The epidemiology of hearing impairment in an Australian adult population

Hearing Loss Prevalence, Years Lived With Disability, and Hearing Aid Use in the United States From 1990 to 2019: Findings From the Global Burden of Disease Study

OBJECTIVES

This article describes key data sources and methods used to estimate hearing loss in the United States, in the Global Burden of Disease study. Then, trends in hearing loss are described for 2019, including temporal trends from 1990 to 2019, changing prevalence over age, severity patterns, and utilization of hearing aids.

DESIGN

We utilized population-representative surveys from the United States to estimate hearing loss prevalence for the Global Burden of Disease study. A key input data source in modeled estimates are the National Health and Nutrition Examination Surveys (NHANES), years 1988 to 2010. We ran hierarchical severity-specific models to estimate hearing loss prevalence. We then scaled severity-specific models to sum to total hearing impairment prevalence, adjusted estimates for hearing aid coverage, and split estimates by etiology and tinnitus status. We computed years lived with disability (YLDs), which quantifies the amount of health loss associated with a condition depending on severity and creates a common metric to compare the burden of disparate diseases. This was done by multiplying the prevalence of severity-specific hearing loss by corresponding disability weights, with additional weighting for tinnitus comorbidity.

RESULTS

An estimated 72.88 million (95% uncertainty interval (UI) 68.53 to 77.30) people in the United States had hearing loss in 2019, accounting for 22.2% (20.9 to 23.6) of the total population. Hearing loss was responsible for 2.24 million (1.56 to 3.11) YLDs (3.6% (2.8 to 4.7) of total US YLDs). Age-standardized prevalence was higher in males (17.7% [16.7 to 18.8]) compared with females (11.9%, [11.2 to 12.5]). While most cases of hearing loss were mild (64.3%, 95% UI 61.0 to 67.6), disability was concentrated in cases that were moderate or more severe. The all-age prevalence of hearing loss in the United States was 28.1% (25.7 to 30.8) higher in 2019 than in 1990, despite stable age-standardized prevalence. An estimated 9.7% (8.6 to 11.0) of individuals with mild to profound hearing loss utilized a hearing aid, while 32.5% (31.9 to 33.2) of individuals with hearing loss experienced tinnitus. Occupational noise exposure was responsible for 11.2% (10.2 to 12.4) of hearing loss YLDs.

CONCLUSIONS

Results indicate large burden of hearing loss in the United States, with an estimated 1 in 5 people experiencing this condition. While many cases of hearing loss in the United States were mild, growing prevalence, low usage of hearing aids, and aging populations indicate the rising impact of this condition in future years and the increasing importance of domestic access to hearing healthcare services. Large-scale audiometric surveys such as NHANES are needed to regularly assess hearing loss burden and access to healthcare, improving our understanding of who is impacted by hearing loss and what groups are most amenable to intervention.

Mixed Evidence of an Association between Self-Rated Hearing Difficulties and Falls: Prospective Analysis of Two Longitudinal Studies

INTRODUCTION

This study aimed to assess the extent to which a single item of self-reported hearing difficulties is associated with future risk of falling among community-dwelling older adults.

METHODS

We used data from two Australian population-based cohorts: three waves from the PATH Through Life study (PATH; n = 2,048, 51% men, age 66.5 ± 1.5 SD years) and three waves from the Concord Health and Ageing in Men Project (CHAMP; n = 1,448, 100% men with mean age 77.3 ± 5.3 SD years). Hearing difficulties were recorded on a four-point ordinal scale in PATH and on a dichotomous scale in CHAMP. The number of falls in the past 12 months was reported at each wave in both studies. In CHAMP, incident falls were also ascertained by triannual telephone call cycles for up to four years. Multivariable-adjusted random intercept negative binomial regression models were used to estimate the association between self-reported hearing difficulties and number of falls reported at the following wave or 4-monthly follow-ups.

RESULTS

In PATH, self-reported hearing difficulties were associated with a higher rate of falls at follow-up (incidence rate ratio = 1.15, 95% CI = 1.03-1.27 per a one-level increase in self-reported hearing difficulties), after adjusting for sociodemographic characteristics, health behaviours, physical functioning, balance, mental health, medical conditions, and medications. There were no significant associations between hearing difficulties and the rate of falls based on either repeated survey or 4-monthly follow-ups in CHAMP.

CONCLUSION

Though we find mixed results, findings from PATH data indicate an ordinal measure of self-reported hearing loss may be predictive of falls incidence in young-old adults. However, the null findings in the male-only CHAMP preclude firm conclusions of a link between hearing loss and falls risk.

Sex-Linked Biology and Gender-Related Research Is Essential to Advancing Hearing Health

There is robust evidence that sex (biological) and gender (behavioral/social) differences influence hearing loss risk and outcomes. These differences are noted for animals and humans-in the occurrence of hearing loss, hearing loss progression, and response to interventions. Nevertheless, many studies have not reported or disaggregated data by sex or gender. This article describes the influence of sex-linked biology (specifically sex-linked hormones) and gender on hearing and hearing interventions, including the role of sex-linked biology and gender in modifying the association between risk factors and hearing loss, and the effects of hearing loss on quality of life and functioning. Most prevalence studies indicate that hearing loss begins earlier and is more common and severe among men than women. Intrinsic sex-linked biological differences in the auditory system may account, in part, for the predominance of hearing loss in males. Sex- and gender-related differences in the effects of noise exposure or cardiovascular disease on the auditory system may help explain some of these differences in the prevalence of hearing loss. Further still, differences in hearing aid use and uptake, and the effects of hearing loss on health may also vary by sex and gender. Recognizing that sex-linked biology and gender are key determinants of hearing health, the present review concludes by emphasizing the importance of a well-developed research platform that proactively measures and assesses sex- and gender-related differences in hearing, including in understudied populations. Such research focus is necessary to advance the field of hearing science and benefit all members of society.

The Combined Effect of Noise and Solvent Exposure on Hearing Loss in the Tire Factory Workers

Noise and organic solvents are common in many industries and both of them affect hearing. In this study, we estimated the concurrent effect of them on hearing by evaluating the existence of notch in audiograms of workers. The number of 540 persons were enrolled in this study after eliminating workers who had the exclusion criteria. We divided them into 4 groups based on their exposure status; no exposure, exposure to noise, exposure to solvent, exposure to both of them. The presence of notch in left, right, or both ears were assessed through Coles model. The rates of notch presence in both ears in the groups of noise and organic solvents exposure, noise exposure only, solvents exposure only were 11.72, 4.49, 1.86 times higher than the control group and sole solvent exposure didn't affect hearing significantly. The same pattern was seen for notch presence in left or right ear and the solvent-noise exposure group had the highest rate of notch presence. This study aims to show the synergic effect of noise and organic solvents exposure on hearing loss. Hence, we recommend implementing a hearing protection program and a higher frequency of audiological assessments in the industries involved with concurrent exposure to noise and organic solvents.

