Self-reported impact of developmental stuttering across the lifespan

Stuttering: Our Current Knowledge, Research Opportunities, and Ways to Address Critical Gaps

Our understanding of the neurobiological bases of stuttering remains limited, hampering development of effective treatments that are informed by basic science. Stuttering affects more than 5% of all preschool-age children and remains chronic in approximately 1% of adults worldwide. As a condition that affects a most fundamental human ability to engage in fluid and spontaneous verbal communication, stuttering can have substantial psychosocial, occupational, and educational impacts on those who are affected. This article summarizes invited talks and breakout sessions that were held in June 2023 as part of a 2-day workshop sponsored by the US National Institute on Deafness and Other Communication Disorders. The workshop encompassed topics including neurobiology, genetics, speech motor control, cognitive, social, and emotional impacts, and intervention. Updates on current research in these areas were summarized by each speaker, and critical gaps and priorities for future research were raised, and then discussed by participants. Research talks were followed by smaller, moderated breakout sessions intended to elicit diverse perspectives, including on the matter of defining therapeutic targets for stuttering. A major concern that emerged following participant discussion was whether priorities for treatment in older children and adults should focus on targeting core speech symptoms of stuttering, or on embracing effective communication regardless of whether the speaker exhibits overt stuttering. This article concludes with accumulated convergent points endorsed by most attendees on research and clinical priorities that may lead to breakthroughs with substantial potential to contribute to bettering the lives of those living with this complex speech disorder.

FreDESS: a clinical tool for perceptual evaluation of stuttering

AIM

Stuttering is a communication disorder that involves both manifest speech disfluencies and associated symptoms. The purpose of the present study was to introduce an easily administered and ecologically valid assessment tool designed for perceptual evaluation of stuttered speech, FreDESS (frequency of stuttering events, duration of events, effort, secondary behaviours, and severity). More specifically, we wanted to study its reliability and validity.

METHOD

Video recordings of conversations with 38 people who stutter (PWS), 19 females and 19 males aged 13-25, were assessed by three speech language pathologists (SLP). Inter- and intrajudge reliability was estimated with intraclass correlation, standard error of measurement, and agreement between listeners. Internal consistency for the FreDESS parameters was estimated with Cronbach's alpha (α). To test the validity of FreDESS, the relationships between the average estimated parameters of frequency, duration, secondary behaviours, and severity of FreDESS and the Stuttering Severity Instrument (SSI-3), were analysed using intraclass correlation.

RESULTS

The interjudge reliability was good, especially for the frequency, duration, and severity parameters (90 per cent + agreement given 1 scale point difference). All parameters of the FreDESS had strong intrajudge reliability (ICC = 0.86-0.94) and the overall internal consistency was high (α = 0.98). The average ratings on the two assessment scales were in line with each other (r = 0.90-0.96), indicating high concurrent validity.

CONCLUSION

The FreDESS scale for the assessment of stuttered speech may be a valuable tool in clinical and research contexts. It is a valid and more time-efficient assessment instrument than the more commonly used SSI.

Adult stuttering prevalence I: Systematic review and identification of stuttering in large populations

PURPOSE

Stuttering epidemiology is reviewed with a primary goal of appraising methods used to identify stuttering in large populations. Secondary goals were to establish a best estimate of adult stuttering prevalence; identify data that could subgroup stuttering based upon childhood versus adult onset and covert versus over behaviour; and conduct a preliminary assessment of the degree to which stuttering features as a co-occurring diagnosis.

METHODS

Systematic review followed PRISMA guidelines. Quality assessment was based on the Joanna Briggs Institute Prevalence Critical Appraisal Tool, with criteria adjusted for appraisal of stuttering.

RESULTS

15 sets of data were assessed for quality, with three meeting criteria for inclusion. These estimated adult stuttering prevalence at 0.67% at age 14-17 years (Taghipour et al., 2013); 0.21% at age 16-20 years (Tsur et al., 2021); and 0.63% when aged over 21 years (Craig et al., 2002).

