Aspects of professional functioning in employees with hearing loss Hanneke E.M. van der Hoek-Snieders
Aspects of professional functioning in employees with hearing loss Hanneke E.M. van der Hoek-Snieders
ISBN: 978-94-6458-758-6 Cover & Lay-out: Publiss | www.publiss.nl Print: Ridderprint | www.ridderprint.nl © Copyright 2023: Hanneke E.M. van der Hoek-Snieders , The Netherlands All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, electronic, mechanical, by photocopying, recording, or otherwise, without the prior written permission of the author.
Aspects of professional functioning in employees with hearing loss ACADEMISCHPROEFSCHRIFT ter verkrijging van de graad van doctor aan de Universiteit van Amsterdam op gezag van de Rector Magnificus prof. dr. ir. P.P.C.C. Verbeek ten overstaan van een door het College voor Promoties ingestelde commissie, in het openbaar te verdedigen in de Agnietenkapel op woensdag 15 maart 2023, te 16.00 uur door Hanneke ElisabethMaria Snieders geboren te Veldhoven
Promotiecommissie Promotor: prof. dr. ir. W.A. Dreschler AMC-UvA Copromotor: dr. M. Boymans LibraRevalidatie& Audiologie Overige leden: prof. dr. ir. J.C.M. Smits AMC-UvA prof. dr. W.J. Fokkens AMC-UvA prof. dr.M.H.W. Frings- Dresen AMC-UvA prof. dr. S.E. Kramer Vrije Universiteit Amsterdam dr. ir. J.A.P.M. de Laat LUMC dr. ir. A.E. Hoetink UMC Utrecht Faculteit der Geneeskunde
Contents General introduction 9 Hearing loss Hearing assessment Hearing-critical job tasks Interventions Outline of the thesis 10 15 20 21 26 Part I: Factors influencing professional functioning 29 Chapter 1 Factors influencing the need for recovery in employees with hearing loss: a cross-sectional study of health administrative data 31 Chapter 2 The relationship between hearing status, listening effort, and the need for recovery in employees of a manufacturing company hearing-critical job tasks 55 Part II: Evaluation of professional functioning 69 Chapter 3 Factors associated with change in the need for recovery and subjective listening effort in employees with hearing loss receiving aural rehabilitation 71 Chapter 4 Communication strategies, personal adjustments, and need for recovery in employees with hearing loss who receive a communication group training 95 Part III: Measuring hearing-critical job tasks 111 Chapter 5 Detectability of auditory warning signals in the ambient noise of Dutch train cabins 113 Chapter 6 Measuring auditory fitness in locomotive engineers: development and validation of a signal detection test 131 General discussion 153 Hearing assessment Research during clinical practice Part I: factors influencing professional functioning Part II: Evaluation of professional functioning Part III: Measuring hearing-critical job tasks Implications for clinical practice Conclusions 155 160 162 163 164 165 167
References 168 List of abbreviations 182 Summary 184 Samenvatting 188 Dankwoord 192 Publications 196 Curriculum vitae 198 Portfolio 199
General introduction
Chapter 1 10 Hearing loss With a prevalence estimate of 1.3 billion adults worldwide, hearing loss is the most common sensory impairment in humans (Ciorba et al., 2012; James et al., 2018). Hearing loss can be related to the anatomy and physiology of the ear, but it can also affect the hearing function, functioning in everyday activities, and participation in life situations (Dillon, 2008). Therefore, hearing can be considered to be a sociocultural phenomenon, rather than an isolated medical problem (Danermark et al., 2013; Granberg et al., 2014). Anatomy and physiology The term hearing loss is used to describe an impairment of one or both ears that results in hearing difficulties. Depending on where the impairment is located, three types of hearing loss can be distinguished: conductive, sensorineural, and mixed hearing loss (Michels et al., 2019). Conductive hearing loss results from a disruption in the ear canal and/or the middle ear, causing sounds to be conducted inefficiently to the inner ear. Possible causes are obstruction of the ear canal – for example by cerumen – or middle ear diseases, such as otitis media. The more common type of hearing loss, sensorineural hearing loss, involves a distorted conversion of sounds in the inner ear and/or the auditory nerve and is most often caused by ageing or by excessive noise exposure (Rabinowitz, 2000). If conductive and sensorineural hearing loss occur in combination it is called mixed hearing loss. Hearing loss can be related to tinnitus or hyperacusis, ear disorders that may share their pathophysiology with that of hearing loss (Nelson & Chen, 2004). One of the possible explanations is that sensorineural hearing loss causes the brain to receive an incongruous neuralmessage. As a reaction, the brainmay ‘turnup the volume’ resulting in either everyday sounds being perceived too loud, even painfully so (hyperacusis) or a persistent perception of a sound that has no external source (tinnitus) (Baguley et al., 2013; Sheldrake et al., 2015). Although most individuals with hyperacusis or tinnitus also suffer from hearing loss, hyperacusis and tinnitus can also occur in isolation. Hearing function For both conductive and sensorineural hearing loss, reduced sensitivity of sounds is the most obvious symptom, requiring soft sounds to be louder to be heard.