The Genetic contribution to solving the cocktail-party problem

Communicating in everyday situations requires solving the cocktail-party problem, or segregating the acoustic mixture into its constituent sounds and attending to those of most interest. Humans show dramatic variation in this ability, leading some to experience real-world problems irrespective of whether they meet criteria for clinical hearing loss. Here, we estimated the genetic contribution to cocktail-party listening by measuring speech-reception thresholds (SRTs) in 425 people from large families and ranging in age from 18 to 91 years. Roughly half the variance of SRTs was explained by genes (h ² = 0.567). The genetic correlation between SRTs and hearing thresholds (HTs) was medium (ρ _G = 0.392), suggesting that the genetic factors influencing cocktail-party listening were partially distinct from those influencing sound sensitivity. Aging and socioeconomic status also strongly influenced SRTs. These findings may represent a first step toward identifying genes for "hidden hearing loss," or hearing problems in people with normal HTs.

Differences in the potential for dementia prevention between major ethnic groups within one country: A cross sectional analysis of population attributable fraction of potentially modifiable risk factors in New Zealand

BACKGROUND

Twelve potentially modifiable risk factors (less education, hypertension, obesity, alcohol, traumatic brain injury (TBI), hearing loss, smoking, depression, physical inactivity, social isolation, diabetes, air pollution) account for an estimated 40% of worldwide dementia cases. We aimed to calculate population attributable fractions (PAFs) for dementia for the four largest New Zealand ethnic groups (European, Māori, Asian, and Pacific peoples) to identify whether optimal dementia prevention targets differed by ethnicity.

METHODS

We calculated risk factor prevalence for 10 risk factors using the New Zealand Health Survey 2018/19 and published reports for hearing loss and TBI prevalences. We calculated the PAF for each risk factor using calculated prevalence and relative risk estimates from previous meta-analyses. To account for risk factor overlap, we calculated communality of risk factors and a weighted PAF.

FINDINGS

The weighted PAF for dementia was 47.7% overall in New Zealand, 47.6% for Europeans, 51.4% for Māori, 50.8% for Pacific peoples, and 40.8% for Asians. Highest PAFs for Europeans were hearing loss (8%) and social isolation (5.7%), and for Asians hearing loss (7.3%) and physical inactivity (5.5%). For Māori and Pacific peoples, highest PAFs were for obesity (7.3% and 8.9% respectively) and hearing loss (6.5% and 6.6%).

INTERPRETATION

New Zealand has higher dementia prevention potential than worldwide estimates with high prevalences of untreated hearing loss and obesity. The relative contribution of individual risk factors PAFs varies by ethnic group. Public health strategies for dementia prevention need to be tailored to these differences.

FUNDING

Health Research Council of New Zealand (HRC:20/021).

Does Sinusitis Affect Lateralization of a Tuning Fork Weber Test?

OBJECTIVE

To describe the effect of sinusitis on Weber test lateralization which normally lateralizes toward the ear of a conductive hearing loss and away from the ear of a sensorineural hearing loss; to investigate whether the presence of an extra-aural condition might affect Weber test results.

STUDY DESIGN

Descriptive study.

SETTING

Tertiary referral center.

SUBJECTS AND METHODS

Consecutive adult patients with maxillary and/or frontal sinusitis were included (study group), as well as patients with normal sinus structure and function (control group) were enrolled between February and September 2019. Presence or absence of paranasal disease and middle ear aeration was confirmed by computerized tomography. Subjects with otologic condition were excluded. The physical examinations, tympanograms, and audiograms were unremarkable. The Weber test consisted of 512, 1024, and 2048 Hz tuning forks that were applied on the central incisors and frontal midline, and lateralization patterns were compared with the extent of paranasal pathology.

RESULTS

There were 44 participants (M:F=26:18), age 19 to 63 years (average 51). The cohort included 39 patients with sinusitis, affecting the frontal and/or maxillary sinus(es), as well as 5 controls without evidence of paranasal disease. There was a match between the extent of paranasal disease and the results of all 3 Weber test frequencies in 35 patients (80%). Omission of the 2048 and 1024 Hz tuning forks from the analysis yielded a match in 40 (91%) and 43 (98%) patients, respectively. No Weber test lateralized to the nondiseased sinus in any subject. Weber test lateralization was observed in 11% of patients, after the sinonasal pathology was successfully addressed.

CONCLUSION

Weber test lateralization in the absence of aural pathology may be explained by asymmetry related to paranasal disease and may alert to its presence.

Hearing loss and access to audiology services in rural victoria: Findings from the crossroads study

Context:

Rural residents can be exposed to high levels of agricultural machinery noise and are at risk of hearing loss.

Aims:

This study aimed to determine audiology service use and rates of hearing loss in a regional area of Australia, using both self-report and audiology testing.

Setting and Design:

A survey of randomly selected households was undertaken and 6432 participants were interviewed face to face about their health, hearing, and use of audiology services. A total of 1454 participants were randomly selected to undertake standard audiology testing.

Material and Methods:

Material Hearing was evaluated using conventional audiometry.

Statistical Analysis Used:

Independent t-tests, Chi-squared tests, and logistic regression were used to examine the association amongbetween hearing loss, use of audiology services, and demographic factors.

Results:

Hearing issues were present in 12.5% of the survey participants. The rate of hearing loss increased significantly with age. Males were significantly more likely to have hearing loss than females (9.5% vs. 5.2%, pP << 0.01). The majority of people who reported accessing audiology services in the past 12 months were satisfied with the care they received (85.2%), and experienced short waiting times for these services (68.2% waited ≤≤ 7 days).

Conclusions:

Males had higher rates of hearing issues than females in this rural area. Audiology services in the region were accessible within short waiting times, and clients were satisfied with the service.

The external phenotype of aging

Aging is widely studied as a physiological process. Segmental aging can also occur prematurely in Mendelian disorders, and these can act this way as excellent sources of information, specifically for the underlying mechanisms. Adequate recognition of such aging characteristics in Mendelian disorders needs a well-defined phenotype of aging. Here the external phenotype of aging is described that can be recognized in the consulting room without major additional studies. Existing definitions of the signs and symptoms in Elements of Morphology or Human Phenotype Ontology are added or a new definition is suggested if none is available.

Gender-specific hearing loss in German adults aged 18 to 84 years compared to US-American and current European studies

INTRODUCTION

From an epidemiological point of view, the increase of pure-tone hearing thresholds as one aspect of biological ageing is moderated by societal factors. Since health policies refer to empirical findings, it is reasonable to replicate population-based hearing surveys and to compare estimates for different birth cohorts from the same regions or, conversely, for the same birth cohorts from different regions.

METHODS

We pooled data from two independent cross-sectional German studies conducted between 2008 and 2012 and including 3105 adults. The increase of thresholds, the prevalence and risk of hearing impairment (HI) by age and gender were compared to results reported for European and US-American studies that were carried out at about the same time. Since these studies differed with regard to the age limits, the statistical approaches and, importantly, their definitions of HI, data adjustments were performed to enable the comparison.

RESULTS

Overall, 15.5% of the participants in the German studies showed a pure-tone average at 0.5, 1, 2, and 4 kHz in the better ear (PTA) greater than 25 dB HL and 8.6% had a PTA of at least 35 dB HL. Based on one-to-one comparisons, the German estimates demonstrated a good agreement to a large Dutch study and with some reservations to a Swedish study, but considerable differences to US-American results. Comprehensive comparisons of the within-study gender differences showed that age-related HI was less and the gender gap was markedly smaller in Europe compared to the US due to the lower HI in males found in the European studies.

