Age-related hearing loss or presbycusis

Impairment of extra-high frequency auditory thresholds in subjects with elevated levels of fasting blood glucose

This study was performed to assess whether there is an association between elevated Fasting Blood Glucose (FBG) and hearing impairment in Bangladeshi population. A total of 142 subjects (72 with elevated FBG; 70 control) were included in the study. The mean auditory thresholds of the control subjects at 1, 4, 8 and 12 kHz frequencies were 6.35 ± 0.35, 10.07 ± 0.91, 27.57 ± 1.82, 51.28 ± 3.01 dB SPL (decibel sound pressure level), respectively and that of the subjects with elevated FBG were 8.33 ± 0.66, 14.37 ± 1.14, 38.96 ± 2.23, and 71.11 ± 2.96 dB, respectively. The auditory thresholds of the subjects with elevated FBG were significantly (p < 0.05) higher than the control subjects at all the above frequencies, although hearing impairment was most evidently observed at an extra-high (12 kHz) frequency. Subjects with a long duration of diabetes (>10 years) showed significantly (p < 0.05) higher level of auditory thresholds at 8 and 12 kHz, but not at 1 and 4 kHz frequencies, compared to subjects with shorter duration of diabetes (≤10 years). In addition, based on the data of odds ratio, more acute impairment of hearing at the extra-high frequency was observed in diabetic subjects of both older (>40 years) and younger (≤40 years) age groups compared to the respective controls. The binary logistic regression analysis showed a 5.79-fold increase in the odds of extra-high frequency hearing impairment in diabetic subjects after adjustment for age, gender and BMI. This study provides conclusive evidence that auditory threshold at an extra-high frequency could be a sensitive marker for hearing impairment in diabetic subjects.

Why Early Tactile Speech Aids May Have Failed: No Perceptual Integration of Tactile and Auditory Signals

Tactile speech aids, though extensively studied in the 1980’s and 1990’s, never became a commercial success. A hypothesis to explain this failure might be that it is difficult to obtain true perceptual integration of a tactile signal with information from auditory speech: exploitation of tactile cues from a tactile aid might require cognitive effort and so prevent speech understanding at the high rates typical of everyday speech. To test this hypothesis, we attempted to create true perceptual integration of tactile with auditory information in what might be considered the simplest situation encountered by a hearing-impaired listener. We created an auditory continuum between the syllables /BA/ and /VA/, and trained participants to associate /BA/ to one tactile stimulus and /VA/ to another tactile stimulus. After training, we tested if auditory discrimination along the continuum between the two syllables could be biased by incongruent tactile stimulation. We found that such a bias occurred only when the tactile stimulus was above, but not when it was below its previously measured tactile discrimination threshold. Such a pattern is compatible with the idea that the effect is due to a cognitive or decisional strategy, rather than to truly perceptual integration. We therefore ran a further study (Experiment 2), where we created a tactile version of the McGurk effect. We extensively trained two Subjects over 6 days to associate four recorded auditory syllables with four corresponding apparent motion tactile patterns. In a subsequent test, we presented stimulation that was either congruent or incongruent with the learnt association, and asked Subjects to report the syllable they perceived. We found no analog to the McGurk effect, suggesting that the tactile stimulation was not being perceptually integrated with the auditory syllable. These findings strengthen our hypothesis according to which tactile aids failed because integration of tactile cues with auditory speech occurred at a cognitive or decisional level, rather than truly at a perceptual level.

Prevalence of ototoxic medication use among older adults in Beaver Dam, Wisconsin

BACKGROUND AND PURPOSE

Drug-related ototoxicity may exacerbate presbycusis (age-related hearing loss); yet, few data are available on the prevalence of ototoxic medication use by older adults. The purposes of this study were to assess the impact of aging and ototoxicity on hearing loss, the prevalence of ototoxic medication use, and select characteristics associated with ototoxic medication use among older adults.

METHODS

Cross-sectional analyses were conducted using select variables extracted from the baseline and 10-year follow-up assessments of the two population-based epidemiological studies to compare two points in time.

RESULTS

Ninety-one percent of the sample was taking a medication reported to be ototoxic. Nonsteroidal anti-inflammatory drugs were the most commonly used (75.2%), followed by acetaminophen (39.9%) and diuretics (35.6%). Hypertension, diabetes, cardiovascular disease, and history of smoking were associated with ototoxic medication use. Participants with hearing loss were taking a significantly greater number of ototoxic medications than those without hearing loss.

CONCLUSION

Known ototoxic medications are widely used. Any subsequent ototoxicity may interact with age changes and a more severe hearing loss than that associated with only age.

IMPLICATIONS FOR PRACTICE

Nurse practitioners should inform older adults about the possibility of drug-related ototoxicity and monitor hearing acuity of all older adults taking known ototoxic medications.

Whole-genome sequencing reveals new insights into age-related hearing loss: cumulative effects, pleiotropy and the role of selection

Age-related hearing loss (ARHL) is the most common sensory disorder in the elderly. Although not directly life threatening, it contributes to loss of autonomy and is associated with anxiety, depression and cognitive decline. To search for genetic risk factors underlying ARHL, a large whole-genome sequencing (WGS) approach has been carried out in a cohort of 212 cases and controls, both older than 50 years to select genes characterized by a burden of variants specific to cases or controls. Accordingly, the total variation load per gene was compared and two groups were detected: 375 genes more variable in cases and 371 more variable in controls. In both cases, Gene Ontology analysis showed that the largest enrichment for biological processes (fold > 5, p-value = 0.042) was the “sensory perception of sound”, suggesting cumulative genetic effects were involved. Replication confirmed 141 genes, while additional analysis based on natural selection led to a prioritization of 21 genes. The majority of them (20 out of 21) showed positive expression in mouse cochlea cDNA and were associated with two functional pathways. Among them, two genes were previously associated with hearing (CSMD1 and PTRPD) and re-sequenced in a large Italian cohort of ARHL patients (N = 389). Results led to the identification of six coding variants not detected in cases so far, suggesting a possible protective role, which requires investigation. In conclusion, we show that this multistep strategy (WGS, selection, expression, pathway analysis and targeted re-sequencing) can provide major insights into the molecular characterization of complex diseases such as ARHL.

Unexpected association between subclinical hearing loss and restorative sleep in a middle-aged and elderly Japanese population

OBJECTIVE

Hearing loss may be associated with certain sleep abnormalities. We recently reported that subclinical hearing loss (SHL) was more prevalent in individuals in a broad Japanese population who slept longer than 8 h; however, the underlying mechanism was unknown. Therefore, we investigated the association between SHL and self-reported restorative sleep (RS), assessed by questionnaire, in a database of 33,888 Japanese aged 40-69 years without overt or diagnosed hearing loss (20,225 men, 13,663 women).

RESULTS

The proportion of individuals with RS (more than half of the subjects) was significantly higher in the group with bilateral than with unilateral SHL at 4000 Hz and intact hearing; however, that was not the case at 1000 Hz, independent of age (P < 0.0001, two-way analysis of variance). Multivariate logistic regression analysis showed that bilateral SHL at 4000 Hz, but not at 1000 Hz, was significantly associated with RS. This relationship was independent of potential relevant confounders, including age, sex, and cardiometabolic risk factors. The present study extends our earlier work by revealing an unexpected association between early hearing impairment and satisfactory sleep in a middle-aged and elderly population. This association requires further confirmation regarding the possible underlying mechanism and clinical relevance.

