Sex-based Differences in Hearing Loss: Perspectives From Non-clinical Research to Clinical Outcomess

Association Between COPD and Hearing Loss

OBJECTIVE

The goal of the present study was to estimate the risk of hearing impairment in patients with COPD using huge nationwide population.

METHODS

A retrospective case-control study was performed using the National Health Insurance Database in South Korea from 2002 through 2019. Totally 614,370 COPD patients and matched 2,170,504 control participants were selected at a 1:4 ratio. Hearing impairment was defined based on the registered data in the Ministry of Health and Welfare of Korea with six levels of severity of hearing impairment. The propensity score was calculated, and overlap-weighted multinomial logistic regression was used to calculate the odds ratios of COPD for hearing impairment.

RESULTS

A total of 2.67% of COPD patients and 1.9% of control participants had hearing impairment. The COPD patients indicated 1.10-1.21 times higher odds for hearing impairment according to the severity of hearing impairment than the control group. In accordance with age and sex, the younger age group (<65 years old) and female group demonstrated higher odds for hearing impairment related to the presence of COPD. The high odds for hearing impairment in patients with COPD was consistent in all other subgroups, except for the underweight group.

CONCLUSIONS

COPD was associated with an increased risk of hearing impairment in the general population in Korea.

LEVEL OF EVIDENCE

3 Laryngoscope, 2024.

The curvature quantification of wave I in auditory brainstem responses detects cochlear synaptopathy in human beings

PURPOSE

Patients with age-related hearing loss complain often about reduced speech perception in adverse listening environment. Studies on animals have suggested that cochlear synaptopathy may be one of the primary mechanisms responsible for this phenomenon. A decreased wave I amplitude in supra-threshold auditory brainstem response (ABR) can diagnose this pathology non-invasively. However, the interpretation of the wave I amplitude in humans remains controversial. Recent studies in mice have established a robust and reliable mathematic algorithm, i.e., curve curvature quantification, for detecting cochlear synaptopathy. This study aimed to determine whether the curve curvature has sufficient test-retest reliability to detect cochlear synaptopathy in aging humans.

METHODS

Healthy participants were recruited into this prospective study. All subjects underwent an audiogram examination with standard and extended high frequencies ranging from 0.125 to 16 kHz and an ABR with a stimulus of 80 dB nHL click. The peak amplitude, peak latency, curvature at the peak, and the area under the curve of wave I were calculated and analyzed.

RESULTS

A total of 80 individuals with normal hearing, aged 18 to 61 years, participated in this study, with a mean age of 26.4 years. Pearson correlation analysis showed a significant negative correlation between curvature and age, as well as between curvature and extended high frequency (EHF) threshold (10-16 kHz). Additionally, the same correlation was observed between age and area as well as age and EHF threshold. The model comparison demonstrated that the curvature at the peak of wave I is the best metric to correlate with EHF threshold.

CONCLUSION

The curvature at the peak of wave I is the most sensitive metric for detecting cochlear synaptopathy in humans  and may be applied in routine diagnostics to detect early degenerations of the auditory nerve.

Alpha9alpha10 knockout mice show altered physiological and behavioral responses to signals in masking noise

Medial olivocochlear (MOC) efferents modulate outer hair cell motility through specialized nicotinic acetylcholine receptors to support encoding of signals in noise. Transgenic mice lacking the alpha9 subunits of these receptors (α9KOs) have normal hearing in quiet and noise, but lack classic cochlear suppression effects and show abnormal temporal, spectral, and spatial processing. Mice deficient for both the alpha9 and alpha10 receptor subunits (α9α10KOs) may exhibit more severe MOC-related phenotypes. Like α9KOs, α9α10KOs have normal auditory brainstem response (ABR) thresholds and weak MOC reflexes. Here, we further characterized auditory function in α9α10KO mice. Wild-type (WT) and α9α10KO mice had similar ABR thresholds and acoustic startle response amplitudes in quiet and noise, and similar frequency and intensity difference sensitivity. α9α10KO mice had larger ABR Wave I amplitudes than WTs in quiet and noise. Other ABR metrics of hearing-in-noise function yielded conflicting findings regarding α9α10KO susceptibility to masking effects. α9α10KO mice also had larger startle amplitudes in tone backgrounds than WTs. Overall, α9α10KO mice had grossly normal auditory function in quiet and noise, although their larger ABR amplitudes and hyperreactive startles suggest some auditory processing abnormalities. These findings contribute to the growing literature showing mixed effects of MOC dysfunction on hearing.

Trends in prevalence of hearing loss in adults in the USA 1999-2018: a cross-sectional study

BACKGROUND

A better understanding of how the prevalence of hearing loss and its associated factors change over time could help in developing an appropriate program to prevent the development of hearing loss.

METHODS

Population-representative cross-sectional data from the United States National Health and Nutrition Examination Survey (NHANES) were used to estimate the trends in the prevalence of hearing loss among adults in the USA over the period 1999-2018. A total of 15,498 adult participants aged 20 years or older had complete audiometric examination data. Logistic regression was employed to evaluate the trend in hearing loss; weighted Rao-Scott χ2 tests and univariate logistic regression analyses were used to examine the association between hearing loss and relevant factors.

RESULTS

The overall hearing loss prevalence in 1999-2018 was 19.1% 19.1 (95% CI, 18.0-20.2%). The prevalence of hearing loss decreased in cycles (P for trend < 0.001). For participants aged 20-69 years, the prevalence decreased from 15.6% (95% CI, 12.9-18.4%) in 1999-2000 to 14.9% (95% CI, 13.2- 16.6%) in 2015-2016; for participants aged > 70 years the prevalence decreased from 79.9% (95% CI, 76.1-83.8%) in 2005-2006 to 64.5% (95% CI, 58.8-70.2%) in 2017-2018. Participants with hearing loss were likely to be older, male, non-Hispanic white, and to have not completed high school. Mild hearing loss was more prevalent among those aged 20-79 years; in those aged over 80 years the prevalence of moderate hearing loss exceeded that of mild loss. Among all otologically normal participants, hearing thresholds increased with age across the entire frequency range.