CONCLUSION

Discrepancies in measurement procedures, conditions, and equipment that complicate the comparison of absolute HI estimates across studies play no or only a marginal role when comparing relative estimates. Hence, the gender gap differences reviewed in this analysis possibly stem from societal conditions that distinguish societies commonly labeled modern industrialized western countries.

Self-reported hearing loss questions provide a good measure for genetic studies: a polygenic risk score analysis from UK Biobank

Age-related hearing impairment (ARHI) is very common in older adults and has major impact on quality of life. The heritability of ARHI has been estimated to be around 50%. The present study aimed to estimate heritability and environmental contributions to liability of ARHI and the extent to which a polygenic risk score (PRS) derived from a recent genome-wide association study of questionnaire items regarding hearing loss using the UK Biobank is predictive of hearing loss in other samples. We examined (1) a sample from TwinsUK who have had hearing ability measured by pure-tone audiogram and the speech-to-noise ratio test as well as questionnaire measures that are comparable with the UK Biobank questionnaire items and (2) European and non-European samples from the UK Biobank which were not part of the original GWAS. Results indicated that the questionnaire items were over 50% heritable in TwinsUK and comparable with the objective hearing measures. In addition, we found very high genetic correlation (0.30-0.84) between the questionnaire responses and objective hearing measures in the TwinsUK sample. Finally, PRS computed from weighted UK Biobank GWAS results were predictive of both questionnaire and objective measures of hearing loss in the TwinsUK sample, as well as questionnaire-measured hearing loss in Europeans but not non-European subpopulations. These results demonstrate the utility of questionnaire-based methods in genetic association studies of hearing loss in adults and highlight the differences in genetic predisposition to ARHI by ethnic background.

Association Between Hearing and Vision Impairment and Risk of Dementia: Results of a Case-Control Study Based on Secondary Data

Introduction: Hearing and vision loss are highly prevalent in elderly adults, and thus frequently occur in conjunction with cognitive impairments. Studies have shown that hearing impairment is associated with a higher risk of dementia. However, evidence concerning the association between vision loss and dementia, as well as the co-occurrence of vision and hearing loss and dementia, has been inconclusive. Objectives: To assess the association between: (i) either hearing or vision loss and the risk of dementia, as well as between; and (ii) the combination of both sensory impairments and the risk of dementia. Methods: This case-control study was based on a 5-year data set that included patients aged 65 years and older who had initially been diagnosed with dementia diseases by one of 1,203 general practitioners in Germany between January 2013 and December 2017. In total, 61,354 identified dementia cases were matched to non-dementia controls, resulting in a sample size of 122,708 individuals. Hearing loss and vision loss were identified using the ICD-10 diagnoses documented in the general practitioners' files prior to the initial dementia diagnosis. Multivariate logistic regression models were fitted to evaluate the associations between visual and/or hearing impairment and the risk of dementia and controlled for sociodemographic and clinical variables. Results: Hearing impairment was documented in 11.2% of patients with a dementia diagnosis and 9.5% of patients without such a diagnosis. Some form of vision impairment was documented in 28.4% of patients diagnosed with dementia and 28.8% of controls. Visual impairment was not significantly associated with dementia (OR = 0.97, CI = 95% 0.97-1.02, p = 0.219). However, patients with hearing impairment were at a significantly higher risk of developing dementia (OR = 1.26, CI = 95% 1.15-1.38, p < 0.001), a finding that very likely led to the observed significant association of the combination of both visual and hearing impairments and the risk of dementia (OR = 1.14, CI = 95% 1.04-1.24, p = 0.005). Discussion: This analysis adds important evidence that contributes to the limited body of knowledge about the association between hearing and/or vision loss and dementia. It further demonstrates that, of the two, only hearing impairment affects patients' cognition and thus contributes to dementia risk.

Relationship between Metabolomics Profile of Perilymph in Cochlear-Implanted Patients and Duration of Hearing Loss

Perilymph metabolomic analysis is an emerging innovative strategy to improve our knowledge of physiopathology in sensorineural hearing loss. This study aims to develop a metabolomic profile of human perilymph with which to evaluate the relationship between metabolome and the duration of hearing loss. Inclusion criteria were eligibility for cochlear implantation and easy access to the round window during surgery; patients with residual acoustic hearing in the ear to be implanted were excluded. Human perilymph was sampled from 19 subjects during cochlear implantation surgery. The perilymph analysis was performed by Liquid Chromatography-High-Resolution Mass and data were analyzed by supervised multivariate analysis based on Partial Least-Squares Discriminant Analysis and univariate analysis. Samples were grouped according to their median duration of hearing loss. We included the age of patients as a covariate in our models. Statistical analysis and pathways evaluation were performed using Metaboanalyst. Nineteen samples of human perilymph were analyzed, and a total of 106 different metabolites were identified. Metabolomic profiles were significantly different for subjects with ≤ 12 or > 12 years of hearing loss, highlighting the following discriminant compounds: N-acetylneuraminate, glutaric acid, cystine, 2-methylpropanoate, butanoate and xanthine. As expected, the age of patients was also one of the main discriminant parameters. Metabolic signatures were observed for duration of hearing loss. These findings are promising steps towards illuminating the pathophysiological pathways associated with etiologies of sensorineural hearing loss, and hold open the possibilities of further explorations into the mechanisms of sensorineural hearing loss using metabolomic analysis.

Consumption of betel quid contributes to sensorineural hearing impairment through arecoline-induced oxidative stress

Betel quid is one of the most widely used psychoactive substances, and is consumed by approximately 10% of the world’s population. In addition to its carcinogenicity, betel quid has also been reported to affect many organs, including the brain, heart, lungs, gastrointestinal tract, and reproductive organs. As betel quid contains several neurotoxic ingredients, we hypothesize that it also possesses ototoxicity and may lead to sensorineural hearing impairment (SNHI). In this study, we investigated the contribution of betel quid consumption to SNHI in a large clinical cohort, and validated the pathogenetic mechanisms in ex vivo tissue explants. We enrolled a total of 2364 volunteers, and determined their audiologic results based on Z-scores converted from their original frequency-specific hearing thresholds. Using generalized linear regression, we identified a positive correlation between betel quid consumption and the Z-scores across different frequencies. Subsequently, we explored the toxicity of arecoline, the main neuroactive component of betel quid, on tissue explants from murine cochleae. Arecoline reduced cell activity in the explant cultures and induced apoptosis in the hair cells, probably through the effects of oxidative stress. These findings have expanded the potential hazards of betel quid to common neurological disorders, and provide insights into preventive strategies against SNHI caused by neurotoxic substances.

Oral and aural problems in Australian Special Olympics athletes

BACKGROUND

Associations between oral and aural problems among children have been explored, but not among adults with intellectual disability (ID), where often, oral and ear pain can be difficult to diagnose.

METHODS

Data included Special Smiles and Healthy Hearing screenings from two Special Olympics (SO) events held in Australia (2013-2014).