A Deterioration in Hearing Is Associated With Functional and Cognitive Impairments, Difficulty With Communication, and Greater Health Instability

Objectives: To examine the relationship between hearing deterioration and several health-related outcomes among home care clients in Ontario. Design: Longitudinal analysis was completed for clients with at least two comprehensive assessments. Hearing status, based on a single item, ranged from zero (no impairment) to three (highly impaired). Hearing deterioration was defined as at least a 1-point decline between subsequent assessments. Results: Seven percent experienced a 1-point deterioration in hearing and roughly 1% had a 2/3-point decline. After adjusting for other covariates, increasing age (odds ratio = 1.94; 95% confidence intervals [CIs] = [1.45, 2.61]) and a diagnosis of Alzheimer’s disease (1.37; CI = [1.04, 1.80]) and other dementias (1.32; CI = [1.07, 1.63]) increased the risk of a 2/3-point deterioration. Conclusion: These findings can assist home care professionals and policy makers in creating and refining interventions to meet the needs of older adults with hearing difficulties.

Mutations in L-type amino acid transporter-2 support SLC7A8 as a novel gene involved in age-related hearing loss

Age-related hearing loss (ARHL) is the most common sensory deficit in the elderly. The disease has a multifactorial etiology with both environmental and genetic factors involved being largely unknown. SLC7A8/SLC3A2 heterodimer is a neutral amino acid exchanger. Here, we demonstrated that SLC7A8 is expressed in the mouse inner ear and that its ablation resulted in ARHL, due to the damage of different cochlear structures. These findings make SLC7A8 transporter a strong candidate for ARHL in humans. Thus, a screening of a cohort of ARHL patients and controls was carried out revealing several variants in SLC7A8, whose role was further investigated by in vitro functional studies. Significant decreases in SLC7A8 transport activity was detected for patient’s variants (p.Val302Ile, p.Arg418His, p.Thr402Met and p.Val460Glu) further supporting a causative role for SLC7A8 in ARHL. Moreover, our preliminary data suggest that a relevant proportion of ARHL cases could be explained by SLC7A8 mutations.

Age-related hearing loss affects about one in three individuals between the ages of 65 and 74. The first symptom is difficulty hearing high-pitched sounds like children’s voices. The disease starts gradually and worsens over time. Changes in the ear, the nerve that connects it to the brain, or the brain itself can cause hearing loss. Sometimes all three play a role. Genetics, exposure to noise, disease, and aging may all contribute. The condition is so complex it is difficult for scientists to pinpoint a primary suspect or develop treatments.

Now, Guarch, Font-Llitjós et al. show that errors in a protein called SLC7A8 cause age-related hearing loss in mice and humans. The SLC7A8 protein acts like a door that allows amino acids – the building blocks of proteins – to enter or leave a cell. This door is blocked in mice lacking SLC7A8 and damage occurs in the part of their inner ear responsible for hearing. As a result, the animals lose their hearing. Next, Guarch, Font-Llitjós et al. scanned the genomes of 147 people from isolated villages in Italy for mutations in the gene for SLC7A8. The people also underwent hearing tests.

Mutations in the gene for SLC7A8 that partially block the door and prevent the flow of amino acids were found in people with hearing loss. Some mutations in SLC7A8 that allow the door to stay open where found in people who could hear. The experiments suggest that certain mutations in the gene for SLC7A8 are likely an inherited cause of age-related hearing loss. It is possible that other proteins that control the flow of amino acids into or out of cells also may play a role in hearing. More studies are needed to see if it is possible to fix errors in the SLC7A8 protein to delay or restore the hearing loss.

Age-Related Differences in Hearing Function and Cochlear Morphology between Male and Female Fischer 344 Rats

Fischer 344 (F344) rats represent a strain that is frequently used as a model for fast aging. In this study, we systematically compare the hearing function during aging in male and female F344 rats, by recording auditory brainstem responses (ABRs) and distortion product otoacoustic emissions (DPOAEs). In addition to this, the functional parameters are correlated with the cochlear histology. The parameters of the hearing function were not different in the young (3-month-old) male and female F344 rats; the gender differences occurred only in adult and aged animals. In 8–24-month-old males, the ABR thresholds were higher and the ABR amplitudes were smaller than those measured in females of the same age. There were no gender differences in the neural adaptation tested by recording ABRs, elicited by a series of clicks with varying inter-click interval (ICI). Amplitudes of DPOAEs in both the males and females decreased with age, but in the males, the decrease of DPOAE amplitudes was faster. In males older than 20 months, the DPOAEs were practically absent, whereas in 20–24-month-old females, the DPOAEs were still measurable. There were no gender differences in the number of surviving outer hair cells (OHC) and the number of inner hair cell ribbon synapses in aged animals. The main difference was found in the stria vascularis (SV). Whereas the SV was well preserved in females up to the age of 24 months, in most of the age-matched males the SV was evidently deteriorated. The results demonstrate more pronounced age-related changes in the cochlear morphology, hearing thresholds, ABR amplitudes and DPOAE amplitudes in F344 males compared with females.

The effects of hearing loss on person-centred care in residential aged care: a narrative review

Person-centred care is achieved through strategies such as effective communication and shared decision-making. Hearing loss can lead to communication breakdown and social isolation in residential aged care. The review aimed to address how hearing loss affects person-centred care in residential aged care settings. Empirical literature was identified through a systematic search of academic databases. Articles were reviewed against an inclusion criteria and general inductive analysis was employed to identify recurring factors across included studies. Six common factors emerged from the data: communication breakdown, the overlap between hearing loss and cognitive impairment, social isolation and reduced social participation, limited access to hearing services, inadequate training provided to care staff, and strategies to improve communication. Recommended strategies to facilitate person-centred care for residents with hearing loss are presented. Further investigation is needed to understand the effects of hearing loss on residents' autonomy and shared decision-making.

Biomarkers of Presbycusis and Tinnitus in a Portuguese Older Population

Introduction: Presbycusis or age-related hearing loss (ARHL) is a ubiquitous health problem. It is estimated that it will affect up to 1.5 billion people by 2025. In addition, tinnitus occurs in a large majority of cases with presbycusis. Glutamate metabotropic receptor 7 (GRM7) and N-acetyltransferase 2 (NAT2) are some of the genetic markers for presbycusis.

Objectives: To explore patterns of hearing loss and the role of GRM7 and NAT2 as possible markers of presbycusis and tinnitus in a Portuguese population sample.

Materials and Methods: Tonal and speech audiometry, tinnitus assessment, clinical interview, and DNA samples were obtained from patients aged from 55 to 75 with or without tinnitus. GRM7 analysis was performed by qPCR. Genotyping of single nucleotide polymorphisms (SNPs) in NAT2 was performed by PCR amplification followed by Sanger sequencing or by qPCR.

Results: We screened samples from 78 individuals (33 men and 45 women). T allele at GRM7 gene was the most observed (60.3% T/T and 33.3% A/T). Individuals with a T/T genotype have a higher risk for ARHL and 33% lower risk for tinnitus, compared to individuals with A/A and A/T genotype, respectively. Being a slow acetylator (53%) was the most common NAT2 phenotype, more common in men (55.8%). Intermediate acetylator was the second most common phenotype (35.9%) also more frequent in men (82.6%). Noise exposed individuals and individuals with ‘high frequency’ hearing loss seem to have a higher risk for tinnitus. Our data suggests that allele AT of GRM7 can have a statistically significant influence toward the severity of tinnitus.

