compared with public officers. Police officers exhibited an increased risk of NIHL compared with general workers (hazard ratio (HR): 1.71, 95% CI: 1.49–1.98) and public officers (HR: 2.19, 95% CI: 1.88–2.56).ConclusionsIt is necessary to prevent NIHL by reducing occupational noise exposure through measures such as wearing earplugs, improving shooting training methods, and improving the shift work system.

Application of the occupational health risk assessment model in predicting the risk of noise-induced hearing loss in noise-polluted manufacturers in southern China

Objective. This study aimed to evaluate the correlation between occupational noise-induced hearing loss (ONIHL) and noise exposure in different positions within manufacturing facilities that primarily produce electronic devices, wooden furniture and hardware machinery in southern China and to investigate the practical application of the risk assessment model. Methods. Noise exposure data were collected from 115 workers in 10 manufacturing industries in southern China through on-site investigation. Subsequently, sample testing was conducted in accordance with Chinese standards. The 31 job positions investigated were classified into two similar exposure groups (SEGs). The occupational health risk assessment (OHRA) model was used to evaluate the risks of ONIHL in various job positions. Results. More than half of the positions in both groups had noise levels exceeding 85 dB. In both SEGs, male workers exhibited similar risk patterns of acquiring hearing impairment, with a more pronounced and earlier risk of hearing loss compared to female workers. Age was also found to be a risk factor for hearing impairments. Conclusion. The ORHA model demonstrated a positive correlation between noise exposure levels and NIHL. This model can help employers assess job management with noise exposure and take measures to implement an effective risk management system.

Making a racket in America's fastest growing sport: Evaluation of noise exposure in pickleball

ObjectiveTo measure noise exposure present on pickleball courts and assess the risk of noise-induced hearing loss (NIHL) per guidelines put forward by the National Institute of Occupational Safety and Health (NIOSH). MethodsObservational study measuring noise levels at multiple recreational pickleball courts in the Richmond, VA area, documenting LAeq, LASmax, and LCpeak at courtside and waiting areas of pickleball courts. Measurements were completed using the NIOSH SLM application on an iPhone 13 with iMM-6 Calibrated Measurement Microphone (equivalent to IEC 61672-1 Class II) that was calibrated using ND-9 Sound Level Calibrator (IEC942 Class I). ResultsAverage sound levels recorded at waiting areas adjacent to the courts, measured in LAeq, LASmax, and LCpeak, were 69.1 dBA, 92.0 dBA, and 112.1 dBC, respectively, while courtside measurements were 69.7 dBA, 92.2 dBA, and 115.6 dBC, respectively. These measurements were within NIOSH and OSHA recommendations. ConclusionThe data demonstrates that randomly sampled pickleball courts have noise levels that do not increase risk for NIHL for participants or bystanders alike based on NIOSH guidelines. However, prolonged noise exposure and ambient noise pollution may have other health implications and warrant further investigations. Level of evidenceLevel 2.

Overview of the Prevalence and Contributing Factors for Occupational Noise-Induced Hearing Loss (NIHL) in Malaysia

INTRODUCTION: This manuscript aims to provide a synopsis of the current situation surrounding noise exposure at work and the risk of noise-induced hearing loss (NIHL) in Malaysia. NIHL is an occupational illness that affects most many people and can be prevented in many countries in the world. The production and agriculture businesses and the extraction of natural resources and urban traffic all contribute to ambient noise levels. Working in a noisy environment is the main occupational risk factor for adult-onset hearing loss. In this study, we investigate the prevalence of NIHL across different industries, as well as research publication trends on NIHL. MATERIAL AND METHODS: Conducted thorough several online databases, like Science Direct, Web of Science, and Google Scholar, for related research that had already been published. The review phases were carried out according to the recommendations laid out by the preferred reporting items for systematic reviews. A set of criteria was developed for selecting relevant studies. RESULTS: The prevalence of NIHL among workers in Malaysia, varies across different industries and has been reported to range from 5.0% to 82.6%. NIHL has multiple contributing factors, including noise intensity, long-term exposure to daily noise, hearing protection devices and age. A review of these studies found varying percentages of individuals affected by each contributing factor. CONCLUSION: Occupational NIHL is a preventable health risk for workers across industries. Employers must adopt engineering and administrative controls (education and training) and provide personal hearing protectors to protect workers from noise.

