Exploring the dynamic changes in factors affecting speech and language outcomes in paediatric cochlear implant users

Multiple factors affect long-term speech and language outcomes in children growing up using cochlear implants (CIs). Influential factors can change over time due to alterations in clinical practice (e.g. updated clinical guidance on indications, introduction of neonatal screening or introduction of meningitis vaccine) or due to developments in society (e.g. population migration affecting cultural/ethnic distribution or socioeconomic changes). If this complex and dynamically changing landscape of influential factors is well understood appropriate interventions can be introduced for families that are most in need of them to facilitate faster rates of language acquisition.

In this research we monitored English speech and language outcomes for children receiving a CI at a central London implant programme from January 1998 to December 2019 with the intention of understanding the most important factors affecting speech and language development and whether these factors changed across the 20-year period. There were 418 children implanted, of which 173 had 5-year post implant speech and language scores. We monitored the distribution of type of onset of loss (congenital, progressive or acquired), age at implantation, home language, socioeconomic status, implant status, core language scores (Clinical Evaluation of Language Fundamentals (CELF) Edition 4). The findings were interpreted with consideration of clinical and societal moderators than can affect outcomes.

In terms of major changes in the population that occurred across the 20-year period we observed an increase in the proportion of children that were implanted with progressive losses. This was most likely affected by the introduction of the UKs National Institution of Health and Care Excellence (NICE) guidance on cochlear implants in 2009, which saw a reduction in the audiometric indication levels such that more children with progressive losses were eligible. There was also an increase in the number of children receiving simultaneous bilateral implants because of that NICE guidance. One of the most striking changes was the increase in the proportion of families who were not native English speakers (75% native English speakers in early years, dropping to 40% in later years), influenced by a change in the migration patterns in the population. There was a reduction in the Index of multiple deprivation (IMD; measure of socio-economic status) with time.

The findings indicated that the majority of children (65%) had severe language delays or were unable to be tested. This figure is often not represented in studies where the inclusion criteria are restricted.

A multinomial logistic regression for core language indicated that the best predictive model comprised of type of onset of severe-to-profound deafness (congenital, progressive, acquired), implant status (unilateral, bimodal, sequential bilateral, simultaneous bilateral), home language (native English, non-native English), and parental education level.