Conclusion: For each increasing year of age the chance of HL increases by 9%. The risk for ARHL was not significantly associated with GRM7 neither NAT2. However, we cannot conclude from our data whether the presence of T allele at GRM7 increases the odds for ARHL or whether the A allele has a protective effect. Genotype A/T at GRM7 could potentially be considered a biomarker of tinnitus severity. This is the first study evaluating the effect of GRM7 and NAT2 gene in tinnitus.

Initial Results of the Early Auditory Referral-Primary Care (EAR-PC) Study

INTRODUCTION

Hearing loss (HL) is the second most common disability in the U.S., yet is clinically underdiagnosed. To manage its common adverse psychosocial and cognitive outcomes, early identification of HL must be improved.

METHODS

A feasibility study conducted to increase screening for HL and referral of patients aged ≥55 years arriving at two family medicine clinics. Eligible patients were asked to complete a self-administered consent form and the Hearing Handicap Inventory (HHI). Independently, clinicians received a brief educational program after which an electronic clinical prompt (intervention) alerted them (blinded to HHI results) to screen for HL during applicable patient visits. Pre- and post-intervention differences were analyzed to assess the proportion of patients referred to audiology and those diagnosed with HL (primary outcomes) and the audiology referral appropriateness (secondary outcome). Referral rates for those who screened positive for HL on the HHI were compared with those who scored negatively.

RESULTS

There were 5,520 eligible patients during the study period, of which 1,236 (22.4%) consented. After the intervention's implementation, audiology referral rates increased from 1.2% to 7.1% (p<0.001). Overall, 293 consented patients (24%) completed the HHI and scored >10, indicating probable HL. Of these 293 patients, 28.0% were referred to audiology versus only 7.4% with scores <10 (p<0.001). Forty-two of the 54 referred patients seen by audiology were diagnosed with HL (78%). Overall, the diagnosis of HL on problem lists increased from 90 of 4,815 patients (1.9%) at baseline to 163 of 5,520 patients (3.0%, p<0.001) over only 8 months.

CONCLUSIONS

The electronic clinical prompt significantly increased audiology referrals for at-risk patients for HL in two family medicine clinics. Larger-scale studies are needed to address the U.S. Preventive Services Task Force call to assess the long-term impact of HL screening in community populations.

Expression patterns of members of the isocitrate dehydrogenase gene family in murine inner ear

Age-related hearing loss (ARHL) is characterized by an age-dependent decline of auditory function characterized by with loss of sensory hair cells, spiral ganglion neurons, and stria vascularis (SV) cells in the cochlea of the inner ear. Aging and age-related diseases result from accumulated oxidative damage caused by reactive oxygen species (ROS) generated by mitochondria. The isocitrate dehydrogenase (IDH) family includes three enzymes in human cells: IDH1, IDH2, and IDH3. Although all three enzymes catalyze the same enzymatic reaction, that is, oxidative decarboxylation of isocitrate to produce α-ketoglutarate, each IDH enzyme has unique features. We identified and characterized IDH expression in the cochlea and vestibule of the murine inner ear. We examined the mRNA expression levels of Idh family members in the cochlea and vestibule using reverse transcription-PCR (RT-PCR) and detected expression of IDH family members in both tissues. We also used immunohistochemistry to localize IDH family members within the cochlea and vestibule of the adult mouse inner ear. IDH1 was detected throughout the cochlea. IDH2 was expressed specifically in the hair cells, spiral ganglion, and stria vascularis. IDH3α was found in the cell bodies of neurons of the spiral ganglion, the stria vascularis, and in types II, IV, and V cells of the spiral ligament in a pattern that resembled the location of the Na⁺, K⁺-ATPase ion channel. We postulate that the IDH family participates in transporting K⁺ ions in the cochlea. In the vestibule, all IDH family members were detected in both hair cells and the vestibular ganglion. We hypothesize that IDH1, IDH2, and IDH3 function to protect proteins in the inner ear from oxidative stress during K⁺ recycling.

Genetic and Environmental Influences on Correlations Between Hearing and Cognitive Functions in Middle and Older Chinese Twins

The genetic and environmental impacts on correlations between hearing and cognitive functions have not been well studied. Cognitive function was evaluated by the Montreal Cognitive Assessment (MoCA). Hearing function was assessed by audiometric pure-tone hearing thresholds at different frequencies, including 0.5 kHz, 1 kHz, 2 kHz, 4 kHz, 8 kHz, and 12.5 kHz, with the lower hearing thresholds indicating better hearing function. Cognitive and hearing functions were measured on 379 complete twin pairs (240 monozygotic and 139 dizygotic pairs) with a median age of 50 years (range: 40-80 years). Bivariate twin models were fitted to quantify the genetic and environmental components of the correlations between hearing and cognitive functions. The analysis showed significantly high genetic correlation between 2 kHz of hearing and cognition (r G = -1.00, 95% CI [-1.00, -0.46]) and moderate genetic correlation between 4 kHz of hearing and cognition (r G = -0.62, 95% CI [-1.00, -0.14]). We found no significant genetic correlations between low as well as high frequencies of hearing and cognition. Low to moderate common and unique environmental correlations were shown between low frequencies of hearing and cognition (-0.13 to -0.39) and the common environmental correlation between 8 kHz, one of the high frequencies of hearing, and cognition (-0.22). The middle frequencies of hearing and cognitive functions may have a shared genetic basis. Low frequencies of hearing and cognition may share similar common and unique environmental factors. At 8 kHz, the high frequency of hearing and cognition may share similar common environment. This twin study detected a significant genetic and environmental basis in the phenotype correlation between cognition and hearing, which differed across frequencies.

Macrophage migration inhibitory factor mediates viability and apoptosis of PVM/Ms through PI3K/Akt pathway

Macrophage migration inhibitory factor (MIF) plays an important role in hearing function; however, the underlying mechanism remains indistinct. PVM/Ms from the stria vascularis of lateral wall of cochlea in young and aged mice were isolated, and the mRNA and protein expression levels were detected. MIF was knocked down or overexpresssed in vitro, and transfection was performed in vivo. Cell viability and apoptosis were determined by MTT assay and flow cytometry analysis, respectively. The hearing ability was tested by the auditory brain stem response. The results showed that MIF expression was significantly downregulated in aged mice. In aged mice, the viability of PVM/Ms significantly decreased, but the apoptotic number markedly increased. MIF knockdown in PVM/Ms in vitro significantly inhibited cell viability and induced cell apoptosis, but MIF overexpression showed contrasting results. Further studies showed that MIF knockdown in young mice resulted in serious hearing loss, but MIF overexpression in aged mice restored the hearing. Si-MIF inhibited the viability and induced apoptosis of PVM/Ms from young mice, whereas Ad-MIF induced the viability and inhibited apoptosis of PVM/Ms from aged mice. Moreover, MIF effectively altered the expression levels of CDK1, BRAF, p-ERK1/2, p-PI3K, and p-Akt. Furthermore, ERK inhibitor PD98059 or PI3K inhibitor LY294002 significantly reversed the effects of Si-MIF on PVM/Ms from young mice, whereas ERK activator EGF or PI3K activator IGF significantly reversed the effects of Ad-MIF on PVM/Ms from aged mice. Taken together, MIF mediates the viability and apoptosis of PVM/Ms, at least partially, through MAPK and/or PI3K/Akt pathway.