General introduction 11 Yet, in case of sensorineural hearing loss, an additional effect is that the distorted conversion of sounds to the brain often causes sounds to be perceived as blurred (Dillon, 2008). Also, discomfort can be experienced when loud sounds are heard, even at levels that are not perceived as annoying by normally-hearing individuals (Levitt, 2001). Consequently, sensorineural hearing loss is characterized by a reduced dynamic range of hearing, meaning that the range between the weakest sound that can be heard and the most intense sound that can be tolerated is often smaller when sensorineural hearing loss is present (Dillon, 2008). Sensorineural hearing loss involves problems with multiple auditory functions that contribute to further distortionof sounds (Dillon, 2008; Plomp, 1978).These auditory functions – specifically spectral, temporal, and spatial resolution – partly share their cause, but affect auditory functioning in different ways. Decreased spectral resolution causes difficulties with recognizing two separate sounds of a different frequency that are presented simultaneously. Decreased spectral and temporal resolution cause the distortion of sounds and difficulties with listening selectively, for example with understanding speech in noise. Lastly, decreased spatial resolution causes a higher sensitivity for loud sounds and causes difficulties with spatial hearing. The impact of hearing loss on hearing function depends on whether one (unilateral hearing loss) or both ears (bilateral hearing loss) are affected. Bilateral hearing loss is most common and results in reduced hearing function as described above. When normal hearing is present in one ear, the reduced sensitivity of sounds is rather modest. Unilateral hearing loss often results in no more than a small attenuation of sounds presented at the affected side, since sounds need to travel around the head to the opposite ear. However, unilateral hearing loss may lead to specific difficulties in case of adverse listening situations. When information of only one ear can be used, it can become more difficult to recognize the meaningful sounds and to filter out the environmental noise (Sargent et al., 2001). Also, unilateral hearing loss causes difficulties with locating a sound source, since the brain needs input of two ears to accurately determine the direction where a signal originates. Personal and environmental factors Many personal and environmental factors interact with hearing loss and its impact on hearing functions, everyday activities, and participation in life situations (Granberg,
Chapter 1 12 2015). Inotherwords, thedegreeof hearing loss aswell as the impactof hearing losson daily life functioning depends on personal and environmental factors. These factors include the presence of environmental noise and reverberation, the use of hearing aids or other assistive technical devices, social support, and the use of compensatory strategies, such as making use of speech reading skills. The impact of hearing loss on work functioning can also be greatly influenced by personal and environmental factors (Granberg &Gustafsson, 2021). For example, a workplace with facilitators – such as supporting colleagues or hearing devices – can improve auditory functioning at work, whereas a workplace with barriers – such as a noisy environment or high auditory demands – can restrict auditory functioning at work. Although there is little knowledge on how personal and environmental factors interact with hearing loss and its consequences on everyday activities and participation in working adults with hearing loss, environmental noise and reverberation have been described to be important factors to consider in this population (Dobie, 2008; Morata et al., 2005). Noise and reverberation Noise can be defined as any unwanted sound that interferes with the sound of interest (Levitt, 2001). When listening to someone’s speech, possible sources of noise are interfering voices, or sounds produced by technical devices in or near by the room. Many job tasks need to be performed in noisy work environments. This is evident in the case of a call-center agent who needs to make phone calls simultaneously with many colleagues in the same room (Beyan et al., 2016), in the case of a nurse who needs to detect 23 different auditory alarms at an intensive care unit (Momtahan et al., 1993), and in the case of a team leader who needs to participate in staff meetings (Laroche & Garcia, 2001). Reverberation occurs when a sound source is accompanied by reflections of multiple sound sources in an enclosed space (Perham et al., 2007). It can be expressed in reverberation time, which is the time it takes for a sound to reduce 60 dB below its original level. The reverberation time depends on the size, shape, and nature of the room. For example, the reverberation time is often higher in rooms with high ceilings and hard surfaces, whereas the reverberation time can be reduced by placing sound-absorbing materials, such as curtains or carpeting. A considerable amount of job tasks is performed in reverberant listening environments, including swimming pools, open offices, and sport halls.
