Investigating intervention dose frequency for children with speech sound disorders and motor speech involvement.

Background: Treatment outcome data for children with severe speech sound disorders with motor speech involvement (SSD-MSI) are derived from Phase I clinical research studies. These studies have demonstrated positive improvements in speech production. Currently there is no research examining the optimal treatment dose frequency for this population. The results of this study, which is the first of its kind, will inform the delivery of effective services for this population.

Aims: To investigate optimal treatment dose frequency for the Motor Speech Treatment Protocol (MSTP) for children with SSD-MSI.

Methods & Procedures: A total of 48 children (aged 43-47 months) with SSD-MSI participated in the study. Participants received 45-min MSTP intervention sessions either once per week (lower dose frequency) or twice per week (higher dose frequency) for a 10-week period. Blinded outcome assessments were carried out at pre- and post-intervention.

Outcomes & Results: Treatment-related change was assessed at body structures, functions and activities participation level as per the World Health Organization's International Classification of Functioning framework: Children and Youth Version (ICF-CY) framework WHO (2007). These measures are related to articulation, functional communication and speech intelligibility. One-way analysis of variance (ANOVA) revealed that for all variables the baseline scores were not statistically different (p > 0.05) between the two dose-frequency groups. Overall, there was a significant main effect of Time (pre-post) across all variables (p < 0.01). However, repeated-measures ANOVA did not result in any statistical interactions (Time × Dose frequency) for any of the variables tested (p > 0.05). Only marginal clinical advantages (< 4% change in intelligibility) were noted with the 10 extra sessions.

Conclusions & Implications: Overall, the MSTP intervention approach in conjunction with home practice led to significant positive changes for all measures in children with SSD-MSI. No statistical differences between high- and low-dose-frequency groups were observed for any of the variables. Clinical effects were examined using effect sizes, as well as changes in articulation, speech intelligibility and functional communication; these differed marginally between the two dose frequencies. This suggests limited benefits of 10 additional sessions per block. Thus, it is recommended that caregivers, speech-language therapists and policy-makers perform a cost-benefit analysis before determining the dose frequency, when considering additional sessions per block.