Evidence-based decision-making in the treatment of speech,language,and communication disorders in Down syndrome;a scoping review

Abstract

This scoping review examined available scientific evidence according to the PRISMA-ScR guideline on the subject of treatment interventions by speech and language therapists of speech, language, and communication needs in people with Down syndrome. A literature search in PubMed, Embase, Cinahl, Cochrane, and Web of Science yielded 41 studies suitable for inclusion. All studies examined the effect of an intervention in speech, language or communicative behaviour, alone or in combination. Most studies were conducted among children, only four were conducted among adults. Twenty-three studies (49%) found statistically significant results. This review may encourage speech and language therapists to incorporate scientific evidence in making their treatment choices. Furthermore, it may inform health care professionals about potential speech and language treatments that can help people with Down syndrome in developing and maintaining their communicative skills. However, future research is needed because little research has been done in this area so far.

Keywords

Down syndrome speech language intervention evidence based

Introduction

As a result of a third copy of chromosome 21, people with Down syndrome have characteristic - particularly facial - physical features, and - varying degrees of - a disorder of intellectual development, as well as an increased incidence of comorbidities such as congenital heart disease and immunological abnormalities (Chapman and Hesketh, 2000; Verstegen and Kusters, 2020). Due to these disabilities, they are followed by paediatricians from birth to puberty, thereafter by, for example, physicians specialised in disorders of intellectual development, as can be the case in the country where the authors come from.

In addition to their specific physical disabilities, people with Down syndrome have difficulties in their speech and language. These difficulties are often greater than to be expected on their level of intelligence (Naess et al., 2011) which has a wide range, from an intelligence quotient of 20 to 69 (Chapman and Hesketh, 2000; van Gameren-Oosterom et al., 2014). Difficulties in speech and language have a substantial and lifelong negative impact on the communicative abilities of people with Down syndrome. As a consequence, people with Down syndrome need to rely on speech and language therapy services throughout their lives (Meyer et al., 2017).

The speech and language development of people with Down syndrome does not proceed differently from typically developing children, but more slowly, and they do not reach full development, although there also are large differences between individuals (Chapman and Hesketh, 2000; Martin et al., 2009). People with Down syndrome usually have more difficulty with expressing themselves (language production) than with understanding (language perception). Regarding language production, their use of vocabulary is relatively better than their use of morphological and syntactic rules (Chapman et al., 2002). Their speech is often marked by specific articulatory problems such as anatomic differences, motor-speech disorders, sensorimotor disorders, and attention-deficit disorders that impede their intelligibility, despite having achieved full speech sound acquisition (Cleland et al., 2010; Kent et al., 2021).

Speech and language therapy aims to address these difficulties, but the focus differs per age category. In 0–3-year-olds, problems in feeding and swallowing, preconditions for communication, and early communication are areas of concern. The focus on speech is marginal in this age category. In 4–6-year-olds, speech, both articulation and intelligibility, gradually becomes more central in addition to language processing, verbal production, and nonverbal expressive skills as age advances. These domains remain important in 7–18-year-olds, but then also phonological awareness and literacy become crucial, particularly at school age (7-12- year-olds). The therapy for adults with Down syndrome concentrates, in addition, on swallowing and on specific language skills such as proper syntax, storytelling, and social interaction (Meyer et al., 2017; Buckley and Prèvost Le, 2002).

In our review study, speech refers to concrete articulation, the motor performance to produce sounds and sound combinations, and intelligibility. Language includes vocabulary, phonology, morphology, and syntax, both from a productive and perceptive perspective. Next to verbal forms of communication, non-verbal forms are taken into account. Communication is defined as interactive meaningful exchanges, using communication capabilities, verbal and nonverbal, to engage in and maintain interactions. For a description of the technical terms used see Table 1.

Table 1.

Description of the technical terms used.

Term	Description
Preconditions for communication	The preconditions for communication are making eye contact (Cetincelik et al., 2021), imitation, taking turns, having a listening attitude
Early communication	Entering interactions, indicating wishes and needs, expressing feelings, acquiring knowledge about the surrounding world, social expressions without using words, for example facial expressions, sounds, manipulation of objects, pointing to objects/ pictures/photos (= communicative functions in the preverbal and early verbal phase)
Communication	Interactive meaningful exchanges, using communication capabilities, verbal and nonverbal, to engage in and maintain interactions
Language	A complex human-specific system for the expression of thoughts, feelings, etc., using sounds, words, and utterances
Articulation	Pronouncing sounds of a language, the motor performance to produce sounds and sound combinations
Intelligibility	The extent to which words and/or utterances are understandable to a listener
Phonological awareness	The metalinguistic ability to recognise and manipulate parts of sentences and words, including their syllables, onset-rime patterns, and phonemes
Literacy	The ability to read and write
Syntax	The arrangement of words and phrases to create well-formed sentences
Social language skills	The skills to interact and communicate with others in a meaningful way, including verbal and nonverbal communication, such as speech, gesture, facial expression, and body language, and how appropriate these interactions are in a given situation
Comprehensibility	The extent to which a listener can understand the contents of what is being said, ranging between fully understanding and no understanding at all
Morphosyntax	Morphosyntax deals with the morphological and syntactic components and their relationship in language structure. Morphology concerns word formation, including inflection, while syntax relates to sentence structure, including word order
Vocabulary	The collection of words and gestures known to an individual person

Speech and language therapy services for people with Down syndrome can be delivered in extramural (for example speech therapy practices, day care centres) and intramural care (for example residential communities, twenty-four-hour care), as well as in schools for mainstream and special education. A specific group of healthcare professionals, mostly general practitioners, paediatricians, ear-nose-throat-specialists, and neurologists are generally referring for speech and language treatment. Other allied professionals may be involved in the referral as well, such as specialised nurses and educational teams, depending on the regulations and practices of the country involved. For this reason, it is important that these professionals are well informed regarding the possibilities of speech and language interventions that can be applied in the treatment of speech, language, and communication needs (SLCN) of people with Down syndrome. This is of particular interest to paediatricians who intensively guide children with Down syndrome throughout their childhood while often having day-to-day supervision within a team of healthcare professionals (Peters, 2023).

Evidence-based practice is important to implement effective treatment (Michie et al., 2005). Evidence-based practice has three elements: 1. External clinical evidence (Research evidence), 2. Individual clinical expertise, and 3. Patients’ values and preferences (Sackett et al., 1996). Unfortunately, research evidence regarding effective speech and language therapy is limited. Nevertheless, speech and language therapists should be aware of those research evidence based interventions that are currently available, to support their decision-making in the choice of treatment options.

Many interventions focusing on speech, language, and communication training are available. In their study on intervention for children with developmental language disorder, Forsythe et al. (2021) listed 360 different interventions, whether or not evidence-based, among practitioners responsible for the management and decision-making regarding the treatment of children in 39 (mostly European) countries. Speech and language therapists will have to make careful considerations in choosing the most appropriate and effective intervention tailored to each individual, especially when a specific additional distinctive factor is involved like Down syndrome. The choice of interventions applied is generally personalised based on the professional expertise of the therapist, and determined by the specific needs, motivation, age, and behaviour of the client. Therefore, in addition to client characteristics also therapist characteristics influence this decision-making; education, experience, ease of use, time spent, what is deemed best for the client and what is considered most efficient, all play a role (Forsythe et al., 2021). Whether a treatment is research evidence based is not often used as a criterium in the choice of an intervention, although therapists with a master-level qualification are more likely to do so (Forsythe et al., 2021). Furthermore, there is a lack of easily accessible and comprehensible information about effective intervention approaches in the treatment of speech and language difficulties in Down syndrome; sources are not always accessible for free and in many countries many speech and language therapists are not affiliated with an organisation that facilitates the use of scientific sources. In addition, many speech and language therapists are still unaccustomed to, unsure of, or do not have sufficient knowledge of how to interpret scientific data (Dodd, 2007; Forsythe et al., 2021; Frizelle et al., 2021). An easily accessible comprehensive overview of the available evidence for such interventions could encourage speech and language therapists to take the aspect of research evidence based more into account when determining their treatment strategy for speech, language, and communication needs of people with Down syndrome. This might facilitate the choice of the most appropriate treatment and provide more positive outcomes (Seager et al., 2022; Dodd, 2007).