General introduction 13 Noise and reverberation complicate the performance of everyday activities that rely on hearing function. In the case of sensorineural hearing loss, this can be explained by the decreased temporal, spectral, and spatial resolution (Dillon, 2008; Plomp, 1978). Temporal, spectral, andspatial resolutionareespecially required innoisyenvironments, with multiple simultaneous or subsequent sounds present. Listening effort increases in the attempt to compensate for the adverse effects of noise, causing participation in noisy situations to be more demanding and fatiguing (Beechey et al., 2020; Hornsby et al., 2016; McGarrigle et al., 2014). Unfortunately, the adverse effects of noise and reverberation can often not be fully compensated for by using extra listening effort; the difficulties with performing auditory tasks often remain in noisy situations. Noise can cause difficulties with performing auditory tasks, but higher noise levels are also associated with increased annoyance and distraction as well as decreased concentration, productivity, and working capacity (Sailer & Hassenzahl, 2000). This is particularly the case in industrial workers, shipyard workers, construction workers, military workers, and farmers (Lie et al., 2016). However, even noise at lower sound levels can cause these negative effects, especially when the complexity of the job task is high (Beaman, 2005; Landström et al., 1995). For example, office workers can be distracted by office noise, particularly from telephone ringing and others talking in the background (Banbury & Berry, 2005; Sundstrom et al., 1994). Individuals that are exposed to occupational noise are at risk for developing noiseinduced hearing loss. It is estimated that eight percent of the Dutch work-force is repeatedly being exposed to excessive noise levels at their workplace (Hooftman et al., 2020). Excessive noise exposure may directly result in a temporary reduction of hearing sensitivity, which is called a temporary threshold shift . This temporary threshold shift will largely disappear within 48 hours after the noise exposure if the ear is given enough rest (Mirza et al., 2018). However, if the noise exposure is persistent, permanent noiseinduced hearing loss will likely occur. This is called a permanent threshold shift. Other harmful effects of occupational noise exposure are tinnitus and hyperacusis. Activities and participation Activities Hearing loss may affect the performance of everyday activities that rely on sufficient hearing function (Granberg, 2015). For instance, reduced sensitivity and distortion of
Chapter 1 14 sounds may result in difficulties with speech understanding during conversations with one or more persons, and the reduced ability to locate sounds may make it difficult to hear cars coming when walking through traffic. Other activities that may be affected by hearing loss are the usage of telecommunication devices and communication strategies, interactions with family or strangers, or interactions in formal relationships. Granberg (2015) investigated everyday activities that are most commonly affected in adults with hearing loss. Her research was performed within the framework of the International Classification of Functioning, disability, and health (ICF). This framework has been introduced in 2001 and allows to examine medical, individual, social, and environmental influences on functioning and disability (World Health Organization, 2001). The research of Granberg (2015) resulted in the development of the ICF core set for hearing loss, including the areas of functioning that are most relevant to describe in adults with hearing loss. The ICF core set for hearing loss is a general framework that can be used to describe the functioning of adults with hearing loss. As stated, formal relationships are a relevant area to describe in this population (Granberg, 2015). More specifically, hearing loss may affect the performance of auditory job tasks. These tasks include speech understanding and detecting, recognizing, and locating sounds (Dreschler & Boermans, 1997; Soli, Giguère, et al., 2018; Tufts et al., 2009). Also, many individuals with hearing loss, tinnitus, or hyperacusis are being hindered by environmental noise at the workplace (World Health Organization, 2011). It is estimated that hearing loss results in difficulties with performing auditory tasks in approximately three percent of the Dutch work force (Sorgdrager, 2015). This percentage is likely to increase, as the society is ageing and the retirement age is being raised. Participation Hearing lossmay affect several aspects of participation in life situations, includingquality of life, communication, interaction with significant others, and work participation (Granberg, 2015; Granberg et al., 2014; Punch et al., 2019). The ICF core set for hearing loss also includes a description of the areas of participation that are relevant for describing the functioning of adults with hearing loss (Granberg, 2015). These areas include private situations with family and friends, such as socializing, community life, sports, arts, culture, religion, and spirituality. Furthermore, work is acknowledged as an important area of participation that is often affected in adults with hearing loss.
General introduction 15 With hearing loss, the performance of job tasks can be more challenging. Individuals with hearing loss often attempt to optimize their perception of the sounds of interest by expanding cognitive resources, causing them to experience higher levels of concentration and listening effort (Beechey et al., 2020; McGarrigle et al., 2014). This increased listening effort is related to psychosocial distress and fatigue (Grimby & Ringdahl, 2000). Hearing loss is related to longer and more intense mental and physical fatigue after a day of work. In other words: adults with hearing loss generally experience higher Need For Recovery (NFR) after work compared to normallyhearing adults (Nachtegaal et al., 2009). It has been shown that the incidence of sick leave due to mental distress is higher in individuals with hearing loss compared to those with normal hearing (Kramer et al., 2006). Also, hearing loss can limit the type or amount of work that can be done, resulting in the feelingof beingunable toperformthe job sufficientlywell (Nachtegaal et al., 2012). Several studies have shown that it is more difficult for individuals with hearing loss to