CONCLUSIONS

The prevalence of hearing loss in USA adults changed over the period 1999-2018. The trends observed provide valuable insight for making public health plans and allocating resources to hearing care. Further investigation is necessary to monitor hearing loss and its potential risk factors.

Early-Onset Hearing Loss in Mouse Models of Alzheimer's Disease and Increased DNA Damage in the Cochlea

There is considerable interest in whether sensory deficiency is associated with the development of Alzheimer's disease (AD). Notably, the relationship between hearing impairment and AD is of high relevance but still poorly understood. In this study, we found early-onset hearing loss in two AD mouse models, 3xTgAD and 3xTgAD/Polβ+/-. The 3xTgAD/Polβ+/- mouse is DNA repair deficient and has more humanized AD features than the 3xTgAD. Both AD mouse models showed increased auditory brainstem response (ABR) thresholds between 16 and 32 kHz at 4 weeks of age, much earlier than any AD cognitive and behavioral changes. The ABR thresholds were significantly higher in 3xTgAD/Polβ+/- mice than in 3xTgAD mice at 16 kHz, and distortion product otoacoustic emission signals were reduced, indicating that DNA damage may be a factor underlying early hearing impairment in AD. Poly ADP-ribosylation and protein expression levels of DNA damage markers increased significantly in the cochlea of the AD mice but not in the adjacent auditory cortex. Phosphoglycerate mutase 2 levels and the number of synaptic ribbons in the presynaptic zones of inner hair cells were decreased in the cochlea of the AD mice. Furthermore, the activity of sirtuin 3 was downregulated in the cochlea of these mice, indicative of impaired mitochondrial function. Taken together, these findings provide new insights into potential mechanisms for hearing dysfunction in AD and suggest that DNA damage in the cochlea might contribute to the development of early hearing loss in AD.

Ototoxicity of polystyrene nanoplastics in mice, HEI-OC1 cells and zebrafish

Polystyrene nanoplastics are a novel class of pollutants. They are easily absorbed by living organisms, and their potential toxicity has raised concerns. However, the impact of polystyrene nanoplastics on auditory organs remains unknown. Here, our results showed that polystyrene nanoplastics entered the cochlea of mice, HEI-OC1 cells, and lateral line hair cells of zebrafish, causing cellular injury and increasing apoptosis. Additionally, we found that exposure to polystyrene nanoplastics resulted in a significant elevation in the auditory brainstem response thresholds, a loss of auditory sensory hair cells, stereocilia degeneration and a decrease in expression of Claudin-5 and Occludin proteins at the blood-lymphatic barrier in mice. We also observed a significant decrease in the acoustic alarm response of zebrafish after exposure to polystyrene nanoplastics. Mechanistic analysis revealed that polystyrene nanoplastics induced up-regulation of the Nrf2/HO-1 pathway, increased levels of malondialdehyde, and decreased superoxide dismutase and catalase levels in cochlea and HEI-OC1 cells. Furthermore, we observed that the expression of ferroptosis-related indicators GPX4 and SLC7A11 decreased as well as increased expression of ACLS4 in cochlea and HEI-OC1 cells. This study also revealed that polystyrene nanoplastics exposure led to increased expression of the inflammatory factors TNF-α, IL-1β and COX2 in cochlea and HEI-OC1 cells. Further research found that the cell apoptosis, ferroptosis and inflammatory reactions induced by polystyrene nanoplastics in HEI-OC1 cells was reversed through the pretreatment with N-acetylcysteine, a reactive oxygen species inhibitor. Overall, our study first discovered and systematically revealed the ototoxicity of polystyrene nanoplastics and its underlying mechanism.

Targeted therapeutic hypothermia protects against noise induced hearing loss

Introduction

Exposure to occupational or recreational loud noise activates multiple biological regulatory circuits and damages the cochlea, causing permanent changes in hearing sensitivity. Currently, no effective clinical therapy is available for the treatment or mitigation of noise-induced hearing loss (NIHL). Here, we describe an application of localized and non-invasive therapeutic hypothermia and targeted temperature management of the inner ear to prevent NIHL.

Methods

We developed a custom-designed cooling neck collar to reduce the temperature of the inner ear by 3-4°C post-injury to deliver mild therapeutic hypothermia.

Results

This localized and non-invasive therapeutic hypothermia successfully mitigated NIHL in rats. Our results show that mild hypothermia can be applied quickly and safely to the inner ear following noise exposure. We show that localized hypothermia after NIHL preserves residual hearing and rescues noise-induced synaptopathy over a period of months.

Discussion

This study establishes a minimally-invasive therapeutic paradigm with a high potential for rapid translation to the clinic for long-term preservation of hearing health.

Hospitalizations, Emergency Department Visits, and Home Health Use Among Older Adults With Sensory Loss

Objectives: This study examines healthcare resource use (hospitalizations, emergency department [ED] visits, and home health episodes) among adults 65 and older diagnosed with hearing, vision, or dual sensory loss (SL) seen in the primary care setting of an academic health system. Methods: Multivariable logistic regression models were used to examine the relationship between SL (identified using ICD-10 codes) and healthcare resource use for 45,000 primary care patients. Results: The sample included 5.5% (N = 2479) with hearing loss, 10.4% (N = 4697) with vision loss, and 1.0% with dual SL (N = 469). Hearing loss increased the likelihood of having an ED visit (OR = 1.22, CI: 1.07-1.39), and home health services (OR = 1.27, CI: 1.07-1.51) compared to older adults without any SL. Vision loss reduced the likelihood of having a hospitalization (OR = .81, CI: .73-.91). Discussion: Findings support research into the drivers of healthcare use among older adults with sensory loss.

