Introduction and rationale
Children have very specific communicative needs because of their unique perception abilities and the necessity for development of speech and language skills; fitting hearing aids to children poses a unique challenge to both clinicians and manufacturers of such devices. Even small age differences in children can result in significant physiological and perceptual variations not typically encountered in adults 1.
Hearing aids are no longer devices for simply amplifying sound. The introduction of digital technology in hearing aids has brought about substantial changes not only in design but also in basic function. Hearing aid technology has progressed considerably over the past 10 years. The introduction of digital signal processing into hearing aids in 1996 allowed advanced signal processing algorithms to be implemented. In 2005, 93% of the hearing aids sold in the US had digital signal processing in them. Over half of the hearing aids prescribed include directional microphones, providing verifiable improvements to speech understanding in noise 2.
The measurement of outcomes in audiology has received considerable attention in recent years 3–5, because of the need to show the efficacy of treatment for consumers. Outcomes measurement allows audiologists to show the benefits that are gained from a hearing aid, as well as to determine the costs of gaining those benefits.
Outcomes are often defined simply as measurable differences resulting from treatment 6; although the definition may be simple, the practice is more complex for several reasons. The first relates to a need to determine what ‘differences’ we should be measuring. That is, are we interested in examining subjective (reported) hearing aid satisfaction, objective (measured) benefit, and/or hours of hearing aid use? Another reason for the complexity is that once we have decided what to measure, we need to select from a plethora of currently available tools 3,4,7.
Humes 8, for instance, showed that hearing aid outcome is a multidimensional construct requiring the evaluation of multiple factors, including aided speech recognition, speech-recognition benefit, subjective sound quality, subjective benefit and satisfaction, and hearing aid use.
The earliest approaches for evaluating the benefits of hearing aids were comparison methods where patient performance with two or three analog hearing aids was evaluated using traditional word recognition tests, such as NU-6 and CID W-22 monosyllabic word lists. Such tests were administered to the patient in the sound field and speech recognition thresholds and word recognition scores were recorded under unaided and aided conditions to determine whether the hearing aids provided benefit. Unfortunately, these speech perception measures of hearing aid benefits have long been criticized for not being sensitive enough to provide the information necessary to determine and define specific hearing aid benefits 9,10. Many of these tests are considered insensitive for objective and accurate measurement of aspects of listeners’ speech perception abilities as a reflection of their performance in realistic listening situations 10.
Given the lack of sensitivity of early speech perception tests, other approaches to hearing aid benefit were incorporated in the 1980s. With the advent of computerized probe microphone real-ear technology, the challenge of developing scientifically based methods of selecting, evaluating, and fitting hearing aids became much easier 11. These objective probe-microphone measurements were used to verify that the prescribed real-ear gain of the hearing aid met the desired targets. This objective measure is critical for providing verification data that determine how the real ear is performing with the hearing aid. The good news is that objective measures of insertion gain provide excellent information about the amount of real-ear gain delivered by the hearing aid; the bad news is that they do not necessarily provide any information about the patient’s speech-understanding ability in realistic listening situations using that hearing aid.
Audiological professionals could use a questionnaire to estimate the extent of the overall benefit gained from hearing aids. Questionnaires can be a very important part of the audiologist’s test battery. Numerous self-assessment questionnaires are commercially available, and they may be used to examine the social, emotional, or physical aspects of hearing loss. They are also useful as a before-and-after measure of hearing aid benefit 12.
In South Sinai, a remote area in Egypt that lacks the availability of medical methods of assessment and management of hearing impairment, a simplified but effective way that proved itself over time emerged: administration of a questionnaire through feedback from parents and care givers. A questionnaire was used to evaluate the outcomes of fitting of new digital hearing aids instead of the old analogues ones to a number of experienced hearing aid children users in South Sinai.
This hearing aid, Unitron 360, is an advanced digital hearing solution especially tailored for individuals with severe to profound hearing loss that was supplied to those children through a project of improving health and nutrition of children living at South Sinai, funded by the European Union, through the South Sinai Regional Development Program. The work was mediated by the National Research Center with the collaboration of the Hearing and Speech Institute in Egypt.
