Adrian Fuente

Organic solvents and hearing loss: The challenge for audiology

Organic solvents have been reported to adversely affect human health, including hearing health. Animal models have demonstrated that solvents may induce auditory damage, especially to the outer hair cells. Research on workers exposed to solvents has suggested that these chemicals may also induce auditory damage through effects on the central auditory pathways. Studies conducted with both animals and humans demonstrate that the hearing frequencies affected by solvent exposure are different to those affected by noise, and that solvents may interact synergistically with noise. The present article aims to review the contemporary literature of solvent-induced hearing loss, and consider the implications of solvent-induced auditory damage for clinical audiologists. Possible audiological tests that may be used when auditory damage due to solvent exposure is suspected are discussed. Sumario Se ha reportado que los solventes orgánicos afectan adversamente la salud humana, incluyen la salud auditiva. Los modelos animales han demostrado que los solventes pueden inducir daño auditivo, especialmente en las células ciliadas externas. La investigación en trabajadores expuestos a solventes sugiere que estos productos químicos pueden también inducir daño auditivo afectando las vías auditivas centrales. Los estudios conducidos en animales y en humanos demuestran que las frecuencias auditivas afectadas por la exposición a solventes son diferentes de las afectadas por el ruido, y que los solventes pueden actuar en sinergia con el ruido. El presente artículo pretende revisar la literatura contemporánea sobre hipoacusia inducida por solventes, y hacer consideraciones clínicas para el audiólogo sobre el daño auditivo inducido por solventes. Se discuten posibles pruebas auditivas que pueden ser utilizadas cuando se sospecha daño auditivo debido a la exposición a solventes.

Assessment of central auditory processing in a group of workers exposed to solvents

Conclusion. Despite having normal hearing thresholds and speech recognition thresholds, results for central auditory tests were abnormal in a group of workers exposed to solvents. Workers exposed to solvents may have difficulties in everyday listening situations that are not related to a decrement in hearing thresholds. A central auditory processing disorder may underlie these difficulties. Objective. To study central auditory processing abilities in a group of workers occupationally exposed to a mix of organic solvents. Materials and methods. Ten workers exposed to a mix of organic solvents and 10 matched non-exposed workers were studied. The test battery comprised pure-tone audiometry, tympanometry, acoustic reflex measurement, acoustic reflex decay, dichotic digit, pitch pattern sequence, masking level difference, filtered speech, random gap detection and hearing-in-noise tests. Results. All the workers presented normal hearing thresholds and no signs of middle ear abnormalities. Workers exposed to solvents had lower results in comparison with the control group and previously reported normative data, in the majority of the tests.

Noise-induced hearing loss in Asia

Abstract The aim of this manuscript is to summarize the current scenarios encompassing noise exposure in the workplace and the risk of noise-induced hearing loss (NIHL) in Asia. NIHL is the most prevalent and preventable occupational disease in most Asian countries. Sources of noise in these countries include manufacturing and agriculture industries, exploitation of natural resources, and urban traffic. The highest attributable fraction of adult-onset hearing loss resulting from noise exposure in the world comes from Asian countries. NIHL is a serious health problem in Asia, not only because of the number of affected labourers, but also because the majority of Asian countries are still developing economies where access to health services and preventive programmes are limited. Lack of awareness about NIHL among employers, employees, and health care professionals is one of the main barriers for the prevention of NIHL in Asia. In this paper, the sources of noise, NIHL prevalence in different industries, local legislation, and research publications on NIHL from Asia are discussed. Sumario El propósito de este manuscrito es resumir los escenarios actuales relacionados con la exposición a ruido en el lugar de trabajo y el riesgo de hipoacusia inducida por ruido (NIHL) en Asia. La NIHL es la enfermedad ocupacional más prevalente y prevenible en la mayoría de los países asiáticos. Las fuentes de ruido en estos países incluyen las industrias de manufactura y agricultura, la explotación de los recursos naturales y el tráfico urbano. La fracción más alta en el mundo atribuible de la hipoacusia de inicio en la edad adulta proveniente de la exposición a ruido, viene de los países asiáticos. La NIHL es un serio problema de salud en Asia, no sólo por el número de trabajadores afectados, sino porque la mayoría de los países asiáticos aún son economías en desarrollo, donde el acceso a los servicios de salud y a los programas preventivos es limitado. La falta de conciencia sobre la NIHL entre los empleadores, los empleados y los profesionales en salud, es una de las principales barreras para la prevención de la NIHL en Asia. En este trabajo, se discuten las fuentes de ruido, la prevalencia de NIHL en las diferentes industrias, la legislación local y las publicaciones de investigación sobre NIHL.