Hearing Loss and Sociodemographic Barriers to Health Care Access Using the All of Us Research Program

OBJECTIVE

To explore how gender and low-income status independently influence general health care access in patients with hearing loss.

STUDY DESIGN

Cross-sectional study.

SETTING

National database.

METHODS

Patients with a diagnosis of sensorineural hearing loss from the National Institutes of Health All of Us database were included. Data entered from May 2018 to November 2022 was analyzed. Patient demographics such as age, gender, educational level, and insurance status were assessed. Multivariate logistic regressions were performed for statistical evaluation.

RESULTS

A subset of 8875 patients (48.3% male, mean age 69) were evaluated. After multivariate analysis, female participants were more likely than male participants to report difficulty affording prescribed medications (odds ratio [OR]: 1.7, p < .0005) and specialists (OR: 1.4, p < 0.005). Female patients were also more likely to delay care due to elder care responsibilities (OR: 2.6, p < .0005), employment obligations (OR: 1.7, p < .0005), and feelings of apprehension in seeing a provider (OR: 1.7, p < .0005). Finally, female participants reported feeling less likely to be involved in their own medical care compared to males (OR: 1.2, p < .005). Low-income (<$25,000) participants reported less likely to feel respected (OR: 3.2, p < .0005) and delivered understandable health information (OR: 2.3, p < .0005) by providers compared to participants of higher income.

CONCLUSION

This work suggests that patients with hearing loss, female gender, and lower socioeconomic status independently introduce barriers to health care access and utilization. These factors should be considered in efforts to promote equity in the care of patients with hearing loss.

Downward trends in the global burden of congenital complete hearing loss in children younger than five years from 1990 to 2030

Background

The global epidemiological data on congenital hearing loss in children is sparse. We aimed to analyse the trends in the burden of complete hearing loss caused by congenital birth defects in children younger than five years from 1990 to 2030.

Methods

Using data from the Global Burden of Disease (GBD) Study 2019, we reported the counts and rates of prevalence and years lived with disability (YLD) by age, sex, and sociodemographic index (SDI). We also forecasted the prevalence rates until 2030 through the autoregressive integrated moving average (ARIMA) and Bayesian age-period-cohort (BAPC) models.

Results

We observed a global prevalence rate of 15.4 (95% uncertainty interval (UI) = 5.8 to 33.8) and a YLD rate of 3.3 (95% UI = 1.1 to 7.1) per 100 000 population in 2019, with both showing downward trends from 1990 to 2019. Regionally, Oceania had the highest prevalence (47.2; 95% UI = 18.8 to 96.6) and YLD (10; 95% UI = 3.2 to 22.8) rates, while Central Europe had the lowest rates. Nationally, the prevalence (85.0; 95% UI = 36.8 to 166.8) and YLD (17.9; 95% UI = 6.6 to 36.9) rates were highest in Myanmar and lowest in Peru. Only the United States of America (2.6%; 95% UI = -4.6 to 14.4) and Norway (0.6%; 95% UI = -6.7 to 16.2) showed upward trends. Compared to girls, the prevalence and YLD rates were higher for boys at global, regional, and five SDI quintile levels, except for Eastern Sub-Saharan Africa. At the global level, downward trends were predicted in prevalence rates from 2019 to 2030 between boys and girls.

Conclusions

Although the global burden of childhood congenital complete hearing loss showed inequalities across locations, sexes, and age groups, we found decreases in the global prevalence rates between 1990 and 2019 and predicted decreases from 2019 to 2030. Better prevention of infectious aetiologies, improving genetic diagnoses, and hearing restoration could alleviate this burden.

Differences Between Self-Reported and Objectively Measured Hearing Loss at Age 61-63 Years: The Newcastle Thousand Families Birth Cohort

PURPOSE

Hearing loss is most prevalent among older adults, yet underestimated by patients, clinicians, and research communities. This study aimed to assess the accuracy of self-reported hearing difficulties among a group of adults aged 61-63 years, against audiometric measures.

METHOD

The analysis used a sample (N = 346) of the Newcastle Thousand Families Study birth cohort. Data from audiological examinations and self-reported hearing difficulties were used to compare subjective and objective hearing. Hearing aid use was also assessed.

RESULTS

Over 40% of the participants had some level of hearing loss (n = 155, 44.8%), and 31% (n = 133) of these reported having hearing problems during subjective assessment. Only 18 (10%) of those with objectively measured hearing loss reported using hearing aids.

CONCLUSIONS

There was an inconsistency between measured and self-perceived hearing loss among adults aged 61-63 years in this cohort. The small number of hearing aid users in the cohort is a concern, in that people in this age group appear not to be getting the help they need. The data also add to the research evidence that people at this age underestimate their hearing loss.

A mouse model of repeated traumatic brain injury-induced hearing impairment: Early cochlear neurodegeneration in the absence of hair cell loss

PURPOSE

Traumatic Brain Injury (TBI) is a major cause of death and disability worldwide. Mounting evidence suggests that even mild TBI injuries, which comprise >75% of all TBIs, can cause chronic post-concussive neurological symptoms, especially when experienced repetitively (rTBI). The most common post-concussive symptoms include auditory dysfunction in the form of hearing loss, tinnitus, or impaired auditory processing, which can occur even in the absence of direct damage to the auditory system at the time of injury. The mechanism by which indirect damage causes loss of auditory function is poorly understood, and treatment is currently limited to symptom management rather than preventative care. We reasoned that secondary injury mechanisms, such as inflammation, may lead to damage of the inner ear and parts of the brain used for hearing after rTBI. Herein, we established a model of indirect damage to the auditory system induced by rTBI and characterized the pathology of hearing loss.