Resolution of Cochlear Inflammation: Novel Target for Preventing or Ameliorating Drug-, Noise- and Age-related Hearing Loss

A significant number of studies support the idea that inflammatory responses are intimately associated with drug-, noise- and age-related hearing loss (DRHL, NRHL and ARHL). Consequently, several clinical strategies aimed at reducing auditory dysfunction by preventing inflammation are currently under intense scrutiny. Inflammation, however, is a normal adaptive response aimed at restoring tissue functionality and homeostasis after infection, tissue injury and even stress under sterile conditions, and suppressing it could have unintended negative consequences. Therefore, an appropriate approach to prevent or ameliorate DRHL, NRHL and ARHL should involve improving the resolution of the inflammatory process in the cochlea rather than inhibiting this phenomenon. The resolution of inflammation is not a passive response but rather an active, highly controlled and coordinated process. Inflammation by itself produces specialized pro-resolving mediators with critical functions, including essential fatty acid derivatives (lipoxins, resolvins, protectins and maresins), proteins and peptides such as annexin A1 and galectins, purines (adenosine), gaseous mediators (NO, H₂S and CO), as well as neuromodulators like acetylcholine and netrin-1. In this review article, we describe recent advances in the understanding of the resolution phase of inflammation and highlight therapeutic strategies that might be useful in preventing inflammation-induced cochlear damage. In particular, we emphasize beneficial approaches that have been tested in pre-clinical models of inflammatory responses induced by recognized ototoxic drugs such as cisplatin and aminoglycoside antibiotics. Since these studies suggest that improving the resolution process could be useful for the prevention of inflammation-associated diseases in humans, we discuss the potential application of similar strategies to prevent or mitigate DRHL, NRHL and ARHL.

The Influence of Social Support and Coping on Quality of Life Among Elderly With Age-Related Hearing Loss

PURPOSE

The consequences of hearing loss hinder the everyday life of older adults and are associated with reduced well-being. The research aim was to explore the influence of hearing problems, various coping strategies, and perceived social support on quality of life.

METHOD

Sixty-five older adults with age-related hearing loss (≥55 years) in Austria participated and completed a paper-pencil survey with standardized questionnaires: Hearing Handicap Inventory for the Elderly (Ventry and Weinstein, 1982), Assessment for Coping and Stress (Laireiter, 1997), short form of the Social Support Questionnaire (Fydrich, Sommer, Tydecks, & Brähler, 2009), and World Health Organization Quality of Life Scale-Brief Version (World Health Organization, 1996).

RESULTS

Quality of life was predicted by perceived social support and the number of comorbid diseases (i.e., the physical, psychological, environmental, and social quality of life was better the greater the extent of perceived social support and poorer the more diseases from which the participants suffered).

CONCLUSIONS

Perceived social support may be a relevant factor to focus on in auditory rehabilitation programs, in particular, for participants who communicate little support in hearing-related situations and are, hence, at a relative disadvantage. The involvement of significant others in counseling could facilitate the everyday life for older adults with age-related hearing loss and their significant others.

Evidence for Behaviorally Segregated, Spatiotemporally Overlapping Subnetworks in Phantom Sound Perception

One of the most intriguing questions in neuroscience is to understand the mechanism of information transfer between different brain areas. Recently, network theory has gained traction and is at the forefront of providing a possible explanation to not only the mechanism of information transfer but also in the identification of different neuropathologies. The perception of a phantom ringing in the ear called tinnitus, similar to other neuropathologies, has been shown to be accompanied by aberrant functional connectivity between different brain areas. Although, there have been independent studies showing that specific groups of areas encode individual symptoms of tinnitus, there has not been one study to show that tinnitus is the unified percept of distinguishable subnetworks encoding different behavioral aspects. This study combines resting-state functional connectivity obtained from the source-localized electroencephalography of 311 tinnitus patients and 264 controls, and a k-fold cross-validation machine learning algorithm to develop a predictive model that verifies the presence of behaviorally specific, spatiotemporally overlapping subnetworks in tinnitus. This reorganization is found to be exclusive to tinnitus, even when compared to physiologically similar disorders such as chronic pain, with each behavioral symptom having a unique oscillatory signature. This frequency-specific transmission of information, called multiplexing, enables different types of information to be carried between two brain regions through the same anatomical connection. In addition to understanding the efficient compensation mechanism of the brain in the presence of multisymptom disorders, the exclusivity of the prediction model presents an encouraging possibility for an objective neural marker for tinnitus.

Association of genetic variations in the mitochondrial DNA control region with presbycusis

Background

The prominent role of mitochondria in the generation of reactive oxygen species, cell death, and energy production contributes to the importance of this organelle in the intracellular mechanism underlying the progression of the common sensory disorder of the elderly, presbycusis. Reduced mitochondrial DNA (mtDNA) gene expression and coding region variation have frequently been reported as being associated with the development of presbycusis. The mtDNA control region regulates gene expression and replication of the genome of this organelle. To comprehensively understand of the role of mitochondria in the progression of presbycusis, we compared variations in the mtDNA control region between subjects with presbycusis and controls.

Methods

A total of 58 presbycusis patients and 220 control subjects were enrolled in the study after examination by the otolaryngologist and audiology tests. Variations in the mtDNA control region were investigated by polymerase chain reaction and Sanger sequencing.

Results

A total of 113 sequence variants were observed in mtDNA, and variants were detected in 100% of patients, with 84% located in hypervariable regions. The frequencies of the variants, 16,223 C>T, 16,311 T>C, 16,249 T>C, and 15,954 A>C, were significantly different between presbycusis and control subjects.

Conclusion

The statistically significant difference in the frequencies of four nucleotide variants in the mtDNA control region of presbycusis patients and controls is in agreement with previous experimental evidence and supports the role of mitochondria in the intracellular mechanism underlying presbycusis development. Moreover, these variants have potential as diagnostic markers for individuals at a high risk of developing presbycusis. The data also suggest the possible presence of changes in the mtDNA control region in presbycusis, which could alter regulatory factor binding sites and influence mtDNA gene expression and copy number.

Accuracy of Mobile-Based Audiometry in the Evaluation of Hearing Loss in Quiet and Noisy Environments

Objectives

(1) To compare the accuracy of 2 previously validated mobile-based hearing tests in determining pure tone thresholds and screening for hearing loss. (2) To determine the accuracy of mobile audiometry in noisy environments through noise reduction strategies.

Study Design

Prospective clinical study.

Setting

Tertiary hospital.

Subjects and Methods

Thirty-three adults with or without hearing loss were tested (mean age, 49.7 years; women, 42.4%). Air conduction thresholds measured as pure tone average and at individual frequencies were assessed by conventional audiogram and by 2 audiometric applications (consumer and professional) on a tablet device. Mobile audiometry was performed in a quiet sound booth and in a noisy sound booth (50 dB of background noise) through active and passive noise reduction strategies.