RESULTS

The SO athletes had poor oral health with a high prevalence (56.8%) of gingival signs and unmet dental needs (66.9%). Over one-third (33.9%) had partially/completely blocked ear canals, over one-fifth (20.7%) had possible middle ear problems, and almost one quarter (23.8%) had some hearing loss. No associations between oral and aural problems were found in the small sample (n = 130) of SO athletes.

CONCLUSIONS

Although SO athletes have unmet needs for both oral and aural health, access to appropriate hygiene care is an important preventive factor that athletes, families, and carers should be made aware of. Regular oral and aural screenings are recommended to identify problems early, because ability to communicate pain and discomfort can be different for this population. A larger sample of SO athletes with tooth and sextant level data could clarify the association between oral and aural problems in people with ID.

Compensated active noise cancellation earphone for audiometric screening tests in noisy environments

Objective: This study investigated hearing screening tests by using a custom-designed compensated hybrid active noise cancellation (ANC) earphone and compared it with TDH39 and Audiocups audiometric earphones under conditions of quiet, 45 dB HL masking narrowband, wideband speech-shaped, and white noise. Design: The hearing screening tests were conducted to characterise the shifts of screening results under noisy conditions, and real-ear attenuations at thresholds were assessed to quantify real-ear noise reduction performance. Study sample: Twenty-four normal-hearing adults, aged 20-25 years, participated in this study. Results: The ANC earphone exhibited significantly lower/better mean screening results than those of the TDH39 earphone at 250 and 500 Hz and those of the Audiocups earphone at 250 Hz under conditions of narrowband, speech-shaped, and white noise. Compared with the TDH39 earphone at 250 and 500 Hz, applying a hybrid ANC earphone reduced the shifts in screening results by 14.2 and 12.3 dB, respectively, under the narrowband noise condition. Conclusion: This study demonstrated that the compensated hybrid ANC earphone provided lower shifts of screening results than the TDH39 and Audiocups earphones and that it was capable of screening at 250 and 500 Hz from 20 dB HL under 45 dB HL masking narrowband and wideband noise.

Noise Induced Hearing Loss among an Occupational Group of Textile Workers in Karachi, Pakistan

A cross sectional survey was conducted among textile workers of six textile factories of different industrial areas of Karachi to determine the frequency of hearing loss. A total of 264 workers were assessed for frequency of hearing loss with audiometric and otoscopic examination conducted by audiologist. About 79% workers had hearing impairment on audiometric assessment having hearing loss ≥25 dB. Of these, 19% of the workers had conductive deafness while 71% had mixed hearing loss. Otoscopic examination revealed that 38% had wax, 41.8 % had ear discharge and 1.6 % had perforation. The multiple logistic regression model shows sound level more than 25 dB aOR: 1.15; 95%CI: 1.10, 1.30 and ear discharge aOR: 2.23; 95%CI: 1.27, 3.92, was found as a strong risk factor of hearing loss (p<0.05). Hearing impairment affects a large proportion of the workers in Pakistan. There is a need for screening of workers exposed to occupational noise. Efforts should be made by the health care system to prevent the problem from an early stage and require effective management of ear-related diseases.

Age-dependent variations of scalp thickness in the area designated for a cochlear implant receiver stimulator

Objective

The integrity of the scalp overlying a cochlear implant receiver stimulator (RS) is critical for the long‐term survival of the implant. Exposure or extrusion of the device will likely result in the need for its removal. There is a global trend of acceleration of population aging, thus raising the prevalence of cochlear implantation (CI) in the elderly. The aim of this study was to define age‐dependent changes in scalp thickness and discuss the implication of that anatomical characteristic for CI in the geriatric population.

Methods

Scalp thickness over the location of the RS in the temporo‐parietal area was measured directly with a needle in patients of various ages.

Results

Two‐hundred thirty‐six temporo‐parietal scalps were measured in patients aged 18 to 85 years. A strong inverse correlation was found between age and scalp thickness (rs = ‐0.723, P < .001). Scalp thickness decreased with age from a mean of 8 mm in the third decade of life to 5 mm in the ninth decade of life.

Conclusion

The human scalp thins with age and most likely undergoes a reduction in its strength. As a consequence, implantable hearing devices that are shielded by the scalp can be at increased risk of exposure and extrusion in the aging recipient. This needs to be taken into account when considering an implantation procedure, the surgical approach and patient instructions on need for and venues for continuing care over time.

Level of Evidence

2B

Hearing Aid Use in Older Adults With Postlingual Sensorineural Hearing Loss: Protocol for a Prospective Cohort Study

Background

Older adults with postlingual sensorineural hearing loss (SNHL) exhibit a poor prognosis that not only includes impaired auditory function but also rapid cognitive decline, especially speech-related cognition, in addition to psychosocial dysfunction and an increased risk of dementia. Consistent with this prognosis, individuals with SNHL exhibit global atrophic brain alteration as well as altered neural function and regional brain organization within the cortical substrates that underlie auditory and speech processing. Recent evidence suggests that the use of hearing aids might ameliorate this prognosis.

Objective

The objective was to study the effects of a hearing aid use intervention on neurocognitive and psychosocial functioning in individuals with SNHL aged ≥55 years.

Methods

All aspects of this study will be conducted at Swinburne University of Technology (Hawthorn, Victoria, Australia). We will recruit 2 groups (n=30 per group) of individuals with mild to moderate SNHL from both the community and audiology health clinics (Alison Hennessy Audiology, Chelsea Hearing Pty Ltd). These groups will include individuals who have worn a hearing aid for, at least, 12 months or never worn a hearing aid. All participants would be asked to complete, at 2 time points (t) including baseline (t=0) and follow-up (t=6 months), tests of hearing and psychosocial and cognitive function and attend a magnetic resonance imaging (MRI) session. The MRI session will include both structural and functional MRI (sMRI and fMRI) scans, the latter involving the performance of a novel speech processing task.

Results

This research is funded by the Barbara Dicker Brain Sciences Foundation Grants, the Australian Research Council, Alison Hennessy Audiology, and Chelsea Hearing Pty Ltd under the Industry Transformation Training Centre Scheme (ARC Project #IC140100023). We obtained the ethics approval on November 18, 2017 (Swinburne University Human Research Ethics Committee protocol number SHR Project 2017/266). The recruitment began in December 2017 and will be completed by December 2020.

Conclusions

This is the first study to assess the effect hearing aid use has on neural, cognitive, and psychosocial factors in individuals with SNHL who have never used hearing aids. Furthermore, this study is expected to clarify the relationships among altered brain structure and function, psychosocial factors, and cognition in response to the hearing aid use.

Trial Registration

Australian New Zealand Clinical Trials Registry: ACTRN12617001616369; https://anzctr.org.au/Trial/Registration/TrialReview.aspx?ACTRN=12617001616369 (Accessed by WebCite at http://www.webcitation.org/70yatZ9ze)

International Registered Report Identifier (IRRID)

RR1-10.2196/9916

Challenges and innovations of drug delivery in older age

Both drug delivery performance and various age-related physical, mental and physiological changes can affect drug effectiveness and safety in elderly patients. The many drug delivery systems developed over the years include recent novel transdermal, nasal, pulmonary and orally disintegrating tablets that provide consistent, precise, timely and more targeted drug delivery. Certain drug delivery systems may be associated with suboptimal outcomes in the elderly because of the nature of drug present, a lack of appreciation of the impact of age-related changes in drug absorption, distribution and clearance, the limited availability of pharmacokinetic, safety and clinical data. Polypharmacy, patient morbidity and poor adherence can also contribute to sub-optimal drug delivery systems outcomes in the elderly. The development of drug delivery systems for the elderly is a poorly realised opportunity, with each system having specific advantages and limitations. A key challenge is to provide the innovation that best meets the specific physiological, psychological and multiple drug requirements of individual elderly patients.

