Hearing

Neural Adaptation at Stimulus Onset and Speed of Neural Processing as Critical Contributors to Speech Comprehension Independent of Hearing Threshold or Age

Background: It is assumed that speech comprehension deficits in background noise are caused by age-related or acquired hearing loss. Methods: We examined young, middle-aged, and older individuals with and without hearing threshold loss using pure-tone (PT) audiometry, short-pulsed distortion-product otoacoustic emissions (pDPOAEs), auditory brainstem responses (ABRs), auditory steady-state responses (ASSRs), speech comprehension (OLSA), and syllable discrimination in quiet and noise. Results: A noticeable decline of hearing sensitivity in extended high-frequency regions and its influence on low-frequency-induced ABRs was striking. When testing for differences in OLSA thresholds normalized for PT thresholds (PTTs), marked differences in speech comprehension ability exist not only in noise, but also in quiet, and they exist throughout the whole age range investigated. Listeners with poor speech comprehension in quiet exhibited a relatively lower pDPOAE and, thus, cochlear amplifier performance independent of PTT, smaller and delayed ABRs, and lower performance in vowel-phoneme discrimination below phase-locking limits (/o/-/u/). When OLSA was tested in noise, listeners with poor speech comprehension independent of PTT had larger pDPOAEs and, thus, cochlear amplifier performance, larger ASSR amplitudes, and higher uncomfortable loudness levels, all linked with lower performance of vowel-phoneme discrimination above the phase-locking limit (/i/-/y/). Conslusions: This study indicates that listening in noise in humans has a sizable disadvantage in envelope coding when basilar-membrane compression is compromised. Clearly, and in contrast to previous assumptions, both good and poor speech comprehension can exist independently of differences in PTTs and age, a phenomenon that urgently requires improved techniques to diagnose sound processing at stimulus onset in the clinical routine.

Prediction of pure tone thresholds using the speech reception threshold and age in elderly individuals with hearing loss

OBJECTIVE

Early detection and effective management of hearing loss constitute the key to improving the quality of life of individuals with hearing loss. However, in standardized pure tone audiometry, it is sometimes difficult for elderly patients to understand and follow all instructions. Audiologists also require time, expertise, and patience to ensure that an elderly can identify the faintest levels of stimuli during a hearing test. Therefore, this study aimed to devise and validate a formula to predict the pure tone threshold at each frequency across 0.5-4 kHz (PTTs) using speech reception threshold.

METHODS

The 1226 audiograms of hearing-impaired individuals aged 60-90 years were reviewed. The random sample function randomly assigned 613 participants to the training and testing sets each. A linear model was created to predict the PTT value at each frequency based on variables significant at all frequencies across 0.5-4 kHz. The adjusted-R2 value was considered to indicate the performance of the predictive model. Pearson's correlation coefficient was used to describe the relationship between the actual and predicted PTT at 0.5, 1, 2, and 4 kHz among the testing set to measure the performance of the proposed model.

RESULTS

The predictive model was devised using variables based on the speech recognition threshold (SRT) after adjusting with age in the training set. The overall prediction accuracy demonstrated a higher adjusted-R2 ranging from 0.74 to 0.89 at frequencies of 0.5, 1, and 2 kHz, whereas a low percentage of explained variance was observed at 4 kHz (adjusted-R2 = 0.41). This predictive model can serve as an adjunctive clinical tool for guiding determination of the PTTs. Moreover, the predicted PTTs can be applied in the hearing aid programming software to set appropriate hearing aid gain using standard prescriptive formulas.

Comparison of Tonotopic and Default Frequency Fitting for Speech Understanding in Noise in New Cochlear Implantees: A Prospective, Randomized, Double-Blind, Cross-Over Study

OBJECTIVES

While cochlear implants (CIs) have provided benefits for speech recognition in quiet for subjects with severe-to-profound hearing loss, speech recognition in noise remains challenging. A body of evidence suggests that reducing frequency-to-place mismatch may positively affect speech perception. Thus, a fitting method based on a tonotopic map may improve speech perception results in quiet and noise. The aim of our study was to assess the impact of a tonotopic map on speech perception in noise and quiet in new CI users.

DESIGN

A prospective, randomized, double-blind, two-period cross-over study in 26 new CI users was performed over a 6-month period. New CI users older than 18 years with bilateral severe-to-profound sensorineural hearing loss or complete hearing loss for less than 5 years were selected in the University Hospital Centre of Rennes in France. An anatomical tonotopic map was created using postoperative flat-panel computed tomography and a reconstruction software based on the Greenwood function. Each participant was randomized to receive a conventional map followed by a tonotopic map or vice versa. Each setting was maintained for 6 weeks, at the end of which participants performed speech perception tasks. The primary outcome measure was speech recognition in noise. Participants were allocated to sequences by block randomization of size two with a ratio 1:1 (CONSORT Guidelines). Participants and those assessing the outcomes were blinded to the intervention.