Results

On average, 91.1% (95% confidence interval [95% CI], 89.1%-93.2%) and 95.8% (95% CI, 93.5%-97.1%) of the threshold values obtained in a quiet sound booth with the consumer and professional applications, respectively, were within 10 dB of the corresponding audiogram thresholds, as compared with 86.5% (95% CI, 82.6%-88.5%) and 91.3% (95% CI, 88.5%-92.8%) in a noisy sound booth through noise cancellation. When screening for at least moderate hearing loss (pure tone average >40 dB HL), the consumer application showed a sensitivity and specificity of 87.5% and 95.9%, respectively, and the professional application, 100% and 95.9%. Overall, patients preferred mobile audiometry over conventional audiograms.

Conclusion

Mobile audiometry can correctly estimate pure tone thresholds and screen for moderate hearing loss. Noise reduction strategies in mobile audiometry provide a portable effective solution for hearing assessments outside clinical settings.

Evaluation of peripheral auditory pathways and brainstem in obstructive sleep apnea

INTRODUCTION

Obstructive sleep apnea causes changes in normal sleep architecture, fragmenting it chronically with intermittent hypoxia, leading to serious health consequences in the long term. It is believed that the occurrence of respiratory events during sleep, such as apnea and hypopnea, can impair the transmission of nerve impulses along the auditory pathway that are highly dependent on the supply of oxygen. However, this association is not well established in the literature.

OBJECTIVE

To compare the evaluation of peripheral auditory pathway and brainstem among individuals with and without obstructive sleep apnea.

METHODS

The sample consisted of 38 adult males, mean age of 35.8 (±7.2), divided into four groups matched for age and Body Mass Index. The groups were classified based on polysomnography in: control (n=10), mild obstructive sleep apnea (n=11) moderate obstructive sleep apnea (n=8) and severe obstructive sleep apnea (n=9). All study subjects denied a history of risk for hearing loss and underwent audiometry, tympanometry, acoustic reflex and Brainstem Auditory Evoked Response. Statistical analyses were performed using three-factor ANOVA, 2-factor ANOVA, chi-square test, and Fisher's exact test. The significance level for all tests was 5%.

RESULTS

There was no difference between the groups for hearing thresholds, tympanometry and evaluated Brainstem Auditory Evoked Response parameters. An association was observed between the presence of obstructive sleep apnea and changes in absolute latency of wave V (p=0.03). There was an association between moderate obstructive sleep apnea and change of the latency of wave V (p=0.01).

CONCLUSION

The presence of obstructive sleep apnea is associated with changes in nerve conduction of acoustic stimuli in the auditory pathway in the brainstem. The increase in obstructive sleep apnea severity does not promote worsening of responses assessed by audiometry, tympanometry and Brainstem Auditory Evoked Response.

The potential role for use of mitochondrial DNA copy number as predictive biomarker in presbycusis

OBJECTIVES

Age-related hearing impairment, or presbycusis, is the most common communication disorder and neurodegenerative disease in the elderly. Its prevalence is expected to increase, due to the trend of growth of the elderly population. The current diagnostic test for detection of presbycusis is implemented after there has been a change in hearing sensitivity. Identification of a pre-diagnostic biomarker would raise the possibility of preserving hearing sensitivity before damage occurs. Mitochondrial dysfunction, including the production of reactive oxygen species and induction of expression of apoptotic genes, participates in the progression of presbycusis. Mitochondrial DNA sequence variation has a critical role in presbycusis. However, the nature of the relationship between mitochondrial DNA copy number, an important biomarker in many other diseases, and presbycusis is undetermined.

METHODS

Fifty-four subjects with presbycusis and 29 healthy controls were selected after ear, nose, throat examination and pure-tone audiometry. DNA was extracted from peripheral blood samples. The copy number of mitochondrial DNA relative to the nuclear genome was measured by quantitative real-time polymerase chain reaction.

RESULTS

Subjects with presbycusis had a lower median mitochondrial DNA copy number than healthy subjects and the difference was statistically significant (P=0.007). Mitochondrial DNA copy number was also significantly associated with degree of hearing impairment (P=0.025) and audiogram configuration (P=0.022).

CONCLUSION

The findings of this study suggest that lower mitochondrial DNA copy number is responsible for presbycusis through alteration of mitochondrial function. Moreover, the significant association of mitochondrial DNA copy number in peripheral blood samples with the degree of hearing impairment and audiogram configuration has potential for use as a standard test for presbycusis, providing the possibility of the development of an easy-to-use biomarker for the early detection of this condition.

Significant association between osteoporosis and hearing loss: a systematic review and meta-analysis

INTRODUCTION

There is inconclusive evidence whether osteoporosis increases risk of hearing loss in current literature.

OBJECTIVE

We conducted this meta-analysis to determine whether there is an association between hearing loss and osteoporosis.

METHODS

This systematic review and meta-analysis was conducted from studies of MEDLINE, EMBASE, and LILACS. Osteoporosis was defined as having a bone mineral density with a T-score of less than -2.5 standard deviation. The outcome was hearing loss as assessed by audiometry or self-reported assessment. Random-effects model and pooled hazard ratio, risk ratio, or odds ratio of hearing loss with 95% confidence intervals were compared between normal bone mineral density and low bone mineral density or osteoporosis.

RESULTS

A total of 16 articles underwent full-length review. Overall, there was a statistically significant increased odds of hearing loss in the low bone mineral density or osteoporosis group with odds ratio of 1.20 (95% confidence intervals 1.01-1.42, p=0.04, I²=82%, P_{heterogeneity}=0.01). However, the study from Helzner et al. reported significantly increase odds of hearing loss in the low bone mineral density in particular area and population included femoral neck of black men 1.37 (95% confidence intervals 1.07-1.76, p=0.01) and total hip of black men 1.36 (95% confidence intervals 1.05-1.76, p=0.02).

CONCLUSION

Our study proposed the first meta-analysis that demonstrated a probable association between hearing loss and bone mineral density. Osteoporosis could be a risk factor in hearing loss and might play an important role in age-related hearing loss.

Association of hearing impairment with insulin resistance, β-cell dysfunction and impaired fasting glucose before onset of diabetes

AIM

Diabetes is a known risk factor for hearing impairment. No study regarding the association of insulin resistance (IR), β-cell dysfunction and impaired fasting glucose (IFG) with hearing impairment has been reported in the population without diabetes. We examined these associations using a representative sample of the Korean population.

METHODS

Participants included 1589 males and 2496 females, who were ≥ 20 years of age and without diabetes from the Korea National Health and Nutritional Examination Surveys of the Korean population (2010). Audiometric tests and laboratory examinations were performed. Homeostasis model assessments of IR and β-cell function (HOMA-IR and HOMA-β) were calculated.

RESULTS

The prevalence of both high- and low-/mid-frequency hearing impairment among subjects with IFG was higher compared with those with normal glycaemia (42.2% vs. 24.5%, 14.7% vs. 7.8%, respectively). After adjustment for age, HOMA-IR and HOMA-β showed significant association with high-frequency hearing impairment in males. In the multiple logistic regression analyses adjusting for confounding variables, the presence of IFG, higher HOMA-IR and lower HOMA-β remained as independent risk factors for high-frequency mild hearing impairment in males < 70 years [odds ratio (OR) 1.441, 95% confidence interval (95% CI), 1.056 to 1.967; OR, 1.448, 95% CI, 1.039 to 2.101; and OR, 0.447, 95% CI, 0.274 to 0.729, P < 0.05, respectively).

CONCLUSIONS

IR, β-cell dysfunction and IFG are associated with high-frequency mild hearing impairment in the male population < 70 years before the onset of diabetes.

