Prevalence and features of comorbid stuttering and speech sound disorder at age 4 years

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.

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.

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.

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.

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.