Introduction
Disabling hearing impairment is the world's most common disability, thought to affect approximately 4 per cent of the global population.Reference Mackenzie and Smith1 Traditionally, hearing levels measured by pure tone audiometry have been used to define and quantify hearing loss for epidemiological purposes. In this way, disabling hearing impairment in adults is defined by the World Health Organization (WHO) as a ‘permanent unaided pure-tone hearing threshold level for the better ear of 41 dB or greater averaged over the frequencies of 0.5, 1, 2 and 4 kHz’.Reference Pascolini and Smith2
The effects of disabling hearing loss on sufferers' quality of life (QoL) can be profound.Reference Fagan3 In children, adequate hearing is needed for the development of speech and language. In adults, those with hearing loss can have difficulty securing employment. Hogan and colleaguesReference Hogan, O'Loughlin, David and Kendig4 found that people with hearing loss were less likely to be found in highly skilled jobs and were over-represented among low-income earners. As the life expectancy of many populations increases, the prevalence of deafness due to age-related cochlear degeneration, with its problems of social isolation, is forecast to greatly increase.5
Chronic suppurative otitis media is a major cause of disabling hearing impairment, particularly in developing countries.Reference Rupa, Jacob and Joseph6, Reference Youngs, Weir, Tharu, Bohara and Bahadur7 In this condition, additional factors other than the magnitude of hearing loss augment the negative effect on QoL. These factors include chronic ear discharge, discomfort and disturbance of balance. In addition, in some cases complications such as facial paralysis and intracranial sepsis can have devastating consequences.
Formal studies of QoL in hearing impairment have suggested that there is often poor correlation between pure tone audiometry and self-reported outcome measures. As such, the consequences of hearing loss as regards lower QoL cannot be predicted from audiometric data alone.Reference Hallberg, Hallberg and Kramer8
This article reviews the literature on QoL assessment in deafness, with particular emphasis on chronic suppurative otitis media.
Functional health status or quality of life?
Many of the measurement instruments discussed in this article actually measure functional health status as opposed to true QoL. Functional health status and QoL are often regarded as synonymous, but their definitions differ slightly. Quality of life, in the context of health, describes the way in which a person's illness affects their physical, social and emotional functioning.Reference Bradlyn, Ritchey, Harris, Moore, O'Brien and Parsons9 It should also take into account the personal values and preferences of the individual with regards to their health.Reference Gill and Feinstein10 Functional health status reflects the way in which a person's illness affects their daily functioning and activities.Reference Spieth and Harris11 Importantly, this differs from QoL in that it is an objective measure which does not include the patient's subjective evaluation of the effect their illness has on their life.Reference Richards and Hemstreet12
Quality of life measures for deafness and chronic otitis media
Quality of life and functional health status measures fall into three different categories: utility, generic and disease-specific.
Utility measures
Utility measures allow overall QoL or functional health status to be measured in the context of the total population. Scores range from 0 (dead) to 1 (perfect health). Utility measures can be applied to anybody and are commonly used for cost–benefit analyses of different treatments or procedures.Reference Furlong, Feeny, Torrance and Barr13 They are an effective means of comparing the QoL or functional health status of an individual to that of the whole population.