METHODS

We established a mouse model of rTBI in order to determine a timeline of auditory pathology following multiple mild injuries. Mice were subject to controlled cortical impact at the skull midline once every 48 h, for a total of 5 hits. Auditory function was assessed via the auditory brainstem response (ABR) at various timepoints post injury. Brain and cochleae were collected to establish a timeline of cellular pathology.

RESULTS

We observed increased ABR thresholds and decreased (ABR) P1 amplitudes in rTBI vs sham animals at 14 days post-impact (dpi). This effect persisted for up to 60 days (dpi). Auditory temporal processing was impaired beginning at 30 dpi. Spiral ganglion degeneration was evident at 14 dpi. No loss of hair cells was detected at this time, suggesting that neuronal loss is one of the earliest notable events in hearing loss caused by this type of rTBI.

CONCLUSIONS

We conclude that rTBI results in chronic auditory dysfunction via damage to the spiral ganglion which occurs in the absence of any reduction in hair cell number. This suggests early neuronal damage that may be caused by systemic mechanisms similar to those leading to the spread of neuronal death in the brain following TBI. This TBI-hearing loss model provides an important first step towards identifying therapeutic targets to attenuate damage to the auditory system following head injury.

Sex and Race Representation in Temporal Bone Histopathology Studies in the United States: A Systematic Review

OBJECTIVES

The author's objective was to evaluate sex and race representation in temporal bone histopathology studies.

DESIGN

PubMed, Embase, Cochrane, Web of Science, and Scopus were searched for studies written in English examining temporal bone histopathology specimens from U.S.-based institutions from January 1, 1947, to September 1, 2021. Two authors then performed "snowballing" by reviewing references from the initial search and included the studies that fulfilled the inclusion criteria. For each study, the following information was collected: publication details, study design, funding, institution from where temporal bone specimens were procured, number of study specimens, and donor demographical information.

RESULTS

The authors found that out of 300 studies, 166 (55%) report sex while only 15 (5%) reported race information. Over the past 70 years, the ratio of studies reporting sex to those that do not has increased from 1.00 to 2.19 and the number of female temporal bone histopathology subjects relative to male has increased from 0.67 to 0.75. Over 90% of studies that do report this information feature participant racial compositions that do not reflect the diversity of the U.S. population.

CONCLUSIONS

Studies of temporal bone histopathology often do not report participant sex or race. The reporting of participant sex and the inclusion of specimens from female donors have both increased over time. However, temporal bone histopathology study cohorts are not representative of the racial diversity of the U.S. population. The otolaryngology community must strive to build temporal bone histopathology libraries that are representative of the diverse U.S. population.

Sex differences in the polygenic architecture of hearing problems in adults

BACKGROUND

Hearing problems (HP) in adults are common and are associated with several comorbid conditions. Its prevalence increases with age, reflecting the cumulative effect of environmental factors and genetic predisposition. Although several risk loci have been already identified, HP biology and epidemiology are still insufficiently investigated by large-scale genetic studies.

METHODS

Leveraging the UK Biobank, the Nurses' Health Studies (I and II), the Health Professionals Follow-up Study, and the Million Veteran Program, we conducted a comprehensive genome-wide investigation of HP in 748,668 adult participants (discovery N = 501,825; replication N = 226,043; cross-ancestry replication N = 20,800). We leveraged the GWAS findings to characterize HP polygenic architecture, exploring sex differences, polygenic risk across ancestries, tissue-specific transcriptomic regulation, cause-effect relationships with genetically correlated traits, and gene interactions with HP environmental risk factors.

RESULTS

We identified 54 risk loci and demonstrated that HP polygenic risk is shared across ancestry groups. Our transcriptomic regulation analysis highlighted the potential role of the central nervous system in HP pathogenesis. The sex-stratified analyses showed several additional associations related to peripheral hormonally regulated tissues reflecting a potential role of estrogen in hearing function. This evidence was supported by the multivariate interaction analysis that showed how genes involved in brain development interact with sex, noise pollution, and tobacco smoking in relation to their HP associations. Additionally, the genetically informed causal inference analysis showed that HP is linked to many physical and mental health outcomes.

CONCLUSIONS

The results provide many novel insights into the biology and epidemiology of HP in adults. Our sex-specific analyses and transcriptomic associations highlighted molecular pathways that may be targeted for drug development or repurposing. Additionally, the potential causal relationships identified may support novel preventive screening programs to identify individuals at risk.

Sex differences in hearing impairment due to diet-induced obesity in CBA/Ca mice

BACKGROUND

Obesity is an independent risk factor for hearing loss. Although attention has focused on major obesity comorbidities such as cardiovascular disease, stroke, and type 2 diabetes, the impact of obesity on sensorineural organs, including the auditory system, is unclear. Using a high-fat diet (HFD)-induced obese mouse model, we investigated the impact of diet-induced obesity on sexual dimorphism in metabolic alterations and hearing sensitivity.

METHODS

Male and female CBA/Ca mice were randomly assigned to three diet groups and fed, from weaning (at 28 days) to 14 weeks of age, a sucrose-matched control diet (10 kcal% fat content diet), or one of two HFDs (45 or 60 kcal% fat content diets). Auditory sensitivity was evaluated based on the auditory brainstem response (ABR), distortion product otoacoustic emission (DPOAE), and ABR wave 1 amplitude at 14 weeks of age, followed by biochemical analyses.