Therefore, the aim of this study is to give such an overview and to fill that gap by answering the following research question: Which research evidence based interventions in the treatment of speech, language, and communication difficulties in people with Down syndrome are available that can be used by speech and language therapists? This can also give referring physicians insight into the possibilities of speech and language therapy for the development and maintenance of capabilities in people with Down syndrome. A scoping review is particularly suited to answer this research question because of its broad and heterogeneous nature, as it summarises the available knowledge and gives the possibility to map and examine all published interventions as mentioned in the research question, including information on their level of evidence (Peters et al., 2015; Tricco et al., 2018).

Method

The checklist Preferred Reporting Items for Systematic Reviews and Meta-Analyses extension for Scoping Reviews (PRISMA-ScR) (Tricco et al., 2018) was used in drafting this review. (Appendix A).

Articles had to meet the following six criteria to be included: (1) focusing on people with Down syndrome; (2) investigating the effect of treatment of speech, language, and communication disorders; (3) the treatment in question is or can be used by speech and language therapists; (4) being written in English; (5) being published in a peer-reviewed journal; (6) being an empirical quantitative, qualitative, or mixed-method study. Studies that did not meet these criteria and were aimed at difficulties as primary oral motor dysfunction, stuttering, aphasia, voice disorders and reading disabilities were excluded. As the aim was to identify research evidence based scientific interventions, grey literature was not included in our search.

PubMed, Embase (OVID), Cinahl, Cochrane and Web of Science were searched up to October 2022. No date limit for publishing was used because few articles have been published on this subject. The search strategies were drawn up by authors one and two, and then discussed with the last author. Three search blocks were drafted: for the domain Down syndrome, for the domain speech, language, and communication disorders, and for the domain speech and language therapy. These were combined in the final search strings, one for each database, which can be found in Appendix B.

The search results were imported in Rayyan QCRI for Systematic Reviews (Ouzzani et al., 2016). Duplicates were removed. Authors one and two first screened the titles and afterwards the abstracts of all publications independently as ‘include’, ‘maybe’ or ‘exclude’. Articles scored as ‘include’ and/or ‘maybe’ by both were included in the next step. Differences in scoring between authors one and two were discussed among authors one, two and five until consensus was reached. The same procedure was thereafter used for the full text selection. There were no key changes made during the selection process. A flow chart of the selection is shown in Figure 1. The citations of all included full text studies were checked for their possible relevance to the purpose of the study by the first author. The same procedure as described above was applied to the cited articles in the included full text studies.

Figure 1.

Flow diagram of the selection process. Based on source: Moher E., Liberati A, Atlman DG, The PRISMA Group (2009) Preferred Reporting Items for Systematic Reviews and Meta-Analysis. The PRISMA Statement PLoS Med 6(7). Flow diagram for the scoping reviewing process.

The database format was jointly developed by authors one, two and five. The variables chosen were related to the included articles (e.g., country of origin, date of publishing) and the key study characteristics. Speech, language, and communication were divided into commonly used general areas (Bishop et al., 2017). The data of three articles were independently extracted by authors one and two. Uncertainties about definitions of the variables were discussed and refined. Variables were added or split in subcategories in consultation with the last author. The final data extraction table and the description of the variables can be found in Appendices C and D. The data extraction was completed by the first author. Halfway through and at the end of the data extraction process uncertainties encountered by this author were discussed with the last author. From studies with a mixed cohort only data relating to people with Down syndrome have been used. The studies included in the four systematic reviews obtained in the search (Barton-Hulsey et al., 2021; Moraleda-Sepúlva et al., 2022; Seager et al., 2022; Smith et al., 2020) were all independently checked by two authors and discussed in a subsequent consensus meeting; when these articles potentially met the inclusion criteria of the current review and had not been obtained in the search they were full text assessed by authors one and five, and if suitable, included for data extraction.

Results

Forty-one studies were included (Figure 1). In the selection process, 27 conflicts were noted during the title/abstract selection phase related to initial differences in interpretation of the focus of the interventions and the composition of the target population. During the full text phase, 15 conflicts were discussed related to the target of the intervention (e.g., is the paper focused on phonological awareness training with an effect to articulation) and the applicability of the intervention to day-to-day practice by speech and language therapists. All conflicts were resolved by consensus agreement.

Characteristics of the included studies are presented in Table 2. The synthesis of the results is presented in Table 3. This table only contains the statistics as presented by the authors in the included studies.

Table 2.

Main characteristics of the included studies presented alphabetically within descending order of year of publication.