maintain employment (Danermark & Gellerstedt, 2004; Emmett & Francis, 2015; Granberg & Gustafsson, 2021). The level of unemployment is higher in populations with hearing loss and taking earlier retirement is more common in individuals with hearing loss. Hearing assessment Several tools and diagnostic instruments can be used to describe, qualify, or quantify the functioning of adults with hearing loss, together capturing all aspects of the ICF framework. Most tools and instruments serve to diagnose a specific aspect of functioning, as will be described below. Additionally, van Leeuwen (2019) developed an ICF-based e-intake tool that can be used in adults with hearing loss. The aimof this tool is to support the identification of problems, personal factors, and environmental factors relevant to the functioning of an individual with hearing loss. Assessment of anatomy and physiology The ear can be inspected for abnormalities using otoscopic inspection of the ear (Hogan & Tadi, 2020). A tuning fork can be used to indicate whether the hearing loss is conductive or sensorineural (Isaacson & Vora, 2003). This inspection is often performed by an otolaryngologist. The status of the tympanic membrane and
Chapter 1 16 the middle ear can be examined in more detail via tympanometry (Rose, 2011). Additionally, the middle ear muscle reflex can be assessed by measuring the response to a high level acoustic stimulus presented in the ear canal (Schairer et al., 2013). Assessment of the hearing function Pure-tone audiometry can be used to assess hearing sensitivity by determining ear specific hearing thresholds at different frequencies (Vogel et al., 2007). Based on this assessment, the degree of hearing loss can be determined (see Table 1). When the degree of higher loss is higher, the difficulties with performing auditory tasks are presumed to be more severe. However, pure-tone audiometry only assesses the ability to detect sounds in a quiet environment and this has been shown to poorly predict other functional hearing abilities (Shub et al., 2020; Tufts et al., 2009). For themedical diagnosis of hearing loss, pure-tone audiometry is necessary, but it does not suffice for the prediction of the consequences of hearing loss on everyday activities. Table 1. Presumed difficulties based on the severity of the hearing loss Degree of hearing loss Pure-tone thresholds Presumed difficulties with performing auditory tasks Normal -10 to 15 dB HL - Mild 15 to 35 dB HL Difficulties with hearing/understanding soft speech, speech at a larger distance, or speech in noisy environments Moderate 35 to 60 dB HL Difficulties with hearing/understanding speech at a normal level, even at close distance or in quiet environments. Possible difficulties with making phone calls Severe 60 to 90 dB HL Difficulties with understanding loud speech, hearing sirens of emergency cars, hearing industrial sounds, and hearing the sound of a closing door Profound >90 dB HL Speech understanding is impossible based on acoustic information only This table was derived from the protocol of the Dutch Board for Occupational Medicine (NVAB) ‘hearing loss and tinnitus’ and was translated to English.The pure-tone thresholds represent the average values of the hearing thresholds at 1000, 2000 and 4000 Hz for the better ear. Assessment of personal and environmental factors Hearing-related coping behavior The Communication Profile for the Hearing Impaired (CPHI) has been developed to assess the coping behavior of individuals with hearing loss (Mokkink et al., 2009). The questionnaire distinguishes adequate coping behavior, such as asking for a
General introduction 17 repeat in case of misunderstanding or good self-acceptance, and inadequate coping behavior, such as avoiding conversations or having feelings of embarrassment as a consequence of communication problems. Noise The amount of noise at theworkplace can be investigated during noisemeasurements at the workplace (South, 2013). Another approach for assessing the amount of noise at the workplace is to ask employees to rate the subjective amount of noise at their workplace, a question that is for example included in the Amsterdam Checklist for Hearing and Work (ACHW) . Other workplace facilitators and barriers can be explored with several scales of the Questionnaire on the Experience and Evaluation of Work (QEEW), such as the scales relationship with colleagues, relationship with supervisor, work pressure, and pace and amount of work (Van Veldhoven et al., 2015). Assessment of activities and participation Aspects of activities and participation can be assessed using hearing tests and questionnaires, including generic, hearing specific, work specific, and hearing & work specific questionnaires. Hearing tests Speech audiometry assesses the ability to repeat monosyllabic words in a quiet listening environment and can be used to predict the ability to understand speech in a quiet environment ( Jerger et al., 1968). It includes monosyllabic words that can be presented in a free field setting or under headphones. Alternative speech stimuli for speech perception tests are digits or everyday sentences, such as the Dutch sentences developed by Plomp and Mimpen (1979), or the VU98 speech material, developed by Versfeld et al. (2000). Speech perception tests can also be performed in adverse listening conditions, such as in reverberation or in noisy environments. The outcome of these tests is the signal-to-noise ratio (SNR), which is defined as the SNR at which fifty percent of the responses is correct. Some of the speech perception tests in noise can be well
