Intervention factors associated with efficacy, when targeting oral language comprehension of children with or at risk for (Developmental) Language Disorder: A meta-analysis.

Background: Language interventions are complex behavioural interventions, making it difficult to distinguish the specific factors contributing to efficacy. The efficacy of oral language comprehension interventions varies greatly, but the reasons for this have received little attention.

Aims: The aim of this meta-analysis was to examine which intervention factors are associated with efficacy (as expressed with effect sizes) regarding interventions aiming to improve oral language comprehension on its own, or together with expressive language, in children under the age of 18 with or at risk for (developmental) language disorder-(D)LD. Whether the interventions for younger and older children differ from one another regarding efficacy or factors possibly associated with efficacy were also examined.

Methods & Procedures: Studies (n = 46) were identified through two systematic scoping reviews. Factors associated with efficacy were categorized according to the internal characteristics of the intervention as well as factors external to the intervention. Statistical analyses were conducted to examine the association between these factors and intervention efficacy as represented by effect sizes on oral language comprehension outcome measures.

Outcomes & Results: Targeting language, language environment or compensatory strategies indicated efficacy, whereas aiming to improve language processing indicated no clinically significant efficacy. Targeting only receptive language was associated with larger effect sizes than targeting both receptive and expressive language. The interventions for younger (2-7 years) and older (8-13 years) children indicated a similar degree of efficacy, but the way in which these results were achieved varied, as comprehension interventions for younger and older children differed from one another. Many factors associated with effect sizes were also associated with each other making interpretation of the results complex.

Conclusions & Implications: These indicative results suggest that it is not reasonable to target language processing, such as auditory processing or automatization, when aiming to improve oral language comprehension. Targeting receptive language only rather than both receptive and expressive language seems preferable to maximize efficacy when aiming to support solely oral language comprehension instead of targeting both expression and comprehension. The qualitative active ingredients of treatment appear to be more important than the number of intervention hours. Although children of different ages can benefit from interventions to enhance oral language comprehension, the child's age needs to be carefully considered to develop interventions that are optimal. Further research with larger data sets regarding factors contributing to efficacy is still needed before applying these results confidently to clinical practice.

What This Paper Adds: What is already known on this subject Little is known about the specific intervention factors associated with efficacy of comprehension interventions, and whether these differ between children of different ages. To be able to choose and create optimal comprehension interventions, a better understanding of the mechanisms of change is needed. What this paper adds to the existing knowledge The results indicate that oral comprehension skills of children aged 2-13 years with or at risk for (D)LD can be supported. Targeting language processing, such as auditory processing or automatization, does not seem reasonable when aiming to support oral comprehension. Rather, the interventions should target children's language skills related to comprehension, their language environment or provide children with compensatory strategies. The types of interventions used with younger and older children differed, such that those used with older children were more targeted, adult-directed, applied in formal activities, as well as used taught strategies and more explicit methods of instruction. What are the potential or actual clinical implications of this work? When developing interventions for oral language comprehension, the child's age needs to be considered. Further, what is targeted in an intervention in relation to the aim of the intervention needs careful consideration. The content of the intervention (therapeutic dose form) appears to have precedence over the amount of intervention.