Noise-Induced Hearing Loss: Should Surgeons Be Wearing Ear Protection During Primary Total Joint Arthroplasty?

The risk of noise-induced hearing loss (NIHL) to orthopedic surgeons due to occupational exposures is unknown. A level of 85 decibels (dB) over an 8-hour time-weighted average (TWA) is considered hazardous. We sought to identify whether manual and/or robotic arthroplasty procedures increase surgeons' risk of developing NIHL. At our institution, we prospectively collected intraoperative recordings with a microphone attached to the surgeon during manual total knee arthroplasty (TKA), manual total hip arthroplasty (THA), and robotic-assisted total knee arthroplasty (RTKA). Recordings taken in the operating room without operating room staff present served as baseline controls. The 172 recordings consisted of 46 baseline, 42 THA, 40 TKA, and 44 RTKA recordings. Decibel levels were reported as "maximum dB level" (the highest sound pressure level using an A-weighted dB scale), "LAeq" (the equivalent continuous sound level), "LCpeak" (the peak sound pressure level using a C-weighted dB scale), and "TWA" (the average dB level projected over an 8-hour period). The percentage of allowable daily noise dose was reported as "dose" and the measured dose projected over 8 hours as "projected dose." The recordings of surgeries had average maximum dB levels ranging from 106.0 to 108.0 dB, all significantly greater than controls. Robotic-assisted total knee arthroplasties had the highest average dose (18.7%) and average projected dose (252.0%). Our review of recordings at a single institution found that noise levels of RTKAs surpassed projected doses of 100%. Orthopedic surgeons performing more than 2 RTKAs per day may be at increased risk of NIHL. Further research is needed to assess the effectiveness of measures such as ear protection to minimize surgeons' exposure.

When does the risk of noise-induced hearing loss become relevant? : The new exposure tables for occupational noise-induced hearing loss (BK-Nr. 2301 traffic light scheme)

When does the risk of noise-induced hearing loss become relevant? : The new exposure tables for occupational noise-induced hearing loss (BK-Nr. 2301 traffic light scheme)

Risk analysis of noise-induced hearing loss of workers in the automobile manufacturing industries based on back-propagation neural network model: a cross-sectional study in Han Chinese population

ObjectivesThis study aims to predict the risk of noise-induced hearing loss (NIHL) through a back-propagation neural network (BPNN) model. It provides an early, simple and accurate prediction method for NIHL.DesignPopulation...

Impact of occupational noise exposure on the hearing level in hospital staffs: a longitudinal study.

The study aimed to evaluate the impact of occupational noise on hearing loss among healthcare workers using audiometry. A longitudinal study was conducted with a six-month follow-up period in a hospital with 21 participants, divided into high-noise-exposure (HNE) and low-noise-exposure (LNE) groups. Mean noise levels were higher in the HNE group (70.4 ± 4.5 dBA), and hearing loss was measured using pure-tone audiometry at baseline and follow-up. The HNE group had significantly higher mean threshold levels at frequencies of 0.25kHz, 0.5kHz, 4.0kHz, and an average of 0.5, 1, 2, and 4kHz (all p-values < 0.05) after the follow-up period. After adjusting for confounding factors, the HNE group had significantly higher hearing loss levels at 0.25kHz, 0.5kHz, and average frequencies of 0.5, 1, 2, and 4kHz compared to the LNE group at the second measurement. Occupational noise levels above 65 dBA over six months were found to cause significant threshold changes at frequencies of 0.25kHz, 0.5kHz, and an average of 0.5-4.0kHz. This study highlights the risk of noise-induced hearing loss among healthcare workers and emphasizes the importance of implementing effective hearing conservation programs in the workplace. Regular monitoring and assessment of noise levels and hearing ability, along with proper use of personal protective equipment, are crucial steps in mitigating the impact of occupational noise exposure on the hearing health of healthcare workers.