Auditory processing tests for Spanish-speaking adults: An initial study

There is no standardized material to assess auditory processing (AP) in Spanish-speaking adults. The purpose of this research was to develop and obtain initial normative data for AP tests for Spanish-speaking adults. The AP tests comprised the Hong Kong CAPA (Hong Kong central auditory processing assessment) including speech-in-noise, binaural fusion, filtered speech, and dichotic digit tests. In addition five tests already developed by other authors, but with no normative data reported for the target population, were included in the study. These tests were staggered spondaic words, random gap detection, pitch pattern sequence, duration pattern sequence, and masking level difference. Forty normal hearing Chilean adults were assessed to obtain the initial normative data. Several correlations were found between tests and between subtests within the same test category. 90th percentiles are suggested as initial normative data. Sumario No existe material estandarizado para evaluar el procesamiento auditivo (AP) en los adultos hablantes del español. El propósito de esta investigación fue desarrollar y obtener datos normativos iniciales para las pruebas de AP en adultos hablantes del español. Las pruebas de AP comprendieron la evaluación del procesamiento auditivo central de Hong Kong (CAPA) que incluye lenguaje en ruido, fusión binaural, lenguaje filtrado y la prueba de dígitos dicóticos. Adicionalmente se incluyeron otras cinco pruebas desarrolladas para esta población por otros autores que carecen de datos normativos. Estas pruebas incluyen palabras espondaicas imbricadas, detección aleatoria de intervalos, secuencia de patrones de tono, secuencia de patrones de duración y diferencia en el nivel de enmascaramiento. Se evaluaron cuarenta adultos chilenos para obtener los datos normativos iniciales. Se encontraron varias correlaciones entre pruebas y entre sub-pruebas dentro de la misma categoría. Se sugieren los percentiles 90 como datos normativos iniciales.

Auditory dysfunction associated with solvent exposure

BackgroundA number of studies have demonstrated that solvents may induce auditory dysfunction. However, there is still little knowledge regarding the main signs and symptoms of solvent-induced hearing loss (SIHL). The aim of this research was to investigate the association between solvent exposure and adverse effects on peripheral and central auditory functioning with a comprehensive audiological test battery.MethodsSeventy-two solvent-exposed workers and 72 non-exposed workers were selected to participate in the study. The test battery comprised pure-tone audiometry (PTA), transient evoked otoacoustic emissions (TEOAE), Random Gap Detection (RGD) and Hearing-in-Noise test (HINT).ResultsSolvent-exposed subjects presented with poorer mean test results than non-exposed subjects. A bivariate and multivariate linear regression model analysis was performed. One model for each auditory outcome (PTA, TEOAE, RGD and HINT) was independently constructed. For all of the models solvent exposure was significantly associated with the auditory outcome. Age also appeared significantly associated with some auditory outcomes.ConclusionsThis study provides further evidence of the possible adverse effect of solvents on the peripheral and central auditory functioning. A discussion of these effects and the utility of selected hearing tests to assess SIHL is addressed.

Central Auditory Damage Induced by Solvent Exposure

Different studies have demonstrated that solvents may induce auditory damage. It has been suggested that part of this damage may be localised in central auditory pathways. The present study aimed to investigate possible auditory processing disorders related to solvent exposure. Thirty solvent-exposed workers and 30 gender-, age- and educational level-matched control subjects were selected to participate in the study. To select participants, a questionnaire, otoscopy, pure-tone audiometry and tympanometry were carried out. Filtered speech (FS), random gap detection (RGD) and hearing-in-noise tests (HINT) were conducted in the selected participants. Both groups of workers presented as a mean normal hearing thresholds. However, significant differences between groups were observed for RGD, FS and HINT. It is concluded that a possible auditory processing disorder may be related to solvent exposure.

Adaptation of the Amsterdam Inventory for Auditory Disability and Handicap into Spanish

Purpose: Self-report questionnaires have been suggested as valuable assessment tools in audiology, especially when investigating the effect of hearing impairment on the everyday lives of adults. Many self-report questionnaires have been developed for English-speaking populations; however, there is a lack of this type of questionnaire for Spanish-speaking patients. The aim of the present research was to adapt the Amsterdam Inventory for Auditory Disability and Handicap (AIADH) into Spanish. Methods: The AIADH consists of 30 questions that deal with real-life listening situations. Each question is accompanied by a picture representing the situation being addressed. Six Spanish-English bilingual speakers and one Spanish-English bilingual speaker participated in the translations and back translations of the English version of the AIADH. Once the adaptation was finalized, 189 normal-hearing and hearing-impaired Spanish-speaking participants completed the Spanish version of the AIADH (S-AIADH). Results: Statistical analysis showed a high Cronbach’s alpha coefficient, indicating good internal reliability. Test-retest scores were highly correlated. Also, the S-AIADH showed good criterion validity. Statistically significant differences for all questionnaire item responses were observed between normal-hearing and hearing-impaired respondents. Conclusions: The AIADH has been adapted into Spanish. Normative data in percentiles have been obtained for clinical use with Spanish-speaking populations, to explore self-reported performance for the hearing functions proposed by the ICF. Implications for Rehabilitation The clinical setting represents an artificial situation and it is not possible to directly assess the patient’s hearing performance in real life situations. For this reason, the use of self-report questionnaires is recommended. Self-report questionnaires are especially useful when investigating hearing disability in a range of listening activities. Thus, hearing rehabilitation can be tailored according to the specific needs of the patient. Self-report questionnaires such as the AIADH may assist to determine the benefits of hearing rehabilitation for the patient throughout a range of activities, for which hearing in essential.