Authors	Date of publishing	Country	Research method	Study design¹	Setting	Age category², y
Boliek, Halpern, Hernandez, Fox, Ramig	2022	Canada	Experiment and interview	Single case multiple baseline study³, interview	Clinical care and home	4-6 7-12
Langlois, Tucker, Sawatzky, Reed, Boliek	2020	Canada	Experiment	A within group, repeated measures design⁴	Unclear	4-6 7-12
Lund, Young, Yarbrough	2020	USA	Experiment	Combination single case design: a repeated acquisition design within alternating treatments⁵	Preschool	4-6
Quinn, Kaiser, Ledford	2019	USA	Experiment	A multiple probe across behaviours design⁶	Preschool	0-3 4-6
Huist, McCarthy, Boster, Benigno	2018	USA	Experiment	Single case multiple baseline study³	Clinical care at home, Clinic	4-6
Rvachew, Folden	2018	Canada	Experiment	Single object randomisation design⁷	Hospital	13-17
Yoder, Camarata, Woynaroski	2016	USA	Experiment	Randomised clinical trial⁸	Primary school	4-6 7-12
Bauer, Jones	2015	USA	Experiment	Two multiple baseline probe designs⁶	Home	0-3
Brown, Woods	2015	USA	Experiment	Single case multiple baseline study³	Home	0-3
Kent-Walsh, Binger, Buchanan	2015	USA	Experiment	A single case, multiple probe, experimental design across participants⁶	Clinic within university	4-6
Knight, Kurtz, Georgiadou	2015	UK	Experiment	Repeated measures design⁴	Unclear	7-12 13-17
Yoder, Woynaroski, Fey, Warren, Gardner	2015	USA	Randomised clinical trial	Repeated measures study⁴	Child Care Centre and home	0-3
Yoder, Woynaroski, Fey, Warren	2014	USA	Experiment	Randomised clinical trial⁸	Child Care Centre and home	0-3
Karaaslan, Mahoney	2013	Turkey	RCT	Repeated measures within and between groups design⁴	Clinical care at home, or clinical care in centre-based facility	0-3 4-6
Sepulveda, Lopez-Villasenor, Heinze	2013	Spain	Experiment	Multiple baseline design⁹	Clinical care	4-6 7-12 13-17
Wright, Kaiser, Reikowsky, Roberts	2013	USA	Experiment	Multiple baseline, across participants design⁹	Clinical care	0-3
Burgoyne, Duff, Clarke, Buckley, Snowling, Hulme	2012	UK	Experiment	Randomised controlled trial⁸	Primary school	4-6 7-12
Mahler, Jones	2012	USA	Experiment	A single subject A-B-A experimental design⁶	Hospital and home	>17
Mengoni, Nash, Hulme	2012	UK	Experiment	Repeated measures between groups design⁴	Primary school, secondary school, special secondary school	7-12 13-17
Sanz, Menendez, Rique	2011	Spain	Experiment	Repeated measures between groups design⁴	Clinical care at home	0-3
Bysterveldt, Gillon, Foster-Cohen	2010	New Zealand	Experiment	Multiple single subject repeated measures⁴	Preschool, home, clinical care	4-6
Kent-Walsh, Binger, Hasham	2010	USA	Experiment	Two single subject multiple probe across participants designs⁶	Clinic within university	4-6
Carlstedt, Henningsson, Dahllöf	2009	Sweden	Experiment	Randomised group design⁹	Hospital and home	0-3
Camarata, Yoder, Camarata	2006	USA	Experiment	Multiple baseline across subjects design³	Hospital	4-6 7-12
Chapman, Sindberg, Bridge, Gigstead, Hesketh	2006	Canada	Experiment	Repeated measures design⁴	Research centre	7-12 13-17 >17
Fey, Warren, Brady, Finestack, Bredin-Oja, Fairchild, Sokol, Yoder	2006	USA	Experiment	Multivariate between groups design¹⁰	Clinical care at home	0-3
Hewitt, Hinkle, Miccio	2005	USA	Experiment	Case study research design¹¹	Sheltered workshop	>17
Harris, Reichle	2004	USA	Experiment	Single subject, multiple probe design⁶	Preschool and home, Primary school and daycare	0-3 4-6
Kay, Chapman, Schwartz	2004	Canada	Experiment	Repeated measures by baseline between groups⁴	Research centre	7-12 13-17 >17
Kennedy, Flynn	2003	New Zealand	Experiment	A multiple baseline across behaviours research design³	Hospital	7-12
Yoder, Warren	2002	USA	Experiment	Randomised between groups experiment⁹	Unknown	0-3
Smith, Neeley, Clymer	2001	Canada	Experiment	Single case design¹²	Hospital and home	0-3
Foreman, Crews	1998	Australia	Experiment	Simple repeated measures technique⁴	Clinical care at home	0-3 4-6
Girolametto, Weitzman, Clements-Baartman	1998	Canada	Experiment	A pretest-posttest control group design with random assignment¹³	Home	0-3
Hohoff, Ehmer	1997	Germany	Experiment	Repeated measures within and between groups design⁴	Hospital	0-3 4-6 7-12
Schery, O’Connor	1997	USA	Experiment	Repeated measures within group design⁴	Home	0-3
Clements-Baartman, Girolametto	1995	Canada	Experiment	A single subject, alternating treatments design⁹	Clinical care at home	4-6
Dodd, Cormack, Woodyatt	1994	USA	Experiment	Repeated measures design⁴	Hospital and home	0-3 4-6
Nì Cholmain	1994	Ireland	Experiment	Repeated measures design⁴	Clinical care and home	4-6
Drash, Raver, Murrin, Tudor	1989	USA	Experiment	Repeated measures design⁴	Hospital	0-3 4-6
Weller, Mahoney	1983	USA	Experiment	Multiple baseline between groups design³	Home	0-3

Experiment = it is investigated what influence a factor (i.e., intervention) manipulated by the researcher has in a certain situation; RCT = randomised controlled trial; y = years of age.

¹All study designs contain a pre-measurement and one or more post-measurements. Type of design as described by the authors. When missing, type was determined in consultation by authors one, two, and five of the current study.

²Participants fall in the age categories according to Meyer et al. (2017) (this is not the exact age range of the participants in the study).

³Single case multiple baseline study = multiple sets of data, before/during/after the intervention, is collected on each subject, or participant, and individually analysed.

⁴Repeated measures design = multiple measures of the same variable taken on the same subjects or matched subjects or over two or more periods.

⁵Repeated acquisition design = a single-case research design that organises the rapid and repeated acquisition of non-reversible behaviours in relation to a recursively implemented intervention. Repeated and rapid measurement of irreversible discrete skills or behaviours through pre-and postintervention probes across different sets of stimuli.

⁶A multiple probe design = an analysis of the relationship between an independent variable and the acquisition of a successive-approximation or chain sequence; preintervention data are collected intermittently rather than continuously on each behaviour. The preintervention condition is referred to as a probe condition rather than as a baseline condition. Once the intervention is introduced, data are collected continuously.

⁷Single object randomisation design = a form of single case research in which sessions are randomly allocated to treatment conditions within subjects.

⁸Randomised controlled trial = the research population is randomly divided into an intervention and a control group to distribute external variables equally and counteract systematic differences. All variables, except the independent variable are controlled or held constant as much as possible so that they do not influence the dependent variable.

⁹Alternating treatment design = rapid and random or semirandom alteration of two or more conditions (interventions), approximately equal probability of being present during each measurement opportunity.

¹⁰Multivariate between groups design = compares the means of more than one variable (at the same time) between groups. The intervention has an effect on more than one variable.

¹¹Case study research design = a detailed examination of a particular case or cases within a real-world context. Pre- and posttreatment assessment.

¹²Single case experimental design = repeated measurements to test the effect of an intervention using a small number of patients (typically one to three), method-specific data analysis, including visual analysis and specific statistics.

¹³Pretest-posttest control group design with random assignment (pretest-posttest randomised experimental design) = participants randomly assigned to treatment or control group. The outcome of interest is measured before the treatment group gets the intervention (pretest) and after the intervention (posttest).

Table 3.

Synthesis of the results.

