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As a group, children with hearing loss show slower language development than their peers with normal hearing. Age of intervention has a profound impact on language outcomes but data examining the correlation between degree of hearing loss and language outcomes are variable. Two approaches are used in the current study to examine this variability. In the first approach, we look at aided speech audibility as a potentially better predictor of communication outcomes than pure tone average. In the second approach, we look at a previously unexplored system in this population: working memory.
We enrolled 16 children with mild to moderately-severe hearing loss (CMML) and 24 children with normal hearing (CNH) between 6 and 9 years of age into the study. Over two visits, participants underwent a battery of tests including measures of auditory perception, working memory, word learning, and vocabulary level. Parents completed questionnaires about their child's behavior and executive skills.
Our results indicate that our measure of aided speech audibility, the aided Speech Intelligibility Index, was a stronger predictor than pure-tone average, spectral peak resolution, age of identification, age of intervention for word recognition score, nonword repetition score, and receptive vocabulary level. Our results showed little difference between CMML and CNH on measures of working memory including forward and backward digit span and phonological coding bias.
We cannot make a strong recommendation for working memory intervention in CMML Reduced audibility causes the most devastating effects on word recognition and vocabulary development. Our results support the recommendation that audibility measures be performed on all children fit with hearing aids and that these measurements be used to flag children who may be at risk for delayed vocabulary acquisition.