CONCLUSION

Systematic review indicates adult stuttering prevalence is between 0.6-0.7%. A false positive paradox follows from the low prevalence of stuttering in the general population, creating a need for very high specificity when measuring stuttering in the general population. Failure to achieve high specificity (99.9% is suggested) leads to loss of statistical power due to presence of false positives. A corollary of the false positive paradox is that sensitivity in measurement of stuttering can be relatively low (90% is suggested) before general population estimates of stuttering prevalence are appreciably affected. Despite this relaxation of measurement requirements regarding sensitivity, covert stuttering is likely to have been underestimated. Covert stuttering might be accounted for using data from prospective cohort studies, however such a revision seems unlikely to exceed the widely-accepted 1% adult stuttering prevalence estimate; see Gattie, Lieven & Kluk (2024 this issue) for an estimate at 0.96 %. When used to estimate stuttering prevalence, data reported by Tsur et al. (2021) are outlying, with the relatively low estimate possibly due to origin as military conscript data and/or generalised healthcare screening.

Adult stuttering prevalence II: Recalculation, subgrouping and estimate of stuttering community engagement

PURPOSE

Epidemiological research of stuttering has frequently focused on children, with a relative paucity of population level data specific to adults. Prevalence data for adults are reassessed here, including a breakdown of whether stuttering is overt or covert, and whether onset was in childhood or adulthood. The engagement of adults who stutter with stuttering communities is also estimated.

METHODS

Prevalence calculations were based on data from studies having the strongest designs, following the systematic review of Gattie, Lieven & Kluk (2024, this issue). Original data for engagement with stuttering communities were gathered from English language internet stuttering support groups, a national stuttering charity in the UK and a regional stuttering support group in Manchester, UK.

RESULTS

Adult stuttering prevalence was estimated at 0.96% (95% CI 0.65, 1.44). This can be broken down to 0.63% overt stuttering (95% CI 0.46, 0.79) comprising 0.53% childhood onset and 0.10% adult onset; and 0.33% covert stuttering (95% CI 0.19, 0.58) comprising 0.28% childhood onset and 0.05% adult onset. Covert stuttering will have been overestimated, and may often be very mild. Engagement with stuttering communities was estimated at 0.99% internationally, 0.63% nationally and 1.01% regionally. Actual engagement will have been lower due to attrition and overcounting.

CONCLUSION

The adult stuttering prevalence estimate of 0.96% is consistent with the widely-cited all ages stuttering prevalence estimate of 1%. Of adults who stutter, fewer than 1% engage with stuttering communities.

Improving Stuttering Through Augmented Multisensory Feedback Stimulation

BACKGROUND/OBJECTIVES

Stuttering is a speech disorder involving fluency disruptions like repetitions, prolongations, and blockages, often leading to emotional distress and social withdrawal. Here, we present Augmented Multisensory Feedback Stimulation (AMFS), a novel personalized intervention to improve speech fluency in people who stutter (PWS). AMFS includes a five-day intensive phase aiming at acquiring new skills, plus a reinforcement phase designed to facilitate the transfer of these skills across different contexts and their automatization into effortless behaviors. The concept of our intervention derives from the prediction of the neurocomputational model Directions into Velocities of Articulators (DIVA). The treatment applies dynamic multisensory stimulation to disrupt PWS' maladaptive over-reliance on sensory feedback mechanisms, promoting the emergence of participants' natural voices.

METHODS

Forty-six PWS and a control group, including twenty-four non-stuttering individuals, participated in this study. Stuttering severity and physiological measures, such as heart rate and electromyographic activity, were recorded before and after the intensive phase and during the reinforcement stage in the PWS but only once in the controls.

RESULTS

The results showed a significant reduction in stuttering severity at the end of the intensive phase, which was maintained during the reinforcement training. Crucially, worse performance was found in PWS than in the controls at baseline but not after the intervention. In the PWS, physiological signals showed a reduction in activity during the training phases compared to baseline.

CONCLUSIONS

Our findings show that AMFS provides a promising approach to enhancing speech fluency. Future studies should clarify the mechanisms underlying such intervention and assess whether effects persist after the treatment conclusion.

Speech characteristics that differentiate stuttering and cluttering in Japanese speakers

Background

Cluttering is a speech disorder distinct from stuttering. Despite this distinction, there is no established method to clearly differentiate the two disorders. This study aimed to use objective criteria to differentiate cluttering from stuttering in Japanese speakers.

Methods

Participants were 32 consecutive native-Japanese speakers who visited the Keio University Hospital between July 2020 and January 2023 with a chief complaint of speech disfluency. One physician and two speech-language-hearing therapists concurred on a stuttering or cluttering diagnosis of the 32 patients based on recordings of the Kitsuon kensa-ho test. The frequencies of stuttering-like disfluencies (SDF) and normal disfluencies (NDF) were calculated from the Kitsuon kensa-ho, and the ratio of disfluencies (RDF) was calculated as the ratio of SDF to NDF. Differences between the cluttering and stuttering groups in the RDF and the mean articulatory rate (MAR) for oral reading and a monologue task were tested using the Mann-Whitney U test. ROC curves were used to determine the sensitivity and specificity that well-distinguished subjects with cluttering from those with stuttering; the experts' diagnosis was the gold standard.

