International Journal of Pediatric Otorhinolaryngology
Listen up: Children with early identified hearing loss achieve age-appropriate speech/language outcomes by 3 years-of-age
Graphical abstract
Introduction
Hearing loss (HL) is the single most common condition affecting newborns in developed societies with one to three infants in every 1000 born with sensorineural hearing loss [1], [2], [3]. Approximately 97% of these children have at least one hearing parent [4]. Thus spoken communication is an understandable and desirable goal for these families [5], [6]. In an effort to realize this goal, research has focused on identifying malleable factors that could facilitate optimal speech/language outcomes (e.g. [7], [8], [9]). Malleable factors are those abilities that can be taught or characteristics that can be changed through treatment [10]. In 2000, research findings from previous decades culminated in the publication of the Office of Disease Prevention and Health 1-3-6 guidelines for best practice [11]. These guidelines recommended the manipulation of a range of malleable factors including: early identification in the form of universal newborn hearing screening (UNHS) by 1 month of age, verification of HL and amplification by 3 months and early intervention by 6 months of age [11], [12]. More recent research has further suggested that early identification coupled with oral intervention [13], [14], optimized amplification via hearing aids or newest generation cochlear implants (CIs) prior to 18 months of age [15] plus early bilateral implantation is associated with improved speech/language outcomes at significantly faster rates relative to children who are late identified [16], [17], [18]. For example, Holt and Svirsky [19], reported that the developmental trajectories of children implanted earlier—prior to age 2 years, were significantly better than those of children implanted later. Moreover, these same children had faster rates of spoken language acquisition compared with children implanted later in life.
While these improvements are encouraging, a fundamental goal of the 1-3-6 guidelines, and in particular UNHS, is to facilitate the development of age-appropriate speech/language outcomes not just improvements relative to later-identified peers [20]. Of the research examining the speech/language outcomes of children with all degrees of HL relative to typically developing hearing peers, findings have been mixed, often difficult to interpret and somewhat conflicting due to the heterogeneity of the children involved in the research [21]. Specifically, children within and across the studies have varied according to factors such as types of HL—congenital or acquired [13]; degrees of HL—from mild to profound [e.g. 22]; amplification devices—hearing aids and/or CIs [e.g. 23]; CI devices and programming strategies—older verses newer technology [24], [25]; communication mode—oral, total communication or sign [e.g. 26]; education and intervention setting [e.g. 15]; child inclusion criteria—population studies including special needs children and/or various intelligence quotients [5], [27].
This complicating factor of participant heterogeneity aside, reports on receptive/expressive language outcomes suggest that approximately 1 in 2 children with early identified profound HL who receive CIs at a mean age of 2.4 years may achieve outcomes commensurate with their hearing peers by around 5–8 years [13], [25]. Other data suggests that age appropriate receptive language scores can be expected by age 4.5 years, provided a child has pre-CI aided thresholds of 65 dB or less, participates in oral early intervention and has received a CI by <20 months of age [28]. Furthermore, it has been reported that word comprehension scores for children who receive a CI at age <2 years can be achieved at “significantly greater” levels than normative peers, particularly for those children who receive a CI prior to 12 months of age [29, p. 1].
Simultaneous, bilateral CIs between the ages of 5–18 months is also associated with higher numbers of children with profound HL being able to achieve receptive and expressive language outcomes not only at faster rates, but also within normative ranges at earlier chronological ages [30]. Specifically, of 21 bilaterally implanted children who had 12 months of CI experience, at an average chronological age of 25 months, 38% achieved receptive language scores within the normal limits (WNL), with 44% WNL for expressive language. By an average chronological age of 3 years and with 24 months of CI use, 60% of these children achieved receptive language and 55% had expressive language scores WNL.
With regard to speech outcomes for children with early identified HL relative to typically developing hearing peers, the literature base is not only small but contradictory. On the one hand, it has been suggested that approximately 50% may attain speech outcomes WNL by 8 years of age [25]. Specifically regarding children diagnosed with HL following UNHS, Yoshinaga-Itano et al. [22, p. 527] reported: “Children in the screen group had significantly more consonants in their spontaneous speech than the children in the no-screen group. The children in the screen group had significantly better speech intelligibility than the children in the no-screen group and significantly more consonant blends”. However, when the EI children with severe/profound HL were separated from this cohort of children with all degrees of HL [31, p. 204], it was reported that at ages 9–59 months, these children were rated by the phonetician, parent, and parent–infant provider as having “almost always unintelligible speech”. Similarly, little or no improvement in speech scores by 5 years of age for children diagnosed with severe/profound HL post UNHS screening has also been observed [26], [31].