RESULTS

We found significant sexual dimorphism in HFD-induced metabolic alterations and obesity-related hearing loss. Male mice exhibited greater weight gain, hyperglycemia, increased ABR thresholds at low frequencies, elevated DPOAE, and lower ABR wave 1 amplitude compared to female mice. The hair cell (HC) ribbon synapse (CtBP2) puncta showed significant sex differences. The serum concentration of adiponectin, an otoprotective adipokine, was significantly higher in female than in male mice; cochlear adiponectin levels were elevated by HFD in female but not male mice. Adiponectin receptor 1 (AdipoR1) was widely expressed in the inner ear, and cochlear AdipoR1 protein levels were increased by HFD, in female but not male mice. Stress granules (G3BP1) were significantly induced by the HFD in both sexes; conversely, inflammatory (IL-1β) responses were observed only in the male liver and cochlea, consistent with phenotype HFD-induced obesity.

CONCLUSIONS

Female mice are more resistant to the negative effects of an HFD on body weight, metabolism, and hearing. Females showed increased peripheral and intra-cochlear adiponectin and AdipoR1 levels, and HC ribbon synapses. These changes may mediate resistance to HFD-induced hearing loss seen in female mice.

Tinnitus Prevalence and Associated Factors among Dental Clinicians in the United Arab Emirates

Dental clinicians are at increased risk for developing tinnitus due to exposure to high levels of occupational noise. This study aimed to determine tinnitus prevalence and associated factors among dental clinicians. Interviews were conducted with 150 randomly selected dental clinicians using a questionnaire. Noise levels were measured at three points of time at the operating area. Tinnitus was reported in 19.33% of the participants. The average noise level was significantly higher among participants with tinnitus compared to those without the condition. More participants complained of intermittent tinnitus and the rest had the constant type, with the latter being significantly more bothersome. The weekly average time of using high-speed handpieces, suction and electric handpieces, age and experience had a significant effect on the presence of tinnitus. Only 2.7% of the participants reported the use of a hearing protection device. Tinnitus is a common finding among dental clinicians especially those with higher levels of occupational noise and more frequent use of noise-generating equipment. Knowledge of tinnitus prevalence aids in realizing the extent of its impact and making informed decisions. These results call for improved awareness of the negative impact of clinically-generated noise and emphasize the importance of preventive measures and periodic audiometry exams.

Self-Reported Sensory Decline in Older Adults Is Longitudinally Associated With Both Modality-General and Modality-Specific Factors

Background and Objectives

Self-reported sensory data provide important insight into an individual's perception of sensory ability. It remains unclear what factors predict longitudinal change in self-reported sensory ability across multiple modalities during healthy aging. This study examined these associations in a cohort of older adults for vision, hearing, taste, and smell.

Research Design and Methods

Data on self-report sensory ability were drawn from 5,065 participants of The Irish Longitudinal Study on Ageing (mean age at baseline = 61.6, SD = 9.5, range 32-93 years; 59% female; resident in the Republic of Ireland) across 6 waves of data collection (2009-2021). Covariates included demographics, lifestyle factors, and measures of sensory, physical, mental, and cognitive health. Independent discrete survival analyses were performed for each sensory modality.

Results

A transition to self-reported fair/poor hearing was most prevalent (21% of the sample), followed by fair/poor vision (19%), smell (11%), and taste (6%). Participants who self-reported fair/poor function in one sensory modality were likely to report fair/poor ability in another sensory modality, although not for all pairings. Only self-rated fair/poor health was associated with increased odds of self-reported fair/poor ability across all sensory modalities. Age was associated with increased odds of self-reported fair/poor hearing, smell, and taste, as was current smoker status (vision, smell, and taste). Several other sensory (e.g., eye disease, hearing aid use) and nonsensory covariates (e.g., education, depression) were associated with the odds of self-reported fair/poor ability in one or two sensory modalities only.

Discussion and Implications

Over time, older adults perceive associations in fair/poor ability for multiple sensory modalities, albeit somewhat inconsistently. Both modality-general and modality-specific factors are associated with a transition from normal to fair/poor sensory ability. These results suggest the need for more routine testing of multiple senses with increasing age.

Objective and Subjective Hearing Difficulties Are Associated With Lower Inhibitory Control

OBJECTIVE

Evidence suggests that hearing loss increases the risk of cognitive impairment. However, the relationship between hearing loss and cognition can vary considerably across studies, which may be partially explained by demographic and health factors that are not systematically accounted for in statistical models.

DESIGN

Middle-aged to older adult participants (N = 149) completed a web-based assessment that included speech-in-noise (SiN) and self-report measures of hearing, as well as auditory and visual cognitive interference (Stroop) tasks. Correlations between hearing and cognitive interference measures were performed with and without controlling for age, sex, education, depression, anxiety, and self-rated health.

RESULTS

The risk of having objective SiN difficulties differed between males and females. All demographic and health variables, except education, influenced the likelihood of reporting hearing difficulties. Small but significant relationships between objective and reported hearing difficulties and the measures of cognitive interference were observed when analyses were controlled for demographic and health factors. Furthermore, when stratifying analyses for males and females, different relationships between hearing and cognitive interference measures were found. Self-reported difficulty with spatial hearing and objective SiN performance were better predictors of inhibitory control in females, whereas self-reported difficulty with speech was a better predictor of inhibitory control in males. This suggests that inhibitory control is associated with different listening abilities in males and females.

CONCLUSIONS

The results highlight the importance of controlling for participant characteristics when assessing the relationship between hearing and cognitive interference, which may also be the case for other cognitive functions, but this requires further investigations. Furthermore, this study is the first to show that the relationship between hearing and cognitive interference can be captured using web-based tasks that are simple to implement and administer at home without any assistance, paving the way for future online screening tests assessing the effects of hearing loss on cognition.

