Potentiation of Chemical Ototoxicity by Noise

Breast cancer and occupation: Non-parametric and parametric net survival analyses among Swiss women (1990–2014)

Introduction

Occupation can contribute to differences in risk and stage at diagnosis of breast cancer. This study aimed at determining whether occupation, along with skill level and the socio-professional category, affect the breast cancer survival (BCS) up to 10 years after diagnosis.

Materials and methods

We used cancer registry records to identify women diagnosed with primary invasive breast cancer in western Switzerland over the period 1990–2014 and matched them with the Swiss National Cohort. The effect of work-related variables on BCS was assessed using non-parametric and parametric net survival methods.

Results

Study sample included 8,678 women. In the non-parametric analysis, we observed a statistically significant effect of all work-related variables on BCS. Women in elementary occupations, with low skill level, and in paid employment not classified elsewhere, had the lowest BCS, while professionals, those with the highest skill level and belonging to top management and independent profession category had the highest BCS. The parametric analysis confirmed this pattern. Considering elementary occupations as reference, all occupations but Craft and related trades had a hazard ratio (HR) below 1. Among professionals, technicians and associate professionals, and clerks, the protective effect of occupation was statistically significant and remained unchanged after adjustment for age, calendar period, registry, nationality, and histological type. After adjusting for tumor stage, the HRs increased only slightly, though turned non-significant. The same effect was observed in top management and independent professions and supervisors, low level management and skilled laborers, compared to unskilled employees.

Conclusion

These results suggest that work-related factors may affect BCS. Yet, this study was conducted using a limited set of covariates and a relatively small study sample. Therefore, further larger studies are needed for more detailed analyses of at risk occupations and working conditions and assessing the potential interaction between work-related variables and tumor stage.

Combined effects of multiple metals on hearing loss: A Bayesian kernel machine regression approach

BACKGROUND

Exposure to heavy elements is considered one of the risks of hearing loss. The combined effect of multiple metals on different hearing losses has not been extensively studied.

METHODS

This study deals with the association between different metals (Ba, Cd, Co, Cs, Mo, Pb, Mn, Sn, Sb, Tl, W) and hearing loss in the 2013-2018 National Health and Nutrition Examination Survey (NHANES). Associations were estimated by a generalized linear regression model (GLM) adjusting for age, gender, race/ethnicity, educational level, marital status, drinking status, hypertension, diabetes, smoking status, noise exposure, body mass index, and income-poverty ratio. The joint effects of mixed exposure were assessed by weighted quantile sum (WQS) model and Bayesian kernel machine regression (BKMR). The effect of multiple metals on speech-frequency hearing loss (SFHL) and high-frequency hearing loss (HFHL) was further calculated. The odds ratio (OR) indicates the risk of every metal exposure.

RESULTS

A total of 2205 adult participants were enrolled from NHANES. Cd, Pb, Sb and Sn had significant effects on total hearing loss. The WQS model found that mixed exposure to heavy elements was significantly positively associated with total hearing loss (OR: 1.136; 95% CI: 1.031, 1.253) after adjusting for various covariates. The ORs of mixed exposure in the SFHL and HFHL groups were 1.066 (95% CI: 0.994, 1.143) and 1.102 (95% CI: 1.013, 1.199), respectively. BKMR found a significant positive association between multiple metals and hearing loss. The results showed that there may be potential interactions between Cd, Pb and other metals.

CONCLUSIONS

Multiple metals have joint effects on hearing loss in the United States. The findings provide practitioners with important scientific evidence for possible interventions.

Mechanisms of Aminoglycoside- and Cisplatin-Induced Ototoxicity

Purpose This review article summarizes our current understanding of the mechanisms underlying acquired hearing loss from hospital-prescribed medications that affects as many as 1 million people each year in Western Europe and North America. Yet, there are currently no federally approved drugs to prevent or treat the debilitating and permanent hearing loss caused by the life-saving platinum-based anticancer drugs or the bactericidal aminoglycoside antibiotics. Hearing loss has long-term impacts on quality-of-life measures, especially in young children and older adults. This review article also highlights some of the current knowledge gaps regarding iatrogenic causes of hearing loss. Conclusion Further research is urgently needed to further refine clinical practice and better ameliorate iatrogenic drug-induced hearing loss.