In another study based on retrospective data, May-Mederake [29] suggested that children aged 33.3 ± 7.3–72.6 ± 16.3 months, who received CIs prior to age 2 years were able to, “perform as well or better than hearing peers in speech and grammar development” (p. 939). It should be noted however, that it was unclear what May-Mederake meant by “speech”. Specifically, May-Mederake reported using the “Sprachentwicklungstest für Kinder” (SETK), which was described as “an age specific speech development test designed for children aged 2–5 years” that “is composed of 4 sub-tests (Word Comprehension, Sentence Comprehension, Word Production and Sentence Production)” (p. 940). The author further describes subtests of the SETK as measuring “Encoding of Semantic Relations, Morphological Syntax and Phonological Working Memory for Nonsense Words” and “word Memory Span” (p. 940). Although the term “speech” has been used in the title of the test, the tests would appear to assess skills associated with receptive and expressive language abilities, rather than speech production. In other research examining the speech production abilities of children with HL, measures typically consider speech intelligibility, consonants and/or vowels evident in a phonetic repertoire, percentage of consonants correct (PCC) or percentage of phonemes (PPC) correct [32], [33], [34]. Although the results of this study were promising, the uncertainty surrounding the reported SETK “speech” measures raises questions about the validity of the statements about the children's actual speech production outcomes. This issue aside, May-Mederake [29], (p. 941) also notes, that despite the promising results, “a significant degree of variation” in the outcomes was present. Reasons for the variability were unclear, given that a range of malleable and non-malleable child characteristics thought to influence speech/language were not reported (e.g. communication mode [e.g. 35]; use of HA prior to CI or use of HA contralaterally post uni-CI [e.g. 36]; type of CI technology/generation of programming strategy [e.g. 37]; demographics, such as child gender, parent education or socioeconomic level [e.g. 38]; format of early intervention—oral, sign, total communication based [e.g. 7]; and amount of parent involvement in therapy [e.g. 39]).
Thus, although it has been established that early identification of HL is better than later, there remains a need for further research on the language and in particular the speech outcomes of children with HL. To help provide parents and clinicians with clear information, this research needs to address the complication of participant heterogeneity by studying a select group of malleable and/or non-malleable factors and controlling others. As noted earlier, malleable factors are characteristics that can be changed or modified (e.g. early verses later diagnosis; type of amplification device) and abilities that can be taught (e.g. sign, total or spoken communication). Non-malleable factors are those present in the child that do not necessarily change (e.g. gender, cause of hearing loss, degree of hearing loss, concomitant diagnoses).
One particular non-malleable factor that has received relatively little attention since the advent of UNHS is the degree of hearing loss. According to Moeller et al. [40], studies of the communication abilities of children with mild-moderate HL are rare. This is thought to be due in part to UNHS programmes not identifying children with mild-moderate HL at the expected prevalence [41], and a greater focus internationally on the detection, genetics and outcomes of children with moderate or greater (>40 dB) hearing losses [42].
Historically, it has been reported that the more severe the HL, the poorer children's outcomes with respect to speech/language abilities [43], [44], [45]. Given that children with severe/profound HL are being identified at earlier ages, and that not all children with mild or mild-moderate HL are being identified via UNHS, there remains a need for research examining the speech/language outcomes to consider the impact of this important non-malleable factor.
Thus, the purpose of this study was twofold. Firstly, to examine the speech/language outcomes of children with HL all of whom share a range of malleable and non-malleable factors, differing and therefore comparing them only with respect to (i) early versus later identified HL, and (ii) degree of hearing loss: mild versus moderate versus severe-profound, at 3-, 4- and 5-years of age. The common malleable factors included, all children were enrolled in the same intervention (specifically auditory-verbal intervention) provided by the same intervention service and also in receipt of hearing aids provided by and programmed by Australian Hearing or CIs from COCHLEAR Ltd. The common non-malleable factors included the children having a congenital sensorineural HL and no additional concomitant diagnoses. The second purpose was to determine whether the children exhibited speech and language abilities commensurate with their typically developing hearing peers, and if so, proportionally how many children, and, by what age.
Section snippets
Materials and methods
This was a mixed prospective/retrospective study of the speech/language outcomes of a cohort of children with HL who all attended oral auditory-verbal (AV) early intervention across 5 regional sites of The Shepherd Centre in the state of New South Wales (NSW), Australia. Post confirmation of HL, all families in NSW receive documentation from an unbiased source regarding intervention facilities available across the state. Parents are encouraged to investigate all options. The Shepherd Centre is
Speech/language abilities of children with early versus late identified hearing loss
The EI group significantly outperformed the LI group on all speech, receptive vocabulary and receptive/expressive language measures at all ages and for all severities of HL. Performance differences commenced at age 3 and increased at ages 4 and 5 years (Table 3). It is interesting to note, however, that from the 4 year test point, most mean standard scores of the LI group fall at the lower limits of the normal range (using SS of 85–115 as WNL) for both speech and language.
Percentage of children with early identified HL achieving age-appropriate speech/language outcomes
The mean standard score
Discussion
The primary purpose of this study was to examine the speech/language outcomes of children with HL all of whom share a range of malleable and non-malleable factors, differing and therefore comparing them only with respect to age of diagnosis (EI versus LI) and degree of HL (mild; moderate; severe/profound). A second purpose was to determine whether the children had age-appropriate speech/language abilities, and if so proportionally, how many and by what age. We were particularly interested in
Conclusions
Our findings provide evidence that it is indeed possible for children with all degrees of EI hearing loss to achieve age-appropriate speech/language outcomes as early as 3 years of age and that this progress can be maintained over the subsequent 2 years. Specifically, these data indicate that if HL is early diagnosed; amplification received by 3 months and regular AV early intervention has commenced by 6 months, as well as a CI provided prior to 18 months of age if required, then it is indeed
Conflict of interest statement
The authors declare that they have no conflicts of interest in the research.
Acknowledgements
The authors wish to thank The Shepherd Centre and the families who participated in this study.
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