Delayed Auditory Feedback alone does not consistently improve fluency in individuals with developmental stutteringDelayed Auditory Feedback Shows Inconsistent Results for Stuttering Fluency

PURPOSE: This systematic review and meta-analysis evaluated the fluency- enhancing effect of DAF alone in individuals with developmental stuttering. METHODS: Following PRISMA 2020 guidelines, we searched multiple databases for studies published between 2000 and 2024. Eligible studies examined DAF conditions applied to speech tasks with stuttering-related outcomes. Meta-analyses were conducted using a random-effects model, with subgroup analyses by disfluency type, delay time, speech task, stuttering severity, and participant age. RESULTS: Of the 194 records screened, eight studies involving a total of 98 participants in total met the inclusion criteria, and five studies involving 61 participants were eligible for quantitative synthesis. Each study included 8-20 participants ranging from school-age children to adults. Most participants were male, and stuttering severity ranged from mild to severe. DAF conditions were evaluated using oral reading and spontaneous speech/monologue tasks. Meta-analysis revealed no significant overall benefit of DAF compared with normal auditory feedback (NAF; mean difference = -1.46, 95% CI [-4.83, 1.91]). CONCLUSION: DAF alone does not consistently reduce disfluencies; however, specific populations and conditions may derive greater benefits from it. Larger, well-controlled studies are needed to clarify its therapeutic potential and clinical applications. WHAT THIS PAPER ADDS: What is already known on this subject Delayed auditory feedback (DAF) has been reported to improve fluency in people who stutter and is used in several assistive devices. However, its independent effect remains unclear because DAF is often combined with other altered auditory feedback conditions. What this study adds to existing knowledge This systematic review and meta-analysis evaluated the exclusive effect of DAF on stuttering. The results indicate that DAF alone does not consistently reduce disfluency compared with NAF, although certain conditions (e.g., shorter delays or reading tasks) may show greater benefits. What are the potential or actual clinical implications of this work? Clinicians should interpret the fluency-enhancing effects of DAF cautiously when used alone. Further well-controlled studies are needed to determine which individuals and speech contexts may benefit most from DAF-based interventions.