Incidence of childhood apraxia of speech (CAS) refers to the number of new cases identified in a specified time period. Prevalence of CAS refers to the number of people who are living with the condition in a given time period.
Prevalence estimates of CAS are unreliable due to the inconsistency of diagnostic guidelines (Shriberg, Aram, & Kwiatkowski, 1997), lack of adequately validated diagnostic tools (McCauley & Strand, 2008), and small sample sizes in relevant studies. These same factors may also play a role in the frequent overidentification of CAS by clinicians (Davis, Jakielski, & Marquardt, 1998; Shriberg & McSweeney, 2002).
CAS was estimated to occur in 1 to 2 children per 1,000 (0.1%–0.2%; Shriberg et al., 1997). It was estimated to be higher in male children than in female children with a 2–3:1 ratio (Hall, Jordan, & Robin, 1993; Lewis et al., 2004). Children with CAS were reported to have a higher likelihood of concomitant language, reading, and/or spelling disorders (Lewis et al., 2004; Lewis & Ekelman, 2007).
CAS, or its characteristics, were reported to have greater prevalence in various syndromes such as galactosemia (Shriberg, Potter, & Strand, 2011), fragile X syndrome (Spinelli, Rocha, Giacheti, & Richieri-Costa, 1995), and velocardiofacial syndrome (Kummer, Lee, Stutz, Maroney, & Brandt, 2007). Although autism spectrum disorder (ASD) has a higher prevalence of concomitant speech delay and speech errors, research indicates that children with ASD do not have a higher prevalence of CAS (Shriberg, Paul, Black, & van Santen, 2011).