RESULTS

Thirteen participants were randomized to each sequence. Two of the 26 participants recruited (one in each sequence) had to be excluded due to the COVID-19 pandemic. Twenty-four participants were analyzed. Speech recognition in noise was significantly better with the tonotopic fitting at all signal-to-noise ratio (SNR) levels tested [SNR = +9 dB, p = 0.002, mean effect (ME) = 12.1%, 95% confidence interval (95% CI) = 4.9 to 19.2, standardized effect size (SES) = 0.71; SNR = +6 dB, p < 0.001, ME = 16.3%, 95% CI = 9.8 to 22.7, SES = 1.07; SNR = +3 dB, p < 0.001 ME = 13.8%, 95% CI = 6.9 to 20.6, SES = 0.84; SNR = 0 dB, p = 0.003, ME = 10.8%, 95% CI = 4.1 to 17.6, SES = 0.68]. Neither period nor interaction effects were observed for any signal level. Speech recognition in quiet ( p = 0.66) and tonal audiometry ( p = 0.203) did not significantly differ between the two settings. 92% of the participants kept the tonotopy-based map after the study period. No correlation was found between speech-in-noise perception and age, duration of hearing deprivation, angular insertion depth, or position or width of the frequency filters allocated to the electrodes.

CONCLUSION

For new CI users, tonotopic fitting appears to be more efficient than the default frequency fitting because it allows for better speech recognition in noise without compromising understanding in quiet.

Quantitative levels of noise exposure and 20-year hearing decline: findings from a prospective cohort study (the HUNT Study)

OBJECTIVE

We aimed to assess the association between occupational noise exposure and long-term hearing decline.

DESIGN

This prospective cohort study used linear regression to investigate the association between occupational noise exposure and 20-year hearing decline, adjusted for important confounders.

STUDY SAMPLE

The Norwegian cohort (N = 4,448) participated in two population-based health studies with pure-tone audiometry; HUNT2 1996-1998 and HUNT4 2017-2019. Exposure assessments included a quantitative job exposure matrix (JEM) and questionnaires.

RESULTS

The participants (40.2% men, 20-39 years at baseline) had a mean 20-year decline (3-6 kHz) of 11.3 ± 9.8 decibels (dB). There was a positive association between 20-year logarithmic average noise level (JEM-based, LEX,20y) and 20-year hearing decline among men. Compared with no exposure ≥80 dB during follow-up, minimum 5 years of exposure ≥85 dB (JEM-based) predicted 2.6 dB (95% CI: 0.2-5.0) larger 20-year decline for workers aged 30-39 years at baseline, and -0.2 dB (95% CI: -2.2 to 1.7) for workers aged 20-29 years. Combining JEM information with self-reported noise exposure data resulted in stronger associations.

CONCLUSION

This large longitudinal study shows an association between JEM-based noise exposure level and increased 20-year hearing decline among men. Contrary to expectations, the associations were weaker among younger workers, which might reflect a latency period.

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

Objective

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

Methods

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

Results

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

Conclusions

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

Validation of SHOEBOX QuickTest Hearing Loss Screening Tool in Individuals With Cognitive Impairment

Objectives: The aim of this study was to validate a novel iPad-based rapid hearing loss screening tool (SHOEBOX QuickTest) in individuals with cognitive impairment.

Design: Cross-sectional validation study.

Setting: Bruyère Research Institute, Ottawa, Canada.

Subjects and Methods: Twenty-five individuals with mild cognitive impairment (MCI) and mild dementia from the Bruyère Memory Program were included in this study. The study consisted of two components: (1) SHOEBOX QuickTest hearing screener and (2) a conventional hearing test (pure tone audiometry).

Measurements: Hearing was assessed at 1,000, 2,000, and 4,000 Hz separately for each ear. The agreement between hearing ability groupings (good vs. reduced) from conventional hearing test and SHOEBOX QuickTest was determined. Specifically, accuracy, sensitivity, specificity, as well as alignment between conventional thresholds and hearing threshold ranges.

Results: An overall accuracy of 84% was observed for SHOEBOX QuickTest, and a sensitivity and specificity of 100 and 66.7%, respectively. 72% ([95% CI], 60.0–84.1%) of conventional audiometry thresholds were within the pre-established 10 dB SHOEBOX QuickTest.

Conclusion: SHOEBOX QuickTest is a valid hearing loss screening tool for individuals with cognitive impairment. Implementing this iPad-based screening tool in memory clinics could not only aid in the timely diagnosis of hearing loss, but also assist physicians in providing a better assessment of cognitive impairment by ruling out hearing loss as a confounding variable.