Global burden of hearing impairment and ear disease

Background

Hearing loss can present at birth or be acquired as a result of illness, middle-ear disease, injury, age, overuse of certain medications, and/or induced by exposure to damaging noise levels. There are serious short-term consequences for people living with hearing impairment, including the effects on language acquisition, education, employment and overall wellbeing. There are also complex long-term implications.

Objectives

This review aimed to present some of the leading causes of ear disease and hearing loss globally, and to identify their impact at both an individual and societal level.

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.

Association of socioeconomic status with hearing loss in Chinese working-aged adults: A population-based study

Hearing loss is the most common sensory impairment, but limited studies focused on the association of socioeconomic status (SES) with hearing loss among adults of working age. This paper aimed to fill this gap among Chinese adults. We obtained data from Ear and Hearing Disorder Survey conducted in four provinces of China in 2014-2015. The survey was based on WHO Ear and Hearing Disorders Survey Protocol and 25,860 adults aged 25 to 59 years were selected in this study. Trained local examiners performed pure tone audiometry to screen people with hearing loss, and those who were screened positively for hearing loss were referred to audiologists to make final diagnosis. SES was measured by occupation, education and income. Results show after adjusting for SES measures and covariates, in urban areas, compared with white-collar workers, blue-collar workers and the unemployed were more likely to have hearing loss, with an odds ratio of 1.2 (95%CI: 1.0, 1.3) and 1.2 (95%CI: 1.0, 1.4), respectively. Compared with people with education of senior high school or above, those with junior high school, primary school and illiteracy had 1.6 (95%CI: 1.4, 1.8), 2.1(95%CI: 1.7, 2.5) and 2.6 (95%CI: 1.9, 3.7) times as likely to have hearing loss, respectively. In rural areas, the unemployed had 1.5 (95%CI: 1.0, 2.3) times the risk of hearing loss compared with white-collar workers, and illiterates had 1.6 (95%CI: 1.6, 2.1) times the risk of hearing loss compared with people with education of senior high school or above, after SES variables and covariates were taken into considerations. Income was not significantly associated with hearing loss in urban and rural areas. In conclusion, SES, in the form of occupation and education, was associated with hearing loss among working-aged population, and further studies are needed to explore the mechanism of such association.

Prevalence of Hazardous Occupational Noise Exposure, Hearing Loss, and Hearing Protection Usage Among a Representative Sample of Working Canadians

OBJECTIVE

The aim of this study was to estimate the prevalence of hearing loss (HL), self-reported occupational noise exposure, and hearing protection usage among Canadians.

METHODS

In-person household interviews were conducted with 3666 participants, aged 16 to 79 years (1811 males) with 94% completing audiometry and distortion-product otoacoustic emission (DPOAE) evaluations. Occupational noise exposure was defined as hazardous when communicating with coworkers at an arm's length distance required speaking in a raised voice.

RESULTS

An estimated 42% of respondents reported hazardous occupational noise exposure; 10 years or more was associated with HL regardless of age, sex or education. Absent DPOAEs, tinnitus, and the Wilson audiometric notch were significantly more prevalent in hazardous workplace noise-exposed workers than in nonexposed. When mandatory, 80% reported wearing hearing protection.

CONCLUSIONS

These findings are consistent with other industrialized countries, underscoring the need for ongoing awareness of noise-induced occupational HL.

Systematic review to evaluate the safety, efficacy and economical outcomes of the Vibrant Soundbridge for the treatment of sensorineural hearing loss

Introduced in the late 90s, the active middle ear implant Vibrant Soundbridge (VSB) is nowadays used for hearing rehabilitation in patients with mild to severe sensorineural hearing loss (SNHL) unable to tolerate conventional hearing aids. In experienced hands, the surgical implantation is fast done, safe and highly standardized. Here, we present a systematic review, after more than 15 years of application, to determine the efficacy/effectiveness and cost-effectiveness, as well as patient satisfaction with the VSB active middle ear implant in the treatment of mild to severe SNHL. A systematic search of electronic databases, investigating the safety and effectiveness of the VSB in SNHL plus medical condition resulted in a total of 1640 papers. After removing duplicates, unrelated articles, screening against inclusion criteria and after in-depth screening, the number decreased to 37 articles. 13 articles were further excluded due to insufficient outcome data. 24 studies remained to be systematically reviewed. Data was searched on safety, efficacy and economical outcomes with the VSB. Safety-oriented outcomes included complication/adverse event rates, damage to the middle/inner ear, revision surgery/explant rate/device failure and mortality. Efficacy outcomes were divided into audiological outcomes, including hearing thresholds, functional gain, speech perception in quiet and noise, speech recognition thresholds, real ear insertion gain and subjective outcomes determined by questionnaires and patient-oriented scales. Data related to quality of life (QALY, ICER) were considered under economical outcomes. The VSB turns out to be a highly reliable and a safe device which significantly improves perception of speech in noisy situations with a high sound quality. In addition, the subjective benefit of the VSB was found to be mostly significant in all studies. Finally, implantation with the VSB proved to be a cost-effective and justified health care intervention.

Outcomes After Cochlear Implantation in the Very Elderly

OBJECTIVE

To evaluate the outcomes after cochlear implantation (CI) in the elderly population, with a particular emphasis on perioperative complications, dizziness, and speech perception outcomes.

STUDY DESIGN

A retrospective cohort study of elderly cochlear implant patients.

SETTING

Tertiary referral center (Cochlear Implant Clinic, Royal Victorian Eye and Ear Hospital, Melbourne).

PATIENTS

All patients aged 75 and above at the time of first cochlear implant (N = 150). Comparison was made between groups aged 85+ to 80-84, and 75-79.

INTERVENTIONS

All patients received Nucleus devices (either CI512 or CI24RE(CA)).

MAIN OUTCOME MEASURES

Speech recognition scores both pre- and postimplantation, symptomatic dizziness and effects upon independent living after surgery, and the incidence of perioperative medical and surgical complications. Complications were classified as major (intrinsic device failure, device migration, extracochlear insertion, meningitis, surgical site infection requiring reoperation, wound breakdown, permanent facial nerve paralysis) and minor (tinnitus, transient facial nerve palsy, facial nerve stimulation, taste disturbance, delayed wound healing).

RESULTS

All three cohorts had poor preoperative speech perception. There was significant improvement in postoperative word scores at 3 and 12 months across all groups. There was no statistically significant difference between the three cohorts in terms of speech recognition outcomes at 3 and 12 months. After surgery, more than 20% of patients at all ages experienced transient imbalance, although the incidence did not differ significantly between age groups (p = 0.71). In total, there were 13 major complications in 7 patients (4.7%), and 28 minor complications in 25 patients (16.7%).