Reference: First Author, Date	Intervention	DS, n	Sample Age, y	Domain of interest	Result	Evidence
Bauer and Jones, 2014	Verbal imitation - and requesting intervention involving multiple opportunities, prompting and high rates of social reinforcement	5	0-1	Speech: articulation, intelligibility	Acquisition of taught verbal imitation of sounds.Taught sounds intelligible to naïve listener.	Evidence on the basis of specific single subject design analysis²
Bauer and Jones, 2014		5	0-1	Communication	Generalisation¹ (spontaneous use) of requesting.
Boliek, 2022	Lee Silverman Voice Treatment LOUD	9	4-8	Speech: articulation, intelligibility	4 of the participants a positive effect, 2 participants a negative effect. All participants demonstrated at least one improvement on treatment outcome measures including single-word intelligibility, speech acoustics, and parent perception of post-treatment changes.	Statistically significant
Brown and Woods, 2015	KidTalk-TaCTICS Project	3	1	Language: morphosyntax	All children increased at least one of their targeted communication levels (outcomes) with differing amounts of variability and maintained at least the second (more sophisticated) target’s level into the maintenance phase.	Evidence on the basis of specific single subject design analysis²
Burgoyne, 2012	Reading Strand and Language Strand	29 intervention group, 28 control group	5-10	Language: vocabulary	Greater progress on taught expressive vocabulary (with small to medium effect sizes) after 20 weeks, no significance after 40 weeks.	Statistically significant No statistical significance
Bysterveldt, 2010	Three components: a parent-implemented home program; centre-based speech–language therapy sessions, and ‘Learning through Computer’ sessions	10	4-5	Speech: articulation	Individual: gains of correct production of target sounds of between 20.8% and 66.64%. Analysis also performed on grouped data.	Statistically significant
Camarata et al., 2006	Broad Target Speech Recast	6	4-7	Speech:Intelligibility	Speech comprehensibility growth in 4 of the 6 participants.Generalisation speech comprehensibility in 2 participants.	Evidence on the basis of specific single subject design analysis²
Camarata et al., 2006	Broad Target Speech Recast	6	4-7	Language: morphosyntax	Growth in sentence length in 5 of the 6 participants. Mean Length of Utterance generalisation in 2 participants.
Carlstedt, 2003	Palatal plate therapy	9 treatment group, 11 control group	0-2	Speech: articulation	Progress in articulation.	No statistical significance
Carlstedt, 2003	Palatal plate therapy	9 treatment group, 11 control group	0-2	Speech: articulation	Deviant pattern with visible tongue at dental and bilabial sounds less present than in control group.	Statistically significant
Chapman, 2006	Memory support and elicited production	19	12-21	Language: vocabulary	Effect memory support and elicited production in comprehension of fast mapped words.	No statistical significance
Chapman, 2006	Memory support and elicited production	19	12-21	Language: vocabulary	Effect memory support and elicited production in production of fast-mapped words.	Statistically significant
Clements, 1995	Elicited imitation (i.e., didactic) intervention	2	4	Language: morphosyntax	Greater productivity and generalisation of two-word semantic relations in the didactic condition.	Evidence on the basis of specific single subject design analysis²
Dodd, 1994	Parents who participated in a training program to teach them the skills needed to become effective agents of speech/language therapy	9	2-6	Speech: articulation	3 of the 9 subjects showed progress in articulation, vocabulary, morphosyntax.	No statistical significance
Dodd, 1994		9	2-6	Language: vocabulary, morphosyntax		No statistical significance
Drash, 1989	Three procedures were added to a therapist’s prompt: 1. positive reinforcement; social reinforcement and opportunity to play with toys, 2. positive reinforcement with light-dimming, 3. positive reinforcement with visual screening through a scarf	15	0-4	Communication	All procedures produced an increase of percentage of response to therapist-initiated prompt over baseline.	Statistically significant
Drash, 1989		15	0-4	Communication	Light-dimming and screening in combination with positive reinforcement were both more effective than positive reinforcement alone.	Statistically significant
Fey, 2006	Responsive education and prelinguistic milieu teaching	13 treatment group 13 no treatment group	2	Communication	Increased rates of imperatives³, declaratives⁴, and total communication.	Statistically significant
Foreman, 1998	Makaton signing, COMPIC system of computerised pictographs	19	2-4	Language: vocabulary	Higher scores of initial communication lexicon with the sign method and multimodal method.	Statistically significant
Girolametto, 1998	Focused stimulation technique used by trained parents (The Hanen Program)	6 treatment group, 6 control group	2-3	Language: vocabulary	Increase of target words compared to control group.	Statistically significant
Harris, 2004	Aided language stimulation activities (non-VOCA; graphic mode communication systems)	2	3-5	Language: vocabulary	Gradual increase in symbol production and comprehension.	No statistical significance
Hewitt, 2005	A hybrid intervention approach to target grammar that combined naturalistic and structured intervention procedures	3	29-52	Language: morphosyntax	Increase of spontaneous productions of target elements of expressive syntax.	Evidence on the basis of specific single subject design analysis²
Hohoff, 1997	Castillo-Morales stimulating plate	20 treatment group 18 control group	2-7	Language: morphosyntax	On average 2 to 3 months faster in development.	No statistical significance
Huist, 2018	Contextualised video vignettes	1	4	Language: vocabulary	80% accuracy of the 10 target concepts.	Evidence on the basis of specific single subject design analysis²
Karaaslan, 2013	Bi-weekly Responsive Teaching parent-child sessions in addition to standard services	7 treatment group 8 control group	2-6	Communication	Increase in interactive engagement compared to control group: increase of 54% in attention and 57% in initiation, to 11% and 7% respectively in control group.	Statistically significant
Kay, 2004	Fast-mapping task complicated by the comprehension of the stories	23	12-20	Language: vocabulary	2 of the 8 taught words were spontaneously produced in story retellings.	No statistical significance
Kay, 2004		23	12-20	Language: vocabulary	Difference in novel word production compared with group of typically developing children.	No statistical significance
Kennedy, 2003	Subset of the Gillon Phonological Awareness Training program (PAT)	3	7-8	Language: phonological awareness	Increased phonological awareness.	Statistically significant
Kennedy, 2003		3	7-8	Speech: articulation, intelligibility	Increased overall percentage consonants correct (PCC)	No statistical significance
Kent, 2015	Aided modeling of treatment and contrastive targets through concentrated modeling and interactive play activities	1	6	Language: morphosyntax	Direct treatment effect: producing a greater number of inverted yes/no questions and to be declaratives within the probes following treatment compared with before treatment.	No evidence on the basis of specific single subject design analysis²
Kent, 2015		1	6	Language: morphosyntax	Some generalisation to novel sentences.	Evidence on the basis of specific single subject design analysis²
Kent, 2010	Improving Partner Applications of Augmentative Communication Techniques (ImPAACT)	3	4-5	Language: vocabulary	All three children demonstrated increases in their turn-taking rates and used a wider range of semantic concept.	Evidence on the basis of specific single subject design analysis²
Kent, 2010		3	4-5	Communication
Knight et al., 2015	Reading words	8	11-14	Speech: articulation, intelligibility	Effect on articulation and intelligibility compared with imitating words or naming pictures.	Statistically significant
Langlois, 2020	Lee Silverman Voice Treatment LOUD	9	4-8	Speech: intelligibility	Increase in intelligibility.	No statistical significance
Lund, 2019	Co-treatment; adapted physical educator and speech-language pathologist	10	4-6	Language: vocabulary (receptive)	Six of the 10 participants learned at least one of the five words introduced	Evidence on the basis of specific single subject design analysis²
Mahler, 2012	Lee Silverman Voice Treatment LOUD	2	33-34	Speech: intelligibility	Increase of 18% in intelligibility of one participant.	Statistically significant
Mengoni, 2013	Spoken nonwords paired with written form as well as pictures	17	7-16	Speech: articulation	Scores higher in the orthography present condition in both groups.	Statistically significant
Mengoni, 2013		17	7-16	Speech: articulation	Differences between the groups.	No statistical difference
Nì Cholmain, 1994	A program that aimed to provide the children with simple uncluttered examples of the organisation of the sounds in the language, in order to encourage them to construe the phonological system of the language. Based on Hodson and Paden (Hodson and Paden, 1983) and Weiner (Weiner, 1981)	6	4-5	Language: phonology, morphosyntax	Beginning of reorganisation of phonological systems and progress in syntax development. PCC pre-therapy ranged from 3% to 38%, while post results ranged from 19% to 88%.	No statistics have been performed
Quinn et al., 2019	Augmentative and alternative communication modelling	4	3-5	Language: Morphosyntax	Increase of percentage of correctly identified symbols and rate of symbolic communication across metrics for three participants	Statistically significant
Rvachew, 2018	Auditory-motor integration sessions, phonological memory and planning sessions	1	15	Speech: articulation	Improvement of speech sound accuracy.	Statistically significant
Sanz, 2010	Social reinforcement: verbal approval with some agreeable gesture	9 treatment group 9 control group	0-2	Language	Improvement of major executions receiving both social reinforcements in treatment group.	No statistical significance
Schery, 1997	Computer language intervention	8	2-3	Language: vocabulary, morphosyntax	Computer-based intervention was as successful as traditional one-to-one language therapy.	No statistical significance
Schery, 1997	Computer language intervention	8	2-3	Language: vocabulary, morphosyntax	Both approaches in themselves have a similar effect on vocabulary and morphosyntax.	Statistically significant
Sepulveda, 2013	A designed morphosyntactic intervention program for children with Down syndrome	10 treatment group 10 control group	6-14	Language: morphology, syntax, semantics, pragmatic	Differences between groups in morphology, semantics and syntax.	Statistical significance
Sepulveda, 2013		10 treatment group 10 control group	6-14	Language: morphology, syntax, semantics, pragmatic	Differences in pragmatic development	No statistical significance
Smith, 2001	Presentation of two types of toys during a regular speech-language therapy session: 1. reactive toys⁵, 2. Nonreactive toys⁶	4	0-2	Language: vocalisations	More vocalisations nonreactive toys.	Statistically significant
Weller, 1983	Total communication: oral language simultaneously paired with manual signs	8 intervention group 7 control group	1-3	Language: vocabulary	70% more lexical items in intervention group than in control group.	No statistical significance
Wright, 2013	Enhanced Milieu Teaching and JASPER (Joint Attention, Symbolic Play and Emotional Regulation) words and signs	4	1-2	Language: vocabulary	Acquisition 10-21 new signs, 3-9 new words. Generalisation use of signs in new location. Small changes use of spoken words at home.	No statistical significance
Yoder and Warren, 2002	Responsivity education for parents and Pre-linguistic Milieu Teaching for children (RPMT)	8 treatment group 9 control group	1	Language: vocabulary	Accelerated growth in lexical density.	No statistical significance
Yoder and Warren, 2002		8 treatment group 9 control group	1	Communication	Accelerated growth in comments. Decelerated growth in requests.	No statistical significance
Yoder, 2014	High dose frequency Milieu Communication Teaching	19 intervention group 16 control group	1-2	Language: vocabulary	32% more words than control group.	No statistical significance
Yoder, 2015	Daily Milieu Communication Teaching	19 treatment group 16 control group	1-2	Language: Vocabulary (receptive) Communication	Increased canonical syllabic communication and receptive vocabulary growth.	Statistically significant
Yoder, 2016	Broad Target Speech Recasts	23 intervention group 28 control group	5-12	Speech: intelligibility	Difference between groups. Both groups together: on average, 58% of students’ utterances were comprehensible in conversational speech	No statistical significance