Multiplex immunohistochemistry reveals cochlear macrophage heterogeneity and local auditory nerve inflammation in cisplatin-induced hearing loss

Inner ear macrophages play a vital role in cochlear homeostasis. Recent studies have demonstrated the existence of macrophages at different sites of the cochlea, with increased cochlear infiltration as an inflammatory response mechanism to injury. However, current methods, such as conventional immunohistochemistry and flow cytometry, provide limited information about the diversity of cochlear macrophages. Recently, multiplex immunohistochemistry (mIHC) successfully identified the heterogeneity of immune cells in cancer tissue and thereby improved our understanding of the disease prognosis. In this study, we modified the mIHC technique for cochlear tissue and utilized it to investigate cochlear macrophage behavior and heterogeneity before and after exposure to ototoxic drugs such as cisplatin. Four-week-old C57BL/6N female mice were intraperitoneally injected with cisplatin at 5 mg/kg/day consecutively for 6 days. Their hearing levels were assessed before and after the injection. Their cochleae were harvested before (day 0) and on days 8 and 15 after the cisplatin injection. Paraffin-embedded sections were sequentially immunostained using macrophage surface markers to identify the different categories of macrophages. Each immunostaining cycle included incubation with primary antibody, incubation with secondary antibody, chromogenic staining, and image scanning. Thereafter, all antibodies were stripped out, and antigen retrieval was performed to prepare the tissue for the next cycle. The results revealed that activated cochlear macrophages were not entirely differentiated into M1 or M2 categories but into multi-marker M1/M2 mixed macrophages. Furthermore, the ratio of these mixed (M1/M2) macrophages to Iba1+ macrophages increased in the auditory nerve after cisplatin exposure, suggesting local auditory nerve inflammation. The increase in the population of activated macrophages in the auditory nerve region was concomitant with the temporary shift of hearing threshold on day 8 post-cisplatin injection. The findings of this study indicate the effectiveness of mIHC in identifying cochlear macrophage heterogeneity both in the resting state and after cisplatin exposure. Therefore, mIHC could be a powerful tool in cochlear immunology research. Our findings may provide new insights into the co-relation between the cochlear macrophage and cisplatin exposure.

Large-scale phenotyping and characterization of age-related hearing loss in outbred CFW mice

Age-related hearing loss (ARHL), or presbycusis, is one of the most prevalent conditions affecting the global population. A substantial fraction of patients with ARHL have no identifiable mutation despite over a hundred having been discovered, suggesting unidentified monogenic or polygenic causes. In this study, we investigated the hearing function of the aging outbred CFW mice through auditory brainstem response (ABR) thresholds. Through the characterization of 1,132 ABRs, we observed significant variation in both absolute thresholds and the effect of aging. We identify eight distinct patterns of hearing loss and were able to categorize nearly all data within these eight categories. Proportions within each category varied immensely between aging timepoints. We observe a small but consistent hearing deficit in female CFW mice. The resulting phenotypic data are a necessity for ARHL association mapping at a higher resolution than has previously been achieved and provides a new resource for studying ARHL.

Estimated Glomerular Filtration Rate and Hearing Impairment in Japan: A Longitudinal Analysis Using Large-Scale Occupational Health Check-Up Data

Several longitudinal studies have examined associations between renal dysfunction and hearing impairment. Here, we explored the longitudinal association between estimated glomerular filtration rate (eGFR) and hearing impairment among the working-age population in Japan. Participants were 88,425 males and 38,722 females aged 20-59 years, without hearing impairment at baseline (2013), who attended Japanese occupational annual health check-ups from 2013 to 2020 fiscal year. eGFR was categorized into four groups (eGFR upper half of ≥90, lower half of ≥90 (reference), 60-89, and <60 mL/min/1.73 m²). Low- and high-frequency hearing impairment were assessed using data from pure-tone audiometric testing. A Cox proportional hazards model was applied to estimate hazard ratio (HR) values for hearing impairment. Low eGFR did not increase the risk of low- or high-frequency hearing impairment. For males, multivariable-adjusted HR of high-frequency hearing impairment was 1.16 (95% confidence interval, 1.01-1.34) for the upper half of the ≥90 mL/min/1.73 m²; however, this positive association between high eGFR and high-frequency hearing impairment did not appear to be robust in a number of sensitivity analyses. We conclude that, among the Japanese working-age population, eGFR was not generally associated with hearing impairment in people of either sex.

Sex and gender differences in dementia

The dementia landscape has undergone a striking paradigm shift. The advances in understanding of neurodegeneration and proteinopathies has changed our approach to patients with cognitive impairment. Firstly, it has recently been shown that the various proteinopathies that are the cause of the dementia begin to build up long before the appearance of any obvious symptoms. This has cemented the idea that there is an urgency in diagnosis as it occurs very late in the pathophysiology of these diseases. Secondly, that accurate diagnosis is required to deliver targeted therapies, that is precision medicine. With this latter point, the realization that various factors of a person need to be considered as they may impact the presentation and progression of disease has risen to the forefront. Two of these factors aside from race and age are biological sex and gender (social construct), as both can have tremendous impact on manifestation of disease. This chapter will cover what is known and remains to be known on the interaction of sex and gender with some of the major causes of dementia.

Efficiency of antioxidant Avenanthramide-C on high-dose methotrexate-induced ototoxicity in mice

Methotrexate (MTX) has been used in treating various types of cancers but can also cause damage to normal organs and cell types. Folinic acid (FA) is a well-known MTX antidote that protects against toxicity caused by the drug and has been used for decades. Since hearing loss caused by MTX treatment is not well studied, herein we aimed to investigate the efficiency of the antioxidant Avenanthramide-C (AVN-C) on high-dose MTX (HDMTX) toxicity in the ear and provide insights into the possible mechanism involved in MTX-induced hearing loss in normal adult C57Bl/6 mice and HEI-OC1 cells. Our results show that the levels of MTX increased in the serum and perilymph 30 minutes after systemic administration. MTX increased hearing thresholds in mice, whereas AVN-C and FA preserved hearing within the normal range. MTX also caused a decrease in wave I amplitude, while AVN-C and FA maintained it at higher levels. MTX considerably damaged the cochlear synapses and neuronal integrity, and both AVN-C and FA rescued the synapses. MTX reduced the cell viability and increased the reactive oxygen species (ROS) level in HEI-OC1 cells, but AVN-C and FA reversed these changes. Apoptosis- and ROS-related genes were significantly upregulated in MTX-treated HEI-OC1 cells; however, they were downregulated by AVN-C and FA treatment. We show that MTX can cause severe hearing loss; it can cross the blood–labyrinth barrier and cause damage to the cochlear neurons and outer hair cells (OHCs). The antioxidant AVN-C exerts a strong protective effect against MTX-induced ototoxicity and preserved the inner ear structures (synapses, neurons, and OHCs) from MTX-induced damage. The mechanism of AVN-C against MTX suggests that ROS is involved in HDMTX-induced ototoxicity.