The effects of aging and sex on detection of ultrasonic vocalizations by adult CBA/CaJ mice (Mus musculus)

Mice are frequently used as animal models for human hearing research, yet their auditory capabilities have not been fully explored. Previous studies have established auditory threshold sensitivities for pure tone stimuli in CBA/CaJ mice using ABR and behavioral methodologies. Little is known about how they perceive their own ultrasonic vocalizations (USVs), and nothing is known about how aging influences this perception. The aim of the present study was to establish auditory threshold sensitivity for several USV types, as well as to track these thresholds across the mouse's lifespan. In order to determine how well mice detect these complex communication stimuli, several CBA/CaJ mice were trained and tested at various ages on a detection task using operant conditioning procedures. Results showed that mice were able to detect USVs into old age. Not surprisingly, thresholds differed for the different USV types. Male mice suffered greater hearing loss than females for all calls but not for 42 kHz tones. In conclusion, the results highlight the importance of studying complex signals across the lifespan.

Protective Effects of Pituitary Adenylate Cyclase-Activating Polypeptide (PACAP) Against Oxidative Stress in Zebrafish Hair Cells

Pituitary adenylate cyclase-activating polypeptide (PACAP) is a pleiotropic neuropeptide, with known antiapoptotic functions. Our previous in vitro study has demonstrated the ameliorative role of PACAP-38 in chicken hair cells under oxidative stress conditions, but its effects on living hair cells is now yet known. Therefore, the aim of the present study was to investigate in vivo the protective role of PACAP-38 in hair cells found in zebrafish (Danio rerio) sense organs-neuromasts. To induce oxidative stress the 5-day postfertilization (dpf) zebrafish larvae were exposed to 1.5 mM H₂O₂ for 15 min or 1 h. This resulted in an increase in caspase-3 and p-38 MAPK level in the hair cells as well as in an impairment of the larvae basic behavior. To investigate the ameliorative role of PACAP-38, the larvae were incubated with a mixture of 1.5 mM H₂O₂ and 100 nM PACAP-38 following 1 h preincubation with 100 nM PACAP-38 only. PACAP-38 abilities to prevent hair cells from apoptosis were investigated. Whole-mount immunohistochemistry and confocal microscopy analyses revealed that PACAP-38 treatment decreased the cleaved caspase-3 level in the hair cells, but had no influence on p-38 MAPK. The analyses of basic locomotor activity supported the protective role of PACAP-38 by demonstrating the improvement of the fish behavior after PACAP-38 treatment. In summary, our in vivo findings demonstrate that PACAP-38 protects zebrafish hair cells from oxidative stress by attenuating oxidative stress-induced apoptosis.

Efeitos da perda auditiva e da cognição no reconhecimento de sentenças

RESUMO Objetivo Avaliar os efeitos da perda auditiva e da cognição no reconhecimento de sentenças em idosos. Métodos Participaram do estudo 30 idosos distribuídos em dois grupos: GI- composto por 17 idosos sem perda auditiva e GII- composto por 13 idosos com perda auditiva de grau leve. Para avaliar a cognição, foi aplicado o Mini Exame do Estado Mental (MEEM) e, para analisar os efeitos auditivos, foi realizado o teste Listas de Sentenças em Português (LSP), no qual foi pesquisado o Limiar de Reconhecimento de Sentenças no Silêncio (LRSS) e a relação sinal/ruído (S/R). Resultados No MEEM, houve um percentual maior de indivíduos com alteração no GI do que no GII. Tanto no LRSS quanto na relação S/R, o GI apresentou menores limiares do que o GII em ambas as orelhas. Em relação aos aspectos cognitivos, não houve diferença estatisticamente significante entre o grupo normal e alterado no MEEM com o LRSS e relação S/R dos grupos GI e GII de ambas as orelhas. Conclusão A perda auditiva de grau leve exerceu influência no reconhecimento de sentenças no silêncio e no ruído. Já os aspectos cognitivos não interferiram no reconhecimento de fala tanto no silêncio quanto no ruído.

Expression levels of the BAK1 and BCL2 genes highlight the role of apoptosis in age-related hearing impairment

Age-related hearing impairment (ARHI) is a progressive and a common sensory disorder in the elderly and will become an increasingly important clinical problem given the growing elderly population. Apoptosis of cochlear cells is an important factor in animal models of ARHI. As these cells cannot regenerate, their loss leads to irreversible hearing impairment. Identification of molecular mechanisms can facilitate disease prevention and effective treatment. In this study, we compared the expression of the genes BAK1 and BCL2 as two arms of the intrinsic apoptosis pathway between patients with ARHI and healthy subjects. ARHI and healthy subjects were selected after an ear nose throat examination, otoscopic investigation, and pure tone audiometry. RNA was extracted from peripheral blood samples, and relative gene expression levels were measured using quantitative real-time polymerase chain reaction. BAK1 and the BAK1/BCL2 ratio were statistically significantly upregulated in the ARHI subjects. The BAK1/BCL2 ratio was positively correlated with the results of the audiometric tests. Our results indicate that BAK-mediated apoptosis may be a core mechanism in the progression of ARHI in humans, similar to finding in animal models. Moreover, the gene expression changes in peripheral blood samples could be used as a rapid and simple biomarker for early detection of ARHI.

Markers of Overall Nutritional Status and Incident Hearing Impairment in Community-Dwelling Older Japanese: The Kurabuchi Study

OBJECTIVES

To examine the association between four markers of overall nutritional status (a serum biomarker (albumin) and three anthropometric indices (body mass index (BMI), midarm circumference (MAC), calf circumference (CC))) and incident hearing impairment in older Japanese adults.

DESIGN

Community-based prospective cohort study.

SETTING

Kurabuchi Town, Gunma Prefecture, Japan.

PARTICIPANTS

Individuals aged 65 and older (143 men, 195 women) without hearing impairment at baseline examination (2005-06) who participated in repeated examinations 4 years later (2009-10) (N = 338).

MEASUREMENTS

The three anthropometric indices were measured at baseline, and nephelometry was used to assess serum albumin levels. Hearing impairment was defined as failure to hear a 30-dB hearing level signal at 1 kHz and a 40-dB signal at 4 kHz in the better ear on pure-tone audiometry.

RESULTS

Over the 4-year period, 16.3% of participants developed hearing impairment. Those with lower marker values had greater risk of hearing impairment than those with higher marker values (multivariable adjusted odds ratio (aOR) = 2.18, 95% confidence interval (CI) = 1.05-4.57 for albumin ≤4.0 g/dL; aOR = 2.72, 95% CI = 1.10-6.71 for BMI <19.0 kg/m(2) ). The pattern of association showed a similar tendency for MAC and CC. Excluding obese participants did not changed the results substantially.

CONCLUSION

Further research is needed to determine whether interventions that improve markers of nutritional status may help prevent age-related hearing loss in older adults.