DS=Down syndrome; PCC=percentage consonants correct; MLU=mean language utterance; y=year; n=number;

¹generalisation = spontaneous use in other situation than the treatment situation;

²(Byiers et al., 2012; Harrington and Velicer, 2015),

³imperative = a sentence type to urge somebody to do something,

declarative = a sentence type to make a statement,

reactive toy = maintains some motion and/or produces some sensory feedback when manipulated by an individual,

nonreactive toy = has limited potential for producing motion and/or sensory feedback when manipulated by an individual.

All included studies examined the effect of an intervention in language (n = 22), speech (n = 9), communication (n = 3), or some combination of these three, being language and speech (n = 3), speech and communication (n = 1), and language and communication (n = 3) (Figure 2). The intensity of the intervention, for example once a week or daily, was investigated by two studies (Yoder et al., 2014; Karaaslan and Mahoney, 2013). Most studies were conducted among children (n = 39), of whom twenty were under three years of age. Only four studies were conducted in adults (Mahler and Jones, 2012; Chapman et al., 2006; Hewitt et al., 2005; Kay-Raining Bird et al., 2004). Twenty-one studies have been carried out in the USA, eight in Canada, both high-income countries, one in a middle-income country, the remaining studies (n = 11) in other high-income countries. The number of studies per intervention varied from one study to seven: Parent mediated training (n = 7), Milieu Training (n = 5), Lee Silverman Voice Treatment (n = 3), other interventions (<3). Of the 41 included studies, 20 (49%) found a statistically significant effect of the applied intervention. Furthermore, nine studies (22%) (Hewitt et al., 2005; Lund et al., 2019; Brown and Woods, 2015; Clements-Baartman and Girolametto, 1995; Huist et al., 2018; Bauer and Jones, 2014; Camarata et al., 2006; Kent-Walsh et al., 2015; Kent-Walsh et al., 2010) determined evidence by applying an analysis method focused on single subject experimental design (Byiers et al., 2012; Harrington and Velicer, 2015). The remaining 12 studies (29%) all mentioned a non-statistical improvement of the target behaviour in the domain of interest due to the intervention used.

Figure 2.

Graphical representation of five relevant features of the 41 studies.

Discussion

This scoping review resulted in an overview of 41 studies related to interventions which are applicable to the treatment of speech, language, and communication disorders by speech and language therapists in people with Down syndrome. This number of studies is low given the high treatment rate of especially children with Down syndrome as advised in guidelines (e.g., Peters, 2023). Besides, only one paper (Sepulveda et al., 2013) described an intervention specifically developed for people with Down syndrome. Reasons for this low number of research based studies could be related to the fact that people with Down syndrome form a relatively small group within the total population treated by speech and language therapists. Also, only a limited group of speech and language therapists actually work with this specific group. Furthermore, speech and language therapists commonly mainly work with individual clinical expertise (Forsythe et al., 2021; Greenwell and Walsh, 2021) as part of evidence-based practice. Moreover, for other groups the number of available research evidence based interventions is limited. This indicates that the proportion of speech and language therapists who are engaged in research activities is relatively low, and that there is a lack of incentive for them to engage in research. Finally, experiences and findings about interventions using case reports are often only described in professional journals; this is considered a lower level of evidence and therefore was not included in our study which focused on research based evidence. Interestingly, we also found interventions in our literature search that are not directly or commonly used by speech and language therapists, such as electropalatographic therapy (Page and Johnson, 2021; Wood et al., 2019; Cleland et al., 2009; Gibbon et al., 2003), orthodontic palatal plate therapy (Javed et al., 2018), stay-play-talk intervention (Severini et al., 2018), and hippotherapy (Jackson-Maldonado, 2019). These too could be a valuable addition to the treatment plan because of their proven effectiveness on speech and language skills. However, in practice these interventions are generally not easily accessible to speech and language therapists in practice e.g. due to barriers in acquiring the necessary equipment and resources. Nevertheless, speech and language therapists should consider discussing these treatments.

Twenty of these 41 studies reported a statistically significant effect; they described a large variety of interventions, only three statistically significant interventions were investigated in three or more studies. The sample sizes of the intervention group with Down syndrome were small in most of the 41 studies (see Figure 2), this could have negatively influenced the outcome of statistical analyses (resulting in ‘no significance’ because of a small sample size). The variety of the interventions and the small sample sizes limit generalisation to the entire population of people with Down syndrome. Nevertheless, this overview of interventions will hopefully encourage speech and language therapists to start taking the factor “research evidence” into account when setting up a tailored treatment plan (next to client and practitioner factors). It also provides information for paediatricians and other healthcare professionals about what speech and language therapy can offer people with Down syndrome in the development and maintenance of their communication abilities. In addition, we hope that the limited number of studies, the wide variety in interventions, and the small sample sizes may be an incentive to perform more research on therapeutic speech and language interventions in people with Down syndrome.