Chapter 1 18 used for screening purposes, such as the digits-in-noise test that can be performed without help of an experimenter (Smits et al., 2013) or the Occupational Ear Check (OEC) that can be completed online (Sheikh Rashid & Dreschler, 2018). The stimuli of the digits-in-noise test are sets of three numbers that need to be entered on a computer. The stimuli of the OEC are monosyllabic words that are represented by nine response buttons on the screen with a picture and the written word. For clinical use, speech perception tests including sentence stimuli are most often used, allowing to predict the ability to understand speech in adverse listening conditions (Plomp &Mimpen, 1979; Versfeld et al., 2000). The presented noise can be either continuous or fluctuating (interrupted). By comparing the outcome of a speech perception test in continuous noise with one performed in fluctuating noise, information is provided on howwell an individual is capable of making use of relative silent periods in the noise. In individuals with normal hearing or conductive hearing loss, the outcome of the test in fluctuating noise is expected to be more favorable than the outcome of the test in continuous noise. For individuals with sensorineural hearing loss this is not the case, since they do not profit this much from temporal gaps due to reduced temporal resolution. To assess the ability of speech understanding of sounds coming from multiple directions, speech perception tests can be performed in a free field condition with separated sound sources. A variety of test conditions has been described, which differ in terms of the number of sound sources, the azimuths at which the sound sources are located, and the type of noise used (Darwin, 2008; Dirks & Wilson, 1969; Gnewikow et al., 2009; Grutters et al., 2007; Ricketts &Henry, 2002; Wagner et al., 2020). The ability to localize sounds can be assessed by asking a test subject to indicate the box where the sound came from (spatial hearing) (Letowski & Letowski, 2012; Santala & Pulkki, 2011; Yost & Brown, 2013). An alternative test to assess the ability to localize sounds is to ask subjects to determine if a sound source is approaching or receding (Andreeva et al., 2018; McCarthy & Olsen, 2017). Questionnaires Several generic, health related questionnaires are available, such as the Medical Outcome Study 36-Item Short-Form Health Survey, the EuroQol, and the Health Utilities Index Mark III (Grutters et al., 2007; McHorney et al., 1993). These
General introduction 19 questionnaires are designed to use in individuals with a wide range of chronic diseases. However, these questionnaires do not recognize communication as a health domain, although communication restrictions are often experienced to be the most important restriction to societal involvement by adults with hearing loss (Granberg, 2015). Hearing specific questionnaires have also been developed to assess several aspects of participation. The review of Bentler and Kramer (2000) describes 33 hearing specific questionnaires, and even more questionnaires have been developed ever since (Granberg, 2015). The reported prevalence of these questionnaires is low. One of the questionnaires that is internationally used to assess the self-reported hearing ability is the Speech Spatial and Qualities of hearing scale (SSQ) (Gatehouse & Noble, 2004). This questionnaire measures the extent of listening difficulties during several daily life activities. The burden of hearing loss on work functioning can be assessed with the NFR scale that is included in the QEEW (Van Veldhoven & Broersen, 2003). The score on this scale has been shown to be a predictor of work stress, subjective health problems, and sick leave (De Croon et al., 2003; Sluiter et al., 2003). The NFR scale can therefore also be used for screening purposes. To our knowledge, there are currently no validated questionnaires measuring aspects participation that are hearing ánd work specific, For Dutch employees, the ACHW is available. Regarding the assessment of participation, this questionnaire includes six questions regarding the subjective listening effort at the workplace, such as the effort it takes to recognize sounds or to communicate in noise. The role of the occupational physician Employees with work functioning difficulties can visit an occupational physician. The role of the occupational physician for employees with hearing loss has been described in the protocol of the Dutch Board for Occupational Medicine (NVAB) entitled ‘hearing loss and tinnitus’. This protocol has been published in 2020 and states that occupational physicians should explore the difficulties inwork functioning that may have been caused by hearing loss. Occupational physicians screen the hearing function of individuals who visit them with hearing loss complaints if no hearing assessment has been performed recently.
Chapter 1 20 This hearing screening consists of pure-tone audiometry. If the patient suffers from tinnitus, the tinnitus complaints, its onset and progress are inventoried. Further, the consequences of the hearing loss on everyday activities and participation are inventoried through self-report, including the difficulties with performing different auditory tasks and the NFR after work. The occupational physician may ask others their opinion about the consequences of hearing loss at work, such as the supervisor or colleagues. Personal and environmental factors are also inventoried by the occupational physician through self-report. The personal factors comprise the general health condition, the quality of sleep, psychosocial problems, and the coping strategies that are used. The environmental factors include the auditory work demands, the amount of noise and reverberation at the workplace, other workplace characteristics such as the work pace and the possibility to participate in job decisions, and the social relationships at work. After formulating the preliminary analysis, occupational physicians can refer to a general practitioner or ENT-specialist for a further assessment of the domain of anatomy and physiology. A referral is sent to an audiological center for further assessment of the other ICF domains, and – if needed – rehabilitation services. Hearing-critical jobs In some jobs, the inability to perform auditory tasks may cause a safety risk to the worker, fellow workers, or the general public (Giguere et al., 2008; Tufts et al., 2009). This is for example true in the military, since danger is posed by a soldier that cannot detect and localize sounds made by unseen adversaries in combat. Other workers that perform hearing-critical tasks include those operating vehicles, firefighters, miners, police constables, and law enforcement officers. Most of these jobs need to be performed in noisy workplaces with noise levels above 70 dBA. Here, difficulties with performing auditory tasks may occur, especially in employees with hearing loss (Soli, Giguère, et al., 2018). When hearing loss may result in difficulties with sufficient performance of crucial, auditory job tasks, job-related inclusion and exclusion criteria for employment can be applied to ensure that individual workers can safely and effectively perform hearing-critical job tasks (Soli, Giguère, et al., 2018).