Aims of work
- To determine the efficacy of the subjective methods in evaluating the outcome of a hearing aid.
- To determine the effect of shifting from analogue to digital hearing aids through assessment of subjective satisfaction.
Patients and methods
Thirty hearing-impaired children and adolescents participated in the study (19 males and 11 females), ranging in age between 4 and 18 years. Children were inhabitants of South Sinai from four areas: Abu Redeis (43.3%), Newibaa (33.3%), Ras Sidre (13.3), and El-Tur (10.0%). They all were hearing-impaired children who were fitted previously with analogue hearing aids.
They were refitted with the hearing aid Unitron 360 (Unitron Hearing GmbH, Kitchener, Ontario, Canada), which is an advanced digital hearing solution especially tailored for individuals with severe to profound hearing loss. Unitron 360 is a super power hearing aid purposely built to allow patients to achieve all the power they need without compromising on advanced features, sound quality, or everyday reliability. This hearing aid has many advantages. It has four-channel signal processing (where the frequency range of the hearing aid is divided into four regions, making its adjustment more accurate), with up to three manual programs for different listening situations, antishock, noise reduction, easy direct audio input (making the hearing aid suitable for group teaching), volume control, and easy telecoil for group teaching.
All children were supplied with this hearing aid through an expanded health project. A consent of parents was obtained for participation in this work. All children were evaluated before fitting with the digital hearing aids (Unitron 360) and then re-evaluated 4 months later.
All children fulfilled the following criteria:
- The degree of hearing loss was within the level target of the supplied hearing aid (which could be corrected with the hearing aids supplied).
- All children were experienced hearing aid users (all were using analogue hearing aids), at least 8 months’ use; thus, the parents and the child could determine the benefits of this digital hearing aid.
At the initial assessment, each child was subjected to a complete audiological evaluation including assessment of history, an otoscopic examination, pure tone audiometry, tympanometry, and determination of acoustic reflex thresholds.
A self-assessment questionnaire was provided to parents to fill by themselves in order to evaluate subjective satisfaction of their analogue hearing aids. Arabic translation of the WILSI questionnaire for children was provided. The questionnaire was divided into three categories (16 questions).
- Category I: For the child’s response to environmental sounds (five questions).
- Category II: For the child’s response to speech sounds (six questions).
- Category III: For speech production (five questions).
The evaluation was carried out on a scale that ranged from better, no change, or worse.
At the end of the 4-month period, the parents were asked to fill another copy of the Arabic translation of the WILSI questionnaire for satisfaction and performance with the digital hearing aid supplied (Unitron 360).
Table 1 shows the results of the present work. The improvement with the use of a digital hearing aid was determined by three groups of questions: category I for the child’s response to environmental sounds, category II for response to speech sounds, and category III for speech production.
The improvement in category 2 was the most obvious, where five out of six questions showed improvement higher than 63%, whereas those with a worse response did not exceed 10%.
The improvement in category 1 was less than that of category 2, and yet, the worse response was minimal (less than 7% for all questions). The improvement in category 3 was the least, ranging between 46 and 60%. This observation is expected as category 3 reflects speech production; this response requires a longer period to evaluate.
It is critically important for an audiologist to determine the outcomes of hearing aid fitting by evaluating treatment efficacy in three different areas: (a) Treatment effectiveness: do the hearing aids improve speech intelligibility under quiet and noise conditions or do they restore normal loudness perception? (b) Treatment efficiency: are certain hearing aids or hearing aid setting/adjustments better than others for improving speech understanding? (c) Treatment effects: does the use of hearing aids improve the patients’ social or emotional well-being or his/her overall quality of life? 13.
There are generally two different philosophies on how to document outcomes from the hearing aid fitting process: those that focus on subjective outcomes (i.e. using questionnaires and interviews to document the opinions and attitudes of the patient) and those that focus on objective outcomes (i.e. using empirical data to verify improvements in performance) 14.