Results

Of the 32 participants, 12 (38%) were diagnosed with cluttering and 20 (62%) with stuttering. The cluttering and stuttering groups were comparable in demographic characteristics. The RDF on monologue task had the highest sensitivity in diagnosing cluttering, and the MAR on monologue task had the highest specificity. Adopting provisional criteria of a monologue RDF greater than 1.2 and a monologue MAR greater than 7.5 produced a sensitivity of 0.92 and a specificity of 0.95.

Conclusion

We conclude that combining monologue RDF and monologue MAR well-distinguished cluttering from stuttering. This method provides new objective diagnostic criteria, which can aid clinicians, therapists, and basic researchers.

Self-Reported Stuttering Severity Is Accurate: Informing Methods for Large-Scale Data Collection in Stuttering

PURPOSE

To our knowledge, there are no data examining the agreement between self-reported and clinician-rated stuttering severity. In the era of big data, self-reported ratings have great potential utility for large-scale data collection, where cost and time preclude in-depth assessment by a clinician. Equally, there is increasing emphasis on the need to recognize an individual's experience of their own condition. Here, we examined the agreement between self-reported stuttering severity compared to clinician ratings during a speech assessment. As a secondary objective, we determined whether self-reported stuttering severity correlated with an individual's subjective impact of stuttering.

METHOD

Speech-language pathologists conducted face-to-face speech assessments with 195 participants (137 males) aged 5-84 years, recruited from a cohort of people with self-reported stuttering. Stuttering severity was rated on a 10-point scale by the participant and by two speech-language pathologists. Participants also completed the Overall Assessment of the Subjective Experience of Stuttering (OASES). Clinician and participant ratings were compared. The association between stuttering severity and the OASES scores was examined.

RESULTS

There was a strong positive correlation between speech-language pathologist and participant-reported ratings of stuttering severity. Participant-reported stuttering severity correlated weakly with the four OASES domains and with the OASES overall impact score.

CONCLUSIONS

Participants were able to accurately rate their stuttering severity during a speech assessment using a simple one-item question. This finding indicates that self-report stuttering severity is a suitable method for large-scale data collection. Findings also support the collection of self-report subjective experience data using questionnaires, such as the OASES, which add vital information about the participants' experience of stuttering that is not captured by overt speech severity ratings alone.

A prospective 14-year follow-up study of the persistence and recovery of stuttering

PURPOSE

To document the trajectory of early childhood stuttering longitudinally for 14. years with a consideration on the features of overt and covert stuttering related to recovery status.

METHOD

Thirty-eight participants were observed longitudinally at three different time points: early childhood (Occasion 1), middle childhood (Occasion 2), and late adolescence (Occasion 3). Data collection involved speech samples and reports of stuttering experiences. Recovery on Occasion 3 was estimated through analysis of speech samples, parent and expert judgments, and self- judgement. Two categories of persistence were used: persistent-subjective (no observable stuttering) and persistent-objective (observable stuttering).

RESULTS

The recovery rate was 65.6%. The majority of the participants showed minimal disfluent speech with 88% showing less than 1% syllables stuttered and 97% showing less than 3% syllables stuttered in the collected speech samples. All participants classified as persistent reported covert symptoms of stuttering. No relapses in recovery were observed between Occasion 2 and Occasion 3. Late recovery was only observed for those classified as persistent-subjective on Occasion 2. About 64% of the participants showing observable stuttering (persistent-objective) on Occasion 2 showed no observable stuttering (persistent-subjective) on Occasion 3.

CONCLUSIONS

Children continue to recover from early childhood stuttering as they age.The inclusion of self-reports adds to the understanding of recovery especially concerning the covert stuttering behaviours. The presence of overt symptoms of stuttering in the speech samples of children aged 7 to 13 years seems to be associated with the likelihood of late recovery of stuttering.

The Association Between Stuttering Burden and Psychosocial Aspects of Life in Adults

PURPOSE

Stuttering is a speech condition that can have a major impact on a person's quality of life. This descriptive study aimed to identify subgroups of people who stutter (PWS) based on stuttering burden and to investigate differences between these subgroups on psychosocial aspects of life.