Most of the included studies in this review focused on children; only four studies focused on adults. This suggests that speech and language therapy for children with Down syndrome may have been given more attention by practitioners as well. The latter is confirmed by a study of Frizelle et al. (2021) in which they observed a strong relationship between the number of treatments and age in people with Down syndrome, with adults receiving fewer treatments than children. Previously, Meyer et al. (2017) also found an influence of age by showing an overview of the number of treatments correlated with age groups in Down syndrome: the younger the age, the higher the number of treatments. The underlying reason for this could be the presumption that there will be no further development of speech and language skills at a later age (Chapman et al., 2002). However, several studies (Frizelle et al., 2021; Chapman et al., 2002; van Gameren-Oosterom et al., 2014; Murphy et al., 2018; Coppens-Hofman et al., 2012) come up with strong arguments why speech and language therapy in adults and adolescents with Down syndrome is useful and important: continuing therapy will maintain and even improve expressive language skills in adolescence. This is important because speech and language abilities are necessary for the development of social skills to build relationships and because they facilitate self-advocacy when making life choices and improve opportunities for open employment and education through better communication.

Another relevant outcome of the included studies is the imbalance in the domain of interest. The vast majority, 28 studies, are related to language, 13 studies to speech and 7 studies to communication. A reason for this imbalance could be related to the therapeutic focus on language in the earliest years of children to promote and trigger language development and interaction. Speech, on the other hand, becomes a therapeutic focus in later years. Moreover, moderate intelligibility is considered to be a characteristic of people with Down syndrome which is therefore not regarded as a priority for treatment, especially at an older age (Meyer et al., 2017; Buckley and Prèvost Le, 2002; Chapman et al., 2002). Another reason is inherent to the classification that has been applied in this review (Bishop et al., 2017): phonology is considered as part of language development and is essential in pronouncing words with the correct sounds. As a consequence, studies specifically mentioning phonology as their topic are classified under language, unlike other studies reporting articulation, speech, or intelligibility. The latter are grouped under speech.

Various studies emphasized the direct importance of treatment of the speech, language, and communication needs in people with Down syndrome (Moraleda-Sepúlva et al., 2022; Smith et al., 2020; Murphy et al., 2018). However, there is little evidence on the effects of the ‘dosage’, i.e., frequency and duration, of interventions. Only two studies included in this review, Yoder et al. (2014) and Karaaslan & Mahoney (2013), examined the effect of a low dose compared to a high dose of the same treatment approach. A larger effect was found at a higher dose. McDaniel and Yoder (2016) mentioned this severely limited empirical evidence related to treatment dose as an impediment to evidence-based treatment decisions. This gap between research results and practice needs to be urgently filled. More research is needed to substantiate the research evidence of treatment intensity of people with Down syndrome for the benefit of practitioners but also to inform national healthcare policy makers. As Murphy et al.(2018) stated: “Targeted, strategic investment is needed to allow practice to be aligned with best evidence, to support and treat people with DS [Down syndrome] effectively, to allow them to reach their maximum potential, and to exercise their rights to communicate as a basic human right. The right to communicate is enshrined in Article 21 of the UNCRPD (Convention on the Rights of Persons with a Disability, United Nations, 2006), and it includes the responsibility of the government to ensure all appropriate supports to develop communication skills, are put in place.”

This study has some limitations. The data extraction was performed by one author; however, the results were discussed afterwards until consensus was reached. Since this was a scoping review, no explicit quality rating of the included studies was performed.

This review has focused on treatments by speech and language therapists for general speech, language and communication needs in people with Down syndrome. Interventions for specific difficulties such as primary oral motor dysfunction, stuttering, aphasia, and reading disabilities were excluded. However, the authors believe that a similar review exploring those difficulties would be an important topic for future research and could be informative as well for speech and language therapists in choosing the most effective and appropriate treatment of these disorders in people with Down syndrome.

The overall conclusion is that more research on interventions in general is necessary, preferably with larger sample sizes of the target group, the people with Down syndrome. Specific themes that need extra attention are treatment intensity, adult intervention, and studies in low- and middle-income countries.

This review is one part of aiming to support speech and language therapists to take ‘research evidence’ into practice by providing a comprehensible summary of the current research-base. Future work could investigate other barriers to implementing research evidence and how research studies can improve this within their designs. This can move the field of speech and language therapists forward.

Supplemental Material

Supplemental Material - Evidence-based decision-making in the treatment of speech, language, and communication disorders in Down syndrome; a scoping review

Supplemental Material for Evidence-based decision-making in the treatment of speech, language, and communication disorders in Down syndrome; a scoping review by Annemieke de Groot, Noortje Eijsvoogel, Gijs van Well, Roeland van Hout and Esther de Vries in Journal of Intellectual Disabilities.

Supplemental Material

Supplemental Material - Evidence-based decision-making in the treatment of speech, language, and communication disorders in Down syndrome; a scoping review

Supplemental Material

Supplemental Material - Evidence-based decision-making in the treatment of speech, language, and communication disorders in Down syndrome; a scoping review

Supplemental Material

Supplemental Material - Evidence-based decision-making in the treatment of speech, language, and communication disorders in Down syndrome; a scoping review

Supplemental Material for Evidence-based decision-making in the treatment of speech, language, and communication disorders in Down syndrome; a scoping review by Annemieke de Groot, Noortje Eijsvoogel, Gijs van Well and Roeland van Hout and Esther de Vries in Journal of Intellectual Disabilities.

Footnotes

Declaration of conflicting interests

The authors declare that there is no conflict of interest with respect to this research, authorship and/or publication of this article.

Funding

The author(s) disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: The university appointment of the first author is financially supported by a grant from ZonMW (nr. 10430072010004; PRIDE study).

ORCID iD

Esther de Vries

Supplemental Material

Supplemental material for this article is available online.

References

Barton-Hulsey

Phinney

Collins

(2021) Augmentative and Alternative Communication Supports for Language and Literacy in Preschool: Considerations for Down Syndrome and Autism Spectrum Disorder. Semin Speech Lang 42(4): 345-362.

Bauer

Jones

(2014) Requesting and Verbal Imitation Intervention for Infants with Down syndrome: Generalization, Intelligibility, and Problem Solving. Journal of Developmental and Physical Disabilities 27(1): 37-66.

Bishop

DVM

Snowling

Thompson

, et al. (2017) Phase 2 of CATALISE: a multinational and multidisciplinary Delphi consensus study of problems with language development: Terminology. J Child Psychol Psychiatry 58(10): 1068-1080.

Boliek

Halpern

Hernandez

, et al. (2022) Intensive Voice Treatment (Lee Silverman Voice Treatment [LSVT LOUD]) for Children With Down Syndrome: Phase I Outcomes. J Speech Lang Hear Res 65(4): 1228-1262.

Brown

Woods

(2015) Effects of a Triadic Parent-Implemented Home-Based Communication Intervention for Toddlers. Journal of Early Intervention 37(1): 44-68.

Buckley

Prèvost Le

(2002) Speech and Language Therapy for children with Down Syndrome. Down Syndrome News and Update 2(2): 70-76.

Burgoyne

Duff

Clarke

, et al. (2012) Efficacy of a reading and language intervention for children with Down syndrome: a randomized controlled trial. J Child Psychol Psychiatry 53(10): 1044-1053.

Byiers

Reichle

Symons

(2012) Single-Subject Experimental Design for Evidence-Based Practice. Am J Speech Lang Pathol 21(4): 397–414.

