Background: Stuttering and speech sound disorder may co-occur during early childhood, although the exact rate of comorbidity in a community-cohort sample remains unknown. In isolation, both disorders have the potential for long-term negative effects. Comorbidity rates of 16%–46% reported in previous studies were based on parent report, speech-language therapist surveys, case file audits or direct observation studies from clinical samples. Rigorous methodology utilising a prospective, longitudinal community-cohort design is required to support these previous findings. Aims: First, to identify the proportion of children with comorbid stuttering and speech sound disorder at 4 years of age drawn from a community-cohort study. Second, to compare demographic and clinical features of this comorbid diagnosis group compared to children with no diagnosis of either disorder, or those with either disorder in isolation. Methods & procedures: Participants were drawn from a prospective, longitudinal community cohort study (the Early Language in Victoria Study) at 4 years of age (n = 1607). Demographic and clinical features for comparison were theoretically driven and included: gender, birth history, feeding status, speech and language status, family history of communication difficulties, maternal education, maternal vocabulary, maternal mental health and socioeconomic status. Outcomes & results: Of the 160 children diagnosed with stuttering between 2 and 4 years of age, 6.88 % (n = 11) also had a speech sound disorder. Given the small sample size and number of comparisons performed, there was insufficient evidence to rule out that group differences observed were not simply due to chance. Conclusions & implications: The prevalence of comorbid stuttering and speech sound disorder was lower in a community cohort compared to that reported in clinical studies. Higher rates reported in clinical samples may be due to increased parental help-seeking behaviour when the two disorders co-occur. Subsequently, these children may present to clinics more frequently. Accurate representation of prevalence allows for population specific research on best practice assessment and intervention. Currently little is known about how best to manage this caseload, therefore more research is required in this area, including the determination of prognostic variables to provide efficient and effective management.
Communication impairment in childhood is relatively common and may involve a number of domains including speech, language, fluency (e.g., stuttering), voice, and/or literacy (Speech Pathology Australia, 2016). Additionally, disorders involving these domains can co-occur. One commonly reported example is when stuttering co-occurs with speech sound disorder (SSD). Stuttering is a neurobiological disorder of communication (Drayna & Kang, 2011) which disturbs the flow of speech (Onslow et al., 2003; Sowman, Crain, Harrison, & Johnson, 2014), and typically appears between the ages of 2 and 4 years (Reilly et al., 2013). Speech sound disorder is a broad term, but here we focus on atypical phonetic or phonological speech errors, or delayed speech errors, which occur beyond age-expected norms (Morgan et al., 2017). The potential negative impact of stuttering is well documented, and can be long reaching across the lifespan (Blood & Blood, 2007; Iverach et al., 2009; Langevin, Packman, & Onslow, 2009; O’Brian, Jones, Packman, Menzies, & Onslow, 2011). For example, stuttering in the preschool years can elicit negative peer interactions (Langevin et al., 2009). In the school years, children who stutter have a heightened risk of being teased and bullied compared to their non-stuttering peers (Blood & Blood, 2007). Adults who stutter are at greater risk of developing mental health disorders (Iverach et al., 2009), and stuttering can effect educational (O’Brian et al., 2011) and vocational attainment (Klein & Hood, 2004). Similar to stuttering, having a SSD may also have negative consequences on an individual across a lifetime (Law, Boyle, Harris, Harkness, & Nye, 1998; Mccormack, Mcleod, Mcallister, & Harrison, 2009). For example, if SSDs persist into the school years, children may be at-risk for poorer literacy outcomes compared to their typical peers (Nathan, Stackhouse, Goulandris, & Snowling, 2004). Additionally, other academic skills may be impacted, as well as poorer psychosocial outcomes and vocational attainment (Mccormack et al., 2009). Given the potential negative impact across stuttering and SSD, it is important to be able to identify and better understand which children are at risk for these conditions when they co-occur to offset potential deleterious and possibly additive long-term effects. Yet the exact rate of co-occurrence of these disorders remains unknown and little is understood of potential prognostic variables in this field. It has been reported that between 16–46 % of children who stutter will also have co-occurring SSDs (Conture, Louko, & Edwards, 1993; Louko, 1995; Melnick & Conture, 2000; Ratner, 1995; Wolk, Blomgren, & Smith, 2000; Wolk, 1998). Yet the methodologies used to determine these rates in the surrounding literature have varied, and may explain the inconsistent findings (Unicomb, 2015). Three main methodological approaches employed in this field have been survey studies, retrospective file (chart) audits, and observation studies of clinical samples, discussed here in turn.