METHOD

The study included 618 adult participants who stutter. They completed a detailed survey examining stuttering symptomatology, impact of stuttering on anxiety, education and employment, experience of stuttering, and levels of depression, anxiety, and stress. A two-step cluster analytic procedure was performed to identify subgroups of PWS, based on self-report of stuttering frequency, severity, affect, and anxiety, four measures that together inform about stuttering burden.

RESULTS

We identified a high- (n = 230) and a low-burden subgroup (n = 372). The high-burden subgroup reported a significantly higher impact of stuttering on education and employment, and higher levels of general depression, anxiety, stress, and overall impact of stuttering. These participants also reported that they trialed more different stuttering therapies than those with lower burden.

CONCLUSIONS

Our results emphasize the need to be attentive to the diverse experiences and needs of PWS, rather than treating them as a homogeneous group. Our findings also stress the importance of personalized therapeutic strategies for individuals with stuttering, considering all aspects that could influence their stuttering burden. People with high-burden stuttering might, for example, have a higher need for psychological therapy to reduce stuttering-related anxiety. People with less emotional reactions but severe speech distortions may also have a moderate to high burden, but they may have a higher need for speech techniques to communicate with more ease. Future research should give more insights into the therapeutic needs of people highly burdened by their stuttering.

SUPPLEMENTAL MATERIAL

https://doi.org/10.23641/asha.25582980.

Stuttering associated with a pathogenic variant in the chaperone protein cyclophilin 40

Stuttering is a common speech disorder that interrupts speech fluency and tends to cluster in families. Typically, stuttering is characterized by speech sounds, words or syllables which may be repeated or prolonged and speech that may be further interrupted by hesitations or 'blocks'. Rare variants in a small number of genes encoding lysosomal pathway proteins have been linked to stuttering. We studied a large four-generation family in which persistent stuttering was inherited in an autosomal dominant manner with disruption of the cortico-basal-ganglia-thalamo-cortical network found on imaging. Exome sequencing of three affected family members revealed the PPID c.808C>T (p.Pro270Ser) variant that segregated with stuttering in the family. We generated a Ppid p.Pro270Ser knock-in mouse model and performed ex vivo imaging to assess for brain changes. Diffusion-weighted MRI in the mouse revealed significant microstructural changes in the left corticospinal tract, as previously implicated in stuttering. Quantitative susceptibility mapping also detected changes in cortico-striatal-thalamo-cortical loop tissue composition, consistent with findings in affected family members. This is the first report to implicate a chaperone protein in the pathogenesis of stuttering. The humanized Ppid murine model recapitulates network findings observed in affected family members.

Cost of Illness and Health-Related Quality of Life for Stuttering: Two Systematic Reviews

PURPOSE

For those who stutter, verbal communication is typically compromised in social situations. This may attract negative responses from listeners and stigmatization by society. These have the potential to impair health-related quality of life across a range of domains, including qualitative and quantitative impacts on speech output, mental health issues, and failure to attain educational and occupational potential. These systematic reviews were designed to explore this matter using traditional health economics perspectives of utility measures and cost of illness.

METHOD

Studies were included if they involved children, adolescents, or adults with stuttering as a primary diagnosis. The quality of life search strategy identified 2,607 reports, of which three were included in the quality of life analysis. The cost of illness search strategy identified 3,778 reports, of which 39 were included in the cost of illness analysis.

RESULTS

Two of the three studies included in the quality of life analysis had a high risk of bias. When measured using utility scores, quality of life for people who stutter was in the range of those reported for chronic health conditions such as diabetes mellitus, cardiovascular disease, and cancer. However, there is little such evidence of quality of life impairment during the preschool years. Studies included in the cost of illness analysis carried considerable risk of bias overall.

CONCLUSIONS

For people who stutter, there are substantive direct and indirect costs of illness. These include impairment, challenges, and distress across many domains throughout life, including income, education, employment, and social functioning. Evidence of quality of life impairment using utility measures is extremely limited. If this situation is not remedied, the lifetime impairment, challenges, and distress experienced by those who stutter cannot be documented in a form that can be used to influence health policy and health care spending.

SUPPLEMENTAL MATERIAL

https://doi.org/10.23641/asha.24168201.