One type of utility measure is the Health Utility Index, three forms of which have been developed.Reference Furlong, Feeny, Torrance and Barr13 The Health Utility Index versions 3 and 2 have six key attributes: sensation and communication (i.e. vision, hearing and speech), happiness, self-care, pain or discomfort, learning and school ability, and physical activity ability.Reference Furlong, Feeny, Torrance and Barr13 The Health Utility Indexes are reliable, sensitive and valid,Reference Furlong, Feeny, Torrance and Barr13 and have previously been used in the context of hearing impairment in both adultsReference Francis, Chee, Yeagle, Cheng and Niparko14 and children.Reference de Wolf, Hol, Mylanus, Sink and Cremers15
The EuroQol-5D (formerly EuroQoL) is another utility measure, produced by a pan-European team. It is composed of six domains: mobility, self-care, main activity, social relationships, pain and mood.16 This instrument was one of three utility measures of QoL compared by Barton et al. Reference Barton, Bankart and Davis17 in the context of hearing impairment; the other two were the Health Utility Index 3 and the Short Form 6D (a derivative of the Short Form 36). Utility scores were calculated for new patients referred to audiology clinics in the UK. The scores differed significantly between all three instruments, leading the authors to conclude that comparing utility scores obtained from different scales is sub-optimal. Whilst the EuroQol-5D was less sensitive to hearing impairment, it was considered a useful scale because it had the practical bonus of brevity, leading to a high response rate in Barton and colleagues' study. Additionally, improvement on its depression subscale had previously been shown to be a good surrogate for improvement of hearing impairment.Reference Joore, Brunenberg, Chenault and Anteunis18
The Assessment of Quality of Life tool is a multi-attribute utility instrument developed using ‘state-of-the-art psychometric procedures’.Reference Hawthorne, Richardson and Osborne19 The instrument measures five domains – illness, physical senses, psychological well-being, independent living and social relationships – and is based on the WHO's definition of health.Reference Hawthorne, Richardson and Osborne19 When compared with four other utility instruments, including Health Utility Index 3 and a derivative of the Short Form 36, evidence suggested that the Assessment of Quality of Life tool was more responsive.Reference Hawthorne, Richardson and Day20 Additionally, it has previously been used in the domain of hearing-related QoL and has been described as ‘well suited’ to this task.Reference Hawthorne, Hogan, Giles, Stewart, Kethel and White21
Generic measures
Generic QoL or functional health status measures can be used to evaluate the impact of hearing impairment. Generic scales are useful because they measure QoL or functional health status across a broad range of conditions and populations. In this way, they can be used to provide a normative score for the population at large, which is useful for comparison. However, they may be less sensitive to changes in QoL or functional health status involving specific conditions; in addition, their generality may mean that they contain questions which are not relevant to the conditions of interest.Reference Patrick and Deyo22
The Medical Outcome Study Short Form 3623 (also termed ‘SF-36’) is a commonly used generic instrument which measures health status across eight domains: physical functioning, physical role functioning, bodily pain, social functioning, mental health, emotional role limitations, vitality and general health perceptions.Reference Ware and Sherbourne23 This tool has previously been used to evaluate QoL in individuals with hearing loss. Severity of hearing loss, as determined by pure tone audiometry, was significantly associated with decreased QoL in both the mental and physical summary scores of the tool.Reference Dalton, Cruickshanks, Klein, Klein, Wiley and Nondahl24 However, in a study involving long-term follow up of post-lingually deaf adults, the Medical Outcome Study Short Form 36 performed inconsistently and was therefore not recommended as the primary generic instrument for assessing QoL in hearing impaired patients, due to poor sensitivity.Reference Damen, Beynon, Krabbe, Mulder and Mylanus25 Other studies support this assertion that the Medical Outcome Study Short Form 36 and other generic measures are not sensitive enough to accurately assess QoL change due to hearing impairment.Reference Bess26 Some have suggested that this is because generic questionnaires such as the Medical Outcome Study Short Form 36 are designed to assess chronic disease and to focus more on physical domain issues such as mobility problems.Reference Bess26 The Short Form 12 is a shortened version of the Medical Outcome Study Short Form 36, which successfully replicates the summary scores of its longer counterpart.Reference Ware, Kosinski and Keller27
The TNO-AZL Infant Quality of Life (also termed ‘TAIQOL’) scale is a generalised, infant-specific measure of QoL. It has 46 items assessing 12 domains such as appetite, social behaviour and communication.Reference Brouwer, Schilder, van Stel, Rovers, Veenhoven and Grobbee28 Brouwer et al. Reference Brouwer, Schilder, van Stel, Rovers, Veenhoven and Grobbee28 found that the TNO-AZL Infant Quality of Life scale had poor discriminant validity in children with recurrent acute otitis media when distinguishing those who rarely suffered otitis media from those in whom it was common.Reference Brouwer, Schilder, van Stel, Rovers, Veenhoven and Grobbee28 The same paper also reported that the TNO-AZL Infant Quality of Life scale had poor sensitivity to change. Despite these drawbacks, Rovers et al. Reference Rovers, Krabbe, Straatman, Ingels, van der Wilt and Zielhuis29 used this scale to measure QoL in children with otitis media with effusion. This study also used another generalised instrument, the Erickson scale, to measure parent–child interaction as an indicator of QoL.