Metal Exposures, Noise Exposures, and Audiometry from E-Waste Workers in Agbogbloshie, Ghana

Metals, such as lead, may be ototoxic, but this property is not well understood, especially in conjunction with noise. This cross-sectional study investigated hearing, noise, and metal biomarkers in informal electronic waste (e-waste) recycling workers in Accra, Ghana. Workers (N = 58) participated in audiometric testing, a survey, blood collection, and personal noise dosimetry. Sixty percent of participants displayed audiometric notches indicative of noise-induced hearing loss (NIHL). Most workers (86%) reported high noise while working. Daily average noise levels were in the range 74.4-90.0 dBA. Linear regression models indicated participants who lived at Agbogbloshie Market for longer periods were significantly associated with worse hearing thresholds at 4 and 6 kHz. The models did not identify blood levels of lead, mercury, or cadmium as significant predictors of worse hearing thresholds or larger noise notches, but increased levels of selenium were significantly associated with better hearing at 6 kHz. Models of thresholds at 4 and 6 kHz were improved by including an interaction term between the maximum noise exposure and the level of zinc in whole blood, suggesting that zinc may protect hearing at lower noise levels, but not at higher levels. Further study of the relationships between elements, noise, and NIHL is needed.

Hepatotoxic effects caused by simultaneous exposure to noise and toluene in New Zealand white rabbits: a biochemical and histopathological study

The aim of this experimental study was to investigate hepatotoxicity effects of noise and toluene, and in particular, to study hepatotoxicity effects of simultaneous exposure to noise and toluene by histopathological and biochemical experiments. To experiment hepatotoxicity effects of noise and toluene, 100 dB white noise and 1000 ppm toluene vapors were generated during two consecutive weeks in healthy male New Zealand White rabbits. Non-simultaneous exposure to noise and toluene increased liver enzymes and the serum levels of superoxide dismutase, malondialdehyde, and total antioxidant capacity, and also decreased serum level of glutathione peroxidase. Alanine transaminase, aspartate transaminase, gamma-glutamyl transferase, malondialdehyde, total antioxidant capacity, and superoxide dismutase levels increased by simultaneous exposure to noise and toluene. Furthermore, catalase and alkaline phosphatase level decreased by simultaneous exposure to noise and toluene. The hematoxylin and eosin stain (H&E) experiments indicated significant swelling, lipidosis, eosinophilic cytoplasm, pyknosis, karyorrhexis, and disruption of the cytoplasmic membrane in the liver tissue due to exposure to noise, toluene and simultaneous exposure to them.

Environmental Exposures and Hearing Loss

Pollutants that contaminate the natural or built environment adversely affect the health of living organisms. Although exposure to many of them could be avoided or minimized by careful preventive measures, it is impossible to totally avoid exposure to all pollutants. Ototraumatic agents, such as noise, chemicals, and heavy metals, are pervasive pollutants, mostly produced by human activity, and are critical factors in inducing acquired hearing loss. More importantly, exposure to these pollutants often occurs concurrently and, therefore, the synergistic interactions potentiate auditory dysfunction in susceptible individuals. Epidemiological studies have provided compelling data on the incidence of auditory dysfunction after exposure to a number of ototraumatic agents in the environment, while animal studies have offered crucial insights for understanding the underlying molecular mechanisms. Together, they provide a framework for developing effective interventional approaches for mitigating the adverse impacts of environmental or occupational exposure to ototraumatic agents. This article provides a brief overview of the common pollutants that cause hearing loss.