Case study: Noise risk assessment of workers at the mechanized mining face of coal mines

An assessment of workers at the mechanized mining face of coal mines was conducted in China. The survey on the current status of subject exposure to noise of coal miners was administered by occupational health investigation and detailed record of work days. The noise dosimeter measurements of 211 workers were obtained, including coal cutting, supporting, transportation, crushing, and auxiliary (such as air pressure, pump, and maintenance). A total of 56.4% of the LEX,8h exceeded 85 dB(A), and the average 8-hour equivalent sound level of the workers at the mechanized mining face of these coal mines was 91.2 dB(A). Within the noise frequency from 500 to 6000 Hz, there was a “V” shift in the displacement value of hearing threshold. At the noise frequency of 4000 Hz, the hearing loss N50 (dB) of workers reached the maximum. The longer the exposure time, the higher risk both in high-frequency hearing loss and noise-induced deafness. The risk of high-frequency hearing loss reached the high-risk level at 25 years of work, while the risk of noise deafness reached the high-risk level after 30 years of work. In addition, the Pearson correlation coefficient between the noise exposure time and the risk of noise-induced hearing loss was high and positively correlated. The results show that the production noise hazards at the mechanized mining face of coal mine are relatively large. High levels of hazardous noise exposure are typical in coal mines. The noise exposure data can help to develop more feasible noise controls for the employer.

Surgeons Who Perform Total Hip Arthroplasty Are at Risk for Noise-Induced Hearing Loss, Especially When Using Automated Broaching.

Noise-induced hearing loss (NIHL) is a serious concern for orthopedic surgeons. The National Institute for Occupational Safety and Health (NIOSH) sets the safe exposure limit at 85 dB for 8 hours, yet operating rooms often surpass this limit. This study investigated if using an automated broaching system exposes orthopedic surgeons to dangerous decibel (dB) levels. A prospective study analyzed 138 intraoperative sound recordings from 92 total hip arthroplasty (THA) surgeries and 46 baseline measurements at an academic-affiliated private practice, using the NIOSH Sound Level Meter (SLM) application and a microphone. The surgeries were categorized into manual and automated broaching. Key metrics measured included maximal dB level (MDL), peak sound pressure (LCpeak), average continuous sound (LAeq), and average weighted sound in an 8-hour period (TWA), along with dose representations, to identify hazardous noise levels. Of the 92 THA sound recordings, 50 used manual broaching and 42 employed automated broaching. Automated broaching exhibited higher noise levels, with an average MDL of 109.92 dBA, a LAeq of 86.09 dBA, a TWA of 76.48 dBA, and a projected noise dose of 137.74%. In contrast, manual broaching exhibited an average MDL of 105.87 dBA, a LAeq of 83.06 dBA, a TWA of 72.82 dBA, and a projected noise dose of 82.02%. This study highlights the auditory risks from automated broach and manual THA surgeries that orthopedic surgeons experience. Manufacturers should focus on reducing instrument noise when designing surgical tools and orthopedic surgeons and operating room staff should take measures to protect themselves from NIHL during surgery. [Orthopedics. 2024;47(6):349-354.].