Non-Syndromic Autosomal Dominant Hearing Loss: The First Italian Family Carrying a Mutation in the NCOA3 Gene

Hearing loss (HL) is the most frequent sensory disorder, affecting about 1-3 per 1000 live births, with more than half of the cases attributable to genetic causes. Despite the fact that many HL causative genes have already been identified, current genetic tests fail to provide a diagnosis for about 40% of the patients, suggesting that other causes still need to be discovered. Here, we describe a four-generation Italian family affected by autosomal dominant non-syndromic hearing loss (ADNSHL), in which exome sequencing revealed a likely pathogenic variant in NCOA3 (NM_181659.3, c.2909G>C, p.(Gly970Ala)), a gene recently described as a novel candidate for ADNSHL in a Brazilian family. A comparison between the two families highlighted a series of similarities: both the identified variants are missense, localized in exon 15 of the NCOA3 gene and lead to a similar clinical phenotype, with non-syndromic, sensorineural, bilateral, moderate to profound hearing loss, with a variable age of onset. Our findings (i.e., the identification of the second family reported globally with HL caused by a variant in NCOA3) further support the involvement of NCOA3 in the etiopathogenesis of ADNSHL, which should, thus, be considered as a new gene for autosomal dominant non-syndromic hearing loss.

Hearing loss and renal syndromes

The association between ear and kidney abnormalities has long been recognized; however, the connection between these two disparate organs is not always straightforward. Although Alport syndrome is the most well-known, there are over 20 disorders that need to be considered in the differential diagnosis of patients with both ear and kidney abnormalities. Commonalities are present between the kidney and ear in a number of structural proteins, developmentally important transcription factors, ciliary proteins, and channel proteins, and mutations in these pathways can lead to disease in both organ systems. This manuscript reviews the congenital disorders with both hearing and kidney manifestations.

Hearing loss in children with e-waste lead and cadmium exposure

Environmental chemical exposure can cause neurotoxicity and has been recently linked to hearing loss in general population, but data are limited in early life exposure to lead (Pb) and cadmium (Cd) especially for children. We aimed to evaluate the association of their exposure with pediatric hearing ability. Blood Pb and urinary Cd were collected form 234 preschool children in 3-7years of age from an electronic waste (e-waste) recycling area and a reference area matched in Shantou of southern China. Pure-tone air conduction (PTA) was used to test child hearing thresholds at frequencies of 0.25, 0.5, 1, 2, 4 and 8kHz. A PTA≥25dB was defined as hearing loss. A higher median blood Pb level was found in the exposed group (4.94±0.20 vs 3.85±1.81μg/dL, p<0.001), while no significance was found for creatinine-adjusted Cd. Compared with the reference group, the exposed group had a higher prevalence of hearing loss (28.8% vs 13.6%, p<0.001). The PTA in the left, right and both ears, and hearing thresholds at average low and high frequency, and single frequency of 0.5, 1 and 2kHz were all increased in the exposed group. Positive correlations of child age and nail biting habit with Pb, and negative correlations of parent education level and child washing hands before dinner with Pb and Cd exposure were observed. Logistic regression analyses showed the adjusted OR of hearing loss for Pb exposure was 1.24 (95% CI: 1.029, 1.486). Our data suggest that early childhood exposure to Pb may be an important risk factor for hearing loss, and the developmental auditory system might be affected in e-waste polluted areas.

Exposures to fine particulate matter (PM2.5) and ozone above USA standards are associated with auditory brainstem dysmorphology and abnormal auditory brainstem evoked potentials in healthy young dogs

BACKGROUND

Delayed central conduction times in the auditory brainstem have been observed in Mexico City (MC) healthy children exposed to fine particulate matter (PM_2.5) and ozone (O₃) above the current United States Environmental Protection Agency (US-EPA) standards. MC children have α synuclein brainstem accumulation and medial superior olivary complex (MSO) dysmorphology. The present study used a dog model to investigate the potential effects of air pollution on the function and morphology of the auditory brainstem.

METHODOLOGY

Twenty-four dogs living in clean air v MC, average age 37.1 ± 26.3 months, underwent brainstem auditory evoked potential (BAEP) measurements. Eight dogs (4 MC, 4 Controls) were analysed for auditory brainstem morphology and histopathology.

RESULTS

MC dogs showed ventral cochlear nuclei hypotrophy and MSO dysmorphology with a significant decrease in cell body size, decreased neuronal packing density with regions in the nucleus devoid of neurons and marked gliosis. MC dogs showed significant delayed BAEP absolute wave I, III and V latencies compared to controls.

CONCLUSIONS

MC dogs show auditory nuclei dysmorphology and BAEPs consistent with an alteration of the generator sites of the auditory brainstem response waveform. This study puts forward the usefulness of BAEPs to study auditory brainstem neurodegenerative changes associated with air pollution in dogs. Recognition of the role of non-invasive BAEPs in urban dogs is warranted to elucidate novel neurodegenerative pathways link to air pollution and a promising early diagnostic strategy for Alzheimer's Disease.