Acquired Central Auditory Processing Disorder in Service Members and Veterans

Purpose A growing body of evidence suggests that military service members and military veterans are at risk for deficits in central auditory processing. Risk factors include exposure to blast, neurotrauma, hazardous noise, and ototoxicants. We overview these risk factors and comorbidities, address implications for clinical assessment and care of central auditory processing deficits in service members and veterans, and specify knowledge gaps that warrant research. Method We reviewed the literature to identify studies of risk factors, assessment, and care of central auditory processing deficits in service members and veterans. We also assessed the current state of the science for knowledge gaps that warrant additional study. This literature review describes key findings relating to military risk factors and clinical considerations for the assessment and care of those exposed. Conclusions Central auditory processing deficits are associated with exposure to known military risk factors. Research is needed to characterize mechanisms, sources of variance, and differential diagnosis in this population. Existing best practices do not explicitly consider confounds faced by military personnel. Assessment and rehabilitation strategies that account for these challenges are needed. Finally, investment is critical to ensure that Veterans Affairs and Department of Defense clinical staff are informed, trained, and equipped to implement effective patient care.

Ototoxicity: Visualized in Concept Maps

Ototoxicity refers to the damage to structures and function of the auditory-vestibular system caused by exogenous agents such as pharmaceuticals, chemicals, and ionizing radiation. There are many potentially ototoxic substances. For example, depending on how ototoxicity is defined, there are 200 to 600 medications that can cause damage to hearing and/or balance. Ototoxicity encompasses cochleotoxicity, vestibulotoxicity, and neurotoxicity. A variety of professional disciplines are involved in determining causation, prevention, and management of ototoxic effects. Research to identify and develop otoprotectants and otorescue agents is emerging and will translate basic scientific discovery into applications for use in hearing conservation programs, safety operations, and clinical care. Original concept maps are presented here to visually represent knowledge pathways, domains, and relationships essential to the understanding of ototoxicity.

Asymmetric sensorineural hearing loss is a risk factor for late-onset hearing loss in pediatric cancer survivors following cisplatin treatment

BACKGROUND

Ototoxicity is a significant complication of cisplatin treatment. Hearing loss can be symmetric or asymmetric, and may decline after therapy. This study examined the risks of asymmetric and late-onset hearing loss (LOHL) in cisplatin-treated pediatric patients with cancer.

METHODS

A retrospective review of 993 patients' medical and audiological charts from August 1990 to March 2015 was conducted using stringent criteria to characterize patients with asymmetric hearing loss (AHL) or LOHL. Audiologic data were reviewed for 248 patients that received cisplatin to assess cisplatin-induced sensorineural hearing loss and its associated risk factors.

RESULTS

Of the patients evaluable for AHL, 26% exhibited this finding. Of those evaluable for LOHL, 42% of the patients' hearing worsened more than 6 months after therapy completion. Radiation and type of cancer diagnosis were major risk factors for both AHL and LOHL. Furthermore, LOHL was linked to age of diagnosis, noncranial radiation, and longer audiologic follow-up. AHL was strongly associated with LOHL-60% of patients with AHL also had LOHL. Logistic regression analysis revealed that patients with AHL (OR 6.3, 95% CI: 2.2-17.8, P = 0.0005) or those receiving radiation (OR 3.2, 95% CI: 1.2-8.6, P = 0.02) were at greatest risk for LOHL.

CONCLUSION

Children receiving cisplatin therapy are at risk for developing AHL and LOHL. Those that have received radiation and/or with AHL are at increased risk for further hearing decline. Long-term monitoring of these patients is important for early intervention as hearing diminishes.

Chronic lead exposure induces cochlear oxidative stress and potentiates noise-induced hearing loss

Acquired hearing loss is caused by complex interactions of multiple environmental risk factors, such as elevated levels of lead and noise, which are prevalent in urban communities. This study delineates the mechanism underlying lead-induced auditory dysfunction and its potential interaction with noise exposure. Young-adult C57BL/6 mice were exposed to: 1) control conditions; 2) 2 mM lead acetate in drinking water for 28 days; 3) 90 dB broadband noise 2 h/day for two weeks; and 4) both lead and noise. Blood lead levels were measured by inductively coupled plasma mass spectrometry analysis (ICP-MS) lead-induced cochlear oxidative stress signaling was assessed using targeted gene arrays, and the hearing thresholds were assessed by recording auditory brainstem responses. Chronic lead exposure downregulated cochlear Sod1, Gpx1, and Gstk1, which encode critical antioxidant enzymes, and upregulated ApoE, Hspa1a, Ercc2, Prnp, Ccl5, and Sqstm1, which are indicative of cellular apoptosis. Isolated exposure to lead or noise induced 8-12 dB and 11-25 dB shifts in hearing thresholds, respectively. Combined exposure induced 18-30 dB shifts, which was significantly higher than that observed with isolated exposures. This study suggests that chronic exposure to lead induces cochlear oxidative stress and potentiates noise-induced hearing impairment, possibly through parallel pathways.