The effects of music listening time with headphones on hearing thresholds among the young population

BackgroundToday, young people who listen to loud music, especially through headphones, are at an extremely high risk of noise-induced hearing loss. The aim of this study was to investigate how young people’s listening habits affect their hearing thresholds. A total of 88 young adults between the ages of 18 and 25 took part in the study, 44 of whom listened to music through headphones while the others did not. The control group was exposed to white noise at 55–65 dB with the Interacoustic AC 40 Hybrid Audiometer, and people who did not use headphones and said they were not exposed to higher levels of sound than the given sample were included in the study. Participants were given a survey to assess their music listening preferences. One hundred twenty-five to 18,000 Hz air conduction hearing thresholds were assessed for all participants.ResultsWhen the pure tone thresholds of the groups were compared, the independent t-test showed that the thresholds of the study group were significantly worse than those of the control group. Bilaterally in the 4000 Hz band and for the left ear in the 6000 Hz band (p < 0.05). There were also significant differences between the groups in the 14,000 Hz and 16,000 Hz bands in the right ear and the 14,000 Hz, 16,000 Hz, and 18,000 Hz bands in the left ear (p < 0.05). Twenty-two participants reported listening to music at a high level, 16 participants at a moderate level, and 6 participants at a very high level.ConclusionAlthough the hearing thresholds of the study group were worse than those of the control group in the 4000 Hz, 6000 Hz, 14,000 Hz, 16,000 Hz, and 18,000 Hz bands, the hearing thresholds of both groups were still within the hearing range and could be classified as normal. It should be remembered that hearing will deteriorate if a person listens to loud or very loud music continuously through headphones. The public, especially young people, should be made aware of this.

Interactions of genetic variations in FAS, GJB2 and PTPRN2 are associated with noise-induced hearing loss: a case-control study in China

BackgroundThis study aimed to screen and validate noise-induced hearing loss (NIHL) associated single nucleotide polymorphisms (SNPs), construct genetic risk prediction models, and evaluate higher-order gene-gene, gene-environment interactions for NIHL in Chinese population.MethodsFirst, 83 cases and 83 controls were recruited and 60 candidate SNPs were genotyped. Then SNPs with promising results were validated in another case-control study (153 cases and 252 controls). NIHL-associated SNPs were identified by logistic regression analysis, and a genetic risk model was constructed based on the genetic risk score (GRS), and classification and regression tree (CART) analysis was used to evaluate interactions among gene-gene and gene-environment.ResultsSix SNPs in five genes were significantly associated with NIHL risk (p < 0.05). A positive dose-response relationship was found between GRS values and NIHL risk. CART analysis indicated that strongest interaction was among subjects with age ≥ 45 years and cumulative noise exposure ≥ 95 [dB(A)·years], without personal protective equipment, and carried GJB2 rs3751385 (AA/AB) and FAS rs1468063 (AA/AB) (OR = 10.038, 95% CI = 2.770, 47.792), compared with the referent group. CDH23, FAS, GJB2, PTPRN2 and SIK3 may be NIHL susceptibility genes.ConclusionGRS values may be utilized in the evaluation of the cumulative effect of genetic risk for NIHL based on NIHL-associated SNPs. Gene-gene, gene-environment interaction patterns play an important role in the incidence of NIHL.

Comparison of the effects of mental fatigue on medial olivocochlear reflex and cortical activity

The medial cochlear reflex (MOCR) is assumed to protects the inner ear from acoustic overexposure. The MOCR strength assay is expected to be applied to screen for individuals at high risk for noise-induced hearing loss. However, the MOCR strength varies from one measurement to another, and it is necessary to identify the factors that cause the MOCR variations for more accurate risk assessment. It has been reported that variations in cortical cognitive function, e.g., attention and expectation, influence MOCR strength. Here we examined the effects of mental fatigue, one of the causes that degrade cognitive functions, on MOCR. The degree of mental fatigue was adjusted by varying the difficulty of a calculation task and investigated the effects on MOCR. To elucidate the mechanism of MOCR variations associated with mental fatigue, cortical activities were evaluated by measuring slow vertex response (SVR). Although MOCR strength and SVR amplitude did not change significantly after the calculation task, two measures had reverse dependence on the difficulty of the calculation task; A moderately difficult calculation task increased SVR amplitude while reduced MOCR strength. The results implicate that MOCR variations associated with mental fatigue can be attributed to cortical activity changes.