The olivocochlear system and protection from acoustic trauma: a mini literature review.

Large intersubject variability in the susceptibility to noise-induced hearing loss (NIHL) is known to occur in both humans and animals. It has been suggested that the olivocochlear system (OCS) plays a significant role in protecting the cochlea from exposure to high levels of noise. A mini literature review about the scientific evidence from animal and human studies about the association between the function of the OCS and susceptibility to NIHL was carried out. Animal data consistently show that de-efferented ears exhibit larger temporary threshold shift (TTS) and permanent threshold shift (PTS) than efferented ears. Data from human studies do not consistently show a correlation between the strength of the OCS function and amount of TTS. Further research on human subjects is required to determine how the OCS function could be used to predict susceptibility to NIHL in individual subjects.

Xylene-induced auditory dysfunction in humans

Objectives: Animal data indicate that xylene induces cochlear dysfunction, characterized by the loss of outer hair cells. There is little evidence regarding xylene-induced ototoxicity in humans. The aim of the study was to investigate the possible adverse effects of xylene on the peripheral and central auditory system in humans. Design: A total of 30 medical laboratory workers who had been exposed to a mixture of xylene isomers, together with 30 nonexposed control participants matched for gender, age, and educational level were selected. Participants of both groups were not exposed to noise levels above 85 dBA time-weighted average. All participants were evaluated with a comprehensive audiological test battery, which included measures of peripheral and central auditory function. Peripheral auditory measures included pure-tone audiometry and distortion product otoacoustic emissions. Behavioral measures of central auditory function included a pitch pattern sequence test, an adaptive test of temporal resolution, a dichotic digit test, and a masking level difference test. The auditory brainstem response was used to objectively evaluate the function of the auditory pathways at the brainstem level. Speech perception in quiet and in noise was evaluated using the Hearing In Noise Test (HINT). The xylene-exposed participants were extensively evaluated with regard to their exposure to both noise and xylene. Noise dosimetry was conducted over an 8-hr work shift to obtain noise-exposure levels for each xylene-exposed worker. Airborne xylene concentrations were obtained at 11 different workstations throughout the medical laboratories, and methyl hippuric acid levels per gram of creatinine in urine were obtained for each xylene-exposed subject. Finally, a detailed interview exploring current and past solvent and noise exposure was conducted. Results: The xylene-exposed participants showed significantly worse pure-tone thresholds in comparison with the nonexposed participants. The xylene-exposed participants demonstrated significantly worse results than the control group participants for the pitch pattern sequence test, dichotic digit test, HINT, and the auditory brainstem response (absolute and interpeak latencies). No significant differences between the xylene-exposed and nonexposed participants were observed for distortion product otoacoustic emissions, adaptive test of temporal resolution, or the masking level difference test. A significant correlation between the concentrations of methyl hippuric acid in urine and pure-tone thresholds (2 to 8 kHz) was found in xylene-exposed workers. Also, participants with high cumulative dose of xylene exposure presented with poorer test results than participants with low cumulative dose of xylene exposure. Conclusions: The results of the present research suggest that xylene is associated with adverse central auditory effects and poorer sound detection abilities in humans. A major limitation of the study is that the results found among xylene-exposed participants cannot be proved to be permanent, and thus further research should be conducted to clarify this limitation. Workers exposed to this chemical should be routinely evaluated with a comprehensive audiological test battery, to detect early signs of auditory dysfunction.

Cantonese Dichotic Digit Test: Test Creation and Normative Values for Children and Adults

Abstract Little standardized assessment material exists in Cantonese for the assessment of auditory processing disorder (APD) in children or in adults. The present study aimed to create and develop normative data for an APD test, the Cantonese Double Dichotic Digit test (CDDT). A dichotic digit test refers to two different digit stimuli that are presented to each ear simultaneously. It has been recommended to include this test within APD test batteries because it is sensitive to APD, easy and fast to administer, and not influenced by mild to moderate hearing loss. Normative data were collected from 40 young adult subjects, aged between 18 and 30 years, and 122 children aged between 6 and 11;11 years. Norms for seven different age subgroups for the right and left ear in the free-recall and directed- right and directed-left conditions were developed. For each age subgroup, two standard deviations below the mean are suggested as cutoff scores. Results were comparable to the findings of other studies of similar speech discrimination assessment material. The CDDTs test-retest reliability was high and this, combined with its administrative convenience, makes it a potentially attractive assessment procedure for cases with suspected APD.