CONCLUSION

Postoperative disequilibrium was commonly observed in this elderly population, yet patients still benefited with improved speech perception after cochlear implantation. Elderly patients can benefit from cochlear implantation, and age should not be a limitation for CI surgery. Cochlear implantation can be done safely and provides significant patient benefits.

Association of oxidative stress gene polymorphisms with presbycusis

INTRODUCTION

Presbycusis is characterised by etiopathological changes in the cochlea of the inner ear due to genetic and environmental factors and has a serious impact on quality of life. The present study was aimed to evaluate the role of oxidant stress gene polymorphisms in the development of presbycusis.

SUBJECTS AND METHODS

220 subjects with confirmed presbycusis from ENT specialists of MAA ENT hospital, Hyderabad, India from 2012 to 2014 were considered for the study. 270 age and sex matched controls were included in the study. Analysis of gene polymorphisms of SNPs cytochrome P450 1A1 (CYP1A1) 3801 T>C, 2455 A>G and 2453 A>C; glutathione S transferase (GST) T1 and M1; N-acetyl transferase (NAT2) 282 C>T and 857 G>A; uncoupled proteins (UCP1) (-3826) A>G and (UCP2) (866)G>A was carried out. Variations in the allelic and genotypic frequencies obtained were computed and analysed using appropriate statistical methods.

RESULTS

The results of the study indicated that CYP1A1 gene polymorphism at 2453 C>A (adjusted OR: 1.59, 95% CI: 1.01-2.87) and 2455 A>G (adjusted OR: 1.87, 95% CI: 1.07-3.37), double null genotype of GSTM1 and GSTT1 (adjusted OR: 8.88, 95% CI: 4.10-19.19), NAT2 gene at C282T (adjusted OR: 1.77, 95% CI: 1.02-3.11) and G590 A (adjusted OR: 1.83, 95% CI 1.20-3.63) and UCP2 (-866) G>A (adjusted OR: 12.39; 95% CI: 6.51-23.56) showed increased risk for presbycusis while CYP1A1 at 3801 T>C and UCP1 (-3286) A>G exhibited no association. The haplotype combinations of T-G-A of CYP1A1 at 3801, 2455 and 2453 positions as well as T-A of NAT2*6 at 282 and 590 positions were found to contribute significant risk for the onset of presbycusis.

CONCLUSIONS

Gene polymorphisms of CYP1A1 (A2455G, C2453A), NAT2*6 (C282T, G590 A), GST T1/M1 (double null genotype) and UCP2 (G-866 A) were found to contribute significant risk to presbycusis.

Normative Hearing Threshold Levels in Koreans with Normal Tympanic Membranes and Estimated Prevalence of Hearing Loss

Objectives

We investigated the normative data on the hearing threshold levels of Koreans with normal tympanic membranes and the prevalence of hearing loss (HL) and nonserviceable hearing using the data from the Korea National Health and Nutrition Examination Surveys (KNHANES) during 2010–2012.

Methods

Data obtained from 16,673 participants ≥12-year-of-age with normal tympanic membranes who completed audiometric testing. We defined HL as the pure tone average (PTA) >25 dB hearing level at 500, 1,000, 2,000, and 3,000 Hz and non-serviceable hearing as PTA >40 dB hearing level.

Results

The hearing levels at some frequencies (0.5, 3, and 6 kHz) did not differ in between the 10’s and 20’s, but the hearing thresholds at all frequencies increased gradually from the 30’s. The hearing thresholds were higher in men than in women at high frequencies (3, 4, and 6 kHz) in the 30’s and older. The prevalence of HL in either ear was 16.5% (estimates of 5.9 million), from 2.4% in the 10’s up to 75.4% in the 70’s and older. The prevalence of nonserviceable hearing in either ear was 6.8% (estimates of 2.5 million) and that of bilateral nonserviceable hearing was 2.5% (estimates of 0.9 million).

Conclusion

Hearing loss aggravated from the 30’s at all frequencies and men showed poorer hearing levels than women at high frequencies. Hearing loss was a common condition and the prevalence of non-serviceable hearing in either ear, which needs hearing rehabilitation to help social communication, was 6.8%. Normative pure tone thresholds at each frequency can be used as referent values when counseling patients complaining of hearing loss.

Perception and Cognition in the Ageing Brain: A Brief Review of the Short- and Long-Term Links between Perceptual and Cognitive Decline

Ageing is associated with declines in both perception and cognition. We review evidence for an interaction between perceptual and cognitive decline in old age. Impoverished perceptual input can increase the cognitive difficulty of tasks, while changes to cognitive strategies can compensate, to some extent, for impaired perception. While there is strong evidence from cross-sectional studies for a link between sensory acuity and cognitive performance in old age, there is not yet compelling evidence from longitudinal studies to suggest that poor perception causes cognitive decline, nor to demonstrate that correcting sensory impairment can improve cognition in the longer term. Most studies have focused on relatively simple measures of sensory (visual and auditory) acuity, but more complex measures of suprathreshold perceptual processes, such as temporal processing, can show a stronger link with cognition. The reviewed evidence underlines the importance of fully accounting for perceptual deficits when investigating cognitive decline in old age.

Age and Gender Effects on Wideband Absorbance in Adults With Normal Outer and Middle Ear Function

PURPOSE

This study examined the effects of age and gender on wideband energy absorbance in adults with normal middle ear function.

METHOD

Forty young adults (14 men, 26 women, aged 20-38 years), 31 middle-aged adults (16 men, 15 women, aged 42-64 years), and 30 older adults (20 men, 10 women, aged 65-82 years) were assessed. Energy absorbance (EA) data were collected at 30 frequencies using a prototype commercial instrument developed by Interacoustics.

RESULTS

Results showed that the young adult group had significantly lower EA (between 400 and 560 Hz) than the middle-aged group. However, the middle-aged group showed significantly lower EA (between 2240 and 5040 Hz) than the young adult group. In addition, the older adult group had significantly lower EA than the young adult group (between 2520 and 5040 Hz). No significant difference in EA was found at any frequency between middle-aged and older adults. Across age groups, gender differences were found with men having significantly higher EA values than women at lower frequencies, whereas women had significantly higher EA at higher frequencies.

CONCLUSIONS

This study provides evidence of the influence of gender and age on EA in adults with normal outer and middle ear function. These findings support the importance of establishing age- and gender-specific EA norms for the adult population.

Subjective and clinically assessed hearing loss; a cross-sectional register-based study on a swedish population aged 18 through 50 years

OBJECTIVES

Questionnaire studies suggest that hearing is declining among young adults. However, few studies have examined the reliability of hearing questionnaires among young adult subjects. This study examined the associations between pure tone audiometrically assessed (PTA) hearing loss and questionnaire responses in young to middle aged adults.

MATERIALS AND METHODS

A cross-sectional study using questionnaire and screening PTA (500 through 6000 Hz) data from 15322 Swedish subjects (62% women) aged 18 through 50 years. PTA hearing loss was defined as a hearing threshold above 20 dB in both ears at one or more frequencies. Data were analysed with chi-square tests, nonlinear regression, binary logistic regression, and the generalized estimating equation (GEE) approach.