General introduction 21 Interventions Prevention Hearing loss that is attributed to occupational noise exposure is potentially preventable (Verbeek et al., 2014). Preventive measures have been described in a Cochrane review (Tikka et al., 2017) and in medical guidelines, such as the Dutch multidisciplinary guideline for the prevention of occupational hearing loss (Sorgdrager et al., 2006). It is important to first identify groups at risk of occupational hearing loss. The first group consists of individuals that work in noise of 80 dBA or higher. For this group, a protocol with a hierarchical order of preventive measures has been designed. Highest in the hierarchical order are measures that reduce or eliminate the source of the workplace noise, by changing materials, processes, or the workplace layout. Second are organizational measures, specifically changing work practices, management policies, or the behavior of workers. Examples are reducing the duration of the noise exposure or reducing the number of employees that is exposed to the noise.Third are measures that intend to increase the use of personal protection devices. Last in the hierarchical order are measures that include monitoring of the hearing levels of exposed workers. Also, it is important that employees at risk for occupational hearing loss receive information and training about the risk of noise exposure. Prevention of hearing loss is an ongoing process, and the efficacy of a prevention program should be evaluated every year. Based on the European Directive 2003/10/EC, preventive measures that must be undertaken by employers are embedded in the Dutch law. Three exposure limits and corresponding actions are defined: • Employees exposed to noise levels at or above 80 dBA should receive information and training on the risks of noise exposure, and should have access to hearing protection devices; • Employees exposed to noise levels above 85 dBA should have access to and use hearing protection devices and have the right to have their hearing checked every four years. Their employers are required to eliminate sound sources whenever reasonable practicable or implement technical or organizational measures to reduce the noise level;
Chapter 1 22 • If the noise level measured at the eardrum exceeds the level of 87 dBA when using hearing protection, direct action is required to reduce the noise level. Technical interventions Manytechnicaldevicesareavailabletofacilitatehearing.Thesecanpartiallycompensate for the listening difficulties that are associated with hearing loss. Conductive hearing loss can often be managed relatively well, but sensorineural and mixed hearing losses are much more difficult to manage (Michels et al., 2019). Fulfilling auditory tasks often remains to require increased attention, concentration, and effort for adults with hearing loss, even if technical devices are used to enhance hearing (Ohlenforst et al., 2017; Shinn-Cunningham&Best, 2008). For example, understanding speech in noise is often more difficult for adults with hearing loss – even when wearing hearing aids – compared to those with normal hearing (Cubick et al., 2018). Hearing aids Providing hearing aids is the primary intervention for adults with hearing loss (Hickson et al., 2013; Kochkin, 2009; Timmer et al., 2015). Essentially, hearing aids act to amplify sounds. A microphone detects a sound, which is processed and delivered as an acoustic signal directly into the external ear canal or through a hollow tube (Hampson, 2012). This amplification can be linear or non-linear and is most of the times non-linear (Dillon, 2008). In the case of linear amplification, all sounds of a given frequency are amplified equally irrespective of the level of the signal, or what other sounds are simultaneously present. In case of non-linear amplification, the amplification of a sound may differ between sounds with different sound levels, or when simultaneous sounds are present. To compensate for the reduced dynamic range in ears with sensorineural hearing loss and to reduce the distortion component of hearing loss, non-linear amplification is important. Earlier in this chapter, we mentioned that the range of levels that can be heard ánd tolerated is often smaller when hearing loss is present. Compression systems in hearing aids aim to adjust the dynamic range of sound levels in the environment to better match with the smaller dynamic range of an individual with hearing loss (Dillon, 2008). When compression is used, the amplification of sounds is automatically adjusted based on the level of the input signal, with higher sound
General introduction 23 levels receiving more reduced amplification (Levitt, 2001). Compression can improve the intelligibility of soft speech, by increasing the sound level. It can also make loud sounds more comfortable, by decreasing the sound level. A disadvantage of compression is that it may increase the level of soft background noise. Hearing aids are able to reduce the effects of noise to some degree (Brons et al., 2013; van den Tillaart-Haverkate et al., 2017). The aim of noise reduction programs in hearing aids is to increase listening comfort in noisy environments by amplifying the speech signal more than the noise. Therefore, the program needs to recognize and analyze the speech and noise separately which can be accomplished since the spectrum of noise differs from the spectrum of speech. In modern hearing aids, directional microphones are used. These microphones are more sensitive to sounds coming frontally than to sounds coming from other directions (Dillon, 2008). Especially in noisy environments with a close, frontal talker, the use of directional microphones can improve speech understanding (Boymans et al., 2008). Disadvantages of directional microphones can be that wanted sounds from other directions may receive insufficient amplifications and that increased internal noise can be experienced in quiet places. Also, a directional microphone is only effective for sounds that are relatively close to the person who is wearing the hearing aids. Many hearing aid features, such as compression or directionality, are useful in some, but not in all situations. The hearing aid fitting can be optimized by using multiple hearing aid programs that are tailored to specific situations. This allows for optimizing the hearing aid settings for different situations, such as situations with or without background noise. Alternative devices The aim of alternative listening devices is to improve hearing and communication outcomes in individuals with hearing loss by amplifying sounds (Maidment et al., 2016; Maidment et al., 2018). These devices can be either stand-alone products that amplify sounds – such as smartphone hearing aid applications – or assistive listening devices that provide additional features to conventional hearing aids. For example, an external microphone or a table microphone may facilitate speech understanding during meetings and wireless products may enhance making a phone call by
Chapter 1 24 connecting the hearing aid to a mobile phone. Maidment et al. (2018) conducted a systematic review and meta-analysis on the efficacy of additional listening devices. Their evidence suggests that the outcome of speech perception tests in noise improve when alternative devices are used compared to using only hearing aids or no other technical devices. However, there was no robust evidence that self-reported outcome measures also improve, including listening effort and quality of life. Hearing protectors Hearing protectors can be used to attenuate loud sounds. A first distinction can be made between ear muffs and earplugs. Ear muffs are rigid cups that completely cover the external ears (Rice & Coles, 1966). They are held in place by an adjustable headband or can be mounted in a helmet. Earplugs are often made of rubber or plastic and are designed to insert into the ear canal. Earplugs can be either disposable, generic (pre-molded), or custom-molded. A second distinction can be made between hearing protectors that provide passive versus active protection. Most hearing protectors provide passive protection. In this type of protectors, the attenuation is provided independently from the level of the sound. Passive hearing protectors have no electrical or digital components in them. Contrarily, in active hearing protectors, the attenuation depends on the level of the sound. Active hearing protectors have mechanical, electrical, or digital components in them. Some active hearing protectors can also provide extra noise reduction by offering a soft sound that is exactly the opposite of the sound wave of the noise. Lastly, some active hearing protectors can be used to communicate with – for example the office headset – or to play music. Hearing protectors attenuate sounds on average with 20 dBA (Brennan-Jones et al., 2020), but have the disadvantage of being uncomfortable to wear, especially when they are worn for a long duration. Another disadvantage of hearing protectors for individuals with hearing loss is that they may even further complicate the performance of auditory tasks (Morata et al., 2005; Smalt et al., 2020). Additional rehabilitation strategies Since technical interventions cannot fully compensate for all consequences of hearing loss, there is often a need for additional rehabilitation strategies (Cox, 2005).