Hearing loss in a pediatric patient following cisplatin chemotherapy and subsequent exposure to excessive noise

Cisplatin is a commonly-used chemotherapeutic agent that is highly-effective against a variety of pediatric cancers. Unfortunately, it may lead to ototoxicity, with serious consequences on the quality of life of survivors. Patients remain at risk of progression of ototoxicity even after completion of treatment. We report the case of a medulloblastoma survivor with previously documented normal hearing, who developed significant hearing loss and tinnitus following exposure to excessive noise at a nightclub three years after completion of treatment. We highlight the importance of long-term audiological follow up and education about the increased risk of hearing loss in this population.

Does interferon beta-1a impact pure-tone hearing sensitivity among individuals with multiple sclerosis?

BACKGROUND

Previous studies reported that particular types of interferon medications might contribute to hearing loss in some patients. The package insert included in the original Food and Drug Administration application for intramuscular interferon beta-1a (Avonex) stated that some patients in the treatment group reported decreased hearing sensitivity.

OBJECTIVE

The purpose of the present investigation was to assess if individuals with multiple sclerosis (MS) taking intramuscular interferon beta-1a have significantly poorer hearing thresholds than those not currently using any disease-modifying therapies.

METHODS

This was a secondary analysis of data collected as part of two larger studies evaluating auditory function in patients with MS. The goal of this analysis was to determine if users of interferon beta-1a do not have significantly worse hearing thresholds than nonusers of disease-modifying therapies, after adjusting for potential confounders. A linear mixed model was fit to the audiometric thresholds of our subjects. This model included interferon beta-1a use, MS disease subtype, gender, test frequency, age, disease duration (number of years), and the Expanded Disability Status Scale score.

RESULTS AND CONCLUSIONS

With all subjects included, there is insufficient evidence to say that intramuscular interferon-beta 1a is not ototoxic (in relation to nonuse of a disease-modifying therapy) at all frequencies tested except 3000 and 6000 Hz. After removing two influential subjects, the results indicated that there is statistical support for no ototoxic effect of intramuscular interferon beta-1a at test frequencies from 250 to 6000 Hz. There is insufficient evidence, however, to rule out an ototoxic effect at 8000 Hz. Future studies should further evaluate the effect of interferon on auditory function in patients with MS. Neuroscience nurses should monitor their patients' hearing throughout the course of treatment.

Ototoxic Substances at the Workplace: a Brief Update

Ototoxic chemicals can impair the sense of hearing and balance. Lately, efforts have been intensified to compile evidence-based lists of workplace agents with ototoxic properties. This article gives a rough overview of the latest relevant publications, which confirm that toluene, styrene, and lead should receive particular attention as ototoxic substances at the workplace. Moreover, there is sufficient evidence that occupational exposure to trichloroethylene, mercury, carbon monoxide, and carbon disulfide can affect the ear. Based on the existing information, industrial hygienists should make sure that occupational health professionals and the workforce are made aware of the risks posed by ototoxic substances; support their replacement or new technical measures to reduce exposure; make these substances a part of regular screening, develop tools that can early diagnose chemically induced hearing impairment, and investigate further into the ototoxic properties of these substances. Further research should focus on quantifying the combined effects of ototoxic substances and noise.

Audiovestibular dysfunction associated with adoptive cell immunotherapy for melanoma

OBJECTIVE

To understand the audiologic and vestibular toxicities associated with adoptive cell immunotherapy (ACI) targeting pigment-pathway antigens on melanoma and to investigate the use of intratympanic steroid injections in the treatment of these toxicities.