Downregulation of inwardly rectifying potassium channel 5.1 expression in C57BL/6J cochlear lateral wall

Age-related hearing loss (AHL) is one of the most common sensory disorders among elderly persons. The inwardly rectifying potassium channel 5.1 (Kir5.1) plays a vital role in regulating cochlear K(+) circulation which is necessary for normal hearing. The distribution of Kir5.1 in C57BL/6J mice cochleae, and the relationship between the expression of Kir5.1 and the etiology of AHL were investigated. Forty C57BL/6J mice were randomly divided into four groups at 4, 12, 24 and 52 weeks of age respectively. The location of Kir5.1 was detected by immunofluorescence technique. The mRNA and protein expression of Kir5.1 was evaluated in mice cochleae using real-time polymerase-chain reactions (RT-PCR) and Western blotting respectively. Kir5.1 was detected in the type II and IV fibrocytes of the spiral ligament in the cochlear lateral wall of C57BL/6J mice. The expression levels of Kir5.1 mRNA and protein in the cochleae of aging C57BL/6J mice were down-regulated. It was suggested that the age-related decreased expression of Kir5.1 in the lateral wall of C57BL/6J mice was associated with hearing loss. Our results indicated that Kir5.1 may play an important role in the pathogenesis of AHL.

Is Body Mass Index Associated With the Development of Age-Related Hearing Impairment in Koreans? The Korean National Health and Nutrition Examination Survey 2009-2012

Objectives

The aim of this study was to evaluate whether body mass index (BMI) is associated with age-related hearing loss (ARHL) in the Asian elderly population.

Methods

Data from the Korean National Health and Nutrition Examination Survey 2009–2012 were used for the analyses. The pure tones at 0.5 and 1 kHz of both ears of each subject were averaged to obtain the low-frequency, those at 2 and 3 kHz were averaged to obtain the mid-frequency, and those at 4 and 6 kHz were averaged to obtain the high-frequency. The average hearing threshold (AHT) was calculated as pure tone average at 4 frequencies in the better ear. ARHL was defined as the AHT >25 dB.

Results

Univariate analyses revealed an increase in the BMI tertile in men was associated with a decreased low-frequency threshold, while an increase in the BMI tertile in women was associated with decreased mid- and high-frequency thresholds. Multivariate analyses adjusted for confounders show no significant differences in low-, mid-, or high-frequency. There was no significant difference in the prevalence of ARHL by BMI tertiles. Linear regression analyses show no association between BMI and low-, mid-, and high-frequency or AHTs. The area under the receiver operating characteristic curve values for AHT was 0.515 in men and 0.522 in women. The logistic regression analyses showed no association between BMI and ARHL in either sex.

Conclusion

BMI is not advantageous for the prediction of ARHL. In future epidemiological studies, BMI as a covariate of obesity may be replaced by other active metabolic parameters that have better predictive ability of ARHL than BMI.

Transcranial Alternating Current Stimulation (tACS) differentially modulates speech perception in young and older adults

BACKGROUND

Normal aging is accompanied by a functional decline in processing temporal features of spoken language, such as voice onset time (VOT). On an electrophysiological level, this finding is paralleled by altered patterns of gamma oscillations.

OBJECTIVE

Using 40 Hz transcranial alternating current stimulation (tACS) over the bilateral auditory cortex, this study aims to compare the effect of tACS to modulate VOT-processing in samples of healthy young and older adults.

METHODS

Twenty-five healthy young (age 20-35 years) and 20 older adults (age 60-75 years) participated in this study. Presented with an auditory phoneme categorization task participants received 40 Hz and 6 Hz tACS on two consecutive sessions.

RESULTS

While 40 Hz tACS diminished task accuracy in young adults, older adults benefitted from this stimulation resulting in a more precise phonetic categorization.

CONCLUSION

The results of the study are discussed with respect to the non-linear relationship between gamma oscillations in the vicinity of the auditory cortex and VOT-processing. The present findings are promising in the context of an intervention for subjects with impaired ability to process temporal acoustic features in the speech signal.

Noise-Induced "Toughening" Effect in Wistar Rats: Enhanced Auditory Brainstem Responses Are Related to Calretinin and Nitric Oxide Synthase Upregulation

An appropriate conditioning noise exposure may reduce a subsequent noise-induced threshold shift. Although this "toughening" effect helps to protect the auditory system from a subsequent traumatic noise exposure, the mechanisms that regulate this protective process are not fully understood yet. Accordingly, the goal of the present study was to characterize physiological processes associated with "toughening" and to determine their relationship to metabolic changes in the cochlea and cochlear nucleus (CN). Auditory brainstem responses (ABR) were evaluated in Wistar rats before and after exposures to a sound conditioning protocol consisting of a broad-band white noise of 118 dB SPL for 1 h every 72 h, four times. After the last ABR evaluation, animals were perfused and their cochleae and brains removed and processed for the activity markers calretinin (CR) and neuronal nitric oxide synthase (nNOS). Toughening was demonstrated by a progressively faster recovery of the threshold shift, as well as wave amplitudes and latencies over time. Immunostaining revealed an increase in CR and nNOS levels in the spiral ganglion, spiral ligament, and CN in noise-conditioned rats. Overall, these results suggest that the protective mechanisms of the auditory toughening effect initiate in the cochlea and extend to the central auditory system. Such phenomenon might be in part related to an interplay between CR and nitric oxide signaling pathways, and involve an increased cytosolic calcium buffering capacity induced by the noise conditioning protocol.

Evaluation of the effects of occupational noise exposure on serum aldosterone and potassium among industrial workers

The existing literature indicates that occupational exposure to noise may have adverse effects on workers' health. The aim of this study was to evaluate the possible effects of exposure to different sound pressure levels (SPLs) on serum aldosterone and potassium concentration among Iranian blue collar workers in Golgohar Mining and Industrial Company in Sirjan, Kerman Province, Iran. This case-control study was performed on 45 workers of Golgohar Mining and Industrial Company. The subjects consisted of 30 workers from manufacturing departments and 15 office employees of the mining company. The controls, mainly with administrative jobs were exposed to 72 dBA SPL. Cases, in two separate groups, were exposed to noise levels of 88 dBA and 103 dBA, respectively. Noise intensity was measured at the desired locations. Noise measurements were performed according to the International Organization for Standardization (ISO) 9612. To measure the serum aldosterone and potassium concentrations, a 5 mL blood sample was taken from each worker at the specified time intervals and aldosterone concentration was determined using enzyme-linked immunosorbent assay (ELISA) test in the laboratory. Repeated measurement and Spearman's correlation coefficient analysis were used with α = 0.05. Exposure to the different levels of sound pressure resulted in different aldosterone concentrations and meanwhile an increase in the SPL did not affect the concentration of potassium. From 10:00 AM to 10:30 AM, as SPL increased, aldosterone concentrations did not increase significantly but from 13:30 PM to 14:00 PM, raised SPL led to a significant increase in aldosterone concentration. However, there was no correlation between the concentration of potassium and different factors. This study indicated that increases in SPLs affect aldosterone concentration but at the same time do not have significant effects on serum potassium level.