RESULTS

The prevalence of PTA hearing loss was 6.0% in men and 2.9% in women (p < 0.001). Slight hearing impairment was reported by 18.5% of the men and 14.8% of the women (p < 0.001), whereas 0.5% of men and women reported very impaired hearing. Using multivariate GEE modelling, the odds ratio of PTA hearing loss was 30.4 (95% CI, 12.7-72.9) in men and 36.5 (17.2-77.3) in women reporting very impaired hearing. The corresponding figures in those reporting slightly impaired hearing were 7.06 (5.25-9.49) in men and 8.99 (6.38-12.7) in women. These values depended on the sound stimulus frequency (p = 0.001). The area under the ROC curve was 0.904 (0.892-0.915) in men and 0.886 (0.872-0.900) in women.

CONCLUSIONS

Subjective hearing impairment predicted clinically assessed hearing loss, suggesting that there is cause for concern as regards the future development of hearing in young to middle-aged people.

Prävalenz von Schwerhörigkeit im Nordwesten Deutschlands

Hintergrund

Der mittlere Luftleitungshörverlust bei 0,5, 1, 2 und 4 kHz („pure tone average“, PTA-4) im besseren Ohr ist das international anerkannte Kriterium der Weltgesundheitsorganisation (WHO) zur Beschreibung des Hörvermögens. Zurzeit gibt es keine epidemiologischen Daten zum Hörverlust in der deutschen Bevölkerung, in der dieses Kriterium verwendet wird.

Methoden

Eine populationstypische Stichprobe erwachsener Personen aus Oldenburg und Emden wurde zu einer eingeladen. Analysiert wird der Zusammenhang von Hörverlusten mit Alter, Geschlecht, Lärm, Berufsbereich und schulischer Bildung. Die alters- und geschlechtsspezifische Prävalenz nach WHO wird mit internationalen Studienergebnissen verglichen.

Ergebnisse

Die Prävalenz von Schwerhörigkeit nach der WHO-Klassifikation lag bei den Studienteilnehmern (n = 1866) bei etwa 16 %. Bei Männern, die häufiger in lärmbelasteten Berufsbereichen tätig waren, wurde eine höhere Prävalenz als bei Frauen gleichen Alters beobachtet. Der Unterschied zwischen den Geschlechtern ist jedoch geringer als in internationalen Vergleichsstudien. Bei Berücksichtigung beruflicher Lärmexposition gleichen sich beide Geschlechter im PTA-4, signifikante Unterschiede zwischen verschiedenen Berufsbereichen aber bleiben erhalten.

Schlussfolgerung

Im internationalen Vergleich liegt die altersabhängige Prävalenz in HÖRSTAT niedrig. Aus den Studienergebnissen der vergangenen 25 Jahre ist eine Tendenz zu abnehmender Prävalenz von Schwerhörigkeit im mittleren bis oberen Altersbereich zu beobachten.

The prevalence and factors associated with hearing impairment in the Korean adults: the 2010-2012 Korea National Health and Nutrition Examination Survey (observational study)

There are few studies that have used audiometric testing to gauge the demographic characteristics and associated risk factors for hearing loss at the national-level. Here, we investigated the weighted prevalence and associated factors of hearing impairment in 16,040 Korean adult population. Subjects completed audiometric test and laboratory examination as part of the data from The 2010-2012 Korea National Health and Nutrition Examination Survey (KNHANES). In our respective study, the overall weighted (n = 33,762,584) prevalence of mild hearing impairment among the Korean adult population was 20.5% (95% clearance [CI], 19.6-21.6), whereas moderate-to-profound hearing impairment was 9.2% (95% CI, 8.6-9.9). The weighted prevalence of mild hearing impairment in younger adults (19-39 years' old) was 4.4% (3.5-5.5), in middle-age adults (40-64 years), it was 21.1% (19.8-22.5), and in older adults (≥65 years' old), it was 69.7% (67.8-71.6). Logistic regression analyses were performed for low/mid frequency or high-frequency mild hearing impairment with age, sex, tobacco use, heavy alcohol use, educational background, occupational noise exposure, obesity, hypertension, diabetes, total serum cholesterol, and estimated glomerular filtration rate (eGFR) <60 mL/min/1.73m² as covariates. The analyses revealed independent correlations between increased age, tobacco use, education, hypertension, and eGFR <60 mL/min/1.73m², and low/mid frequency and high frequency mild hearing impairment. High frequency mild hearing impairment was positively correlated with male sex, diabetes, and an increase in total serum cholesterol. Taken together, hearing impairment in Korea is highly prevalent with approximately one-fifth of Korean adult reporting mild hearing impairment. This study suggests that individuals with cardiovascular risk factors such as hypertension, diabetes, smoking, increased serum cholesterol, or decreased eGFR are at particular risk of developing hearing impairment. As such, these groups may benefit from hearing loss screening in addition to those groups typically considered to be of elevated risk including geriatrics, those of low socioeconomic status, and those with considerable occupational noise exposure.

Hearing in middle age: a population snapshot of 40- to 69-year olds in the United Kingdom

OBJECTIVES

To report population-based prevalence of hearing impairment based on speech recognition in noise testing in a large and inclusive sample of U.K. adults aged 40 to 69 years. The present study is the first to report such data. Prevalence of tinnitus and use of hearing aids is also reported.

DESIGN

The research was conducted using the UK Biobank resource. The better-ear unaided speech reception threshold was measured adaptively using the Digit Triplet Test (n = 164,770). Self-report data on tinnitus, hearing aid use, noise exposure, as well as demographic variables were collected.

RESULTS

Overall, 10.7% of adults (95% confidence interval [CI] 10.5-10.9%) had significant hearing impairment. Prevalence of tinnitus was 16.9% (95%CI 16.6-17.1%) and hearing aid use was 2.0% (95%CI 1.9-2.1%). Odds of hearing impairment increased with age, with a history of work- and music-related noise exposure, for lower socioeconomic background and for ethnic minority backgrounds. Males were at no higher risk of hearing impairment than females.

CONCLUSIONS

Around 1 in 10 adults aged 40 to 69 years have substantial hearing impairment. The reasons for excess risk of hearing impairment particularly for those from low socioeconomic and ethnic minority backgrounds require identification, as this represents a serious health inequality. The underuse of hearing aids has altered little since the 1980s, and is a major cause for concern.

Deafness in cochlear and auditory nerve disorders

Sensorineural hearing loss is the most common type of hearing impairment worldwide. It arises as a consequence of damage to the cochlea or auditory nerve, and several structures are often affected simultaneously. There are many causes, including genetic mutations affecting the structures of the inner ear, and environmental insults such as noise, ototoxic substances, and hypoxia. The prevalence increases dramatically with age. Clinical diagnosis is most commonly accomplished by measuring detection thresholds and comparing these to normative values to determine the degree of hearing loss. In addition to causing insensitivity to weak sounds, sensorineural hearing loss has a number of adverse perceptual consequences, including loudness recruitment, poor perception of pitch and auditory space, and difficulty understanding speech, particularly in the presence of background noise. The condition is usually incurable; treatment focuses on restoring the audibility of sounds made inaudible by hearing loss using either hearing aids or cochlear implants.