STUDY DESIGN

Prospective nonrandomized study.

SETTING

Tertiary clinical research center.

METHODS

Thirty-two patients with progressive metastatic melanoma who failed conventional therapy underwent ACI with T cells genetically modified to target MART-1 (n = 18) or gp100 (n = 14). All patients received serial audiometric testing. Vestibular testing was performed on patients with vestibular complaints. Patients with significant deficits received intratympanic steroid injections.

RESULTS

Of 32 patients, 15 had no hearing change, 9 had mild hearing loss, and 8 had moderate hearing loss following treatment. Ten patients received intratympanic steroid injections for mild (n = 2) or moderate (n = 7) hearing loss or for significant imbalance (n = 1). Of those with mild hearing loss (n = 9), all but 1 recovered to pretreatment hearing levels. Four of 8 patients with moderate hearing loss recovered to baseline hearing levels, and 4 had partial recovery. All 7 patients with posttreatment vestibular complaints had demonstrable vestibular dysfunction. Three of these patients demonstrated recovery to normal vestibular function. The number of modified T cells infused for therapy correlated with the degree of audiovestibular deficit.

CONCLUSION

Adoptive cell immunotherapy targeting pigment-pathway cell proteins, a novel therapy for melanoma, can induce hearing loss and vestibular dysfunction. The presumed mechanism of autoimmune attack on normal melanocytes in the cochlear stria vascularis and in the vestibular organs demonstrates the importance of melanocytes in normal inner ear function.

Progressive hearing loss after completion of cisplatin chemotherapy is common and more pronounced in children without spontaneous otoacoustic emissions before chemotherapy

OBJECTIVE

High frequency hearing loss following cisplatin chemotherapy is frequent in children and often necessitates the fitting of hearing aids. During therapy, hearing is usually monitored. Post-therapeutic follow-up does not routinely include monitoring of hearing, although there are indications that hearing thresholds can decline after therapy.

METHODS

Pure-tone audiograms taken from 27 children (17 males, 10 females) treated with cisplatin at Muenster university hospital (mean age 9.84 years, standard deviation 3.67 years) including an audiological follow-up at least 6 months after therapy, were analyzed retrospectively.

RESULTS

In follow-up tests after completion of therapy, 24.1% of all ears showed an increase in mean high frequency hearing thresholds (4-8 kHz). Post-therapeutic hearing deterioration was significant at 4 kHz and significantly more pronounced in children without measurable spontaneous otoacoustic emissions (SOAE) before therapy. Post-therapeutic hearing deterioration did not occur in ears with normal pure tone thresholds (≤ 10dB at all frequencies) after cisplatin therapy. No correlation was found between post-therapeutic hearing deterioration and cranial irradiation.

CONCLUSIONS

Cisplatin chemotherapy follow-up should include audiological monitoring in all children with elevated pure tone thresholds after therapy. Routine SOAE measurements taken as part of baseline audiometry before the start of chemotherapy can be taken into consideration.

Mechanisms Involved in Ototoxicity

The modern era of evidence-based ototoxicity emerged in the 1940s following the discovery of aminoglycosides and their ototoxic side effects. New classes of ototoxins have been identified in subsequent decades, notably loop diuretics, antineoplastic drugs, and metal chelators. Ototoxic drugs are frequently nephrotoxic, as both organs regulate fluid and ion composition. The mechanisms of ototoxicity are as diverse as the pharmacological properties of each ototoxin, though the generation of toxic levels of reactive oxygen species appears to be a common denominator. As mechanisms of cytotoxicity for each ototoxin continue to be elucidated, a new frontier in ototoxicity is emerging: How do ototoxins cross the blood-labyrinth barrier that tightly regulates the composition of the inner ear fluids? Increased knowledge of the mechanisms by which systemic ototoxins are trafficked across the blood-labyrinth barrier into the inner ear is critical to developing new pharmacotherapeutic agents that target the blood-labyrinth barrier to prevent trafficking of ototoxic drugs and their cytotoxic sequelae.