Bysterveldt van

Gillon

Foster-Cohen

(2010) Integrated speech and phonological awareness intervention for pre-school children with Down syndrome. Int J Lang Commun Disord 45(3): 320-335.

10.

Camarata

Yoder

Camarata

(2006) Simultaneous treatment of grammatical and speech-comprehensibility deficits in children with Down syndrome. Downs Syndr Res Pract 11(1): 9-17.

11.

Carlstedt

Henningsson

Dahllof

(2003) A four-year longitudinal study of palatal plate therapy in children with Down syndrome: effects on oral motor function, articulation and communication preferences. Acta Odontol Scand 61(1): 39-46.

12.

Cetincelik

Rowland

Snijders

(2021) Do the eyes have it? A systematic review on the role of eye gaze in infant language development. Front. of psychology 11(1): 1-16.

13.

Chapman

Hesketh

(2000) Behavioral phenotype of individuals with Down syndrome. Ment Retard Dev Disabil Res Rev 6(2): 84-95.

14.

Chapman

Hesketh

Kistler

(2002) Predicting longitudinal change in language production and comprehension in individuals with Down syndrome: hierarchical linear modeling. J Speech Lang Hear Res 45(5): 902-915.

15.

Chapman

Sindberg

Bridge

, et al. (2006) Elicited Production on Fast Mapping of New Words by Adolescents With Down Syndrome. Journal of Speech, Language and Hearing Research 49: 3-15.

16.

Cleland

Timmins

Wood

, et al. (2009) Electropalatographic therapy for children and young people with Down's syndrome. Clin Linguist Phon 23(12): 926-939.

17.

Cleland

Wood

Hardcastle

, et al. (2010) Relationship between speech, oromotor, language and cognitive abilities in children with Down's syndrome. Int J Lang Commun Disord 45(1): 83-95.

18.

Clements-Baartman

Girolametto

(1995) Facilitating The Acquisition Of Two-Word Semantic Relations By Preschoolers With Down Syndrome: Efficacy Of Interactive Versus Didactic Therapy. Journal of Speech-Language Pathology and Audiology 19(2): 103-111.

19.

Coppens-Hofman

Maassen

BAM

Schrojenstein van Lantman-Valk de

HMJ

, et al. (2012) Speech difficulties and poor speech intelligibility in adults with Down syndrome: a review of the literature. Journal of Hearing Science 2(1): 9-16.

20.

Dodd

McCormack

Woodyatt

(1994) Evaluation of an Intervention Program: Relation Between Childrens's Phonology and Parents' Communicative Behavior. American Journal of Mental Retardation 98(5): 632-645.

21.

Dodd

(2007) Evidence-based practice and speech-language pathology: strengths, weaknesses, opportunities and threats. Folia Phoniatr Logop 59(3): 118-129.

22.

Drash

Raver

Murrin

, et al. (1989) Three Procedures for Increasing Vocal Response to Therapist Prompt in Infants and Children With Down Syndrome. American Journal on Mental Retardation 94(1): 64-73.

23.

Fey

Warren

Brady

, et al. (2006) Early Effects of Responsivity Education/Prelinguistic Milieu Teaching for Children With Developmental Delays and Their Parents. Journal of Speech, Language and Hearing Research 49: 526-547.

24.

Foreman

Crews

(1998) Using augmentative communication with infants and young children with Down syndrome. Downs Syndr Res Pract 5(1): 16-25.

25.

Forsythe

Murphy

Tulip

, et al. (2021) Why Clinicians Choose Their Language Intervention Approach: An International Perspective on Intervention for Children with Developmental Language Disorder. Folia Phoniatr Logop 73(6): 537-551.

26.

Frizelle

Ceroni

Bateman

, et al. (2021) Speech and language therapy services for people with Down syndrome: The disparity between research and practice. Journal of Policy and Practice in Intellectual Disabilities 19(2): 171-182.

27.

Gibbon

McNeill

Wood

, et al. (2003) Changes in linguapalatal contact patterns during therapy for velar fronting in a 10-year-old with Down's syndrome. Int J Lang Commun Disord 38(1): 47-64.

28.

Girolametto

Weitzman

Clements-Baartman

(1998) Vocabulary Intervention for Children with Down Syndrome: Parent Training Using Focused Stimulation. The Transdisciplinary Journal 8(2): 109-126.

29.

Greenwell

Walsh

(2021) Evidence-Based Practice in Speech-Language Pathology: Where Are We Now? Am J Speech Lang Pathol 30(1): 186-198.

30.

Harrington

Velicer

(2015) Comparing Visual and Statistical Analysis in Single-Case Studies Using Published Studies. Multivariate Behav Res 50(2): 162-183.

31.

Harris

Reichle

(2004) The Impact of Aided Language Stimulation on Symbol Comprehension and Production in Children With Moderate Cognitive Disabilities. American Journal of Speech-Language Pathology 13: 155-167.

32.

Hewitt

Hinkle

Miccio

(2005) Intervention to Improve Expressive Grammar for Adults With Down Syndrome. Communication Disorders Quarterly 26(3): 144-155.

33.

Hodson

Paden

(1983) Targeting Intelligible Speech. California: College Hill Press.

34.

Hohoff

Ehmer

(1997) Effects of the Castillo-Morales Stimulating Plate on Speech Development of Children with Down's Syndrome. Journal of Orofacial Orthopedics: Fortschritte der Kieferorthopädie 58(6): 330-339.

35.

Huist

McCarthy

Boster

, et al. (2018) Using Video to Teach Early Language Concepts and Symbols to Children With Complex Communication Needs. Communication Disorders Quarterly 41(2): 110-122.

36.

Jackson-Maldonado

(2019) Hippotherapy and the Communicative Abilities of Children With Down Syndrome: A Preliminary Study. Communication Disorders Quarterly 42(2): 81-92.

37.

Javed

Akram

Barillas

, et al. (2018) Outcome of orthodontic palatal plate therapy for orofacial dysfunction in children with Down syndrome: A systematic review. Orthod Craniofac Res 21(1): 20-26.

38.

Karaaslan

Mahoney

(2013) Effectiveness of responsive teaching with children with Down syndrome. Intellect Dev Disabil 51(6): 458-469.

39.

Kay-Raining Bird

Chapman

Schwartz

(2004) Fast Mapping of Words and Story Recall by Individuals With Down Syndrome. Journal of Speech, Language and Hearing Research 47: 1286-1300.

40.

Kennedy

Flynn

(2003) <Kennedy 2003.pdf>. Research in Developmental Disabilities 24: 44-57.

41.

Kent-Walsh

Binger

Buchanan

(2015) Teaching children who use augmentative and alternative communication to ask inverted yes/no questions using aided modeling. Am J Speech Lang Pathol 24(2): 222-236.

42.

Kent-Walsh

Binger

Hasham

(2010) Effects of parent instruction on the symbolic communication of children using augmentative and alternative communication during storybook reading. Am J Speech Lang Pathol 19(2): 97-107.

43.

Kent

Eichhorn

Wilson

, et al. (2021) Auditory-Perceptual Features of Speech in Children and Adults With Down Syndrome: A Speech Profile Analysis. J Speech Lang Hear Res 64(4): 1157-1175.

44.

Knight

Kurtz

Georgiadou

(2015) Speech production in children with Down's syndrome: The effects of reading, naming and imitation. Clin Linguist Phon 29(8-10): 598-612.

45.

