Longitudinal Predictors of Aided Speech Audibility in Infants and Children.

OBJECTIVES: Amplification is a core component of early intervention for children who are hard of hearing, but hearing aids (HAs) have unique effects that may be independent from other components of the early intervention process, such as caregiver training or speech and language intervention. The specific effects of amplification are rarely described in studies of developmental outcomes. The primary purpose of this article is to quantify aided speech audibility during the early childhood years and examine the factors that influence audibility with amplification for children in the Outcomes of Children with Hearing Loss study.
DESIGN: Participants were 288 children with permanent hearing loss who were followed as part of the Outcomes of Children with Hearing Loss study. All of the children in this analysis had bilateral hearing loss and wore air-conduction behind-the-ear HAs. At every study visit, hearing thresholds were measured using developmentally appropriate behavioral methods. Data were obtained for a total of 1043 audiometric evaluations across all subjects for the first four study visits. In addition, the aided audibility of speech through the HA was assessed using probe microphone measures. Hearing thresholds and aided audibility were analyzed. Repeated-measures analyses of variance were conducted to determine whether patterns of thresholds and aided audibility were significantly different between ears (left versus right) or across the first four study visits. Furthermore, a cluster analysis was performed based on the aided audibility at entry into the study, aided audibility at the child's final visit, and change in aided audibility between these two intervals to determine whether there were different patterns of longitudinal aided audibility within the sample.
RESULTS: Eighty-four percent of children in the study had stable audiometric thresholds during the study, defined as threshold changes <10 dB for any single study visit. There were no significant differences in hearing thresholds, aided audibility, or deviation of the HA fitting from prescriptive targets between ears or across test intervals for the first four visits. Approximately 35% of the children in the study had aided audibility that was below the average for the normative range for the Speech Intelligibility Index based on degree of hearing loss. The cluster analysis of longitudinal aided audibility revealed three distinct groups of children: a group with consistently high aided audibility throughout the study, a group with decreasing audibility during the study, and a group with consistently low aided audibility.
CONCLUSIONS: The current results indicated that approximately 65% of children in the study had adequate aided audibility of speech and stable hearing during the study period. Limited audibility was associated with greater degrees of hearing loss and larger deviations from prescriptive targets. Studies of developmental outcomes will help to determine how aided audibility is necessary to affect developmental outcomes in children who are hard of hearing.