Sex-specific associations between diabetes mellitus and hearing loss in the middle-aged and elderly: a national cohort study of Chinese adults

OBJECTIVE

To examine the association between diabetes and hearing loss and whether the association varied by sex.

METHODS

This cohort study based on nationally representative data from the China Health and Retirement Longitudinal Study included 16140 Chinese adults aged over 45 years between 2011 and 2018. Diabetes was identified by blood glucose, HbA_1c, and a self-reported diagnosis at baseline. The main outcome is self-reported incident hearing loss. Cox proportional hazards regression models were performed to estimate the risk of hearing loss.

RESULTS

We documented 2388 cases of hearing loss during a median 6.9 years of follow-up. The incidence rate was 29.64 (95% CI 28.07-31.29) per 1000 person-years in women and 25.23 (95% CI 23.77-26.78) per 1000 person-years in men. After adjustment, the HR of hearing loss associated with diabetes was 1.20 (95% CI 1.01-1.42) for women and 0.97 (95% CI 0.78-1.19) for men. Compared with poor control of blood sugar, the OR for hearing loss for women with good glycemic control was reduced from 5.08 (95%CI 1.31-19.66) to 1.26 (95%CI 0.69-2.28), and the corresponding OR for men was 1.65 (95% CI 0.61-4.44) to 0.50 (95%CI 0.18-1.38).

CONCLUSIONS

In conclusion, we identified a differential effect of sex on hearing loss risk with more pronounced effects for women. Our data suggest that good blood glucose control is helpful to prevent hearing loss.

Auditory Brainstem Responses Predict Behavioral Deficits in Rats with Varying Levels of Noise-Induced Hearing Loss

Intense noise exposure is a leading cause of hearing loss, which results in degraded speech sound discrimination ability, particularly in noisy environments. The development of an animal model of speech discrimination deficits due to noise induced hearing loss (NIHL) would enable testing of potential therapies to improve speech sound processing. Rats can accurately detect and discriminate human speech sounds in the presence of quiet and background noise. Further, it is known that profound hearing loss results in functional deafness in rats. In this study, we generated rats with a range of impairments which model the large range of hearing impairments observed in patients with NIHL. One month after noise exposure, we stratified rats into three distinct deficit groups based on their auditory brainstem response (ABR) thresholds. These groups exhibited markedly different behavioral outcomes across a range of tasks. Rats with moderate hearing loss (30 dB shifts in ABR threshold) were not impaired in speech sound detection or discrimination. Rats with severe hearing loss (55 dB shifts) were impaired at discriminating speech sounds in the presence of background noise. Rats with profound hearing loss (70 dB shifts) were unable to detect and discriminate speech sounds above chance level performance. Across groups, ABR threshold accurately predicted behavioral performance on all tasks. This model of long-term impaired speech discrimination in noise, demonstrated by the severe group, mimics the most common clinical presentation of NIHL and represents a useful tool for developing and improving interventions to target restoration of hearing.

Estradiol Protects against Noise-Induced Hearing Loss and Modulates Auditory Physiology in Female Mice

Recent studies have identified sex-differences in auditory physiology and in the susceptibility to noise-induced hearing loss (NIHL). We hypothesize that 17β-estradiol (E2), a known modulator of auditory physiology, may underpin sex-differences in the response to noise trauma. Here, we gonadectomized B6CBAF1/J mice and used a combination of electrophysiological and histological techniques to study the effects of estrogen replacement on peripheral auditory physiology in the absence of noise exposure and on protection from NIHL. Functional analysis of auditory physiology in gonadectomized female mice revealed that E2-treatment modulated the peripheral response to sound in the absence of changes to the endocochlear potential compared to vehicle-treatment. E2-replacement in gonadectomized female mice protected against hearing loss following permanent threshold shift (PTS)- and temporary threshold shift (TTS)-inducing noise exposures. Histological analysis of the cochlear tissue revealed that E2-replacement mitigated outer hair cell loss and cochlear synaptopathy following noise exposure compared to vehicle-treatment. Lastly, using fluorescent in situ hybridization, we demonstrate co-localization of estrogen receptor-2 with type-1C, high threshold spiral ganglion neurons, suggesting that the observed protection from cochlear synaptopathy may occur through E2-mediated preservation of these neurons. Taken together, these data indicate the estrogen signaling pathways may be harnessed for the prevention and treatment of NIHL.

Audio-vestibular disorders and pregnancy: A systematic review

PURPOSE

During pregnancy a woman's body undergoes many physiological changes that involve all systems and organs, including sensory ones. We conducted this systematic review to highlight current evidence and treatment options in pregnant women with audio-vestibular disorders.

MATERIALS AND METHODS

A search was made on the following databases: PubMed, PubMed Central, Web of Science and Scopus. This research protocol was deposited in the PROSPERO Database.

