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 compared hearing aid (HA) fitting outcomes and developmental outcomes of children with hearing loss at 5 years of age. Design and study sample: HA settings of 232 children that were fit according to either the NAL or the DSL prescription were analysed as part of a longitudinal study on outcomes of children with hearing impairment (LOCHI). A randomised trial of prescription was implemented for a subset of 163 children for comparison of fitting and developmental outcomes. Results: Deviation from targets and root-mean-square (rms) error in HA fitting revealed no significant difference between fitting prescriptions. Aided audibility as 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 levels. When hearing loss desensitization was incorporated in the calculation of SII, the randomised trial of prescription revealed differences in audibility between prescription groups only at low input levels, but not at medium or high input levels. There were no significant group differences in speech production, perception, language and functional outcomes. Conclusions: Proximity to prescriptive targets were similar between fitting prescriptions. Although aided audibility varied between groups, developmental outcomes were similar.