Expanding the speech and language phenotype in Koolen-de Vries syndrome: late onset and periodic stuttering a novel feature

Speech and language impairment is core in Koolen-de Vries syndrome (KdVS), yet only one study has examined this empirically. Here we define speech, language, and functional/adaptive behaviour in KdVS; while deeply characterising the medical/neurodevelopmental phenotype in the largest cohort to date. Speech, language, literacy, and social skills were assessed using standardised measures, alongside an in-depth health and medical questionnaire. 81 individuals with KdVS were recruited (35 female, mean age 9y 10mo), 56 of whom harboured the typical 500-650 kb 17q21.31 deletion. The core medical phenotype was intellectual disability (largely moderate), eye anomalies/vision disturbances, structural brain anomalies, dental problems, sleep disturbance, musculoskeletal abnormalities, and cardiac defects. Most were verbal (62/81, 76.5%), while minimally-verbal communicators used alternative and augmentative communication (AAC) successfully in spite of speech production delays. Speech was characterised by apraxia (39/61, 63.9%) and dysarthria (28/61, 45.9%) in verbal participants. Stuttering was described in 36/47 (76.6%) verbal participants and followed a unique trajectory of late onset and fluctuating presence. Receptive and expressive language abilities were commensurate with one another, but literacy skills remained a relative weakness. Social competence, successful behavioural/emotional control, and coping skills were areas of relative strength, while communication difficulties impacted daily living skills as an area of comparative difficulty. Notably, KdVS individuals make communication gains beyond childhood and should continue to access targeted therapies throughout development, including early AAC implementation, motor speech therapy, language/literacy intervention, as well as strategies implemented to successfully navigate activities of daily living that rely on effective communication.

Dissecting structural connectivity of the left and right inferior frontal cortex in children who stutter

Inferior frontal cortex pars opercularis (IFCop) features a distinct cerebral dominance and vast functional heterogeneity. Left and right IFCop are implicated in developmental stuttering. Weak left IFCop connections and divergent connectivity of hyperactive right IFCop regions have been related to impeded speech. Here, we reanalyzed diffusion magnetic resonance imaging data from 83 children (41 stuttering). We generated connection probability maps of functionally segregated area 44 parcels and calculated hemisphere-wise analyses of variance. Children who stutter showed reduced connectivity of executive, rostral-motor, and caudal-motor corticostriatal projections from the left IFCop. We discuss this finding in the context of tracing studies from the macaque area 44, which leads to the need to reconsider current models of speech motor control. Unlike the left, the right IFCop revealed increased connectivity of the inferior posterior ventral parcel and decreased connectivity of the posterior dorsal parcel with the anterior insula, particularly in stuttering boys. This divergent connectivity pattern in young children adds to the debate on potential core deficits in stuttering and challenges the theory that right hemisphere differences might exclusively indicate compensatory changes that evolve from lifelong exposure. Instead, early right prefrontal connectivity differences may reflect additional brain signatures of aberrant cognition-emotion-action influencing speech motor control.

A Cross-Sectional Investigation of the Impact of Stuttering on Swedish Females and Males in Childhood, Adolescence, and Young Adulthood

PURPOSE

We aimed to cross-sectionally describe the impact of stuttering on persons who stutter (PWS): children, adolescents, and young adults. Based on previous research on PWS and psychosocial health in the general population, we hypothesized that (a) the adverse impact of stuttering in PWS would be larger among adolescents than children and young adults and that (b) females, especially adolescent females, would report being more adversely impacted by their stuttering than males.

METHOD

We pooled samples of Swedish PWS, obtaining 162 individuals (75 females and 87 males), aged 7-30 years. We measured the impact of stuttering using age-relevant versions of the Overall Assessment of the Speaker's Experience of Stuttering (OASES). The relationship between OASES score, age, and sex was described using a polynomial model with an interaction term between age and sex to allow for potential differences between females and males' age-related curves.

RESULTS

The average trends were that (a) the impact of stuttering was greater for the adolescents than for the children and young adults, and (b) females, especially adolescent females, were on average more impacted by their stuttering than males. Taking self-reported speech fluency into account did not change this pattern.

CONCLUSIONS

In line with findings on psychosocial health, communication attitude, and self-esteem in the general population, the impact of stuttering seems to be particularly adverse among adolescents, especially female adolescents. Thus, clinicians need to be aware of the risk that young girls who stutter may develop a negative attitude to speech and communication, and this should also be communicated to caregivers and teachers.

SUPPLEMENTAL MATERIAL

https://doi.org/10.23641/asha.21554877.

The importance of understanding the broader experience of stuttering

This commentary is on the original article by Boyce et al. on pages 1297–1306 of this issue.