RESULTS

After application of inclusion-exclusion criteria, 30 manuscripts were included in the review. Many authors (14/15) found a slight alteration of audiometric tests during pregnancy, with a reported recovery postpartum in most of the studies (5/7). Regarding sudden sensorineural hearing loss (SSNHL), we found four articles for a total of 69 patients: the treatment of choice was intravenous Dextran 40 and intra-tympanic corticosteroids. Most included studies (4/6) found neither clinical nor epidemiological associations between otosclerosis and pregnancy in large-based sample studies. Few investigations regarded Eustachian tube function and vertigo.

CONCLUSIONS

According to our results, many variations of hearing acuity during pregnancy are slight and transient and require only clinical observation. In large samples, otosclerosis appeared not to be associated with pregnancy. Clinicians should consider intra-tympanic steroids in managing SSNHL during pregnancy. Further more accurate research is needed to deepen and clarify the association between pregnancy and audio-vestibular disorders.

Sex Differences in Otolaryngology: Focus on the Emerging Role of Estrogens in Inflammatory and Pro-Resolving Responses

Otolaryngology (also known as ear, nose, and throat (ENT)) diseases can be significantly affected by the level of sex hormones, which indicates that sex differences affect the manifestation, pathophysiology, and outcomes of these diseases. Recently, increasing evidence has suggested that proinflammatory responses in ENT diseases are linked to the level of sex hormones. The sex hormone receptors are present on a wide variety of immune cells; therefore, it is evident that they play crucial roles in regulating the immune system and hence affect the disease progression of ENT diseases. In this review, we focus on how sex hormones, particularly estrogens, regulate ENT diseases, such as chronic rhinosinusitis, vocal fold polyps, thyroid cancer, Sjögren’s syndrome, and head and neck cancers, from the perspectives of inflammatory responses and specialized proresolving mediator-driven resolution. This paper aims to clarify why considering sex differences in the field of basic and medical research on otolaryngology is a key component to successful therapy for both males and females in the future.

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.

Patterns of hearing changes in women and men from denarians to nonagenarians

Background

Hearing loss needs to be diagnosed and treated early, especially in older individuals, since presbycusis potentially increases the risk of depression and dementia. However, standard data on hearing thresholds across the life-span in Japanese individuals are lacking.

Methods

In a retrospective consecutive sample of 10681 native-Japanese speakers (37.3% men; 10-99 years; left-right hearing threshold difference of <15 dB for all tested pure tones; free of external, middle, or inner ear disease), we determined standard age-decade and sex-specific pure-tone air-conduction (125, 250, 500, 1000, 2000, 4000, and 8000 Hz) hearing threshold norms. The main outcome measures were pure-tone averages for both ears by age-decade and sex.

Findings

For participants in their 20s, hearing thresholds at higher frequencies (>1000 Hz) were significantly worse in men than in women. For participants ≥70 years, hearing thresholds at low frequencies were higher in women. Hearing thresholds at 1000, 2000, and 4000 Hz tended to deteriorate, starting in the teenage years through the 50s, with some decades showing significantly worse decline. Sex differences were absent in the youngest and oldest groups.

Interpretation

Standard age- and sex-specific audiometric data reported here for Japanese individuals over nine age-decades are based on the largest dataset analyzed to date. While hearing thresholds of men and women in the very young and the very old age groups were indistinguishable in their cohorts, patterns of hearing changes for other age cohorts differed by direction and sex.

Funding

The authors had no outside funding for this study.

Sex difference in the efferent inner hair cell synapses of the aging murine cochlea

Efferent innervation of the inner hair cells changes over time. At an early age in mice, inner hair cells receive efferent feedback, which helps fine-tune tonotopic maps in the brainstem. In adulthood, inner hair cell efferent innervation wanes but increases again in older animals. It is not clear, however, whether age-related inner hair cell efferents increase along the entire range of the cochlear frequencies, or if this increase is restricted to a particular frequency-region, and whether this phenomenon occurs in both sexes. Age-related hearing loss, presbycusis, affects men and women differently. In mice, this difference is also strain specific. In aging black six mice, the auditory brainstem response thresholds increase in females earlier than in males. Here, we study age-related increase of the inner hair cell efferent innervation throughout the cochlea before hearing onset, in one month old and in ten months old and older male and female black six mice. We collected confocal images of immunostained inner hair cell efferents and quantified the labeled terminals in the entire cochlea using a machine learning algorithm. The overall number of the inner hair cell efferents in both sexes did not change significantly between age-groups. The distribution of the inner hair cell efferent innervation did not differ across frequencies in the cochlea. However, in females, inner hair cells received on average up to four times more efferent innervation than in males per each of the frequency regions tested. Sex differences were also found in the oldest age-group tested (≥ 10 months) where on average inner hair cells received six times more efferents in females than in males of matching age. Our findings emphasize the importance of including both sexes in sensorineural hearing loss research.

Linking anatomical and physiological markers of auditory system degeneration with behavioral hearing assessments in a mouse (Mus musculus) model of age-related hearing loss

Age-related hearing loss is a very common sensory disability, affecting one in three older adults. Establishing a link between anatomical, physiological, and behavioral markers of presbycusis in a mouse model can improve the understanding of this disorder in humans. We measured age-related hearing loss for a variety of acoustic signals in quiet and noisy environments using an operant conditioning procedure and investigated the status of peripheral structures in CBA/CaJ mice. Mice showed the greatest degree of hearing loss in the last third of their lifespan, with higher thresholds in noisy than in quiet conditions. Changes in auditory brainstem response thresholds and waveform morphology preceded behavioral hearing loss onset. Loss of hair cells, auditory nerve fibers, and signs of stria vascularis degeneration were observed in old mice. The present work underscores the difficulty in ascribing the primary cause of age-related hearing loss to any particular type of cellular degeneration. Revealing these complex structure-function relationships is critical for establishing successful intervention strategies to restore hearing or prevent presbycusis.