The Glasgow Health Status Inventory is a generic measure which assesses QoL and which has been used for a range of ENT conditions.30 This tool is complemented by the Glasgow Benefit Inventory, which assesses QoL in relation to a temporal event, in most cases an ENT surgical intervention.30 The Glasgow Benefit Inventory is a sensitive measureReference Robinson, Gatehouse and Browning31 and has been used successfully to assess QoL change following a wide range of ENT procedures, indicating its reliability.Reference Salhab, Matai and Salam32 Both the Glasgow Health Status Inventory and the Glasgow Benefit Inventory have 18 questions in total, comprising three subscales: generic, social support and physical health.
However, using psychometric procedures the Glasgow Health Status Inventory has been successfully reduced to an 11-item instrument, the Hearing Participation Scale.Reference Hawthorne and Hogan33 This abbreviated version asks questions relating to self esteem, social handicap and hearing handicap.Reference Hawthorne and Hogan33 Its correlation with the Glasgow Health Status Inventory is 0.95,Reference Hawthorne and Hogan33 and it therefore offers a reliable alternative. The Hearing Participation Scale is at least as valid, reliable and sensitive as its longer predecessor.Reference Hawthorne and Hogan33
Disease-specific measures for otitis media
Disease-specific measures are instruments specifically designed to produce QoL or functional health status data for an individual disease. This makes them more sensitive than generic measures. However, a normal population baseline cannot be calculated for comparison because disease-specific questionnaires cannot be answered unless the subject has the disease in question.
There are a number of instruments used to assess the QoL or functional health status of patients with otitis media. These include the Otitis Media Clinical Severity Index,Reference Alsarraf, Jung, Perkins, Crowley and Gates34 a 10-item instrument focussing on 2 domains: physical and emotional. It is designed to be administered by a doctor and to measure functional health status in children aged one to three years.Reference Alsarraf, Jung, Perkins, Crowley and Gates34 This instrument has been found to be responsive, to measure the severity of otitis media reliably, to have high discriminant validity (i.e. the ability to discriminate between individuals with and without ear disease) and to be internally consistent.Reference Alsarraf, Jung, Perkins, Crowley and Gates34
The Otitis Media Functional Status QuestionnaireReference Alsarraf, Jung, Perkins, Crowley and Gates34 is also designed for children aged between one and three years. It is administered by the child's parent or carer and comprises 14 items covering all functional domains: physical, emotional and social. It is responsive, reliable, valid, internally consistent and has good discriminant validity.Reference Alsarraf, Jung, Perkins, Crowley and Gates34 In a further study involving 383 children with recurrent acute otitis media, which aimed to determine the reliability and validity of various questionnaires assessing QoL and functional health status, the Otitis Media Functional Status Questionnaire was found to be internally consistent and reliable in terms of test–retest scores.Reference Brouwer, Schilder, van Stel, Rovers, Veenhoven and Grobbee28
The Otitis Media DiaryReference Alsarraf, Jung, Perkins, Crowley and Gates34 is another instrument designed for children aged one to three years, which measures functional health status. It consists of a single scale with three items. It has good discriminant validity and high internal consistency, and is responsive, reliable and valid.Reference Alsarraf, Jung, Perkins, Crowley and Gates34
The Otitis Media 6-item survey (also termed ‘OM-6’) is an instrument which measures functional health status. It addresses the physical, emotional, social and family aspects of well-being. In a large review of functional health status and QoL instruments used to assess otitis media in children, the Otitis Media 6-item survey was found to be the best measure of functional health status.Reference Brouwer, Maille, Rovers, Grobbee, Sanders and Schilder35 It has high test–retest reliability and construct validity, and is reliable and responsive.Reference Rosenfeld, Goldsmith, Tetlus and Balzano36
The Otitis Media Outcome 22 toolReference Richards and Giannoni37 is a 22-question outcomes measure based on the smaller Otitis Media 6-item survey, a responsive, validated and reliable QoL score.Reference Rosenfeld, Goldsmith, Tetlus and Balzano36, Reference Rosenfeld, Bhaya, Bower, Brookhouser, Casselbrant and Chan38 The Otitis Media Outcome 22 tool has been administered before and after bilateral myringotomy and tympanostomy tube placement in order to assess the QoL outcomes of surgical intervention for otitis media with effusion.Reference Korsten-Meijer, Wit and Albers39 It has been shown to be valid and responsive. As a general point, it is important to remember that assessing QoL can be difficult in many otitis media patients because a large proportion are young children and therefore their parent or carer must answer on their behalf.