Noise-Induced Hearing Threshold Shift Correlated with Body Weight and External-Ear Amplification in Chinchilla: a Preliminary Analysis

BackgroundExternal-ear amplification (EEA) has been shown to vary from 5–19 dB-A in large datasets of pediatric, adolescent, and adult human participants. However, variable EEA is an overlooked characteristic that likely plays a role in individual noise-induced hearing loss (NIHL) susceptibility. A noise exposure varying 5–19 dB-A translates to high-EEA individuals theoretically experiencing 3–4 times greater NIHL risk than low-EEA individuals.ObjectiveThe purpose of this preliminary analysis was to test the hypothesis that higher EEA is correlated with increased noise-induced threshold shift susceptibility.DesignNine chinchillas were exposed to 4-kHz octave-band noise at 89 dB-SPL for 24 h. Auditory brainstem response thresholds were obtained pre-exposure, 24-h post-exposure, and 4-week post-exposure. Relationships between EEA and threshold shift were analyzed.ResultsOpen-ear EEA ranged 11–19 dB-SPL, and occluded-ear EEA ranged 10–21 dB-SPL. Higher occluded-ear EEA was correlated with increased NIHL susceptibility (p = 0.04), as was lower body weight (p = 0.01). Male animals exhibited more threshold shift than female animals (p = 0.02), lower body weight than female animals (p = 0.02), and higher occluded-ear EEA (male mean = 18 dB; female mean = 15 dB).ConclusionsTaken together, increased threshold shift susceptibility was observed in the smallest animals, animals with the highest occluded-ear EEA, and in male animals (which tended to have higher occluded-ear EEA). Given the established relationship between smaller body size and higher occluded-ear EEA, these preliminary results suggest that body size (and occluded-ear EEA; a function of body size) could be a potential, underlying driver of NIHL susceptibility differences, rather than true sex differences.

Risk of noise-induced hearing loss in the spine surgeon

Occupation-related noise-induced hearing loss (NIHL) has both negative economic and quality of life implications. The risk spine surgeons undertake in regards to NIHL during operative intervention is unknown. Governing bodies, including the National Institute for Occupational Safety and Health, have recommended exposure limits not to exceed 85 decibels (dB) over 8 hours. The purpose of this study is to characterize noise exposure to spine surgeons in the operating room (OR). Prospective collection of intraoperative recordings of spinal surgeries (cervical and thoracic/lumbar) was undertaken. Data gathered included procedure, operative duration, presence of background music, and noise information. Noise information included maximum decibel level (MDL), Peak level (LCPeak), Equivalent continuous sound pressure level, time weighted average (TWA), dose, and projected dose. Noise measurements were compared with baseline controls with and without music (empty ORs). Two hundred seven noise recordings were analyzed. One hundred eighteen of those being spinal surgeries, 49 baseline recordings without music, and 40 with music. Maximum decibel level reached a maximum value of 111.5 dBA, with an average amongst surgical recordings of 103 dBA. Maximum decibel level exceeded 85 dBA in 100% of cases and was greater than 100 dBA in 78%. The maximum LCPeak recorded was 132.9 dBC with an average of 120 dBC. Furthermore, the average dose was 7.8% with an average projected dose of 26.5%. The highest dose occurred during a laminectomy at 72.9% of daily allowable noise. Maximum projected dose yielded 156% during a 3-level anterior cervical discectomy and fusion. Spine surgeons are routinely exposed to damaging noise levels (>85 dBA) during operative intervention. With spine surgeons often performing multiple surgeries a day, the cumulative risk of noise exposure cannot be ignored. The synergistic effects of continuous and impact noise places spine surgeons at risk for the development of occupation-related NIHL.