The Effect of Aging and the High-Frequency Auditory Threshold on Speech-Evoked Mismatch Negativity in a Noisy Background

Mismatch negativity (MMN) has been widely used to study the function of central auditory processing in the elderly. However, current research has not yet considered the effect of noise and high-frequency hearing threshold on MMN in the elderly. The aim of this study was to evaluate the effect of aging and high-frequency hearing loss on speech-related MMN in noisy backgrounds. Additionally, the possible mechanisms of central auditory processing dysfunction in the elderly were investigated. Fifty people aged 61-80 (70 ± 5.8) years were recruited for this study. They were divided into a 61- to 70-year-old group and a 71- to 80-year-old group. Fifty younger adults aged 21-40 (31 ± 5.3) years were recruited as healthy controls. Pure-tone hearing thresholds were recorded. A speech discrimination score (SDS) and a speech-evoked MMN under white noise with a bandwidth from 125 to 8,000 Hz background condition were recorded. The relationships between SDS and MMN latency and amplitude were analyzed. The effects of age and binaural 2,000-, 4,000- and 8,000-Hz pure-tone hearing thresholds on MMN latency and amplitude were analyzed. We found that the hearing thresholds of 2,000, 4,000 and 8,000 Hz in the 61- to 70-year-old and 71- to 80-year-old groups were higher than those in the control group. The SDS in a noisy background in the 61- to 70-year-old and 71- to 80-year-old groups were lower than those in the control group. Speech-evoked MMN latency was longer in the 61- to 70-year-old and in the 71- to 80-year-old groups than in the control group (215.8 ± 14.2 ms). SDS and speech-evoked MMN latency were negatively correlated. Age and speech-evoked MMN latency were positively correlated, as were the binaural 4,000- to 8,000-Hz pure-tone hearing thresholds and speech-evoked MMN. This study suggests that in elderly subjects, the function of preattentive central auditory processing changes. Additionally, increasing age and high-frequency hearing thresholds create a synergy in neurons that is weakened in the MMN time window, which may be a cause of central auditory processing disorders in elderly subjects in noisy background conditions.

Genetics of Hearing Loss: Syndromic

Hearing loss (HL) is one of the most common birth defects in developed countries and is a diverse pathologic condition with different classifications. One of these is based on the association with other clinical features, defined as syndromic hearing loss (SHL). Determining the cause of the HL in these patients is extremely beneficial as it enables a personalized approach to caring for the individual. Early screening can further aid in optimal rehabilitation for a child's development and growth. The advancement of high-throughput sequencing technology is facilitating rapid and low-cost diagnostics for patients with SHL.

Factors Associated With Age-related Hearing Impairment: A Retrospective Cohort Study

Age-related hearing impairment (ARHI) is a complex degenerative disease in the elderly. As multiple factors interact during the development of ARHI, it is important to elucidate the major influencing factors to understand and prevent ARHI. We aimed to identify risk factors associated with the development of ARHI with a retrospective cohort from 2001 to 2010. The records of the adult subjects over 40 years of age who consecutively underwent a comprehensive health checkup including pure-tone audiometry at the Health Promotion Center were reviewed. During this period, 1560 subjects who underwent pure-tone audiometry more than twice, had no other otologic diseases, and were followed-up more than 2 years were included. A pure-tone average (PTA: 0.5, 1, 2, 4 kHz) was calculated. Development of ARHI was defined as a PTA at follow-up more than 10 dB greater than the baseline PTA. Times to the first development of ARHI were investigated. Overall, 12.7% of subjects developed ARHI within the first 4 years. High blood ionized calcium (hazard ratio [HR] 0.084), albumin (HR 0.239), systolic blood pressure (HR 0.577), thyroid hormone (T3) (HR 0.593), and alpha fetoprotein levels (HR 0.883) were associated with decreased hazard for the development of ARHI. In contrast, high blood high-density lipoprotein (HR 2.105), uric acid (HR 1.684), total protein (HR 1.423), and total bilirubin levels (HR 1.220) were potential risk factors for the development of ARHI. Development of ARHI is common among the aged population, and a variety of factors may interact during this process. The results of this study can be used for counseling of adults at high-risk of developing ARHI with regard to regular audiological check-up.

Hearing Aid Use and Associated Factors in South Korea

Despite the high prevalence of hearing impairment in the elderly, the rate of hearing aid use is still low. The objectives of this study were to report the nation-wide prevalence of hearing aid use in the Korean population and to determine the associated factors with hearing aid use utilizing a nationally representative data set.We obtained data from the 2010 to 2012 Korea National Health and Nutrition Examination Surveys, which were cross-sectional surveys of the civilian, noninstitutionalized population of the Republic of Korea at age ≥40 years (N = 12,709). A field survey team performed interviews as well as physical examinations. Hearing aid use was assessed using an interviewer-administered questionnaire and pure-tone audiometry was administered for all participants in a sound-attenuating booth. Prevalence of hearing aid acquisition and regular use were calculated in participants who reported perceived hearing loss and who have bilateral hearing thresholds exceeding the 40 dB hearing level. Multivariable analyses were used to examine the associated factors with hearing aid use.The prevalence of hearing aid acquisition and regular use was 17.4% and 12.6%, respectively, in South Korea. Increased hearing threshold (OR 1.05, 95% CI 1.03-1.07), severe perceived hearing loss (OR 10.73, 95% CI 4.52-25.46), annoying tinnitus (OR 3.30, 95% CI 1.61-6.74), balance problems (OR 0.39, 95% CI 0.18-0.86), and myopia (OR 0.30, 95% CI 0.12-0.76) were associated factors of regular use of hearing aids.The prevalence of hearing aid use in Korea is relatively low. Finding relevant factors of hearing aid use could provide further insight in setting up hearing-rehabilitation strategy for the elderly with significant hearing loss.

The Genetic Architecture of Hearing Impairment in Mice: Evidence for Frequency-Specific Genetic Determinants

Genome-wide association studies (GWAS) have been successfully applied in humans for the study of many complex phenotypes. However, identification of the genetic determinants of hearing in adults has been hampered, in part, by the relative inability to control for environmental factors that might affect hearing throughout the lifetime, as well as a large degree of phenotypic heterogeneity. These and other factors have limited the number of large-scale studies performed in humans that have identified candidate genes that contribute to the etiology of this complex trait. To address these limitations, we performed a GWAS analysis using a set of inbred mouse strains from the Hybrid Mouse Diversity Panel. Among 99 strains characterized, we observed approximately two-fold to five-fold variation in hearing at six different frequencies, which are differentiated biologically from each other by the location in the cochlea where each frequency is registered. Among all frequencies tested, we identified a total of nine significant loci, several of which contained promising candidate genes for follow-up study. Taken together, our results indicate the existence of both genes that affect global cochlear function, as well as anatomical- and frequency-specific genes, and further demonstrate the complex nature of mammalian hearing variation.

Methylprednisolone use during radiotherapy extenuates hearing loss in patients with nasopharyngeal carcinoma

OBJECTIVES/HYPOTHESIS

To investigate the hearing protective effects of methylprednisolone use during radiotherapy in patients with nasopharyngeal carcinoma.

STUDY DESIGN

Prospective, controlled clinical study.

METHODS

Fifty-three patients with nasopharyngeal carcinoma (106 ears). Twenty-five patients (50 ears) received radiotherapy with intravenous methylprednisolone for 14 days, and another 28 patients (56 ears) received radiotherapy alone. Pure tone audiometry, distortion product otoacoustic emission (DPOAE), and auditory brainstem responses (ABR) results were reviewed before and 1 year after radiotherapy.

RESULT

One year after radiotherapy, the air-and-bone conduction pure tone hearing thresholds increased, and the DPOAE levels decreased in the control group. There was no difference in the ABR wave I, III, and V latencies and the I to V interwave latencies before and 1 year after radiotherapy. The pure tone air conduction thresholds decreased, and the DPOAE levels increased in the treatment group compared with the control group.

CONCLUSION

Early sensorineural hearing loss after radiotherapy primarily affected the outer hair cells. The use of methylprednisolone during radiotherapy can extenuate early sensorineural hearing loss caused by irradiation.