As Mendel 15 stated that subjective outcomes seem to have become the ‘gold standard’ for the evaluation of hearing aid benefits, our work focused on assessing the effect of shifting from analogue to digital hearing aids through subjective satisfaction using the Arabic version of the WILSI questionnaire. Our study was carried out on children from different cities in South Sinai (Abu Redeis, Ras Sudr, Newbaa, and El-Tur).
The analysis of the results of the self-assessment questionnaire WLSI was a very important step in the comparison between the newly fitted digital hearing aid and the previous analogue ones. As shown in Table 1, when analyzing the response of children to environmental sounds (category I), a high number of children showed a better response to the hearing aid on shifting from analogue to digital. Taking question no. 4 as an example, we found that 23 children (76.67%) showed marked improvement in recognizing sounds coming from the back as reported by parents, whereas two children (6.67%) reacted negatively to the new hearing aid. The parents of five children (16.67%) reported that they did not notice any difference. The responses of children to environmental sounds (category 1) are presented in Table 1. The questionnaire used was tailored for children. Sometimes, parents had to be taught on the use of the test, and we retested some of the children to ensure accuracy.
On reviewing the results of the three studied categories, we found that for almost all results, the greatest number of children showed a better response. The least number showed a worse response and no more than 11 cases (63.67%) as maximum showed no response. As a whole, the results of the questionnaire showed a significant improvement with a shift to digital hearing aid use in the three categories.
The improvement detected in the response to speech sounds, which is the most important category, as it will lead to speech production, which is our aim, is because of the advantage of digital technology in the application of output shaping through the use of more than one channel (four channels in Unitron 360). By shaping the output across each channel, one can maintain most intensity cues of speech and therefore maximize residual hearing, as children use intensity cues to discriminate phonemes more than adults 16.
The improvement in category 3 was the least, ranging between 46 and 60%. This observation is expected as category 3 reflects speech production; this response requires a longer period to evaluate.
The poor response to the shift from the use of analogue to digital hearing aids found in some of our tested children in the three categories was expected as the child may react to increase gain for soft sounds by complaining that the hearing aid is noisy in a quiet environment, or a decrease in output for high input sounds by complaining that the hearing aid is too soft or not powerful enough; this is in agreement with the results of Donald and Randi 17, who proved that most children adapt to this change in signal processing gradually as they gain the advantage of increased audibility and decreased discomfort of loud sounds. Approximately10 children (33.33%) showed almost no change; this may be attributed to the short span of the usage of a digital hearing aid.
Researches have also shown that expectations for hearing aid outcomes can affect individuals’ willingness to acquire a hearing aid, their satisfaction with the aids 18, and the frequency with which they wear the hearing aids 19. A mismatch between expectations and actual outcome that results in disappointment will likely lead to decreased use of hearing aids. However, the relationship between expectations and outcome has been shown by some studies to change over time. Saunders and Jutai 20 found that the longer individuals wear hearing aids, the more positive their reported outcome, and that the prefitting expectations of nonhearing aid users are higher than the satisfaction scores of hearing aid users with 6 weeks to 1 year of experience, but are similar to those of individuals who have worn hearing aids for longer than 1 year. These findings have important clinical implications in terms of counseling of individuals with newly fitted hearing aids to determine the benefits of the new hearing aid and the 30-day hearing aid trial period. Although presumably audiologists explain to their patients that ‘it takes time to get used to wearing hearing aids,’ explaining that improvements in perceived benefit continue throughout the first year of use is important.
Subjective impression of parents could be taken as an indication of a proper hearing aid fitting process.
A shift from analogue to digital hearing aids is beneficial for children.
- Special care should be offered to remote areas in order to improve the level of assessment and proper management of children in these areas.
- Proper counseling and continuous follow-up, together with increasing social and educational levels in remote areas, will provide better hearing aid response in an informative and educational manner for parents.
- Subjective methods in the evaluation of the outcome of a hearing aid are effective and digital hearing aids are superior to analogue aids. A shift is valuable if financial support is available.
This document has been produced with the financial assistance of EU. The contents of the document are the sole responsibility of Professor Yamamah, and can under no circumstances be considered as reflecting the position of EU.
Conflicts of interest
There are no conflicts of interest.
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