What does hearing-aid use tell us?

Is more always better when it comes to hearing-aid use? Hearing-aid use is typically seen as an indicator of success: the more people use their hearing aids, the better. Three Eriksholm studies investigate this assumption.

The views of both users and dispensers regarding optimal hearing-aid use are being assessed. Differences between self-reported hearing-aid use time and objectively measured hearing-aid use time are also being investigated. 

What is optimal hearing-aid use? Focus groups with hearing-aid clients and dispensers

This focus group study was initiated in 2011 and completed in 2012. Participants in this study were 17 adults with hearing impairment who own hearing aids and 13 hearing-aid dispensers. Participants were recruited in the Copenhagen area (Denmark) and in the Manchester area (UK). Each participant took part in one of four focus group sessions, during which they described their views of what optimal hearing-aid use is (definition) and what contributes to it. 

A content analysis of the focus group transcripts was completed to extract the main definitions and determinants of optimal hearing-aid use.

Both clients and hearing-aid dispensers described optimal hearing-aid use as being frequent and regular and driven by the individual needs of the clients. When describing determinants of optimal hearing-aid use, both clients and dispensers mentioned the role of the client, the role of the dispenser, and the role of the hearing aid. They both highlighted the importance of client access to information. However, how clients and dispensers described the influence of these determinants varied somewhat.

Clients emphasised the role of the hearing aid in achieving optimal hearing- aid use. From a client perspective, hearing aids which performed well and which had relevant features were most central. In contrast, dispensers emphasised the role of a good client-dispenser relationship in achieving optimal hearing-aid use. From the dispensers’ perspective, dispensers who were able to understand the needs of the clients and to instruct clients appropriately were most central. It is commendable that dispensers acknowledge the importance of the client-dispenser relationship, but given clients’ focus on hearing aids, dispensers might wish to describe more explicitly to their clients how their intervention can extend beyond provision of the optimal hearing aid.

Differences between self-reported hearing-aid use and objectively measured hearing-aid use (data logging)

Previous studies found that, on average, users over-report their daily amount of hearing-aid use compared to objective measures such as data-logging. However, the reasons for this are unclear. This study assessed data-logged and self-reported amount of hearing-aid use in a clinical sample of hearing-aid users. It identified predictors of data-logged hearing-aid use, self-reported hearing-aid use, and hearing-aid use over-report. In total, this observational study recruited 228 adult hearing-aid users from 22 private hearing clinics in the Netherlands and in Denmark. Most participants were over the age of 65 and retired, were fitted binaurally, and had financially contributed to the cost of their hearing aids.

Participants had on average a mild-to-severe sloping bilateral hearing impairment. Participants completed a purposefully designed questionnaire regarding hearing-aid use and the International Outcome Inventory – Hearing Aids (IOI-HA). Dispensers collected data-logging information and audiometric results. Multiple linear regression was used to identify predictors of data-logged hearing-aid use, self-reported hearing-aid use, and hearing-aid use over-report when controlling for covariates. Data-logging showed on average 10.5 hours of hearing-aid use, whilst participants reported on average 11.8 hours of daily hearing-aid use. The average over-report of daily hearing-aid use was 1.2 (1 hour and 11 minutes). Cluster analysis identified two main data-logged patterns: “Regular”, where hearing aids are typically switched on for between 12 and 20 hours before their user switches them off (57% of the sample) and “On-off”, where hearing aids are typically switched on for shorter periods of time (43% of the sample). In terms of self-report, 77% of the sample described their hearing aid use to be the same every day.

Participants for whom data-logging showed an “On-off” pattern or who reported their hearing aid use to be different from day to day had significantly fewer data-logged and self-reported hours of hearing aid use. Having an “On-off” data-logging pattern or describing hearing aid use as the same every day was associated with a significantly greater hearing aid use over-report.

Data-logged and self-reported use patterns significantly predicted data-logged hearing-aid use, self-reported hearing-aid use, and over-report when controlling for covariates. The results point to patterns of hearing-aid use as being at least as important a concept as amount of hearing-aid use. Dispensers should consider discussing not only the “how much”, but also the “how” of hearing-aid use with their clients.