In a large review of questionnaires designed to measure QoL or functional health status in children with chronic otitis media, Timmerman et al. Reference Timmerman, Meesters, Speyer and Anteunis40 found that the Otitis Media 8-30 (also termed ‘OM8-30’), Otitis Media Outcome 22 and Otitis Media 6-item surveys provided the best picture of functional health status in this patient group. The latter two surveys are discussed above. The Otitis Media 8-30 surveyReference Haggard, Smith, Rosenfeld and Bluestone41 is a 32-item instrument which assesses functional health status and is completed by the parent or carer. It is designed for children aged between three and eight years with chronic otitis media with effusion, and has been found to be valid, consistent and reliable.Reference Timmerman, Meesters, Speyer and Anteunis40
The Speech, Spatial and Qualities of Hearing scale (also termed ‘SSQ’) is not specific for otitis media but can be used to assess hearing loss in this condition. It measures hearing impairment across a wide range of domains. Its authors state that it ‘shows promise as an instrument for assessing interventions’ and that it addresses ‘novel and significant dimensions of everyday hearing’ such as listening to simultaneous speech sources and listening to musical instruments.Reference Gatehouse and Noble42 As a result of these features, it performed well when assessing the degree of handicap in patients with symmetrical versus asymmetrical hearing loss,Reference Noble and Gatehouse43 and when assessing the effect of bilateral versus unilateral hearing aids. It has also been successfully used to evaluate the benefit of cochlear implantation.Reference Noble, Tyler, Dunn and Bhullar44
Outcome measures for tympanoplasty surgery
In the field of chronic suppurative otitis media, QoL instruments have been principally utilised to assess the outcome of reconstructive middle-ear surgery.
The (modified) Amsterdam Inventory of Auditory Disability and Handicap is a self-administered, 30-item instrument which is reliable and valid.Reference Meijer, Wit, TenVergert, Albers and Muller Kobold45 Korsten-Meijer et al. Reference Korsten-Meijer, Wit and Albers39 used this tool to compare the relationship between perceived auditory disability and audiometry data collected before and after tympanoplasty. A small improvement in hearing following tympanoplasty was found to be complemented by a small improvement in (modified) Amsterdam Inventory of Auditory Disability and Handicap score, although the latter was below the level required to indicate ‘true’ change for most patients. However, there was a significant relationship between audiometric improvement and improvement in perceived disability post-surgery. Korsten-Meijer et al. concluded that perceived disability can be affected by minor hearing losses, and that the amount of hearing improvement following surgery is the strongest factor influencing perceived disability, rather than achievement of a specific hearing level per se. Additionally, these authors found that adequate hearing levels bilaterally were required for patient satisfaction in the majority of cases.
However, this latter finding has been contradicted by results from studies using the Glasgow Benefit Inventory. BrowningReference Browning46 used this instrument as an outcome measure following tympanoplasty surgery, and found that the greatest benefit was reported by those patients who had a bilateral but asymmetrical hearing impairment pre-operatively, and who post-operatively had a unilateral normal ear but retained an asymmetrical hearing threshold. Browning's Glasgow Benefit Inventory findings did agree, however, with Korsten-Meijer and colleagues' observationReference Korsten-Meijer, Wit and Albers39 that patient satisfaction correlated with the magnitude of post-operative hearing improvement rather than the achievement of a specific hearing level. This conclusion forms part of the ‘Glasgow Rule of Thumb’ relating to patient benefit following surgery.Reference Browning46
The Chronic Otitis Media Outcome Test 15 is a 15-item, disease-specific QoL measure for chronic otitis media. It is reliable, valid and sensitive.Reference Baumann, Kurpiers, Plinkert and Praetorius47 Baumann et al. Reference Baumann, Gerendas, Plinkert and Praetorius48 used this tool, together with the Medical Outcome Study Short Form 36 (a generic measure), to assess QoL changes following tympanoplasty for chronic otitis media. They reported that the Medical Outcome Study Short Form 36 did not detect a change in QoL following surgery, suggesting poor sensitivity as an outcome measure in this setting. However, the Chronic Otitis Media Outcome Test 15 (hearing function subscale) detected improved QoL following tympanoplasty, which was related to changes in audiometry data, thus illustrating the effectiveness of this latter tool as a QoL measure in chronic otitis media.