General introduction 25 The framework of aural rehabilitation is therefore increasingly applied in audiology (Ferguson et al., 2019). The aim of aural rehabilitation is to reduce the difficulties of individuals with hearing loss in daily life functioning, including difficulties in work participation. This can be achieved by the provision of technical interventions, but aural rehabilitation also includes three other components – perceptual training, instruction, and counselling – that may contribute to the reduction of difficulties with performing everyday tasks of societal involvement (Boothroyd, 2007, 2017). The four components of aural rehabilitation can be provided separately or in combination. Perceptual training includes training of speech reading or auditory skills. The rationale is that speech perception performance can improve when hearing impaired individuals extract more information from the speech signal or the context. Instruction mainly focusses on how technical devices can be used properly and may include demonstrating or coaching. The focus of counselling is to help with developing effective coping behavior. Aural rehabilitation can be provided in different forms (Boothroyd, 2010). It may consist of individual training, which has the advantage that it can be tailored specifically to individual needs. However, the variation of inputs – different voices, experiences of others – is small during individual training. Alternatively, aural rehabilitation can consist of group training with a clinician, which has the advantage that the participants might benefit from the interactions with their peers. In the Netherlands, group training involving aural rehabilitation is often referred to as a communication course. These communication courses are offered by several universitymedical centers and audiological centers, and consist of approximately ten to twelve sessions that include speech reading training, instruction, and counselling. Occupational health interventions The protocol of the Dutch Board for Occupational Medicine (NVAB) ‘hearing loss and tinnitus’ provides a framework for occupational physicians on the interventions that can be provided to individuals with work functioning difficulties caused by hearing loss. Several interventions have been suggested regarding external factors. Firstly, occupational physicians can investigate what measures could optimize the acoustic environment of the workplace. For example, environmental noise can be reduced by removing technical devices that produce noise – such as the printer – from the
Chapter 1 26 workplace and room reverberation can be reduced with absorbent surfaces. Also, changing the sound of the telephone, or the sound of safety alarm systems can make them more audible. Secondly, organizational changes can be suggested to facilitate work functioning, such as working from home more often, taking more breaks, or spreading out meetings over the day. Lastly, providing information to the supervisor or colleagues can stimulate them to be more understanding and supportive. If technical interventions, aural rehabilitation, and occupational health interventions insufficiently enable job performance, changing work can be considered. Regarding the personal factors, providing information is suggested to be an important intervention for occupational physicians to provide. This includes information on hearing loss, the possible consequences of hearing loss for work functioning, options for technical interventions, communication strategies to use with colleagues, and websites where more information is provided. Additionally, the occupational physician can provide information on the possibilities for aural rehabilitation. Occupational physicians can send a referral for the interventions of interest. For example, the employee can be referred to an audiological center to start with a communication course, to a speech therapist for a training in speech reading, or to a social worker or psychologist for personal coaching. Outline of the thesis This thesis covers several aspects of professional functioning in employees with hearing loss. The following research aims are addressed: • To explore what hearing-related, personal, and environmental factors influence the difficulties of employees with hearing loss and how these factors interfere with each other; • To evaluate the effect of current rehabilitation practices measured with tools that are currently used in audiological practice; • To evaluate tests that can be used to assess the performance of hearingcritical job tasks and to describe the development of a new tool to evaluate the ability to detect auditory warning signals.
Part I Factors influencing professional functioning
Chapter 1 Factors influencing the need for recovery in employees with hearing loss: a cross-sectional study of health administrative data Hanneke E.M. van der Hoek-Snieders Monique Boymans Bas Sorgdrager Wouter A. Dreschler Adapted from: International Archives of Occupational and Environmental Health 2020, 93(8), 1023-1035
Chapter 1 32 Abstract Objective Need for recovery is a predictor of work stress and health problems, but its underlying factors are not yet well understood. We aimed to identify hearing-related, work-related, and personal factors influencing need for recovery in hearing-impaired employees. Methods We retrospectively identified hearing-impaired employees (N = 294) that were referred to the Amsterdam University Medical Center between 2004 and 2019. Routinely obtained healthcare data were used, including a survey and hearing assessments. A directed acyclic graph was constructed, revealing the hypothesized structure of factors influencing need for recovery as well as the minimal set of factors needed for multiple regression analysis. Results Four variables were included in the regression analysis. In total, 46.1 percent of the variance in need for recovery was explained by the factors ‘feeling that something should change at work’ (B = 19.01, p < 0.001), subjective listening effort (B = 1.84, p < 0.001), personal adjustments scale score (B = − 0.34, p < .001), and having a moderate/poor general health condition (B = 20.06, p < 0.001). Although degree of hearing loss was associated with subjective listening effort, the direct association between degree of hearing loss and need for recovery was not significant. Conclusions The results suggest that theway employees perceive their hearing loss and how they cope with it directly influence need for recovery, rather than their measured degree of hearing loss. Additionally, general health condition was found to be an independent factor for need for recovery.The results should be confirmed by future, longitudinal research.
