Stuttering is widely studied in the general population, but far less is known about how it presents in individuals with Down syndrome. In a 2025 study, Vanderbilt Kennedy Center (VKC) researchers combined clinical expertise, electronic health records (EHRs), and genetic analysis to better understand speech differences in individuals with Down syndrome.
With partial funding from a VKC Nicholas Hobbs Discovery Award, the project, Phenomic and Genomic Characterizations of Stuttering in Trisomy 21, was led by a multidisciplinary team that included Jennifer E. Below, Ph.D., Stephen Camarata, Ph.D., Robin Jones, Ph.D., and Dillon G. Pruett, Ph.D., who co-conceptualized the work during his time at Vanderbilt and continues to collaborate from Florida State University.
To better understand how often stuttering occurs in individuals with Down syndrome and what it may be associated with clinically, the research team analyzed thousands of de‑identified EHRs from Vanderbilt University Medical Center’s Synthetic Derivative database. These data were linked with genetic information from BioVU, Vanderbilt’s DNA biobank.
Starting with nearly 4,600 individuals diagnosed with Down syndrome, researchers used keyword searches, text‑mining algorithms, and detailed manual chart reviews to identify documented cases of stuttered speech. Through this rigorous process, the team confirmed 98 individuals with Down syndrome who exhibited stuttering.
Robin Michael Jones, Ph.D.
“Speech and language differences are very common in people with Down syndrome, but when we examined medical records, we found far less documentation of specific speech characteristics than we expected,” said Jones, associate professor of Hearing and Speech Sciences and a VKC Member. “That doesn’t mean the challenges aren’t there. It often means they’re being addressed outside of traditional medical settings, such as schools or private therapy clinics.”
“This work highlights both the power and the limitations of electronic health records,” said Pruett. “EHRs can reveal important patterns at a large scale, but they also reflect what clinicians choose or are prompted to document. Speech differences are often underrepresented.”
When researchers compared individuals with Down syndrome who stuttered to those who did not, clear differences emerged. Those in the Down syndrome‑plus‑stuttering group had a higher number of co‑occurring medical conditions overall.
“These weren’t unusual conditions for people with Down syndrome,” Jones explained. “We saw higher rates of speech and language disorders, sleep disturbances, thyroid disease, and ear or vision issues—things that are already known to be common in this population. What stood out was the clustering, suggesting that stuttering may be part of a broader or more complex clinical profile.”
The findings raise important questions about whether stuttering in Down syndrome could serve as a marker for more pervasive developmental or medical involvement, rather than existing as an isolated speech difference.
Beyond medical comorbidities, the study uncovered another underexplored dimension: emotional experience. In a subset of records, clinicians had documented frustration, concern, or emotional distress related to speech difficulties.
“In developmental stuttering, we know that emotional reactions can significantly affect quality of life,” Pruett said. “What’s striking is how little we’ve examined these experiences in individuals with intellectual and developmental disabilities. These records remind us that people with Down syndrome are aware of their speech and can be impacted by it emotionally.”
The researchers emphasize that recognizing these emotional components is critical for providing person‑centered, compassionate care.
In a smaller but significant component of the study, the team investigated whether genetic factors associated with developmental stuttering in the general population might also contribute to stuttered speech in Down syndrome.
Using a developmental stuttering polygenic risk score, researchers compared genetic data from individuals with Down syndrome who stuttered and those who did not. Although the sample size was limited, the results suggested that the polygenic risk score was modestly predictive of stuttering status.
“These findings are preliminary, but they’re exciting,” said Pruett. “They suggest that stuttering in Down syndrome may share some underlying genetic architecture with developmental stuttering more broadly. That opens the door to new questions about shared biological mechanisms.”
This study represents one of the first large‑scale efforts to systematically identify and characterize stuttering in individuals with Down syndrome using both clinical and genetic data. By improving methods for identifying speech differences in EHRs, the work lays important groundwork for future screening, research, and treatment approaches.
“Our hope is that this work encourages more intentional recognition of speech differences in medical records,” Jones said. “Better documentation leads to better understanding and ultimately, better care.”
Top photo by Adobe Stock