Langlois

Tucker

Sawatzky

, et al. (2020) Effects of an intensive voice treatment on articulatory function and speech intelligibility in children with motor speech disorders: A phase one study. J Commun Disord 86: 106003.

46.

Lund

Young

Yarbrough

(2019) The Effects of Co-Treatment on Concept Development in Children With Down Syndrome. Communication Disorders Quarterly 41(3): 176-187.

47.

Mahler

Jones

(2012) Intensive treatment of dysarthria in two adults with Down syndrome. Dev Neurorehabil 15(1): 44-53.

48.

Martin

Klusek

Estigarribia

Robers

(2009) Language characteristics of individuals with Down syndrome. Topics in Language Disorders, 29: 112-132.

49.

McDaniel

Yoder

(2016) Pursuing precision speech-language therapy services for children with Down syndrome. Semin Speech Lang 37: 239–251.

50.

Mengoni

Nash

Hulme

(2013) The benefit of orthographic support for oral vocabulary learning in children with Down syndrome. J Child Lang 40(1): 221-243.

51.

Meyer

Theodoros

Hickson

(2017) Management of swallowing and communication difficulties in Down syndrome: A survey of speech-language pathologists. Int J Speech Lang Pathol 19(1): 87-98.

52.

Michie

Johnston

Abraham

, et al. (2005) Making psychological theory useful for implementing evidence based practice: a consensus approach. Qual Saf Health Care 14(1): 26-33.

53.

Moraleda-Sepúlva

López-Resa

Pulido-García

, et al. (2022) Language intervention in Down syndrome: a systematic literature review. Int. J. Environ. Res. Public Health 19(6043).

54.

Murphy

Lyons

Carroll

, et al. (2018) Communication as a human right: Citizenship, politics and the role of the speech-language pathologist. Int J Speech Lang Pathol 20(1): 16-20.

55.

Naess

Lyster

Hulme

, et al. (2011) Language and verbal short-term memory skills in children with Down syndrome: a meta-analytic review. Res Dev Disabil 32(6): 2225-2234.

56.

Nì Cholmáin

(1994) Working on Phonology with Young Children with Down Syndrome - A Pilot Study. Journal of Clinical Speech & Language Studies 1: 14-35.

57.

Ouzzani

Hammady

Fedorowicz

, et al. (2016) Rayyan-a web and mobile app for systematic reviews. Syst Rev 5(1): 210.

58.

Page

Johnson

(2021) Electropalatographic Therapy and Speech Production for Children With Down Syndrome. Perspectives of the ASHA Special Interest Groups 6(2): 485-493.

59.

Peters

Godfrey

Khalil

, et al. (2015) Guidance for conducting systematic scoping reviews. Int J Evid Based Healthc 13(3): 141-146.

60.

Peters

VJT

(2023) Multidisciplinary Care of Children with Down syndrome in the Netherlands: A Modular Perspective. Medical Research Archives 11(3).

61.

Quinn

Kaiser

Ledford

(2019) Teaching preschoolers with Down syndrome using augmentative and alternative communication modeling during small group dialogic reading. Am J Speech Lang Pathol 29: 80–100.

62.

Rvachew

Folden

(2018) Speech therapy in adolescents with Down syndrome: In pursuit of communication as a fundamental human right. Int J Speech Lang Pathol 20(1): 75-83.

63.

Sackett

Rosenberg

WMC

Gray

JAM

Haynes

Richardson

(1996) Evidence-based Medicine-What it is and what it isn’t. BMJ 312(7023): 71-72.

64.

Sanz

Menéndez

Rosique

(2010) Study of different social rewards used in Down’s syndrome children’s early stimulation. Early Child Development and Care 181(4): 487-492.

65.

Schery

O’Connor

(1997) Language Intervention: Computer Training for Young Children with Special Needs. British Journal of Educational Technology 28(4): 271-279.

66.

Seager

Sampson

Sin

, et al. (2022) A systematic review of speech, language and communication interventions for children with Down syndrome from 0 to 6 years. Int J Lang Commun Disord 57(2): 441-463.

67.

Sepulveda

Lopez-Villasenor

Heinze

(2013) Can individuals with Down syndrome improve their grammar? Int J Lang Commun Disord 48(3): 343-349.

68.

Severini

Ledford

Barton

, et al. (2018) Implementing Stay-Play-Talk With Children Who Use AAC. Topics in Early Childhood Special Education 38(4): 220-233.

69.

Smith

Hokstad

Naess

(2020) Children with Down syndrome can benefit from language interventions; Results from a systematic review and meta-analysis. J Commun Disord 85: 105992.

70.

Smith

Neeley

Clymer

(2001) Effects of Reactive and Nonreactive Toys on the Vocalizations of Toddlers With Down Syndrome. The Transdisciplinary Journal 11(2): 83-89.

71.

Tricco

Lillie

Zarin

, et al. (2018) PRISMA Extension for Scoping Reviews (PRISMA-ScR): Checklist and Explanation. Ann Intern Med 169(7): 467-473.

72.

van Gameren-Oosterom

HBM

Fekkes

Oudesluys-Murphy

, et al. (2014) Zelfredzaamheid van jongeren met Down-syndroom. Ned Tijdschr Geneeskd 158(A7983): 1–5.

73.

Verstegen

RHJ

Kusters

MAA

(2020) Inborn Errors of Adaptive Immunity in Down Syndrome. J Clin Immunol 40(6): 791-806.

74.

Weiner

(1981) Treatment of phonological disability using the method of meaningful minimal contrast. Two case studies. Journal of Speech and Hearing Disorders 46: 97-103.

75.

Weller

Mahoney

(1983) A Comparison of Oral and Total Communication Modalities on the Language Training of Young Mentally Handicapped Children. Education and Training of the Mentally Retarded 16(2): 103-110.

76.

Wood

Timmins

Wishart

, et al. (2019) Use of electropalatography in the treatment of speech disorders in children with Down syndrome: a randomized controlled trial. Int J Lang Commun Disord 54(2): 234-248.

77.

Wright

Kaiser

Reikowsky

, et al. (2013) Effects of a naturalistic sign intervention on expressive language of toddlers with Down syndrome. J Speech Lang Hear Res 56(3): 994-1008.

78.

Yoder

Woynaroski

Fey

, et al. (2014) Effects of dose frequency of early communication intervention in young children with and without Down syndrome. Am J Intellect Dev Disabil 119(1): 17-32.

79.

Yoder

Camarata

Woynaroski

(2016) Treating Speech Comprehensibility in Students With Down Syndrome. J Speech Lang Hear Res 59(3): 446-459.

80.

Yoder

Warren

(2002) Effects of Prelinguistic Milieu Teaching and Parent Responsivity Education on Dyads Involving Children With Intellectual Disabilities. Journal of Speech, Language and Hearing Research 45: 1158-1174.

81.

Yoder

Woynaroski

Fey

, et al. (2015) Why Dose Frequency Affects Spoken Vocabulary in Preschoolers With Down Syndrome. Am J Intellect Dev Disabil 120(4): 302-314.

Supplementary Material

Please find the following supplemental material available below.

For Open Access articles published under a Creative Commons License, all supplemental material carries the same license as the article it is associated with.

For non-Open Access articles published, all supplemental material carries a non-exclusive license, and permission requests for re-use of supplemental material or any part of supplemental material shall be sent directly to the copyright owner as specified in the copyright notice associated with the article.

0.00 MB

0.01 MB

0.38 MB

0.40 MB

0.17 MB