Tool for hearing-aid use goal setting and assessment

This study, which is the third and final research project on the topic of hearing-aid use, was initiated in 2012 and is ongoing. The purpose of this study is to develop and test a tool that facilitates hearing-aid use goal setting and assessment in a clinical audiological setting. The tool incorporates the knowledge gained from the two previous studies as it takes into account the individual needs of the client and patterns of hearing-aid use. The tool was developed at the Eriksholm Research Centre during the second half of 2012 in an iterative process integrating input from both internal and external audiologists, designers, and anthropologists. The tool has been pilot tested with audiologists (n=4) and adults with hearing impairment taking part in a hearing aid fitting (n=12) in Denmark. The tool is now being tested in a larger population of adults with hearing impairment attending audiology appointments in Canada and in the United Kingdom.

We hope that the results can inform clinical practice surrounding hearing-aid use, for example when it comes to assessment methods. The findings could also result in fitting software which better facilitates dispensers’ use of data-logging with clients 

Further reading

Laplante-Lévesque A, Jensen LD, Dawes P, Nielsen, C (2013). Optimal hearing aid use: Focus groups with hearing aid clients and audiologists. Ear & Hearing, 34(2), p. 193-202.

Laplante-Lévesque A, Nielsen C, Jensen LD, Naylor G. (In Press). Patterns of hearing aid usage predict hearing aid use amount (data-logged and self-reported) and over-report. Journal of the American Academy of Audiology

Early multi-channel, non-linear prescription: MultiFocus

After Villchur’s seminal publication on recruitment in sensorineural hearing loss and its compensation via multi-channel compression³, many laboratories (Eriksholm included) began to research the idea. A long series of in-house studies progressed from rack equipment to configurable, wearable prototypes.

Comparing performance and preference for various combinations of compression action in a two-channel device, it was concluded that the best arrangement involved fast-acting compression with a low compression threshold in the low-frequency (below 1500 Hz) channel, and linear gain in the high frequencies. This was an unexpected result. Even more surprising was the conclusion that with this hearing aid, most users did not need to adjust the volume control. The final outcome of this work was MultiFocus, the world’s first hearing-aid without a volume control⁴. MultiFocus was fitted using proprietary prescription rules derived from the research studies.

Going digital: DigiFocus and the beginning of multi-prescription fitting software

In 1995, Oticon announced its first fully digital hearing aid, DigiFocus. Some years before that, research had begun to investigate the best ways to exploit the flexibility of the upcoming device. A series of studies at Linköping University by Lunner et al. began to reveal that the optimal configuration of gain and compression in a multi-channel aid depends on the audiometric configuration of the user⁵.

Based on these studies, the original general-purpose prescription formulae for fitting DigiFocus (‘Adaptive Speech Alignment’ (ASA)) was supplemented with the ‘SKI’ prescription for precipitous high-frequency losses. By now, fitting was done via software, and algorithms could be incorporated for recommending which prescription to choose, based on the client’s audiogram.

Beyond the audiogram: further personalisation

The issue of candidature had been apparent from early on in all the above work, as there were sometimes distinct groups of people liking or disliking the experimental prescriptions being tested. This was the background for the large study of candidature, which compared various linear and non-linear prescriptions, including contrasts in compression time constants. Strong patterns of differential benefit for individual hearing-aid users appeared, indicating that the choice of prescription makes a difference.

Further reading

¹ McCandless GA, Lyregaard PE. Prescription of gain/output (POGO) for hearing aids. Hearing Instruments 34:1 p.16-21, 1983.

² Lyregaard PE. POGO and the theory behind. Proc. 13th Danavox Symposium, p. 81-96, 1988.

³ Villchur E. Signal processing to improve speech intelligibility in perceptive deafness J. Acoust. Soc. Am. Volume 53, Issue 6, pp. 1646-1657, 1973.

⁴ Brunved PB. How studying loudness growth led to the development of MultiFocus. Hearing instruments 45:Supplement 1 p. 8-10, 1994.

⁵ Lunner T, Hellgren J, Arlinger S, Elberling C. A digital filter-bank hearing aid. Predicting user preference and performance for two signal processing algorithms. Ear and Hearing 18:1 p. 12-25, 1997.