The added value of a bilateral hearing aid fitting

Researcher(s): M. Boymans, PhD.
Supervisor(s): prof. W.A. Dreschler, PhD.

Background:
Although normal hearing human beings use two ears, unilateral hearing aids are prescribed for a number of hearing impaired listeners. This study investigates whether the benefits of the use of two ears by normal hearing subjects can be maintained for hearing impaired listeners by bilateral fitting of hearing aids. Thusfar there is lack of experimental evidence and therefore the Health insurance Board of the Netherlands (CVZ) has asked the PACT-Foundation to initiate a broad investigation into the benefit of bilateral hearing aids. Ten audiological centres are participants in this multi centre study. The main part of this project has been developed by the AMC and the VU Medical Centre in Amsterdam.

Aim:
To describe and evaluate the common practice in the prescription of bilateral hearing aids and the assessments of benefits to hearing aids.

Method:
The PACT-project consists of three parts: review of recent literature, a retrospective study and a prospective study.
In the retrospective study 1000 files of consecutive hearing aid fittings for one or two hearing aids have been evaluated. Two years after the approval we sent an elaborate questionnaire to all patients. 505 subjects returned their questionnaires which have been used for the evaluation of the long-term effects. Relations have been investigated between anamnestic audiological and subjective data.
In the prospective study we selected subjects from the regular practice who are willing to try two hearing aids in the trial period. Before the trial we conducted several diagnostic tests in order to collect information about binaural functioning and the critical signal to noise ratio per ear. This additional information is important because it is hard to find a valid criterium for the reimbursement of two hearing aids on the basis of routine audiometric data. After the trial period a number of evaluation tests were conducted with one and two hearing aids. Furthermore a questionnaire was used in which differences between one or two hearing aids were judged by the subjects for different acoustical situations. In this prospective study 214 subjects participated.

Future research:
The different parts of this studie have been described in international publications and are part of the Ph.D. Thesis of dr. M. Boymans, titled “Intelligent processing to optimise the benefits of hearing aids”.
All results have also been described in the CVZ-report 119 (see www.cvz.nl). Based on the results on this project the Health insurance Board of the Nethelands (CVZ) has advised the Ministery of Health to extend the criteria for reimbursement to hearing aids.


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