The Chronic Ear Survey is a disease-specific QoL instrument designed specifically for chronic otitis media, and assesses the effect of treatment on QoL. It is reliable and valid, with moderate sensitivity,Reference Wang, Nadol, Merchant, Austin and Gliklich49 although some believe it poorly reports the QoL impact of functional and psychological problems resulting from ear disease.Reference Baumann, Gerendas, Plinkert and Praetorius48 Nadol et al. Reference Nadol, Staecker and Gliklich50 conducted a prospective assessment of a group of patients pre- and post-tympanoplasty, and found the Chronic Ear Survey to be a reliable, valid and accurate outcome measure in this setting.
The Hearing Satisfaction Scale is a 13-item instrument which is reliable, valid and sensitive.Reference Stewart, Jenkins, Coker, Jerger and Loiselle51 It was developed specifically to assess functional status in patients with conductive hearing loss. It has been used successfully to assess functional status following tympanoplasty.Reference Stewart, Coker, Jenkins, Manolidis and Bautista52
Quality of life measures for hearing impairment in the developing world
There is little published research focussing specifically on QoL or functional health status measures appropriate for hearing impaired individuals in a developing world context. The International Outcome Inventory for Hearing Aids was designed as an outcome measure of audiological rehabilitation which would be applicable to patients from different countries and varying socioeconomic and cultural backgrounds. It has been translated into over 20 languages,Reference Cox, Stephens and Kramer53 and has been used to evaluate the success of hearing aid use in Nigeria,Reference Olusanya54 China,Reference Liu, Zhang, Liu, Chen, Han and Zhang55 South AfricaReference Pienaar, Stearn and Swanepoel56 and elsewhere.
The Client-Oriented Scale of Improvement tool and the Profile of Hearing Aid Performance – Chinese version instrument have both been used to evaluate the effectiveness of affordable hearing aids in hearing impaired adults in China.Reference McPherson and Wong57 The Chronic Ear Survey, discussed above, has also been translated into Chinese and used effectively.Reference Wang, Chu, Liang, Tai and Gliklich58 There is interest in the development of internationally applicable QoL and/or functional health status measures of general hearing impairment.Reference Danermark, Cieza, Gangé, Gimigliano, Granberg and Hickson59
Developing effective QoL measures of hearing impairment in developing world patients is important, because many of the existing QoL or functional health status instruments are not immediately applicable to a developing world setting. For example, the Glasgow Benefit Inventory and Glasgow Health Status Inventory include items relating to frequency of visits to a family doctor; this item is not applicable to countries with poorly developed healthcare systems, where family physicians may not be available or are far too expensive for most citizens to access.
Conclusion
There are a number of measures available to assess the impact of hearing impairment on QoL. The great advantage of generic measures such as the Medical Outcome Study Short Form 36 is that they can be used to compare different diseases and thus can be useful in resource allocation and general burden of disease studies. Their disadvantage is that they are not disease-specific and can therefore under-estimate the effect of a particular disease on QoL. Disease-specific measures are more sensitive, and a number of these have been shown to be useful in hearing impaired individuals. Although quantification of hearing loss by pure tone audiometry is essential, this assessment does not always correlate with measures of QoL. In chronic otitis media, other factors (such as discharge) can create an additional disease burden over and above that imposed by hearing impairment. In developing world settings, assessment of QoL is particularly important and presents unique challenges. Further research in this area is needed.
