Hearing aid fitting and developmental outcomes of children fit according to either the NAL or DSL prescription: fit-to-target, audibility, speech and language abilities

Abstract

Objective: This study examined the influence of prescription on hearing aid (HA) fitting characteristics and 5-year developmental outcomes of children. Design: A randomised controlled trial implemented as part of a population-based study on Longitudinal Outcomes of Children with Hearing Impairment (LOCHI). Study sample: Two-hundred and thirty-two children that were fit according to either the National Acoustic Laboratories (NAL) or Desired Sensation Level (DSL) prescription. Results: Deviation from targets and root-mean-square error in HA fitting revealed no significant difference between fitting prescriptions. Aided audibility quantified by using the Speech Intelligibility Index (SII) model showed that DSL provided higher audibility than NAL at low and medium input levels but not at high input level. After allowing for hearing loss desensitisation, differences in audibility between prescription groups were significant only at low input level. The randomised trial of prescription that was implemented for 163 children revealed no significant between-group differences in speech production, perception, and language; but parent-rated functional performance was higher for the DSL than for the NAL group. Conclusions: Proximity to prescriptive targets was similar between fitting prescriptions. The randomised trial revealed differences in aided audibility at low input level between prescription groups, but no significant differences in speech and language abilities.

Key Words:

• Children
• hearing loss
• hearing aids
• hearing-aid prescription
• audibility
• outcomes

Acknowledgements

We gratefully thank all the children, their families and their teachers for participation in this study. We are also indebted to the many persons who served as clinicians for the study participants or assisted in other clinical or administrative capacities at Australian Hearing, Catherine Sullivan Centre, Hear and Say Centre, Royal Institute for Deaf and Blind Children, and the Shepherd Centre. We also thank Julia Day for input and assistance with data collection.

Declaration of interest

All authors, except the third author, are employees of the National Acoustics Laboratories.

The third author has a part-time Audiology practice, Johnson Hearing Technology and Communication, PLLC.

Funding

This work was partly supported by the National Institute on Deafness and Other Communication Disorders (Award Number R01DC008080). The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institute on Deafness and Other Communication Disorders or the National Institutes of Health, or the U.S. Department of Veterans Affairs.

The project was also partly supported by the Commonwealth of Australia through the Office of Hearing Services. We acknowledge the financial support of the HEARing CRC, established and supported under the Cooperative Research Centres Program of the Australian Government. We also acknowledge the support provided by New South Wales Department of Health, Australia; Phonak Ltd; and the Oticon Foundation.