Relation between speech-in-noise threshold, hearing loss and cognition from 40-69 years of age

BACKGROUND

Healthy hearing depends on sensitive ears and adequate brain processing. Essential aspects of both hearing and cognition decline with advancing age, but it is largely unknown how one influences the other. The current standard measure of hearing, the pure-tone audiogram is not very cognitively demanding and does not predict well the most important yet challenging use of hearing, listening to speech in noisy environments. We analysed data from UK Biobank that asked 40-69 year olds about their hearing, and assessed their ability on tests of speech-in-noise hearing and cognition.

METHODS AND FINDINGS

About half a million volunteers were recruited through NHS registers. Respondents completed 'whole-body' testing in purpose-designed, community-based test centres across the UK. Objective hearing (spoken digit recognition in noise) and cognitive (reasoning, memory, processing speed) data were analysed using logistic and multiple regression methods. Speech hearing in noise declined exponentially with age for both sexes from about 50 years, differing from previous audiogram data that showed a more linear decline from <40 years for men, and consistently less hearing loss for women. The decline in speech-in-noise hearing was especially dramatic among those with lower cognitive scores. Decreasing cognitive ability and increasing age were both independently associated with decreasing ability to hear speech-in-noise (0.70 and 0.89 dB, respectively) among the population studied. Men subjectively reported up to 60% higher rates of difficulty hearing than women. Workplace noise history associated with difficulty in both subjective hearing and objective speech hearing in noise. Leisure noise history was associated with subjective, but not with objective difficulty hearing.

CONCLUSIONS

Older people have declining cognitive processing ability associated with reduced ability to hear speech in noise, measured by recognition of recorded spoken digits. Subjective reports of hearing difficulty generally show a higher prevalence than objective measures, suggesting that current objective methods could be extended further.

Lithium alters the morphology of neurites regenerating from cultured adult spiral ganglion neurons

The small-molecule drug lithium (as a monovalent ion) promotes neurite regeneration and functional recovery, is easy to administer, and is approved for human use to treat bipolar disorder. Lithium exerts its neuritogenic effect mainly by inhibiting glycogen synthase kinase 3, a constitutively-active serine/threonine kinase that is regulated by neurotrophin and "wingless-related MMTV integration site" (Wnt) signaling. In spiral ganglion neurons of the cochlea, the effects of lithium and the function of glycogen synthase kinase 3 have not been investigated. We, therefore, set out to test whether lithium modulates neuritogenesis from adult spiral ganglion neurons. Primary cultures of dissociated spiral ganglion neurons from adult mice were exposed to lithium at concentrations between 0 and 12.5 mM. The resulting neurite morphology and growth-cone appearance were measured in detail by using immunofluorescence microscopy and image analysis. We found that lithium altered the morphology of regenerating neurites and their growth cones in a differential, concentration-dependent fashion. Low concentrations of 0.5-2.5 mM (around the half-maximal inhibitory concentration for glycogen synthase kinase 3 and the recommended therapeutic serum concentration for bipolar disorder) enhanced neurite sprouting and branching. A high concentration of 12.5 mM, in contrast, slowed elongation. As the lithium concentration rose from low to high, the microtubules became increasingly disarranged and the growth cones more arborized. Our results demonstrate that lithium selectively stimulates phases of neuritogenesis that are driven by microtubule reorganization. In contrast, most other drugs that have previously been tested on spiral ganglion neurons are reported to inhibit neurite outgrowth or affect only elongation. Lithium sensitivity is a necessary, but not sufficient condition for the involvement of glycogen synthase kinase 3. Our results are, therefore, consistent with, but do not prove lithium inhibiting glycogen synthase kinase 3 activity in spiral ganglion neurons. Experiments with additional drugs and molecular-genetic tools will be necessary to test whether glycogen synthase kinase 3 regulates neurite regeneration from spiral ganglion neurons, possibly by integrating neurotrophin and Wnt signals at the growth cone.

Efficacy of the active middle-ear implant in patients with sensorineural hearing loss

Introduction:

This systematic review aims to advise on the effectiveness of the active middle-ear implant in patients with sensorineural hearing loss, compared with external hearing aids.

Methods:

A systematic search of several electronic databases, including PubMed and Embase, was used to identify relevant studies for inclusion.

Results:

Fourteen comparative studies were included. Nine studies reported on the primary outcome of functional gain: one found that the middle-ear implant was significantly better than external hearing aids (p < 0.001), while another found that external hearing aids were generally significantly better than middle-ear implants (p < 0.05). Six of the seven remaining studies found that middle-ear implants were better than external hearing aids, although generally no clinically significant difference (i.e. ≥10 dB) was seen.

Conclusion:

Generally, the active middle-ear implant appears to be as effective as the external hearing aid in improving hearing outcomes in patients with sensorineural hearing loss.

Neurotrophin gene therapy for sustained neural preservation after deafness

The cochlear implant provides auditory cues to profoundly deaf patients by electrically stimulating the residual spiral ganglion neurons. These neurons, however, undergo progressive degeneration after hearing loss, marked initially by peripheral fibre retraction and ultimately culminating in cell death. This research aims to use gene therapy techniques to both hold and reverse this degeneration by providing a sustained and localised source of neurotrophins to the deafened cochlea. Adenoviral vectors containing green fluorescent protein, with or without neurotrophin-3 and brain derived neurotrophic factor, were injected into the lower basal turn of scala media of guinea pigs ototoxically deafened one week prior to intervention. This single injection resulted in localised and sustained gene expression, principally in the supporting cells within the organ of Corti. Guinea pigs treated with adenoviral neurotrophin-gene therapy had greater neuronal survival compared to contralateral non-treated cochleae when examined at 7 and 11 weeks post injection. Moreover; there was evidence of directed peripheral fibre regrowth towards cells expressing neurotrophin genes after both treatment periods. These data suggest that neurotrophin-gene therapy can provide sustained protection of spiral ganglion neurons and peripheral fibres after hearing loss.

Hearing loss and risk of early retirement. The HUNT study

BACKGROUND

We explore the possible consequences of measured hearing impairment (HI) and perceived hearing difficulties for early retirement in a large population-based study. Furthermore, we study whether having a part-time position was associated with measured HI and perceived hearing difficulties in the same population.

METHODS

This study included 25,740 persons from the Nord-Trøndelag Health Study (HUNT) aged 20-54 years at baseline in HUNT1 (1984-1986) who also participated in the follow up, HUNT2, including a hearing examination 11 years later. Logistic regression analysis was conducted for men and women separately and in two age strata. Effects of low-, middle- and high-frequency hearing levels were explored, adjusting for each other. Further adjustment was made for socio-economic class and general health in HUNT1.

RESULTS

The risk of early retirement increased with degree of loss of low-frequency hearing in young and middle-aged men and middle-aged women. The middle-aged men and women experiencing hearing disability had an increased risk of early retirement. Degree of hearing level was not associated with part-time work, but in middle-aged men, awareness of having a hearing loss was associated with part-time employment.

CONCLUSIONS

Degree of low-frequency hearing loss was associated with early retirement but not with part-time work. Perceived hearing disability increased the risk of early retirement in middle-aged men and women and also the risk of part-time work in middle-aged men.