Part I: Factors inflencing professional functioning 33 Introduction Hearing loss is a common occupational malady (Backenroth-Ohsako et al., 2003; May, 2000). Prevalence estimates vary from 7 to 31 percent and increase with age and exposure to noise (Hasson et al., 2010; Masterson et al., 2016; May, 2000; Nelson et al., 2005). It is estimated that 3 percent of theDutchwork force experiences difficulties in their job due to their hearing loss (Sorgdrager, 2015).These difficulties often result in greater levels of fatigue, fear, social isolation, and psychophysiological stress, caused by the fact that hearing loss goes along with increased listening effort during activities, such as communicating in background noise or localizing sounds (Hornsby & Kipp, 2016; Kramer et al., 2006; Morata et al., 2005; Ohlenforst et al., 2017; Svinndal et al., 2018). Adverse implications for work are sick leave due to mental distress, unemployment, and earlier retirement (Danermark & Gellerstedt, 2004; Hasson et al., 2011; Kramer et al., 2006; Punch, 2016). The degree of hearing loss is significantly associated with need for recovery (NFR) (Nachtegaal et al., 2009), a measure that can contribute to early identification of occupational diseases (De Croon et al., 2003; Moriguchi et al., 2010; Sluiter et al., 2003; Sluiter, 1999). NFR has been defined as the need to recuperate from work- induced fatigue, primarily experienced after a day of work ( Jansen et al., 2002; Van Veldhoven & Broersen, 2003). The degree of NFR is determined by the intensity of mental and physical work-induced fatigue and by the period required to return to a normal level of functioning. NFR can be measured with the validated Questionnaire on the Experience and Evaluation of Work (QEEW), which includes 11 dichotomous statements, such as ‘I find it hard to relax at the end of a working day’ and ‘When I get home, people should leave me alone for some time’ (Van Veldhoven & Broersen, 2003). NFR is a predictor of work stress, subjective health problems, and sick leave (De Croon et al., 2003; Sluiter et al., 2003). In line with the International Classification of Functioning, Disability and Health (ICF) (Organization, 2001), NFR has been described to be a complex construct that is influenced by disease specific, personal, and environmental factors (Gommans et al., 2015). Despite the importance of the outcome NFR both from health and economic perspectives, the studies examining NFR in patients with hearing loss are scarce. To our knowledge, three studies have been reported so far. In the cross-sectional study by Nachtegaal et al. (2009), the relationship between NFR and hearing status was
Chapter 1 34 examined in 925 normally-hearing and hearing-impaired working adults. NFR was assessed with the QEEW and hearing status with the national hearing test (Smits et al., 2006), a speech-in-noise test that was performed over the internet. Their regression analysis showed that poorer hearing was significantly associated with higher NFR. In the cross-sectional study by Juul Jensen et al. (2018), the relationship between NFR and tinnitus was examined in 32 hearing aid users of which 16 were suffering from tinnitus. NFR was assessed with a Danish translation of the QEEW and tinnitus with the Tinnitus Handicap Inventory. The authors reported that the degree of tinnitus severity was significantly associated with higher NFR. Finally, a randomized controlled trial has been reported by Gussenhoven et al. (2017) in a population of 136 hearing-impaired employees. The study evaluated the effectiveness of a vocational enablement protocol on NFR as compared to usual care for hearingimpaired employees.This protocol is amultidisciplinary programof care that consists of vocational andaudiological components, suchas an intake interview conducted by the psychologist or social worker and clinical occupational physician, the performance of pure-tone audiometry and a speech-in-noise test, and a multidisciplinary team meeting in which the technical, speech therapeutic, and psychosocial intervention options are discussed (Gussenhoven et al., 2012). The intervention of the control group consisted of any kind of another audiological revalidation. NFR had not significantly changed after 12 months follow-up, and there were no significant differences between the intervention and the control group (Gussenhoven et al., 2017). The authors concluded that NFRmay not adequately capture what is covered in the vocational enablement protocol. However, it is unclear how many employees received technical, speech therapeutic, and psychosocial interventions and thus which interventions did not influence NFR. Further, because the factors influencing NFR in hearing-impaired employees are not yet well understood, it is difficult to indicate which changes in degree of hearing loss could have an effect on NFR. Multiple studies have indicated work characteristics influencing NFR, such as the number of working hours ( Jansen et al., 2002; Verdonk et al., 2010), lack of participation in work decisions (Van Veldhoven & Broersen, 2003), and problems in the relationship with colleagues (Kiss et al., 2008; Van Veldhoven & Broersen, 2003). Highjobdemands and low job support are associatedwithhighNFRandmixed results are presented for job control (Kiss et al., 2008; Kraaijeveld et al., 2014; Sluiter et al., 2001; Sonnentag & Zijlstra, 2006; Van der Hulst et al., 2006). Job demands
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